WorldWideScience

Sample records for hydraulic fracturing stress

  1. Dynamic Response in Transient Stress-Field Behavior Induced by Hydraulic Fracturing

    Science.gov (United States)

    Jenkins, Andrew

    Hydraulic fracturing is a technique which is used to exploit geologic features and subsurface properties in an effort to increase production in low-permeability formations. The process of hydraulic fracturing provides a greater surface contact area between the producing formation and the wellbore and thus increases the amount of recoverable hydrocarbons from within the reservoir. The use of this stimulation technique has brought on massive applause from the industry due to its widespread success and effectiveness, however the dynamic processes that take part in the development of hydraulic fractures is a relatively new area of research with respect to the massive scale operations that are seen today. The process of hydraulic fracturing relies upon understanding and exploiting the in-situ stress distribution throughout the area of study. These in-situ stress conditions are responsible for directing fracture orientation and propagation paths throughout the period of injection. The relative magnitude of these principle stresses is key in developing a successful stimulation plan. In horizontal well plan development the interpretation of stress within the reservoir is required for determining the azimuth of the horizontal well path. These horizontal laterals are typically oriented in a manner such that the well path lies parallel to the minimum horizontal stress. This allows for vertical fractures to develop transversely to the wellbore, or normal to the least principle stress without the theoretical possibility of fractures overlapping, creating the most efficient use of the fluid energy during injection. The orientation and magnitude of these in-situ stress fields however can be dynamic, controlled by the subsequent fracture propagation and redistribution of the surrounding stresses. That is, that as the fracture propagates throughout the reservoir, the relative stress fields surrounding the fractures may see a shift and deviate from their original direction or

  2. Hydraulic fracturing of rock-fill dam

    Directory of Open Access Journals (Sweden)

    Jun-Jie WANG

    2016-02-01

    Full Text Available The condition in which hydraulic fracturing in core of earth-rock fill dam maybe induced, the mechanism by which the reason of hydraulic fracturing canbe explained, and the failure criterion by which the occurrence of hydraulicfracturing can be determined, were investigated. The condition dependson material properties such as, cracks in the core and low permeability ofcore soil, and “water wedging” action in cracks. An unsaturated core soiland fast impounding are the prerequisites for the formation of “waterwedging” action. The mechanism of hydraulic fracturing can be explainedby fracture mechanics. The crack propagation induced by water pressuremay follow any of mode I, mode II and mixed mode I-II. Based on testingresults of a core soil, a new criterion for hydraulic fracturing was suggested,from which mechanisms of hydraulic fracturing in the core of rock-fill damwere discussed. The results indicated that factors such as angle betweencrack surface and direction of principal stress, local stress state at thecrack, and fracture toughness KIC of core soil may largely affect theinduction of hydraulic fracturing and the mode of the propagation of thecrack.The condition in which hydraulic fracturing in core of earth-rock fill dam maybe induced, the mechanism by which the reason of hydraulic fracturing canbe explained, and the failure criterion by which the occurrence of hydraulicfracturing can be determined, were investigated. The condition dependson material properties such as, cracks in the core and low permeability ofcore soil, and “water wedging” action in cracks. An unsaturated core soiland fast impounding are the prerequisites for the formation of “waterwedging” action. The mechanism of hydraulic fracturing can be explainedby fracture mechanics. The crack propagation induced by water pressuremay follow any of mode I, mode II and mixed mode I-II. Based on testingresults of a core soil, a new criterion for hydraulic fracturing

  3. Mechanics of Hydraulic Fractures

    Science.gov (United States)

    Detournay, Emmanuel

    2016-01-01

    Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

  4. Direct Imaging of Natural Fractures and Stress Compartments Stimulated by Hydraulic Fracturing

    Science.gov (United States)

    Lacazette, A.; Vermilye, J. M.

    2014-12-01

    This contribution will present results from passive seismic studies of hydraulic fracture treatments in North American and Asian basins. One of the key data types is a comparatively new surface-based seismic imaging product - "Tomographic Fracture Images®" (TFI®). The procedure is an extension of Seismic Emission Tomography (SET), which is well-established and widely used. Conventional microseismic results - microearthquake hypocenter locations, magnitudes, and focal mechanism solutions - are also obtained from the data via a branch of the processing workflow. TFI is accomplished by summing the individual time steps in a multidimensional SET hypervolume over extended periods of time, such as an entire frac stage. The dimensions of a SET hypervolume are the X, Y, and Z coordinates of the voxels, the time step (typically on the order of 100 milliseconds), and the seismic activity value. The resulting summed volume is skeletonized to produce images of the main fracture surfaces, which are known to occupy the maximum activity surfaces of the high activity clouds from theory, field studies, and experiments. The orientation vs. area of the resulting TFIs can be analyzed in detail and compared with independent data sets such as volumetric structural attributes from reflection seismic data and borehole fracture data. We find that the primary effect of hydraulic fracturing is to stimulate preexisting natural fracture networks and faults. The combination of TFIs with hypocenter distributions and microearthquake focal mechanisms provides detailed information on subsurface stress compartmentalization. Faults are directly imaged which allows discrimination of fault planes from auxiliary planes of focal mechanism solutions. Examples that will be shown include simultaneous movement on a thrust fault and tear fault and examples of radically different stress compartments (e.g. extensional vs. wrench faulting) stimulated during a single hydraulic fracture treatment. The figure

  5. Hydraulic fracture considerations in oil sand overburden dams

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, R.; Madden, B.; Danku, M. [Syncrude Canada Ltd., Fort McMurray, AB (Canada)

    2008-07-01

    This paper discussed hydraulic fracture potential in the dry-filled temporary dams used in the oil sands industry. Hydraulic fractures can occur when reservoir fluid pressures are greater than the minimum stresses in a dam. Stress and strain conditions are influenced by pore pressures, levels of compaction in adjacent fills as well as by underlying pit floor and abutment conditions. Propagation pressure and crack initiation pressures must also be considered in order to provide improved hydraulic fracture protection to dams. Hydraulic fractures typically result in piping failures. Three cases of hydraulic fracture at oil sands operations in Alberta were presented. The study showed that hydraulic fracture failure modes must be considered in dam designs, particularly when thin compacted lift of dry fill are used to replace wetted clay cores. The risk of hydraulic fractures can be reduced by eliminating in situ bedrock irregularities and abutments. Overpressure heights, abutment sloping, and the sloping of fills above abutments, as well as the dam's width and base conditions must also be considered in relation to potential hydraulic fractures. It was concluded that upstream sand beaches and internal filters can help to prevent hydraulic fractures in dams in compacted control zones. 5 refs., 16 figs.

  6. Effect of Random Natural Fractures on Hydraulic Fracture Propagation Geometry in Fractured Carbonate Rocks

    Science.gov (United States)

    Liu, Zhiyuan; Wang, Shijie; Zhao, Haiyang; Wang, Lei; Li, Wei; Geng, Yudi; Tao, Shan; Zhang, Guangqing; Chen, Mian

    2018-02-01

    Natural fractures have a significant influence on the propagation geometry of hydraulic fractures in fractured reservoirs. True triaxial volumetric fracturing experiments, in which random natural fractures are created by placing cement blocks of different dimensions in a cuboid mold and filling the mold with additional cement to create the final test specimen, were used to study the factors that influence the hydraulic fracture propagation geometry. These factors include the presence of natural fractures around the wellbore, the dimension and volumetric density of random natural fractures and the horizontal differential stress. The results show that volumetric fractures preferentially formed when natural fractures occurred around the wellbore, the natural fractures are medium to long and have a volumetric density of 6-9%, and the stress difference is less than 11 MPa. The volumetric fracture geometries are mainly major multi-branch fractures with fracture networks or major multi-branch fractures (2-4 fractures). The angles between the major fractures and the maximum horizontal in situ stress are 30°-45°, and fracture networks are located at the intersections of major multi-branch fractures. Short natural fractures rarely led to the formation of fracture networks. Thus, the interaction between hydraulic fractures and short natural fractures has little engineering significance. The conclusions are important for field applications and for gaining a deeper understanding of the formation process of volumetric fractures.

  7. Hydraulic fracturing rock stress measurement at Haestholmen, Finland

    International Nuclear Information System (INIS)

    Ljunggren, C.; Klasson, H.

    1992-12-01

    This report presents hydraulic fracturing measurements in two boreholes located on the Haestholmen island near Loviisa, Finland. The aim of the measurements was to provide stress data, forming input for the design of an underground facility for disposal of low- and medium-level waste as well as future plant decommissioning radioactive waste from the IVO reactor units situated on Haestholmen. The theoretical background to the hydrofracturing method is summarized, as is the equipment and experimental procedures used in the present case. All results obtained are presented and critically discussed. The final stress parameters presented are magnitudes and directions of the maximum and minimum horizontal stresses. Testing was successfully completed according to schedule in both boreholes.(orig.)

  8. A review on hydraulic fracturing of unconventional reservoir

    Directory of Open Access Journals (Sweden)

    Quanshu Li

    2015-03-01

    Full Text Available Hydraulic fracturing is widely accepted and applied to improve the gas recovery in unconventional reservoirs. Unconventional reservoirs to be addressed here are with very low permeability, complicated geological settings and in-situ stress field etc. All of these make the hydraulic fracturing process a challenging task. In order to effectively and economically recover gas from such reservoirs, the initiation and propagation of hydraulic fracturing in the heterogeneous fractured/porous media under such complicated conditions should be mastered. In this paper, some issues related to hydraulic fracturing have been reviewed, including the experimental study, field study and numerical simulation. Finally the existing problems that need to be solved on the subject of hydraulic fracturing have been proposed.

  9. Method for stress determination in N, E, and T tunnels, Nevada Test Site, by hydraulic fracturing, with a comparison of overcoring methods

    International Nuclear Information System (INIS)

    Miller, C.H.

    1976-01-01

    Twenty-nine intervals in 10 core holes were hydraulically fractured in N, E, and T tunnels, Nevada Test Site, during 1974. Certain pressures were determined and related to the ambient stress field, but the orientation of the hydraulic fractures was not measured. These data and data from previous investigations in G tunnel indicated that both the magnitude of the hydraulic pressures and the direction of fracturing are independent of the orientation of the core holes. The maximum and minimum principal compressive stresses determined by the hydraulic fracturing methods are good approximations of those determined by nearby overcore methods. The data show that a good approximation of the magnitudes of the maximum and minimum principal stress axes can be obtained from several hydrofractured intervals in one core hole. Furthermore, if fracture orientation can be measured, then the direction of minimum principal compressive stress can be determined and the orientation of the plane of the maximum and intermediate principal compressive stresses can also be determined

  10. Toughness-Dominated Regime of Hydraulic Fracturing in Cohesionless Materials

    Science.gov (United States)

    Germanovich, L. N.; Hurt, R. S.; Ayoub, J.; Norman, W. D.

    2011-12-01

    This work examines the mechanisms of hydraulic fracturing in cohesionless particulate materials with geotechnical, geological, and petroleum applications. For this purpose, experimental techniques have been developed, and used to quantify the initiation and propagation of hydraulic fractures in saturated particulate materials. The fracturing liquid is injected into particulate materials, which are practically cohesionless. The liquid flow is localized in thin self-propagating crack-like conduits. By analogy we call them 'cracks' or 'hydraulic fractures.' When a fracture propagates in a solid, new surfaces are created by breaking material bonds. Consequently, the material is in tension at the fracture tip. Because the particulate material is already 'fractured,' no new surface is created and no fracturing process per se is involved. Therefore, the conventional fracture mechanics principles cannot be directly applied. Based on the laboratory observations, performed on three particulate materials (Georgia Red Clay, silica flour, and fine sand, and their mixtures), this work offers physical concepts to explain the observed phenomena. The goal is to determine the controlling parameters of fracture behavior and to quantify their effects. An important conclusion of our work is that all parts of the cohesionless particulate material (including the tip zone of hydraulic fracture) are likely to be in compression. The compressive stress state is an important characteristic of hydraulic fracturing in particulate materials with low, or no, cohesion (such as were used in our experiments). At present, two kinematic mechanisms of fracture propagation, consistent with the compressive stress regime, can be offered. The first mechanism is based on shear bands propagating ahead of the tip of an open fracture. The second is based on the tensile strain ahead of the fracture tip and reduction of the effective stresses to zero within the leak-off zone. Scaling indicates that in our

  11. Physical simulation study on the hydraulic fracture propagation of coalbed methane well

    Science.gov (United States)

    Wu, Caifang; Zhang, Xiaoyang; Wang, Meng; Zhou, Longgang; Jiang, Wei

    2018-03-01

    As the most widely used technique to modify reservoirs in the exploitation of unconventional natural gas, hydraulic fracturing could effectively raise the production of CBM wells. To study the propagation rules of hydraulic fractures, analyze the fracture morphology, and obtain the controlling factors, a physical simulation experiment was conducted with a tri-axial hydraulic fracturing test system. In this experiment, the fracturing sample - including the roof, the floor, and the surrounding rock - was prepared from coal and similar materials, and the whole fracturing process was monitored by an acoustic emission instrument. The results demonstrated that the number of hydraulic fractures in coal is considerably higher than that observed in other parts, and the fracture morphology was complex. Vertical fractures were interwoven with horizontal fractures, forming a connected network. With the injection of fracturing fluid, a new hydraulic fracture was produced and it extended along the preexisting fractures. The fracture propagation was a discontinuous, dynamic process. Furthermore, in-situ stress plays a key role in fracture propagation, causing the fractures to extend in a direction perpendicular to the minimum principal stress. To a certain extent, the different mechanical properties of the coal and the other components inhibited the vertical propagation of hydraulic fractures. Nonetheless, the vertical stress and the interfacial property are the major factors to influence the formation of the "T" shaped and "工" shaped fractures.

  12. Impact of ductility on hydraulic fracturing in shales

    Science.gov (United States)

    MacMinn, Chris; Auton, Lucy

    2016-04-01

    Hydraulic fracturing is a method for extracting natural gas and oil from low-permeability rocks such as shale via the high-pressure injection of fluid into the bulk of the rock. The goal is to initiate and propagate fractures that will provide hydraulic access deeper into the reservoir, enabling gas or oil to be collected from a larger region of the rock. Fracture is the tensile failure of a brittle material upon reaching a threshold tensile stress, but some shales have a high clay content and may yield plastically before fracturing. Plastic deformation is the shear failure of a ductile material, during which stress relaxes through irreversible rearrangements of the particles of the material. Here, we investigate the impact of the ductility of shales on hydraulic fracturing. We first consider a simple, axisymmetric model for radially outward fluid injection from a wellbore into a ductile porous rock. We use this model to show that plastic deformation greatly reduces the maximum tensile stress, and that this maximum stress does not always occur at the wellbore. We then complement these results with laboratory experiments in an analogue system, and with numerical simulations based on the discrete element method (DEM), both of which suggest that ductile failure can indeed dramatically change the resulting deformation pattern. These results imply that hydraulic fracturing may fail in ductile rocks, or that the required injection rate for fracking may be much larger than the rate predicted from models that assume purely elastic mechanical behavior.

  13. kISMET: Stress analysis and intermediate-scale hydraulic fracturing at the Sanford Underground Research Facility

    Science.gov (United States)

    Dobson, P. F.; Oldenburg, C. M.; Wu, Y.; Cook, P. J.; Kneafsey, T. J.; Nakagawa, S.; Ulrich, C.; Siler, D. L.; Guglielmi, Y.; Ajo Franklin, J. B.; Rutqvist, J.; Daley, T. M.; Birkholzer, J. T.; Wang, H. F.; Lord, N.; Haimson, B. C.; Sone, H.; Vigilante, P.; Roggenthen, W.; Doe, T.; Lee, M.; Ingraham, M. D.; Huang, H.; Mattson, E.; Johnson, T. C.; Zhou, J.; Zoback, M. D.; Morris, J.; White, J. A.; Johnson, P. A.; Coblentz, D. D.; Heise, J.

    2017-12-01

    In 2015, we established a field test facility at the Sanford Underground Research Facility (SURF), and in 2016 we carried out in situ hydraulic fracturing experiments to characterize the stress field, understand the effects of crystalline rock fabric on fracturing, and gain experience in monitoring using geophysical methods. The kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) project test site was established in the West Access Drift at the 4850 ft level, 1478 m below ground in phyllite of the Precambrian Poorman Formation. The kISMET team drilled and cored five near-vertical boreholes in a line on 3 m spacing, deviating the two outermost boreholes slightly to create a five-spot pattern around the test borehole centered in the test volume 40 m below the drift invert (floor) at a total depth of 1518 m. Laboratory measurements of core from the center test borehole showed P-wave velocity heterogeneity along each core indicating strong, fine-scale ( 1 cm or smaller) changes in the mechanical properties of the rock. Tensile strength ranges between 3‒7.5 MPa and 5‒12 MPa. Pre-fracturing numerical simulations with a discrete element code were carried out to predict fracture size and magnitude of microseismicity. Field measurements of the stress field were made using hydraulic fracturing, which produced remarkably uniformly oriented fractures suggesting rock fabric did not play a significant role in controlling fracture orientation. Electrical resistivity tomography (ERT) and continuous active seismic source monitoring (CASSM) were deployed in the four monitoring boreholes, and passive seismic accelerometer-based measurements in the West Access Drift were carried out during the generation of a larger fracture (so-called stimulation test). ERT was not able to detect the fracture created, nor did the accelerometers in the drift, but microseismicity was detected for the first (deepest) hydraulic-fracturing stress measurement. Analytical

  14. Quantifying Discrete Fracture Network Connectivity in Hydraulic Fracturing Stimulation

    Science.gov (United States)

    Urbancic, T.; Ardakani, E. P.; Baig, A.

    2017-12-01

    Hydraulic fracture stimulations generally result in microseismicity that is associated with the activation or extension of pre-existing microfractures and discontinuities. Microseismic events acquired under 3D downhole sensor coverage provide accurate event locations outlining hydraulic fracture growth. Combined with source characteristics, these events provide a high quality input for seismic moment tensor inversion and eventually constructing the representative discrete fracture network (DFN). In this study, we investigate the strain and stress state, identified fracture orientation, and DFN connectivity and performance for example stages in a multistage perf and plug completion in a North American shale play. We use topology, the familiar concept in many areas of structural geology, to further describe the relationships between the activated fractures and their effectiveness in enhancing permeability. We explore how local perturbations of stress state lead to the activation of different fractures sets and how that effects the DFN interaction and complexity. In particular, we observe that a more heterogeneous stress state shows a higher percentage of sub-horizontal fractures or bedding plane slips. Based on topology, the fractures are evenly distributed from the injection point, with decreasing numbers of connections by distance. The dimensionless measure of connection per branch and connection per line are used for quantifying the DFN connectivity. In order to connect the concept of connectivity back to productive volume and stimulation efficiency, the connectivity is compared with the character of deformation in the reservoir as deduced from the collective behavior of microseismicity using robustly determined source parameters.

  15. 3D Simulation of Multiple Simultaneous Hydraulic Fractures with Different Initial Lengths in Rock

    Science.gov (United States)

    Tang, X.; Rayudu, N. M.; Singh, G.

    2017-12-01

    Hydraulic fracturing is widely used technique for extracting shale gas. During this process, fractures with various initial lengths are induced in rock mass with hydraulic pressure. Understanding the mechanism of propagation and interaction between these induced hydraulic cracks is critical for optimizing the fracking process. In this work, numerical results are presented for investigating the effect of in-situ parameters and fluid properties on growth and interaction of multi simultaneous hydraulic fractures. A fully coupled 3D fracture simulator, TOUGH- GFEM is used for simulating the effect of different vital parameters, including in-situ stress, initial fracture length, fracture spacing, fluid viscosity and flow rate on induced hydraulic fractures growth. This TOUGH-GFEM simulator is based on 3D finite volume method (FVM) and partition of unity element method (PUM). Displacement correlation method (DCM) is used for calculating multi - mode (Mode I, II, III) stress intensity factors. Maximum principal stress criteria is used for crack propagation. Key words: hydraulic fracturing, TOUGH, partition of unity element method , displacement correlation method, 3D fracturing simulator

  16. Hydraulic fracture propagation modeling and data-based fracture identification

    Science.gov (United States)

    Zhou, Jing

    Successful shale gas and tight oil production is enabled by the engineering innovation of horizontal drilling and hydraulic fracturing. Hydraulically induced fractures will most likely deviate from the bi-wing planar pattern and generate complex fracture networks due to mechanical interactions and reservoir heterogeneity, both of which render the conventional fracture simulators insufficient to characterize the fractured reservoir. Moreover, in reservoirs with ultra-low permeability, the natural fractures are widely distributed, which will result in hydraulic fractures branching and merging at the interface and consequently lead to the creation of more complex fracture networks. Thus, developing a reliable hydraulic fracturing simulator, including both mechanical interaction and fluid flow, is critical in maximizing hydrocarbon recovery and optimizing fracture/well design and completion strategy in multistage horizontal wells. A novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple nonplanar fractures' propagation in both homogeneous and heterogeneous reservoirs with or without pre-existing natural fractures. Initiation, growth, and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. This physics-based modeling approach leads to realistic fracture patterns without using the empirical rock failure and fracture propagation criteria required in conventional continuum methods. Based on this model, a sensitivity study is performed to investigate the effects of perforation spacing, in-situ stress anisotropy, rock properties (Young's modulus, Poisson's ratio, and compressive strength), fluid properties, and natural fracture properties on hydraulic fracture propagation. In addition, since reservoirs are buried thousands of feet below the surface, the

  17. The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

    Directory of Open Access Journals (Sweden)

    Lianchong Li

    2016-03-01

    Full Text Available To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, a series of simulations on the hydraulic fracturing are performed. In the simulations, three points, i.e., (1 confining stresses, representing the effect of in situ stresses, (2 strength of the interfaces, and (3 material properties of the layers on either side of the interface, are crucial in fracturing across interfaces between two adjacent rock layers. Numerical results show that the hydrofracture propagation within a layered sequence of sedimentary rocks is controlled by changing in situ stresses, interface properties, and lithologies. The path of the hydraulic fracture is characterized by numerous deflections, branchings, and terminations. Four types of potential interaction, i.e., penetration, arrest, T-shaped branching, and offset, between a hydrofracture and an interface within the layered rocks are formed. Discontinuous composite fracture segments resulting from out-of-plane growth of fractures provide a less permeable path for fluids, gas, and oil than a continuous planar composite fracture, which are one of the sources of the high treating pressures and reduced fracture volume.

  18. The Influence of Hydraulic Fracturing on Carbon Storage Performance

    Science.gov (United States)

    Fu, Pengcheng; Settgast, Randolph R.; Hao, Yue; Morris, Joseph P.; Ryerson, Frederick J.

    2017-12-01

    Conventional principles of the design and operation of geologic carbon storage (GCS) require injecting CO2 below the caprock fracturing pressure to ensure the integrity of the storage complex. In nonideal storage reservoirs with relatively low permeability, pressure buildup can lead to hydraulic fracturing of the reservoir and caprock. While the GCS community has generally viewed hydraulic fractures as a key risk to storage integrity, a carefully designed stimulation treatment under appropriate geologic conditions could provide improved injectivity while maintaining overall seal integrity. A vertically contained hydraulic fracture, either in the reservoir rock or extending a limited height into the caprock, provides an effective means to access reservoir volume far from the injection well. Employing a fully coupled numerical model of hydraulic fracturing, solid deformation, and matrix fluid flow, we study the enabling conditions, processes, and mechanisms of hydraulic fracturing during CO2 injection. A hydraulic fracture's pressure-limiting behavior dictates that the near-well fluid pressure is only slightly higher than the fracturing pressure of the rock and is insensitive to injection rate and mechanical properties of the formation. Although a fracture contained solely within the reservoir rock with no caprock penetration, would be an ideal scenario, poroelastic principles dictate that sustaining such a fracture could lead to continuously increasing pressure until the caprock fractures. We also investigate the propagation pattern and injection pressure responses of a hydraulic fracture propagating in a caprock subjected to heterogeneous in situ stress. The results have important implications for the use of hydraulic fracturing as a tool for managing storage performance.

  19. Application of hydraulic fracturing to determine virgin in situ stress state around Waste Isolation Pilot Plant - in situ measurements

    International Nuclear Information System (INIS)

    Wawersik, W.R.; Stone, C.M.

    1985-10-01

    Hydraulic fracturing tests were carried out in horizontal drillholes in rock salt in the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. It was determined that the virgin in situ stress field is isotropic or nearly isotropic. The inferred magnitude of the isotropic in situ stress falls between bounds of 14.28 MPa and 17.9 MPa for the average breakdown/reopening pressures and driving pressures. The best estimate from instantaneous shut-in pressures is 16.61 MPa. Given some uncertainties about the interpretation of hydraulic fracturing data in salt, all of the foregoing values are in acceptable agreement with an average calculated isotropic in situ stress of 14.9 MPa at an average depth of 657 m below surface. Interpretations of breakdown and reopening pressures are based on finite element analyses of the relaxed stress field around a borehole in salt. This stress field varies little between approximately 50 and 200 days after drilling. The finite element analyses were also used to interpret the observed stable pressure-time signatures with little or no pressure drops during primary breakdown of the salt formation. The conclusion about the isotropic nature of the virgin in situ stress field is supported by observations of the induced fracture patterns. The report includes a comparison of the hydrofrac data in the WIPP with the published results of hydraulic fracturing tests in salt at three other locations. 75 refs., 21 figs., 4 tabs

  20. Failure Mode of the Water-filled Fractures under Hydraulic Pressure in Karst Tunnels

    Directory of Open Access Journals (Sweden)

    Dong Xin

    2017-06-01

    Full Text Available Water-filled fractures continue to grow after the excavation of karst tunnels, and the hydraulic pressure in these fractures changes along with such growth. This paper simplifies the fractures in the surrounding rock as flat ellipses and then identifies the critical hydraulic pressure values required for the occurrence of tensile-shear and compression-shear failures in water-filled fractures in the case of plane stress. The occurrence of tensile-shear fracture requires a larger critical hydraulic pressure than compression-shear failure in the same fracture. This paper examines the effects of fracture strike and lateral pressure coefficient on critical hydraulic pressure, and identifies compression-shear failure as the main failure mode of water-filled fractures. This paper also analyses the hydraulic pressure distribution in fractures with different extensions, and reveals that hydraulic pressure decreases along with the continuous growth of fractures and cannot completely fill a newly formed fracture with water. Fracture growth may be interrupted under the effect of hydraulic tensile shear.

  1. Numerical Simulation of Hydraulic Fracture Propagation Guided by Single Radial Boreholes

    Directory of Open Access Journals (Sweden)

    Tiankui Guo

    2017-10-01

    Full Text Available Conventional hydraulic fracturing is not effective in target oil development zones with available wellbores located in the azimuth of the non-maximum horizontal in-situ stress. To some extent, we think that the radial hydraulic jet drilling has the function of guiding hydraulic fracture propagation direction and promoting deep penetration, but this notion currently lacks an effective theoretical support for fracture propagation. In order to verify the technology, a 3D extended finite element numerical model of hydraulic fracturing promoted by the single radial borehole was established, and the influences of nine factors on propagation of hydraulic fracture guided by the single radial borehole were comprehensively analyzed. Moreover, the term ‘Guidance factor (Gf’ was introduced for the first time to effectively quantify the radial borehole guidance. The guidance of nine factors was evaluated through gray correlation analysis. The experimental results were consistent with the numerical simulation results to a certain extent. The study provides theoretical evidence for the artificial control technology of directional propagation of hydraulic fracture promoted by the single radial borehole, and it predicts the guidance effect of a single radial borehole on hydraulic fracture to a certain extent, which is helpful for planning well-completion and fracturing operation parameters in radial borehole-promoted hydraulic fracturing technology.

  2. Hydraulic fracturing in shales: the spark that created an oil and gas boom

    Science.gov (United States)

    Olson, J. E.

    2017-12-01

    In the oil and gas business, one of the valued properties of a shale was its lack of flow capacity (its sealing integrity) and its propensity to provide mechanical barriers to hydraulic fracture height growth when exploiting oil and gas bearing sandstones. The other important property was the high organic content that made shale a potential source rock for oil and gas, commodities which migrated elsewhere to be produced. Technological advancements in horizontal drilling and hydraulic fracturing have turned this perspective on its head, making shale (or other ultra-low permeability rocks that are described with this catch-all term) the most prized reservoir rock in US onshore operations. Field and laboratory results have changed our view of how hydraulic fracturing works, suggesting heterogeneities like bedding planes and natural fractures can cause significant complexity in hydraulic fracture growth, resulting in induced networks of fractures whose details are controlled by factors including in situ stress contrasts, ductility contrasts in the stratigraphy, the orientation and strength of pre-existing natural fractures, injection fluid viscosity, perforation cluster spacing and effective mechanical layer thickness. The stress shadowing and stress relief concepts that structural geologists have long used to explain joint spacing and orthogonal fracture pattern development in stratified sequences are key to understanding optimal injection point spacing and promotion of more uniform length development in induced hydraulic fractures. Also, fracture interaction criterion to interpret abutting vs crossing natural fracture relationships in natural fracture systems are key to modeling hydraulic fracture propagation within natural fractured reservoirs such as shale. Scaled physical experiments provide constraints on models where the physics is uncertain. Numerous interesting technical questions remain to be answered, and the field is particularly appealing in that better

  3. Hydraulic Fracturing and Microseismicity: Global Perspective in Oil Exploration

    Directory of Open Access Journals (Sweden)

    J.R. Kayal

    2017-09-01

    Full Text Available Induced microseismicity is a common phenomenon in oil and gas reservoirs due to changes in internal stress accompanied by hydraulic fracturing and oil-gas extraction. These microseismicity can be monitored to understand the direction and type of hydraulic fracturing and pre-existing faults by precise hypocenter location and focal mechanism studies. Normal as well as strike-slip faulting earthquakes occur due to opening up of new cracks/fractures, and thrust/reverse faulting earthquakes due to compaction or closing of existing fractures. Further, frequency-magnitude relation (b-value and fractal dimension (D-value of the spatial and temporal clusterization of induced microseismicity may be much useful to characterize the fractures / existing faults and the stress regimes. Seismic tomography, on the other hand, can image the heterogeneous velocity structures / perturbations in the reservoir due to fractures and oil-gas-water contents. A few global case studies are illustrated to understand these processes and to draw attention towards importance of these studies in oil industries.

  4. Deformation Behavior between Hydraulic and Natural Fractures Using Fully Coupled Hydromechanical Model with XFEM

    Directory of Open Access Journals (Sweden)

    Fei Liu

    2017-01-01

    Full Text Available There has been a growing consensus that preexisting natural fractures play an important role during stimulation. A novel fully coupled hydromechanical model using extended finite element method is proposed. This directly coupled scheme avoids the cumbersome process during calculating the fluid pressure in complicated fracture networks and translating into an equivalent nodal force. Numerical examples are presented to simulate the hydraulic fracture propagation paths for simultaneous multifracture treatments with properly using the stress shadow effects for horizontal wells and to reveal the deformation response and interaction mechanism between hydraulic induced fracture and nonintersected natural fractures at orthotropic and nonorthotropic angles. With the stress shadow effects, the induced hydraulic flexural fracture deflecting to wellbore rather than transverse fracture would be formed during the progress of simultaneous fracturing for a horizontal well. The coupled hydromechanical simulation reveals that the adjacent section to the intersection is opened and the others are closed for orthogonal natural fracture, while the nonorthogonal natural fracture is activated near the intersection firstly and along the whole section with increasing perturbed stresses. The results imply that the induced hydraulic fracture tends to cross orthotropic natural fracture, while it is prior to being arrested by the nonorthotropic natural fracture.

  5. A Hydraulic Stress Measurement System for Deep Borehole Investigations

    Science.gov (United States)

    Ask, Maria; Ask, Daniel; Cornet, Francois; Nilsson, Tommy

    2017-04-01

    Luleå University of Technology (LTU) is developing and building a wire-line system for hydraulic rock stress measurements, with funding from the Swedish Research Council and Luleå University of Technology. In this project, LTU is collaborating with University of Strasbourg and Geosigma AB. The stress state influences drilling and drillability, as well as rock mass stability and permeability. Therefore, knowledge about the state of in-situ stress (stress magnitudes, and orientations) and its spatial variation with depth is essential for many underground rock engineering projects, for example for underground storage of hazardous material (e.g. nuclear waste, carbon dioxide), deep geothermal exploration, and underground infrastructure (e.g. tunneling, hydropower dams). The system is designed to conduct hydraulic stress testing in slim boreholes. There are three types of test methods: (1) hydraulic fracturing, (2) sleeve fracturing and (3) hydraulic testing of pre-existing fractures. These are robust methods for determining in situ stresses from boreholes. Integration of the three methods allows determination of the three-dimensional stress tensor and its spatial variation with depth in a scientific unambiguously way. The stress system is composed of a downhole and a surface unit. The downhole unit consists of hydraulic fracturing equipment (straddle packers and downhole imaging tool) and their associated data acquisition systems. The testing system is state of the art in several aspects including: (1) Large depth range (3 km), (2) Ability to test three borehole dimensions (N=76 mm, H=96 mm, and P=122 mm), (3) Resistivity imager maps the orientation of tested fracture; (4) Highly stiff and resistive to corrosion downhole testing equipment; and (5) Very detailed control on the injection flow rate and cumulative volume is obtained by a hydraulic injection pump with variable piston rate, and a highly sensitive flow-meter. At EGU General Assembly 2017, we would like to

  6. Geotechnical site assessment methodologies relevant to potential deep underground disposal facilities: with particular reference to the determination of in situ rock stress by the hydraulic fracturing method

    International Nuclear Information System (INIS)

    Monaghan, B.G.; Richards, L.R.

    1986-10-01

    A final report summarizing the research conducted on geotechnical site assessment methodologies relevant to Land 3/4 sites. Two areas of research have been investigated; in situ stress determination by the hydraulic fracturing method in basic volcanics and sediments and the laboratory determination of hydraulic fracture tensile strength. The analysis and interpretation of the hydraulic fracturing test data from a programme of testing in the Vale of Belvoir is discussed in detail particularly in respect of the effects of pore water pressure and fluid diffusion in the rocks being tested. The regional stress regime of the Vale of Belvoir is discussed with respect to the results of the in situ stress determination. A method for determining the hydraulic fracture tensile strength in the laboratory is described. The results of a series of laboratory tests on rock core are reported. (author)

  7. Numerical Evaluation and Optimization of Multiple Hydraulically Fractured Parameters Using a Flow-Stress-Damage Coupled Approach

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2016-04-01

    Full Text Available Multiple-factor analysis and optimization play a critical role in the the ability to maximizethe stimulated reservoir volume (SRV and the success of economic shale gas production. In this paper, taking the typical continental naturally fractured silty laminae shale in China as anexample, response surface methodology (RSM was employed to optimize multiple hydraulic fracturing parameters to maximize the stimulated area in combination with numerical modeling based on the coupled flow-stress-damage (FSD approach. This paper demonstrates hydraulic fracturing effectiveness by defining two indicesnamelythe stimulated reservoir area (SRA and stimulated silty laminae area (SLA. Seven uncertain parameters, such as laminae thickness, spacing, dip angle, cohesion, internal friction angle (IFA, in situ stress difference (SD, and an operational parameter-injection rate (IR with a reasonable range based on silty Laminae Shale, Southeastern Ordos Basin, are used to fit a response of SRA and SLA as the objective function, and finally identity the optimum design under the parameters based on simultaneously maximizingSRA and SLA. In addition, asensitivity analysis of the influential factors is conducted for SRA and SLA. The aim of the study is to improve the artificial ability to control the fracturing network by means of multi-parameteroptimization. This work promises to provide insights into the effective exploitation of unconventional shale gas reservoirs via optimization of the fracturing design for continental shale, Southeastern Ordos Basin, China.

  8. A Thermoelastic Hydraulic Fracture Design Tool for Geothermal Reservoir Development

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad Ghassemi

    2003-06-30

    Geothermal energy is recovered by circulating water through heat exchange areas within a hot rock mass. Geothermal reservoir rock masses generally consist of igneous and metamorphic rocks that have low matrix permeability. Therefore, cracks and fractures play a significant role in extraction of geothermal energy by providing the major pathways for fluid flow and heat exchange. Thus, knowledge of conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fracture are created in the reservoir using hydraulic fracturing. At times, the practice aims to create a number of parallel fractures connecting a pair of wells. Multiple fractures are preferred because of the large size necessary when using only a single fracture. Although the basic idea is rather simple, hydraulic fracturing is a complex process involving interactions of high pressure fluid injections with a stressed hot rock mass, mechanical interaction of induced fractures with existing natural fractures, and the spatial and temporal variations of in-situ stress. As a result it is necessary to develop tools that can be used to study these interactions as an integral part of a comprehensive approach to geothermal reservoir development, particularly enhanced geothermal systems. In response to this need we have set out to develop advanced thermo-mechanical models for design of artificial fractures and rock fracture research in geothermal reservoirs. These models consider the significant hydraulic and thermo-mechanical processes and their interaction with the in-situ stress state. Wellbore failure and fracture initiation is studied using a model that fully couples poro-mechanical and thermo-mechanical effects. The fracture propagation model is based on a complex variable and regular displacement discontinuity formulations. In the complex variable approach the displacement discontinuities are

  9. Intermediate-Scale Hydraulic Fracturing in a Deep Mine - kISMET Project Summary 2016

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, C. M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Dobson, P. F. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wu, Y. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Cook, P. J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kneafsey, T. J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nakagawa, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ulrich, C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Siler, D. L. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Guglielmi, Y. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ajo-Franklin, J. B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Rutqvist, J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Daley, T. M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Birkholzer, J. T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wang, H. F. [Univ. of Wisconsin, Madison, WI (United States); Lord, N. E. [Univ. of Wisconsin, Madison, WI (United States); Haimson, B. C. [Univ. of Wisconsin, Madison, WI (United States); Sone, H. [Univ. of Wisconsin, Madison, WI (United States); Vigilante, P. [Univ. of Wisconsin, Madison, WI (United States); Roggenthen, W. M. [South Dakota School of Mines and Technology, Rapid City, SD (United States); Doe, T. W. [Golder Associates Inc., Toronto, ON (Canada); Lee, M. Y. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ingraham, M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Huang, H. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mattson, E. D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhou, J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johnson, T. J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Morris, J. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); White, J. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Johnson, P. A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Coblentz, D. D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Heise, J. [Stanford Underground Research Facility, Lead, SD (United States); Zoback, M. D. [Stanford Univ., CA (United States)

    2016-11-04

    In support of the U.S. DOE SubTER Crosscut initiative, we established a field test facility in a deep mine and designed and carried out in situ hydraulic fracturing experiments in the crystalline rock at the site to characterize the stress field, understand the effects of rock fabric on fracturing, and gain experience in monitoring using geophysical methods. The project also included pre- and post-fracturing simulation and analysis, laboratory measurements and experiments, and we conducted an extended analysis of the local stress state using previously collected data. Some of these activities are still ongoing. The kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) experiments meet objectives in SubTER’s “stress” pillar and the “new subsurface signals” pillar. The kISMET site was established in the West Access Drift of SURF 4850 ft (1478 m) below ground (on the 4850L) in phyllite of the Precambrian Poorman Formation. We drilled and cored five near-vertical boreholes in a line on 3 m spacing, deviating the two outermost boreholes slightly to create a five-spot pattern around the test borehole centered in the test volume at ~1528 m (5013 ft). Laboratory measurements of core from the center test borehole showed P-wave velocity heterogeneity along each core indicating strong, fine-scale (~1 cm or smaller) changes in the mechanical properties of the rock. The load-displacement record on the core suggests that the elastic stiffness is anisotropic. Tensile strength ranges between 3-7.5 MPa and 5-12 MPa. Permeability measurements are planned, as are two types of laboratory miniature hydraulic fracturing experiments to investigate the importance of rock fabric (anisotropy and heterogeneity) on near-borehole hydraulic fracture generation. Pre-fracturing numerical simulations with INL’s FALCON discrete element code predicted a fracture radius of 1.2 m for a corresponding injection volume of 1.2 L for the planned fractures, and

  10. Adaptive Finite Element-Discrete Element Analysis for Microseismic Modelling of Hydraulic Fracture Propagation of Perforation in Horizontal Well considering Pre-Existing Fractures

    Directory of Open Access Journals (Sweden)

    Yongliang Wang

    2018-01-01

    Full Text Available Hydrofracturing technology of perforated horizontal well has been widely used to stimulate the tight hydrocarbon reservoirs for gas production. To predict the hydraulic fracture propagation, the microseismicity can be used to infer hydraulic fractures state; by the effective numerical methods, microseismic events can be addressed from changes of the computed stresses. In numerical models, due to the challenges in accurately representing the complex structure of naturally fractured reservoir, the interaction between hydraulic and pre-existing fractures has not yet been considered and handled satisfactorily. To overcome these challenges, the adaptive finite element-discrete element method is used to refine mesh, effectively identify the fractures propagation, and investigate microseismic modelling. Numerical models are composed of hydraulic fractures, pre-existing fractures, and microscale pores, and the seepage analysis based on the Darcy’s law is used to determine fluid flow; then moment tensors in microseismicity are computed based on the computed stresses. Unfractured and naturally fractured models are compared to assess the influences of pre-existing fractures on hydrofracturing. The damaged and contact slip events were detected by the magnitudes, B-values, Hudson source type plots, and focal spheres.

  11. Electromagnetic Monitoring of Hydraulic Fracturing: Relationship to Permeability, Seismicity, and Stress

    Science.gov (United States)

    Thiel, Stephan

    2017-09-01

    Hydraulic fracking is a geoengineering application designed to enhance subsurface permeability to maximize fluid and gas flow. Fracking is commonly used in enhanced geothermal systems (EGS), tight shale gas, and coal seam gas (CSG) plays and in CO_2 storage scenarios. Common monitoring methods include microseismics and mapping small earthquakes with great resolution associated with fracture opening at reservoir depth. Recently, electromagnetic (EM) methods have been employed in the field to provide an alternative way of direct detection of fluids as they are pumped in the ground. Surface magnetotelluric (MT) measurements across EGS show subtle yet detectable changes during fracking derived from time-lapse MT deployments. Changes are directional and are predominantly aligned with current stress field, dictating preferential fracture orientation, supported by microseismic monitoring of frack-related earthquakes. Modeling studies prior to the injection are crucial for survey design and feasibility of monitoring fracks. In particular, knowledge of sediment thickness plays a fundamental role in resolving subtle changes. Numerical forward modeling studies clearly favor some form of downhole measurement to enhance sensitivity; however, these have yet to be conclusively demonstrated in the field. Nevertheless, real surface-based monitoring examples do not necessarily replicate the expected magnitude of change derived from forward modeling and are larger than expected in some cases from EGS and CSG systems. It appears the injected fluid volume alone cannot account for the surface change in resistivity, but connectedness of pore space is also significantly enhanced and nonlinear. Recent numerical studies emphasize the importance of percolation threshold of the fracture network on both electrical resistivity and permeability, which may play an important role in accounting for temporal changes in surface EM measurements during hydraulic fracking.

  12. Selective perceptions of hydraulic fracturing.

    Science.gov (United States)

    Sarge, Melanie A; VanDyke, Matthew S; King, Andy J; White, Shawna R

    2015-01-01

    Hydraulic fracturing (HF) is a focal topic in discussions about domestic energy production, yet the American public is largely unfamiliar and undecided about the practice. This study sheds light on how individuals may come to understand hydraulic fracturing as this unconventional production technology becomes more prominent in the United States. For the study, a thorough search of HF photographs was performed, and a systematic evaluation of 40 images using an online experimental design involving N = 250 participants was conducted. Key indicators of hydraulic fracturing support and beliefs were identified. Participants showed diversity in their support for the practice, with 47 percent expressing low support, 22 percent high support, and 31 percent undecided. Support for HF was positively associated with beliefs that hydraulic fracturing is primarily an economic issue and negatively associated with beliefs that it is an environmental issue. Level of support was also investigated as a perceptual filter that facilitates biased issue perceptions and affective evaluations of economic benefit and environmental cost frames presented in visual content of hydraulic fracturing. Results suggested an interactive relationship between visual framing and level of support, pointing to a substantial barrier to common understanding about the issue that strategic communicators should consider.

  13. Numerical Simulation of the Propagation of Hydraulic and Natural Fracture Using Dijkstra’s Algorithm

    Directory of Open Access Journals (Sweden)

    Yanfang Wu

    2016-07-01

    Full Text Available Utilization of hydraulic-fracturing technology is dramatically increasing in exploitation of natural gas extraction. However the prediction of the configuration of propagated hydraulic fracture is extremely challenging. This paper presents a numerical method of obtaining the configuration of the propagated hydraulic fracture into discrete natural fracture network system. The method is developed on the basis of weighted fracture which is derived in combination of Dijkstra’s algorithm energy theory and vector method. Numerical results along with experimental data demonstrated that proposed method is capable of predicting the propagated hydraulic fracture configuration reasonably with high computation efficiency. Sensitivity analysis reveals a number of interesting observation results: the shortest path weight value decreases with increasing of fracture density and length, and increases with increasing of the angle between fractures to the maximum principal stress direction. Our method is helpful for evaluating the complexity of the discrete fracture network, to obtain the extension direction of the fracture.

  14. Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field

    International Nuclear Information System (INIS)

    Stock, J.M.; Healy, J.H.; Hickman, S.H.; Zoback, M.D.

    1985-01-01

    Hydraulic fracturing stress measurements and acoustic borehole televiewer logs were run in holes USW G-1 and USW G-2 at Yucca Mountain as part of the Nevada Nuclear Waste Storage Investigations for the U. S. Department of Energy. Eight tests in the saturated zone, at depths from 646 to 1288 m, yielded values of the least horizontal stress S/sub h/ that are considerably lower than the vertical principal stress S/sub v/. In tests for which the greatest horizontal principal stress S/sub H/ could be determined, it was found to be less than S/sub v/, indicating a normal faulting stress regime. The borehole televiewer logs showed the presence of long (in excess of 10 m), vertical, drilling-induced fractures in the first 300 m below the water table. These are believed to form by the propagation of small preexisting cracks under the excess downhole fluid pressures (up to 5.2 MPa) applied during drilling. The presence of these drilling-induced hydrofractures provides further confirmation of the low value of the least horizontal stresses. A least horizontal principal stress direction of N60 0 W--N65 0 W is indicated by the orientation of the drilling-induced hydrofractures (N25 0 E--N30 0 E), and the orientation of stress-induced well bore breakouts in the lower part of USW G-2 (N65 0 W). This direction is in good agreement with indicators of stress direction from elsewhere at the Nevada Test Site. The observed stress magnitudes and directions were examined for the possibility of slip on preexisting faults. Using these data, the Coulomb criterion for frictional sliding suggests that for coefficients of friction close to 0.6, movement on favorably oriented faults could be expected

  15. Investigation of hydraulic fracture re-orientation effects in tight gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Hagemann, B.; Wegner, J.; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE

    2013-08-01

    In tight gas formations where the low matrix permeability prevents successful and economic production rates, hydraulic fracturing is required to produce a well at economic rates. The initial fracture opens in the direction of minimum stress and propagates into the direction of maximum stress. As production from the well and its initial fracture declines, re-fracturing treatments are required to accelerate recovery. The orientation of the following hydraulic fracture depends on the actual stress-state of the formation in the vicinity of the wellbore. Previous investigations by Elbel and Mack (1993) demonstrated that the stress alters during depletion and a stress reversal region appears. This behavior causes a different fracture orientation of the re-fracturing operation. For the investigation of re-fracture orientation a two-dimensional reservoir model has been designed using COMSOL Multiphysics. The model represents a fractured vertical well in a tight gas reservoir of infinite thickness. A time dependent study was set up to simulate the reservoir depletion by the production from the fractured well. The theory of poroelasticity was used to couple the fluid flow and geo-mechanical behavior. The stress state is initially defined as uniform and the attention is concentrated to the alteration of stress due to the lowered pore pressure. Different cases with anisotropic and heterogeneous permeability are set up to determine its significance. The simulation shows that an elliptical shaped drainage area appears around the fracture. The poroelastic behavior effects that the stress re-orientates and a stress reversal region originates, if the difference between minimum and maximum horizontal stresses is small. The consideration of time indicates that the dimension of the region initially extends fast until it reaches its maximum. Subsequently, the stress reversal region's extent shrinks slowly until it finally disappears. The reservoir characteristics, e.g. the

  16. Self-potential observations during hydraulic fracturing

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Jeffrey R.; Glaser, Steven D.

    2007-09-13

    The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of -200 mV/MPa. However for pressure drops >2 MPa, the magnitude of the Cc increases by 80% in an exponential trend. This increasing Cc is related to increasing permeability at high pore pressures caused by dilatancy of micro-cracks, and is explained by a decrease in the hydraulic tortuosity. Resistivity measurements reveal a decrease of 2% prior to hydraulic fracturing and a decrease of {approx}35% after fracturing. An asymmetric spatial SP response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing, and in most cases this SP variation revealed the impending crack geometry seconds before failure. At rupture, injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity, and an anomalous SP spike is observed. After fracturing, the spatial SP distribution reveals the direction of fracture propagation. Finally, during tensile cracking in a point load device with no water flow, a SP spike is observed that is caused by contact electrification. However, the time constant of this event is much less than that for transients observed during hydraulic fracturing, suggesting that SP created solely from material fracture does not contribute to the SP response during hydraulic fracturing.

  17. Hydraulic fracturing in granite under geothermal conditions

    Science.gov (United States)

    Solberg, P.; Lockner, D.; Byerlee, J.D.

    1980-01-01

    The experimental hydraulic fracturing of granite under geothermal conditions produces tensile fracture at rapid fluid injection rates and shear fracture at slow injection rates and elevated differential stress levels. A sudden burst of acoustic emission activity accompanies tensile fracture formation whereas the acoustic emission rate increases exponentially prior to shear fracture. Temperature does not significantly affect the failure mechanism, and the experimental results have not demonstrated the occurrence of thermal fracturing. A critical result of these experiments is that fluid injection at intermediate rates and elevated differential stress levels increases permeability by more than an order of magnitude without producing macroscopic fractures, and low-level acoustic emission activity occurs simultaneously near the borehole and propagates outward into the specimen with time. Permeability measurements conducted at atmospheric pressure both before and after these experiments show that increased permeability is produced by permanent structural changes in the rock. Although results of this study have not demonstrated the occurrence of thermal fracturing, they suggest that fluid injection at certain rates in situ may markedly increase local permeability. This could prove critical to increasing the efficiency of heat exchange for geothermal energy extraction from hot dry rock. ?? 1980.

  18. Near Wellbore Hydraulic Fracture Propagation from Perforations in Tight Rocks: The Roles of Fracturing Fluid Viscosity and Injection Rate

    Directory of Open Access Journals (Sweden)

    Seyed Hassan Fallahzadeh

    2017-03-01

    Full Text Available Hydraulic fracture initiation and near wellbore propagation is governed by complex failure mechanisms, especially in cased perforated wellbores. Various parameters affect such mechanisms, including fracturing fluid viscosity and injection rate. In this study, three different fracturing fluids with viscosities ranging from 20 to 600 Pa.s were used to investigate the effects of varying fracturing fluid viscosities and fluid injection rates on the fracturing mechanisms. Hydraulic fracturing tests were conducted in cased perforated boreholes made in tight 150 mm synthetic cubic samples. A true tri-axial stress cell was used to simulate real far field stress conditions. In addition, dimensional analyses were performed to correspond the results of lab experiments to field-scale operations. The results indicated that by increasing the fracturing fluid viscosity and injection rate, the fracturing energy increased, and consequently, higher fracturing pressures were observed. However, when the fracturing energy was transferred to a borehole at a faster rate, the fracture initiation angle also increased. This resulted in more curved fracture planes. Accordingly, a new parameter, called fracturing power, was introduced to relate fracture geometry to fluid viscosity and injection rate. Furthermore, it was observed that the presence of casing in the wellbore impacted the stress distribution around the casing in such a way that the fracture propagation deviated from the wellbore vicinity.

  19. Hydraulic fracturing chemicals and fluids technology

    CERN Document Server

    Fink, Johannes

    2013-01-01

    When classifying fracturing fluids and their additives, it is important that production, operation, and completion engineers understand which chemical should be utilized in different well environments. A user's guide to the many chemicals and chemical additives used in hydraulic fracturing operations, Hydraulic Fracturing Chemicals and Fluids Technology provides an easy-to-use manual to create fluid formulations that will meet project-specific needs while protecting the environment and the life of the well. Fink creates a concise and comprehensive reference that enables the engineer to logically select and use the appropriate chemicals on any hydraulic fracturing job. The first book devoted entirely to hydraulic fracturing chemicals, Fink eliminates the guesswork so the engineer can select the best chemicals needed on the job while providing the best protection for the well, workers and environment. Pinpoints the specific compounds used in any given fracturing operation Provides a systematic approach to class...

  20. A Hydraulic Stress Measurement System for Investigations at Depth in Slim Boreholes

    Science.gov (United States)

    Ask, M. V. S.; Ask, D.; Cornet, F. H.; Nilsson, T.; Talib, M.; Sundberg, J.

    2017-12-01

    Knowledge of the state of stress is essential to most underground work in rock mechanics as it provides means to analyze the mechanical behavior of a rock mass, serve as boundary condition in rock engineering problems, and help understand rock mass stability and groundwater flow. Luleå University of Technology (LTU) has developed and built a wire-line system for hydraulic rock stress measurements in slim boreholes together with the University of Strasbourg and Geosigma AB. The system consists of a downhole- and a surface unit. The downhole unit consists of hydraulic fracturing equipment (straddle packers and downhole imaging tool) and their associated data acquisition systems. The surface unit comprises of a 40-foot container permanently mounted on a trailer, which is equipped with a tripod, wire-line winches, water hydraulics, and a generator. The surface unit serves as a climate-independent on-site operations center, as well as a self-supporting transport vessel for the entire system. Three hydraulic stress testing methods can be applied: hydraulic fracturing, sleeve fracturing and hydraulic testing of pre-existing fractures. The three-dimensional stress tensor and its variation with depth within a continuous rock mass can be determined in a scientific unambiguously way by integrating results from the three test methods. The testing system is state of the art in several aspects including: (1) Large depth range (3 km), (2) Ability to test three borehole dimensions, (3) Resistivity imager maps the orientation of tested fracture (which is highlighted); (4) Highly stiff and resistive to corrosion downhole testing equipment; and (5) Very detailed control on the injection flow rate and cumulative volume is obtained by a hydraulic injection pump with variable piston rate, and a highly sensitive flow-meter. These aspects highly reduce measurement-related uncertainties of stress determination. Commissioning testing and initial field tests are scheduled to occur in a 1200

  1. kISMET: Stress and fracture characterization in a deep mine

    Science.gov (United States)

    Oldenburg, C. M.; Dobson, P. F.; Daley, T. M.; Birkholzer, J. T.; Cook, P. J.; Ajo Franklin, J. B.; Rutqvist, J.; Siler, D.; Kneafsey, T. J.; Nakagawa, S.; Wu, Y.; Guglielmi, Y.; Ulrich, C.; Marchesini, P.; Wang, H. F.; Haimson, B. C.; Sone, H.; Vigilante, P.; Roggenthen, W.; Doe, T.; Lee, M.; Mattson, E.; Huang, H.; Johnson, T. C.; Morris, J.; White, J. A.; Johnson, P. A.; Coblentz, D. D.; Heise, J.

    2016-12-01

    We are developing a community facility called kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) at the Sanford Underground Research Facility (SURF) in Lead, SD. The purpose of kISMET is to investigate stress and the effects of rock fabric on hydraulic fracturing. Although findings from kISMET may have broad applications that inform stress and fracturing in anisotropic rock, results will be most applicable to improving control of hydraulic fracturing for enhanced geothermal systems (EGS) in crystalline rock. At the kISMET site on the 4850 ft (1480 m depth) level of SURF, we have drilled and cored an array of nearly vertical boreholes in Precambrian phyllite. The array consists of four 50-m deep monitoring boreholes surrounding one 100-m deep borehole forming a 6 m-wide five-spot pattern at a depth of 1530 m. Previous investigations of the stress field at SURF suggest that the principal stress s1 is nearly vertical. By aligning the kISMET boreholes approximately with σ1, fractures created in the center borehole should in theory be perpendicular to σ3, the least principal horizontal stress. But the phyllite at kISMET has a strong fabric (foliation) that could influence fracturing. Stress measurements and stimulation using hydraulic fracturing will be carried out in the center borehole using a straddle packer and high-pressure pump. We will use an impression packer and image logs after stress testing and stimulation to determine fracture orientation and extent at the center borehole. In order to study the control of stress, rock fabric, and stimulation approach on size, aperture, and orientation of hydraulic fractures, we will carefully monitor the stress measurements and stimulation. For example, we will use continuous active source seismic (CASSM) in two of the monitoring boreholes to measure changes in seismic-wave velocity as water fills the fracture. Second, near real-time electrical resistance tomography (ERT) will be used in

  2. Influence of perforation erosion on multiple growing hydraulic fractures in multi-stage fracturing

    Directory of Open Access Journals (Sweden)

    Yongming Li

    2018-02-01

    Full Text Available In multi-stage hydraulic fracturing, the limited-entry method is widely used to promote uniform growth of multiple fractures. However, this method's effectiveness may be lost because the perforations will be eroded gradually during the fracturing period. In order to study the influence of perforation erosion on multiple growing hydraulic fractures, we combined the solid–fluid coupled model of hydraulic fracture growth with an empirical model of perforation erosion to implement numerical simulation. The simulations show clearly that the erosion of perforation will significantly deteriorate the non-uniform growth of multiple fractures. Based on the numerical model, we also studied the influences of proppant concentration and injection rates on perforation erosion in multi-stage hydraulic fracturing. The results indicate that the initial erosion rates become higher with the rising proppant concentration, but the growth of multiple hydraulic fractures is not sensitive to the varied proppant concentration. In addition, higher injection rates are beneficial significantly to the limited-entry design, leading to more uniform growth of fractures. Thus, in multi-stage hydraulic fracturing enough high injection rates are proposed to keep uniform growths. Keywords: Unconventional oil and gas reservoir, Horizontal well, Perforation friction, Perforation erosion, Multi-stage hydraulic fracturing, Numerical simulation, Mathematic model, Uniform growth of fractures

  3. The Role of the Rock on Hydraulic Fracturing of Tight Shales

    Science.gov (United States)

    Suarez-Rivera, R.; Green, S.; Stanchits, S.; Yang, Y.

    2011-12-01

    in relation to the in-situ stresses, have a dominant role in promoting fracture branching and abrupt changes in direction. In general, the problem can be conceptualized as a competition between the effect of stresses (traditional mechanics of homogeneous media) and the effect of rock fabric (the mechanics of heterogeneous media). When the stress difference is low and the rock fabric pronounced, the rock fabric defines the direction of propagation. When the stress difference is high and the fabric is weak, the stress contrast dominates the process. In real systems, both effects compete and result in the complexity that we infer from indirect observations. In this paper we discuss the role of rock fabric on fracture complexity during hydraulic fracture propagation. We show that understanding the far field stresses is not enough to understand fracture propagation and complexity. Understanding the rock-specifically the larger-scale textural features that define the reservoir fabric-is fundamental to understand fracture complexity and fracture containment. We use laboratory experiments with acoustic emission localization to monitor fracturing and making inferences about the large-scale rock behavior. We also show that the fracture geometry, even for the same connected surface area, has significant well production and reservoir recovery implications.

  4. Hydraulic fracturing tests in anhydrite interbeds in the WIPP, Marker Beds 139 and 140

    Energy Technology Data Exchange (ETDEWEB)

    Howard, C L [RE/SPEC Inc., Albuquerque, NM (United States); Wawersik, W. R.; Carlson, L. V.; Henfling, J. A.; Borns, D. J.; Beauheim, R. L.; Roberts, R. M.

    1997-05-01

    Hydraulic fracturing tests were integrated with hydrologic tests to estimate the conditions under which gas pressure in the disposal rooms in the Waste Isolation Pilot Plant, Carlsbad, NM (WIPP) will initiate and advance fracturing in nearby anhydrite interbeds. The measurements were made in two marker beds in the Salado formation, MB139 and MB140, to explore the consequences of existing excavations for the extrapolation of results to undisturbed ground. The interpretation of these measurements is based on the pressure-time records in two injection boreholes and several nearby hydrologic observation holes. Data interpretations were aided by post-test borehole video surveys of fracture traces that were made visible by ultraviolet illumination of fluorescent dye in the hydraulic fracturing fluid. The conclusions of this report relate to the upper- and lower-bound gas pressures in the WIPP, the paths of hydraulically and gas-driven fractures in MB139 and MB140, the stress states in MB139 and MB140, and the probable in situ stress states in these interbeds in undisturbed ground far away from the WIPP.

  5. Measuring the initial earth pressure of granite using hydraulic fracturing test; Goseong and Yuseong areas

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoung Yoon; Bae, Dae Seok; Kim, Chun Soo; Kim, Kyung Su; Koh, Young Kwon; Won, Kyung Sik [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-02-01

    This report provides the initial earth pressure of granitic rocks obtained from Deep Core Drilling Program which is carried out as part of the assessment of deep geological environmental condition. These data are obtained by hydraulic fracturing test in three boreholes drilled up to 350{approx}500 m depth at the Yuseong and Goseong sites. These sites were selected based on the result of preliminary site evaluation study. The boreholes are NX-size (76 mm) and vertical. The procedure of hydraulic fracturing test is as follows: - Selecting the testing positions by preliminary investigation using BHTV logging. - Performing the hydraulic fracturing test at each selected position with depth.- Estimating the shut-in pressure by the bilinear pressure-decay-rate method. - Estimating the fracture reopening pressure from the pressure-time curves.- Estimating the horizontal principal stresses and the direction of principal stresses. 65 refs., 39 figs., 12 tabs. (Author)

  6. An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut

    Science.gov (United States)

    Lane, J.W.; Williams, J.H.; Johnson, C.D.; Savino, D.M.; Haeni, F.P.

    2002-01-01

    The U.S. Geological Survey conducted an integrated geophysical and hydraulic investigation at the Norden Systems, Inc. site in Norwalk, Connecticut, where chlorinated solvents have contaminated a fractured-rock aquifer. Borehole, borehole-to-borehole, surface-geophysical, and hydraulic methods were used to characterize the site bedrock lithology and structure, fractures, and transmissive zone hydraulic properties. The geophysical and hydraulic methods included conventional logs, borehole imagery, borehole radar, flowmeter under ambient and stressed hydraulic conditions, and azimuthal square-array direct-current resistivity soundings. Integrated interpretation of geophysical logs at borehole and borehole-to-borehole scales indicates that the bedrock foliation strikes northwest and dips northeast, and strikes north-northeast to northeast and dips both southeast and northwest. Although steeply dipping fractures that cross-cut foliation are observed, most fractures are parallel or sub-parallel to foliation. Steeply dipping reflectors observed in the radar reflection data from three boreholes near the main building delineate a north-northeast trending feature interpreted as a fracture zone. Results of radar tomography conducted close to a suspected contaminant source area indicate that a zone of low electromagnetic (EM) velocity and high EM attenuation is present above 50 ft in depth - the region containing the highest density of fractures. Flowmeter logging was used to estimate hydraulic properties in the boreholes. Thirty-three transmissive fracture zones were identified in 11 of the boreholes. The vertical separation between transmissive zones typically is 10 to 20 ft. Open-hole and discrete-zone transmissivity was estimated from heat-pulse flowmeter data acquired under ambient and stressed conditions. The open-hole transmissivity ranges from 2 to 86 ft2/d. The estimated transmissivity of individual transmissive zones ranges from 0.4 to 68 ft2/d. Drawdown monitoring

  7. Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks

    Science.gov (United States)

    Chen, Mingjie; Sun, Yunwei; Fu, Pengcheng; Carrigan, Charles R.; Lu, Zhiming; Tong, Charles H.; Buscheck, Thomas A.

    2013-08-01

    Hydraulic fracturing has been used widely to stimulate production of oil, natural gas, and geothermal energy in formations with low natural permeability. Numerical optimization of fracture stimulation often requires a large number of evaluations of objective functions and constraints from forward hydraulic fracturing models, which are computationally expensive and even prohibitive in some situations. Moreover, there are a variety of uncertainties associated with the pre-existing fracture distributions and rock mechanical properties, which affect the optimized decisions for hydraulic fracturing. In this study, a surrogate-based approach is developed for efficient optimization of hydraulic fracturing well design in the presence of natural-system uncertainties. The fractal dimension is derived from the simulated fracturing network as the objective for maximizing energy recovery sweep efficiency. The surrogate model, which is constructed using training data from high-fidelity fracturing models for mapping the relationship between uncertain input parameters and the fractal dimension, provides fast approximation of the objective functions and constraints. A suite of surrogate models constructed using different fitting methods is evaluated and validated for fast predictions. Global sensitivity analysis is conducted to gain insights into the impact of the input variables on the output of interest, and further used for parameter screening. The high efficiency of the surrogate-based approach is demonstrated for three optimization scenarios with different and uncertain ambient conditions. Our results suggest the critical importance of considering uncertain pre-existing fracture networks in optimization studies of hydraulic fracturing.

  8. The study of crosslinked fluid leakoff in hydraulic fracturing physical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Grothe, Vinicius Perrud; Ribeiro, Paulo Roberto [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia de Petroleo; Sousa, Jose Luiz Antunes de Oliveira e [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia. Dept. de Estruturas; Fernandes, Paulo Dore [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2000-07-01

    The fluid loss plays an important role in the design and execution of hydraulic fracturing treatments. The main objectives of this work were: the study of the fluid loss associated with the propagation of hydraulic fractures generated at laboratory; and the comparison of two distinct methods for estimating leakoff coefficients - Nolte analysis and the filtrate volume vs. square root of time plot. Synthetic rock samples were used as well as crosslinked hydroxypropyl guar (HPG) fluids in different polymer concentrations. The physical simulations comprised the confinement of (0.1 x 0.1 x 0.1) m{sup 3} rock samples in a load cell for the application of an in situ stress field. Different flow rates were employed in order to investigate shear effects on the overall leakoff coefficient. Horizontal radial fractures were hydraulically induced with approximate diameters, what was accomplished by controlling the injection time. Leakoff coefficients determined by means of the pressure decline analysis were compared to coefficients obtained from static filtration tests, considering similar experimental conditions. The research results indicated that the physical simulation of hydraulic fracturing may be regarded as an useful tool for evaluating the effectiveness of fracturing fluids and that it can supply reliable estimates of fluid loss coefficients. (author)

  9. Microseismic imaging using Geometric-mean Reverse-Time Migration in Hydraulic Fracturing Monitoring

    Science.gov (United States)

    Yin, J.; Ng, R.; Nakata, N.

    2017-12-01

    Unconventional oil and gas exploration techniques such as hydraulic fracturing are associated with microseismic events related to the generation and development of fractures. For example, hydraulic fracturing, which is popular in Southern Oklahoma, produces earthquakes that are greater than magnitude 2.0. Finding the accurate locations, and mechanisms, of these events provides important information of local stress conditions, fracture distribution, hazard assessment, and economical impact. The accurate source location is also important to separate fracking-induced and wastewater disposal induced seismicity. Here, we implement a wavefield-based imaging method called Geometric-mean Reverse-Time Migration (GmRTM), which takes the advantage of accurate microseismic location based on wavefield back projection. We apply GmRTM to microseismic data collected during hydraulic fracturing for imaging microseismic source locations, and potentially, fractures. Assuming an accurate velocity model, GmRTM can improve the spatial resolution of source locations compared to HypoDD or P/S travel-time based methods. We will discuss the results from GmRTM and HypoDD using this field dataset and synthetic data.

  10. Characteristic Length Scales in Fracture Networks: Hydraulic Connectivity through Periodic Hydraulic Tests

    Science.gov (United States)

    Becker, M.; Bour, O.; Le Borgne, T.; Longuevergne, L.; Lavenant, N.; Cole, M. C.; Guiheneuf, N.

    2017-12-01

    Determining hydraulic and transport connectivity in fractured bedrock has long been an important objective in contaminant hydrogeology, petroleum engineering, and geothermal operations. A persistent obstacle to making this determination is that the characteristic length scale is nearly impossible to determine in sparsely fractured networks. Both flow and transport occur through an unknown structure of interconnected fracture and/or fracture zones making the actual length that water or solutes travel undetermined. This poses difficulties for flow and transport models. For, example, hydraulic equations require a separation distance between pumping and observation well to determine hydraulic parameters. When wells pairs are close, the structure of the network can influence the interpretation of well separation and the flow dimension of the tested system. This issue is explored using hydraulic tests conducted in a shallow fractured crystalline rock. Periodic (oscillatory) slug tests were performed at the Ploemeur fractured rock test site located in Brittany, France. Hydraulic connectivity was examined between three zones in one well and four zones in another, located 6 m apart in map view. The wells are sufficiently close, however, that the tangential distance between the tested zones ranges between 6 and 30 m. Using standard periodic formulations of radial flow, estimates of storativity scale inversely with the square of the separation distance and hydraulic diffusivity directly with the square of the separation distance. Uncertainty in the connection paths between the two wells leads to an order of magnitude uncertainty in estimates of storativity and hydraulic diffusivity, although estimates of transmissivity are unaffected. The assumed flow dimension results in alternative estimates of hydraulic parameters. In general, one is faced with the prospect of assuming the hydraulic parameter and inverting the separation distance, or vice versa. Similar uncertainties exist

  11. Uncertainty in hydraulic tests in fractured rock

    International Nuclear Information System (INIS)

    Ji, Sung-Hoon; Koh, Yong-Kwon

    2014-01-01

    Interpretation of hydraulic tests in fractured rock has uncertainty because of the different hydraulic properties of a fractured rock to a porous medium. In this study, we reviewed several interesting phenomena which show uncertainty in a hydraulic test at a fractured rock and discussed their origins and the how they should be considered during site characterisation. Our results show that the estimated hydraulic parameters of a fractured rock from a hydraulic test are associated with uncertainty due to the changed aperture and non-linear groundwater flow during the test. Although the magnitude of these two uncertainties is site-dependent, the results suggest that it is recommended to conduct a hydraulic test with a little disturbance from the natural groundwater flow to consider their uncertainty. Other effects reported from laboratory and numerical experiments such as the trapping zone effect (Boutt, 2006) and the slip condition effect (Lee, 2014) can also introduce uncertainty to a hydraulic test, which should be evaluated in a field test. It is necessary to consider the way how to evaluate the uncertainty in the hydraulic property during the site characterisation and how to apply it to the safety assessment of a subsurface repository. (authors)

  12. The Process of Hydraulic Fracturing

    Science.gov (United States)

    Hydraulic fracturing, know as fracking or hydrofracking, produces fractures in a rock formation by pumping fluids (water, proppant, and chemical additives) at high pressure down a wellbore. These fractures stimulate the flow of natural gas or oil.

  13. Seismic monitoring of hydraulic fracturing: techniques for determining fluid flow paths and state of stress away from a wellbore

    Energy Technology Data Exchange (ETDEWEB)

    Fehler, M.; House, L.; Kaieda, H.

    1986-01-01

    Hydraulic fracturing has gained in popularity in recent years as a way to determine the orientations and magnitudes of tectonic stresses. By augmenting conventional hydraulic fracturing measurements with detection and mapping of the microearthquakes induced by fracturing, we can supplement and idependently confirm information obtained from conventional analysis. Important information obtained from seismic monitoring includes: the state of stress of the rock, orientation and spacing of the major joint sets, and measurements of rock elastic parameters at locations distant from the wellbore. While conventional well logging operations can provide information about several of these parameters, the zone of interrogation is usually limited to the immediate proximity of the borehole. The seismic waveforms of the microearthquakes contain a wealth of information about the rock in regions that are otherwise inaccessible for study. By reliably locating the hypocenters of many microearthquakes, we have inferred the joint patterns in the rock. We observed that microearthquake locations do not define a simple, thin, planar distribution, that the fault plane solutions are consistent with shear slippage, and that spectral analysis indicates that the source dimensions and slip along the faults are small. Hence we believe that the microearthquakes result from slip along preexisting joints, and not from tensile extension at the tip of the fracture. Orientations of the principal stresses can be estimated by using fault plane solutions of the larger microearthquakes. By using a joint earthquake location scheme, and/or calibrations with downhole detonators, rock velocities and heterogeneities thereof can be investigated in rock volumes that are far enough from the borehole to be representative of intrincis rock properties.

  14. Numerical Simulation of Hydraulic Fracturing in Low-/High-Permeability, Quasi-Brittle and Heterogeneous Rocks

    Science.gov (United States)

    Pakzad, R.; Wang, S. Y.; Sloan, S. W.

    2018-04-01

    In this study, an elastic-brittle-damage constitutive model was incorporated into the coupled fluid/solid analysis of ABAQUS to iteratively calculate the equilibrium effective stress of Biot's theory of consolidation. The Young's modulus, strength and permeability parameter of the material were randomly assigned to the representative volume elements of finite element models following the Weibull distribution function. The hydraulic conductivity of elements was associated with their hydrostatic effective stress and damage level. The steady-state permeability test results for sandstone specimens under different triaxial loading conditions were reproduced by employing the same set of material parameters in coupled transient flow/stress analyses of plane-strain models, thereby indicating the reliability of the numerical model. The influence of heterogeneity on the failure response and the absolute permeability was investigated, and the post-peak permeability was found to decrease with the heterogeneity level in the coupled analysis with transient flow. The proposed model was applied to the plane-strain simulation of the fluid pressurization of a cavity within a large-scale block under different conditions. Regardless of the heterogeneity level, the hydraulically driven fractures propagated perpendicular to the minimum principal far-field stress direction for high-permeability models under anisotropic far-field stress conditions. Scattered damage elements appeared in the models with higher degrees of heterogeneity. The partially saturated areas around propagating fractures were simulated by relating the saturation degree to the negative pore pressure in low-permeability blocks under high pressure. By replicating previously reported trends in the fracture initiation and breakdown pressure for different pressurization rates and hydraulic conductivities, the results showed that the proposed model for hydraulic fracture problems is reliable for a wide range of

  15. Hydraulic conductivity of rock fractures

    International Nuclear Information System (INIS)

    Zimmerman, R.W.; Bodvarsson, G.S.

    1994-10-01

    Yucca Mountain, Nevada contains numerous geological units that are highly fractured. A clear understanding of the hydraulic conductivity of fractures has been identified as an important scientific problem that must be addressed during the site characterization process. The problem of the flow of a single-phase fluid through a rough-walled rock fracture is discussed within the context of rigorous fluid mechanics. The derivation of the cubic law is given as the solution to the Navier-Stokes equations for flow between smooth, parallel plates, the only fracture geometry that is amenable to exact treatment. The various geometric and kinetic conditions that are necessary in order for the Navier-Stokes equations to be replaced by the more tractable lubrication or Hele-Shaw equations are studied and quantified. Various analytical and numerical results are reviewed pertaining to the problem of relating the effective hydraulic aperture to the statistics of the aperture distribution. These studies all lead to the conclusion that the effective hydraulic aperture is always less than the mean aperture, by a factor that depends on the ratio of the mean value of the aperture to its standard deviation. The tortuosity effect caused by regions where the rock walls are in contact with each other is studied using the Hele-Shaw equations, leading to a simple correction factor that depends on the area fraction occupied by the contact regions. Finally, the predicted hydraulic apertures are compared to measured values for eight data sets from the literature for which aperture and conductivity data were available on the same fracture. It is found that reasonably accurate predictions of hydraulic conductivity can be made based solely on the first two moments of the aperture distribution function, and the proportion of contact area. 68 refs

  16. Hydraulic Fracturing: Paving the Way for a Sustainable Future?

    Directory of Open Access Journals (Sweden)

    Jiangang Chen

    2014-01-01

    Full Text Available With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment.

  17. Hydraulic fracturing: paving the way for a sustainable future?

    Science.gov (United States)

    Chen, Jiangang; Al-Wadei, Mohammed H; Kennedy, Rebekah C M; Terry, Paul D

    2014-01-01

    With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment.

  18. Hydraulic fracture diagnostic: recent advances and their impact; Analyses de la fracturation hydraulique: progres recents et leur impact

    Energy Technology Data Exchange (ETDEWEB)

    Wolhart, St.L. [GRI, United States (United States)

    2000-07-01

    The use of hydraulic fracturing has grown tremendously since its introduction over 50 years ago. Most wells in low permeability reservoirs are not economic without hydraulic fracture stimulation. Hydraulic fracturing is also seeing increasing use in high permeability applications. The success of this technology can be attributed to the great strides made in three areas: hydraulic fracture theory and modeling, improved surface and subsurface equipment and advanced fluid systems and proppers. However, industry still has limited capabilities when it comes to determining the geometry of the created hydraulic fracture. This limitation, in turn places limits on the continued improvement of hydraulic fracturing as a means to optimize productivity and recovery. GRI's Advanced Hydraulic Fracture Diagnostics Program has developed two new technologies, microseismic hydraulic fracture mapping and downhole tilt-meter hydraulic fracture mapping, to address this limitation. These two technologies have been utilized to improve field development and reduce hydraulic fracturing costs. This paper reviews these technologies and presents case histories of their use. (author)

  19. Rock Springs Site 12 hydraulic/explosive true in situ oil shale fracturing experiment

    Energy Technology Data Exchange (ETDEWEB)

    Parrish, R.L.; Boade, R.R.; Stevens, A.L.; Long, A. Jr.; Turner, T.F.

    1980-06-01

    The experiment plan involved the creation and characterization of three horizontal hydraulic fractures, followed by the insertion and simultaneous detonation of slurry explosive in the two lower fractures. Core analyses, wellbore logging, and airflow and /sup 85/Kr tracer tests were used for site characterization and assessment of the hydraulic and explosive fracturing. Tiltmeters, wellhead pressure and flow gages, and in-formation pressure, flow and crack-opening sensors were used to monitor hydrofracture creation and explosive insertion. Explosive detonation diagnostic data were taken with stress and time-of-arrival gages and surface and in-formation accelerometers. The post-fracturing assessments indicated that: (1) hydrofracture creation and explosive insertion and detonation were accomplished essentially as planned; (2) induced fractures were randomly distributed through the shale with no extensively fractured regions or dislocation of shale; and (3) enhancement of permeability was limited to enlargement of the explosive-filled fractures.

  20. Injection of radioactive waste by hydraulic fracturing at West Valley, New York. Volume 3. Appendices

    International Nuclear Information System (INIS)

    1978-05-01

    Ten appendices are included: log data, elastic constants for transversely isotropic elastic media by ultrasonic velocity measurement, fracture toughness anisotropy of West Valley shale, in-situ stress measurement techniques, stress measurement data, hydraulic fracturing measurements, enhancement of horizontal crack initiation by jetting, finite element programs for analysis of crack propagation and for groundwater flow analysis, and well data

  1. Effect of rock rheology on fluid leak- off during hydraulic fracturing

    Science.gov (United States)

    Yarushina, V. M.; Bercovici, D.; Oristaglio, M. L.

    2012-04-01

    In this communication, we evaluate the effect of rock rheology on fluid leak­off during hydraulic fracturing of reservoirs. Fluid leak-off in hydraulic fracturing is often nonlinear. The simple linear model developed by Carter (1957) for flow of fracturing fluid into a reservoir has three different regions in the fractured zone: a filter cake on the fracture face, formed by solid additives from the fracturing fluid; a filtrate zone affected by invasion of the fracturing fluid; and a reservoir zone with the original formation fluid. The width of each zone, as well as its permeability and pressure drop, is assumed to remain constant. Physical intuition suggests some straightforward corrections to this classical theory to take into account the pressure dependence of permeability, the compressibility or non-Newtonian rheology of fracturing fluid, and the radial (versus linear) geometry of fluid leak­off from the borehole. All of these refinements, however, still assume that the reservoir rock adjacent to the fracture face is non­deformable. Although the effect of poroelastic stress changes on leak-off is usually thought to be negligible, at the very high fluid pressures used in hydraulic fracturing, where the stresses exceed the rock strength, elastic rheology may not be the best choice. For example, calculations show that perfectly elastic rock formations do not undergo the degree of compaction typically seen in sedimentary basins. Therefore, pseudo-elastic or elastoplastic models are used to fit observed porosity profiles with depth. Starting from balance equations for mass and momentum for fluid and rock, we derive a hydraulic flow equation coupled with a porosity equation describing rock compaction. The result resembles a pressure diffusion equation with the total compressibility being a sum of fluid, rock and pore-space compressibilities. With linear elastic rheology, the bulk formation compressibility is dominated by fluid compressibility. But the possibility

  2. Connection between tectonic stresses and well fracturing data

    Energy Technology Data Exchange (ETDEWEB)

    Scheidegger, A E [Imperial Oil Res. Lab., Calgary, CA

    1961-01-01

    Theoretical considerations of hydraulic well fracturing normally utilize a model in which the borehole is assumed to be a cylinder of infinite length. This leads to treatment of the induced stress state in two dimensions. The two-dimensional model is obviously an oversimplification. Therefore, a three-dimensional model is proposed in which the well pressure is assumed to be equivalent to a spherical pressure center. The bottom hole pressure during fracturing is determined by 4 variables; i.e., the 3 principal geological stresses and the rock strength. The response to fracturing is determined primarily by the prevailing stress state and to a lesser degree by the rock strength. The fracture condition is formulated and the model is used in the calculation of geological stresses from well data.

  3. Characterisation of hydraulically-active fractures in a fractured ...

    African Journals Online (AJOL)

    ... in the initial stage of a site investigation to select the optimal site location or to evaluate the hydrogeological properties of fractures in underground exploration studies, such as those related geothermal reservoir evaluation and radioactive waste disposal. Keywords: self-potential method, hydraulically-conductive fractures, ...

  4. A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation

    Directory of Open Access Journals (Sweden)

    Zhiheng Zhao

    2016-07-01

    Full Text Available To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale formation, were prepared to conduct the hydraulic fracturing experiments. The results reveal that the breakdown pressure increases with the rise of thickness and strength of interbeds under the same in-situ field stress and injection rate. In addition, for the model blocks with thick and high strength interbeds, the hydraulic fracture has difficulty crossing the interbeds and is prone to divert along the bedding faces, and the fracturing effectiveness is not good. However, for the model blocks with thin and low strength interbeds, more long branches are generated along the main fracture, which is beneficial to the formation of the fracture network. What is more, combining the macroscopic descriptions with microscopic observations, the blocks with thinner and lower strength interbeds tend to generate more micro-fractures, and the width of the fractures is relatively larger on the main fracture planes. Based on the experiments, it is indicated that the propagation of hydraulic fractures is strongly influenced by the characteristics of interbeds, and the results are instructive to the understanding and evaluation of the fracability in the continental shale formation.

  5. Seismic characteristics of tensile fracture growth induced by hydraulic fracturing

    Science.gov (United States)

    Eaton, D. W. S.; Van der Baan, M.; Boroumand, N.

    2014-12-01

    Hydraulic fracturing is a process of injecting high-pressure slurry into a rockmass to enhance its permeability. Variants of this process are used for unconventional oil and gas development, engineered geothermal systems and block-cave mining; similar processes occur within volcanic systems. Opening of hydraulic fractures is well documented by mineback trials and tiltmeter monitoring and is a physical requirement to accommodate the volume of injected fluid. Numerous microseismic monitoring investigations acquired in the audio-frequency band are interpreted to show a prevalence of shear-dominated failure mechanisms surrounding the tensile fracture. Moreover, the radiated seismic energy in the audio-frequency band appears to be a miniscule fraction (<< 1%) of the net injected energy, i.e., the integral of the product of fluid pressure and injection rate. We use a simple penny-shaped crack model as a predictive framework to describe seismic characteristics of tensile opening during hydraulic fracturing. This model provides a useful scaling relation that links seismic moment to effective fluid pressure within the crack. Based on downhole recordings corrected for attenuation, a significant fraction of observed microseismic events are characterized by S/P amplitude ratio < 5. Despite the relatively small aperture of the monitoring arrays, which precludes both full moment-tensor analysis and definitive identification of nodal planes or axes, this ratio provides a strong indication that observed microseismic source mechanisms have a component of tensile failure. In addition, we find some instances of periodic spectral notches that can be explained by an opening/closing failure mechanism, in which fracture propagation outpaces fluid velocity within the crack. Finally, aseismic growth of tensile fractures may be indicative of a scenario in which injected energy is consumed to create new fracture surfaces. Taken together, our observations and modeling provide evidence that

  6. Fluid driven fracture mechanics in highly anisotropic shale: a laboratory study with application to hydraulic fracturing

    Science.gov (United States)

    Gehne, Stephan; Benson, Philip; Koor, Nick; Enfield, Mark

    2017-04-01

    The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the

  7. Rock mechanics in the disposal of radioactive wastes by hydraulic fracturing

    Energy Technology Data Exchange (ETDEWEB)

    McClain, W C

    1968-01-01

    The ultimate capacity of a hydraulic-fracturing waste disposal facility is governed primarily by the integrity of the rocks overlying the injected wastes. The objective of this study is to analyze theoretically the stresses and strains generated by the injected wastes in an effort to understand the behavior of the system sufficiently well that the failure mechanism can be predicted and the capacity of the injection well estimated. The surface uplifts at Oak Ridge National Laboratory's fracturing site were compared with theoretical curves obtained by assuming the uplifts to be inversely analogous to the subsidence which occurs over mining excavations. This analysis, based on assumptions of homogeneity, isotropy, and linear elasticity, provided considerable insight into the mechanics of the process. The most probable mechanism of failure of the rock appears to be by the formation of a vertical instead of a horizontal fracture. Fracture orientation is controlled primarily by the orientation of the principal stress field in the rock. Each successive waste injection slightly modifies this stress field toward a condition more favorable to the formation of a vertical fracture. (16 refs.)

  8. Hydraulic properties of 3D rough-walled fractures during shearing: An experimental study

    Science.gov (United States)

    Yin, Qian; Ma, Guowei; Jing, Hongwen; Wang, Huidong; Su, Haijian; Wang, Yingchao; Liu, Richeng

    2017-12-01

    This study experimentally analyzed the influence of shear processes on nonlinear flow behavior through 3D rough-walled rock fractures. A high-precision apparatus was developed to perform stress-dependent fluid flow tests of fractured rocks. Then, water flow tests on rough-walled fractures with different mechanical displacements were conducted. At each shear level, the hydraulic pressure ranged from 0 to 0.6 MPa, and the normal load varied from 7 to 35 kN. The results show that (i) the relationship between the volumetric flow rate and hydraulic gradient of rough-walled fractures can be well fit using Forchheimer's law. Notably, both the linear and nonlinear coefficients in Forchheimer's law decrease during shearing; (ii) a sixth-order polynomial function is used to evaluate the transmissivity based on the Reynolds number of fractures during shearing. The transmissivity exhibits a decreasing trend as the Reynolds number increases and an increasing trend as the shear displacement increases; (iii) the critical hydraulic gradient, critical Reynolds number and equivalent hydraulic aperture of the rock fractures all increase as the shear displacement increases. When the shear displacement varies from 0 to 15 mm, the critical hydraulic gradient ranges from 0.3 to 2.2 for a normal load of 7 kN and increases to 1.8-8.6 for a normal load of 35 kN; and (iv) the Forchheimer law results are evaluated by plotting the normalized transmissivity of the fractures during shearing against the Reynolds number. An increase in the normal load shifts the fitted curves downward. Additionally, the Forchheimer coefficient β decreases with the shear displacement but increases with the applied normal load.

  9. Periodic Hydraulic Testing for Discerning Fracture Network Connections

    Science.gov (United States)

    Becker, M.; Le Borgne, T.; Bour, O.; Guihéneuf, N.; Cole, M.

    2015-12-01

    Discrete fracture network (DFN) models often predict highly variable hydraulic connections between injection and pumping wells used for enhanced oil recovery, geothermal energy extraction, and groundwater remediation. Such connections can be difficult to verify in fractured rock systems because standard pumping or pulse interference tests interrogate too large a volume to pinpoint specific connections. Three field examples are presented in which periodic hydraulic tests were used to obtain information about hydraulic connectivity in fractured bedrock. The first site, a sandstone in New York State, involves only a single fracture at a scale of about 10 m. The second site, a granite in Brittany, France, involves a fracture network at about the same scale. The third site, a granite/schist in the U.S. State of New Hampshire, involves a complex network at scale of 30-60 m. In each case periodic testing provided an enhanced view of hydraulic connectivity over previous constant rate tests. Periodic testing is particularly adept at measuring hydraulic diffusivity, which is a more effective parameter than permeability for identify the complexity of flow pathways between measurement locations. Periodic tests were also conducted at multiple frequencies which provides a range in the radius of hydraulic penetration away from the oscillating well. By varying the radius of penetration, we attempt to interrogate the structure of the fracture network. Periodic tests, therefore, may be uniquely suited for verifying and/or calibrating DFN models.

  10. An XFEM Model for Hydraulic Fracturing in Partially Saturated Rocks

    Directory of Open Access Journals (Sweden)

    Salimzadeh Saeed

    2016-01-01

    Full Text Available Hydraulic fracturing is a complex multi-physics phenomenon. Numerous analytical and numerical models of hydraulic fracturing processes have been proposed. Analytical solutions commonly are able to model the growth of a single hydraulic fracture into an initially intact, homogeneous rock mass. Numerical models are able to analyse complex problems such as multiple hydraulic fractures and fracturing in heterogeneous media. However, majority of available models are restricted to single-phase flow through fracture and permeable porous rock. This is not compatible with actual field conditions where the injected fluid does not have similar properties as the host fluid. In this study we present a fully coupled hydro-poroelastic model which incorporates two fluids i.e. fracturing fluid and host fluid. Flow through fracture is defined based on lubrication assumption, while flow through matrix is defined as Darcy flow. The fracture discontinuity in the mechanical model is captured using eXtended Finite Element Method (XFEM while the fracture propagation criterion is defined through cohesive fracture model. The discontinuous matrix fluid velocity across fracture is modelled using leak-off loading which couples fracture flow and matrix flow. The proposed model has been discretised using standard Galerkin method, implemented in Matlab and verified against several published solutions. Multiple hydraulic fracturing simulations are performed to show the model robustness and to illustrate how problem parameters such as injection rate and rock permeability affect the hydraulic fracturing variables i.e. injection pressure, fracture aperture and fracture length. The results show the impact of partial saturation on leak-off and the fact that single-phase models may underestimate the leak-off.

  11. Influence of fracture extension on in-situ stress in tight reservoir

    Science.gov (United States)

    Zhang, Yongping; Wei, Xu; Zhang, Ye; Xing, Libo; Xu, Jianjun

    2018-01-01

    Currently, hydraulic fracturing is an important way to develop low permeability reservoirs. The fractures produced during the fracturing process are the main influencing factors of changing in-situ stress. In this paper, the influence of fracture extension on in-situ stress is studied by establishing a mathematical model to describe the relationship between fracture length and in-situ stress. The results show that the growth rate gradually decreases after the fracture reaches a certain length with the increase of fracturing time; the continuous extension of the fracture is the main factor to change the in-situ stress. In order to reduce the impact on the subsequent fracture extension due to the changing of in-situ stress, controlling fracturing time and fracture length without affecting the stimulated reservoir effect is an important way. The results presented in this study can effectively reduce the impact of changing of in-situ stress on subsequent fracturing construction.

  12. Application of the boundary elements method for modeling of the fracture of cylindrical bodies by hydraulic fracturing

    Science.gov (United States)

    Legan, M. A.; Blinov, V. A.; Larichkin, A. Yu; Novoselov, A. N.

    2017-10-01

    Experimental study of hydraulic fracturing of thick-walled cylinders with a central circular hole was carried out using the machine that creates a high oil pressure. Experiments on the compression fracture of the solid cylinders by diameter and rectangular parallelepipeds perpendicular to the ends were carried out with a multipurpose test machine Zwick / Roell Z100. Samples were made of GF-177 material based on cement. Ultimate stresses in the material under study were determined for three types of stress state: under compression, with a pure shear on the surface of the hole under frecking conditions and under a compound stress state under conditions of diametral compression of a solid cylinder. The value of the critical stress intensity factor of GF-177 material was obtained. The modeling of the fracturing process taking into account the inhomogeneity of the stress state near the hole was carried out using the boundary elements method (in the variant of the fictitious load method) and the gradient fracture criterion. Calculation results of the ultimate pressure were compared with values obtained analytically on the basis of the Lame solution and with experimental data.

  13. Database for Hydraulically Conductive Fractures. Update 2010

    International Nuclear Information System (INIS)

    Tammisto, E.; Palmen, J.

    2011-02-01

    Posiva flow logging (PFL) with 0.5 m test interval and made in 10 cm steps can be used for exact depth determination of hydraulically conductive fractures. Together with drillhole wall images and fracture data from core logging PFL provides possibilities to detect single conductive fractures. In this report, the results of PFL are combined to the fracture data in drillholes OL-KR49 .. OL-KR53, OL-KR50B, OL-KR52B and OLKR53B and pilot holes ONK-PH11 - ONK-PH13. The results are used mainly in development of hydroDFN- models. The conductive fractures were first recognised from the PFL data and digital drillhole images and then the fractures from the core logging corresponding to the ones picked from the digital drillhole images were identified. The conductive fractures were recognised from the images primarily based on openness of fractures or a visible flow in the image. In most of the cases of measured flow, no tails of flow were seen in the image. In these cases, the conductive fractures were recognised from the image based on openness of fractures and a matching depth. According to the results the hydraulically conductive fractures/zones can be distinguished from the drillhole wall images in most cases. An important phase in the work is to calibrate the depth of the image and the flow logging with the sample length. The hydraulic conductivity is clearly higher in the upper part of the bedrock in the depth range 0-150 m below sea level than deeper in the bedrock. The frequency of hydraulically conductive fractures detected in flow logging (T > 10 -10 -10 -9 m 2 /s) in depth range 0-150 m varies from 0.07 to 0.84 fractures/meter of sample length. Deeper in the rock the conductive fractures are less frequent, but occur often in groups of few fractures. In drillholes OL-KR49 .. OL-KR53, OL-KR50B, OL-KR52B and OL-KR53B about 8.5 % of all fractures and 4.4 % of the conductive fractures are within HZ-structures. (orig.)

  14. Observations of a potential size-effect in experimental determination of the hydraulic properties of fractures

    International Nuclear Information System (INIS)

    Witherspoon, P.A.; Amick, C.H.; Gale, J.E.; Iwai, K.

    1979-05-01

    In several recent investigations, experimental studies on the effect of normal stress on the hydraulic conductivity of a single fracture were made on three rock specimens ranging in cross-sectional area from 0.02 m 2 to over 1.0 m 2 . At the maximum stress levels that could be attained (10 to 20 MPa), minimum values of the fracture hydraulic conductivity were not the same for each rock specimen. These minimum values increased with specimen size, indicating that the determination of fracture conductivity may be significantly influenced by a size effect. The implications of these results are important. Cores collected in the field are normally not larger than 0.15 m in diameter. However, the results of this work suggest that when this size core is used for laboratory investigations, the results may be nonconservative in that fracture permeabilities will be significantly lower than will be found in the field. 6 figures

  15. Ground source energy in crystalline bedrock - increased energy extraction by using hydraulic fracturing in boreholes

    Energy Technology Data Exchange (ETDEWEB)

    Ramstad, Randi Kalstad

    2004-11-01

    central borehole encircled by four satellite boreholes 13 metres away from the central borehole. The central borehole at EAB was flanked with two boreholes 16 and 20 metres away. In operation mode, groundwater was pumped from the satellite boreholes, heat exchanged, and re-injected into the groundwater magazine via the central borehole. Routine operation of the plants has not yet been initiated. The main findings from this study can be summarized as follows: (1) Hydraulic fracturing with water-only results in an overall increase in water yield for the hard rock borehole. (2) Hydraulic fracturing with injection of sand as propping agent also leads to an increased water yield. (3) The use of sand as propping agent seems to be more required in fractures with high counter pressure, in this study higher than approximately 40 bars, compared with fractures with lower counter pressure. The particle size of the sand should also be adjusted to the appearing counter pressure, and injection of coarser sand is recommended in fractures with lower counter pressures. (4) Comparing the results from the hydraulic fracturing performed at Bryn and EAB shows that the pressure levels, required to create new fractures, varied considerably. The maximum pressures present at Bryn were higher than the corresponding pressures at EAB. At Bryn 70% (44 out of 63) of the pressure-time curves from the hydraulic fracturing with water-only were interpreted as initiation or reopening of fractures, while the number for EAB was 97% (36 out of 37). The lower degree of fracturing at Bryn is likely to be a result of high rock stresses and high tensile strength of the bedrock, also confirmed by the results from the rock stress measurements performed at Bryn. Considering the bedrock at EAB, characterized as nodular limestone, the tensile strength is assumed to be less than the values for the low-metamorphic sandstone present at Bryn. (5) The infiltration rate in the central boreholes is a critical factor for the

  16. Disclosure of hydraulic fracturing fluid chemical additives: analysis of regulations.

    Science.gov (United States)

    Maule, Alexis L; Makey, Colleen M; Benson, Eugene B; Burrows, Isaac J; Scammell, Madeleine K

    2013-01-01

    Hydraulic fracturing is used to extract natural gas from shale formations. The process involves injecting into the ground fracturing fluids that contain thousands of gallons of chemical additives. Companies are not mandated by federal regulations to disclose the identities or quantities of chemicals used during hydraulic fracturing operations on private or public lands. States have begun to regulate hydraulic fracturing fluids by mandating chemical disclosure. These laws have shortcomings including nondisclosure of proprietary or "trade secret" mixtures, insufficient penalties for reporting inaccurate or incomplete information, and timelines that allow for after-the-fact reporting. These limitations leave lawmakers, regulators, public safety officers, and the public uninformed and ill-prepared to anticipate and respond to possible environmental and human health hazards associated with hydraulic fracturing fluids. We explore hydraulic fracturing exemptions from federal regulations, as well as current and future efforts to mandate chemical disclosure at the federal and state level.

  17. Data Analytics of Hydraulic Fracturing Data

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jovan Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Viswanathan, Hari [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffery [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Middleton, Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-11

    These are a set of slides on the data analytics of hydraulic fracturing data. The conclusions from this research are the following: they proposed a permeability evolution as a new mechanism to explain hydraulic fracturing trends; they created a model to include this mechanism and it showed promising results; the paper from this research is ready for submission; they devised a way to identify and sort refractures in order to study their effects, and this paper is currently being written.

  18. XFEM modeling of hydraulic fracture in porous rocks with natural fractures

    Science.gov (United States)

    Wang, Tao; Liu, ZhanLi; Zeng, QingLei; Gao, Yue; Zhuang, Zhuo

    2017-08-01

    Hydraulic fracture (HF) in porous rocks is a complex multi-physics coupling process which involves fluid flow, diffusion and solid deformation. In this paper, the extended finite element method (XFEM) coupling with Biot theory is developed to study the HF in permeable rocks with natural fractures (NFs). In the recent XFEM based computational HF models, the fluid flow in fractures and interstitials of the porous media are mostly solved separately, which brings difficulties in dealing with complex fracture morphology. In our new model the fluid flow is solved in a unified framework by considering the fractures as a kind of special porous media and introducing Poiseuille-type flow inside them instead of Darcy-type flow. The most advantage is that it is very convenient to deal with fluid flow inside the complex fracture network, which is important in shale gas extraction. The weak formulation for the new coupled model is derived based on virtual work principle, which includes the XFEM formulation for multiple fractures and fractures intersection in porous media and finite element formulation for the unified fluid flow. Then the plane strain Kristianovic-Geertsma-de Klerk (KGD) model and the fluid flow inside the fracture network are simulated to validate the accuracy and applicability of this method. The numerical results show that large injection rate, low rock permeability and isotropic in-situ stresses tend to lead to a more uniform and productive fracture network.

  19. The Effect of Loading Rate on Hydraulic Fracturing in Synthetic Granite - a Discrete Element Study

    Science.gov (United States)

    Tomac, I.; Gutierrez, M.

    2015-12-01

    Hydraulic fracture initiation and propagation from a borehole in hard synthetic rock is modeled using the two dimensional Discrete Element Method (DEM). DEM uses previously established procedure for modeling the strength and deformation parameters of quasi-brittle rocks with the Bonded Particle Model (Itasca, 2004). A series of simulations of laboratory tests on granite in DEM serve as a reference for synthetic rock behavior. Fracturing is enabled by breaking parallel bonds between DEM particles as a result of the local stress state. Subsequent bond breakage induces fracture propagation during a time-stepping procedure. Hydraulic fracturing occurs when pressurized fluid induces hoop stresses around the wellbore which cause rock fracturing and serves for geo-reservoir permeability enhancement in oil, gas and geothermal industries. In DEM, a network of fluid pipes and reservoirs is used for mathematical calculation of fluid flow through narrow channels between DEM particles, where the hydro-mechanical coupling is fully enabled. The fluid flow calculation is superimposed with DEM stress-strain calculation at each time step. As a result, the fluid pressures during borehole pressurization in hydraulic fracturing, as well as, during the fracture propagation from the borehole, can be simulated. The objective of this study is to investigate numerically a hypothesis that fluid pressurization rate, or the fluid flow rate, influences upon character, shape and velocity of fracture propagation in rock. The second objective is to better understand and define constraints which are important for successful fracture propagation in quasi-brittle rock from the perspective of flow rate, fluid density, viscosity and compressibility relative to the rock physical properties. Results from this study indicate that not only too high fluid flow rates cause fracture arrest and multiple fracture branching from the borehole, but also that the relative compressibility of fracturing fluid and

  20. Hydrodynamic analysis of clastic injection and hydraulic fracturing structures in the Jinding Zn-Pb deposit, Yunnan, China

    Directory of Open Access Journals (Sweden)

    Guoxiang Chi

    2012-01-01

    Full Text Available The Jinding Zn-Pb deposit has been generally considered to have formed from circulating basinal fluids in a relatively passive way, with fluid flow being controlled by structures and sedimentary facies, similar to many other sediments-hosted base metal deposits. However, several recent studies have revealed the presence of sand injection structures, intrusive breccias, and hydraulic fractures in the open pit of the Jinding deposit and suggested that the deposit was formed from explosive release of overpressured fluids. This study reports new observations of fluid overpressure-related structures from underground workings (Paomaping and Fengzishan, which show clearer crosscutting relationships than in the open pit. The observed structures include: 1 sand (±rock fragment dikes injecting into fractures in solidified rocks; 2 sand (±rock fragment bodies intruding into unconsolidated or semi-consolidated sediments; 3 disintegrated semi-consolidated sand bodies; and 4 veins and breccias formed from hydraulic fracturing of solidified rocks followed by cementation of hydrothermal minerals. The development of ore minerals (sphalerite in the cement of the various clastic injection and hydraulic fractures indicate that these structures were formed at the same time as mineralization. The development of hydraulic fractures and breccias with random orientation indicates small differential stress during mineralization, which is different from the stress field with strong horizontal shortening prior to mineralization. Fluid flow velocity may have been up to more than 11 m/s based on calculations from the size of the fragments in the clastic dikes. The clastic injection and hydraulic fracturing structures are interpreted to have formed from explosive release of overpressured fluids, which may have been related to either magmatic intrusions at depth or seismic activities that episodically tapped an overpressured fluid reservoir. Because the clastic injection

  1. Experimental Analysis of Hydraulic Fracture Growth and Acoustic Emission Response in a Layered Formation

    Science.gov (United States)

    Ning, Li; Shicheng, Zhang; Yushi, Zou; Xinfang, Ma; Shan, Wu; Yinuo, Zhang

    2018-04-01

    Microseismic/acoustic emission (AE) monitoring is an essential technology for understanding hydraulic fracture (HF) geometry and stimulated reservoir volume (SRV) during hydraulic fracturing in unconventional reservoirs. To investigate HF growth mechanisms and features of induced microseismic/AE events in a layered formation, laboratory fracturing experiments were performed on shale specimens (30 cm × 30 cm × 30 cm) with multiple bedding planes (BPs) under triaxial stresses. AE monitoring was used to reveal the spatial distribution and hypocenter mechanisms of AE events induced by rock failure. Computerized tomography scanning was used to observe the internal fracture geometry. Experimental results showed that the various HF geometries could be obviously distinguished based on injection pressure curves and AE responses. Fracture complexity was notably increased when vertically growing HFs connected with and opened more BPs. The formation of a complex fracture network was generally indicated by frequent fluctuations in injection pressure curves, intense AE activity, and three-dimensionally distributed AE events. Investigations of the hypocenter mechanisms revealed that shear failure/event dominated in shale specimens. Shear and tensile events were induced in hydraulically connected regions, and shear events also occurred around BPs that were not hydraulically connected. This led to an overestimation of HF height and SRV in layered formations based on the AE location results. The results also showed that variable injection rate and using plugging agent were conducive in promoting HF to penetrate through the weak and high-permeability BPs, thereby increasing the fracture height.

  2. Experimental validation of microseismic emissions from a controlled hydraulic fracture in a synthetic layered medium

    Science.gov (United States)

    Roundtree, Russell

    , this provides one of the best far field (away from the well bore) measurements to assess hydraulic fracture behavior. It also provides a calibration tool to extend laboratory results to field scale endeavors. The identification of strong microseismic activity at stress states far below fracture initiation confirms that rocks are critically stressed meta-stable materials and that microseismicity is caused by stress changes, not fractures directly. Advancements are necessary to fully exploit the potential of the microseismic method in laboratory sized samples. Both processing and visualization enhancements are necessary to realize the full benefits of this promising technology in the laboratory environment.

  3. Hydro-mechanical coupled simulation of hydraulic fracturing using the eXtended Finite Element Method (XFEM)

    Science.gov (United States)

    Youn, Dong Joon

    This thesis presents the development and validation of an advanced hydro-mechanical coupled finite element program analyzing hydraulic fracture propagation within unconventional hydrocarbon formations under various conditions. The realistic modeling of hydraulic fracturing is necessarily required to improve the understanding and efficiency of the stimulation technique. Such modeling remains highly challenging, however, due to factors including the complexity of fracture propagation mechanisms, the coupled behavior of fracture displacement and fluid pressure, the interactions between pre-existing natural and initiated hydraulic fractures and the formation heterogeneity of the target reservoir. In this research, an eXtended Finite Element Method (XFEM) scheme is developed allowing for representation of single or multiple fracture propagations without any need for re-meshing. Also, the coupled flows through the fracture are considered in the program to account for their influence on stresses and deformations along the hydraulic fracture. In this research, a sequential coupling scheme is applied to estimate fracture aperture and fluid pressure with the XFEM. Later, the coupled XFEM program is used to estimate wellbore bottomhole pressure during fracture propagation, and the pressure variations are analyzed to determine the geometry and performance of the hydraulic fracturing as pressure leak-off test. Finally, material heterogeneity is included into the XFEM program to check the effect of random formation property distributions to the hydraulic fracture geometry. Random field theory is used to create the random realization of the material heterogeneity with the consideration of mean, standard deviation, and property correlation length. These analyses lead to probabilistic information on the response of unconventional reservoirs and offer a more scientific approach regarding risk management for the unconventional reservoir stimulation. The new stochastic approach

  4. Simulations of hydraulic fracturing and leakage in sedimentary basins

    Energy Technology Data Exchange (ETDEWEB)

    Lothe, Ane Elisabeth

    2004-01-01

    Hydraulic fracturing and leakage of water through the caprock is described from sedimentary basin over geological time scale. Abnormal pressure accumulations reduce the effective stresses in the underground and trigger the initiation of hydraulic fractures. The major faults in the basin define these pressure compartments. In this Thesis, basin simulations of hydraulic fracturing and leakage have been carried out. A simulator (Pressim) is used to calculate pressure generation and dissipitation between the compartments. The flux between the compartments and not the flow within the compartments is modelled. The Griffith-Coulomb failure criterion determines initial failure at the top structures of overpressured compartments, whereas the frictional sliding criterion is used for reactivation along the same fractures. The minimum horizontal stress is determined from different formulas, and an empirical one seems to give good results compared to measured pressures and minimum horizontal stresses. Simulations have been carried out on two datasets; one covering the Halten Terrace area and one the Tune Field area in the northern North Sea. The timing of hydraulic fracturing and amount of leakage has been quantified in the studies from the Halten Terrace area. This is mainly controlled by the lateral fluid flow and the permeability of the major faults in the basin. Low fault permeability gives early failure, while high fault permeabilities results in no or late hydraulic fracturing and leakage from overpressured parts of the basin. In addition to varying the transmissibility of all faults in a basin, the transmissibility across individual faults can be varied. Increasing the transmissibility across faults is of major importance in overpressured to intermediately pressured areas. However, to obtain change in the flow, a certain pressure difference has to be the situation between the different compartments. The coefficient of internal friction and the coefficient of frictional

  5. Hydraulic fracturing proppants

    Directory of Open Access Journals (Sweden)

    V. P. P. de Campos

    Full Text Available Abstract Hydrocarbon reservoirs can be classified as unconventional or conventional depending on the oil and gas extraction difficulty, such as the need for high-cost technology and techniques. The hydrocarbon extraction from bituminous shale, commonly known as shale gas/oil, is performed by using the hydraulic fracturing technique in unconventional reservoirs where 95% water, 0.5% of additives and 4.5% of proppants are used. Environmental problems related to hydraulic fracturing technique and better performance/development of proppants are the current challenge faced by companies, researchers, regulatory agencies, environmentalists, governments and society. Shale gas is expected to increase USA fuel production, which triggers the development of new proppants and technologies of exploration. This paper presents a review of the definition of proppants, their types, characteristics and situation in the world market and information about manufacturers. The production of nanoscale materials such as anticorrosive and intelligent proppants besides proppants with carbon nanotubes is already carried out on a scale of tonnes per year in Belgium, Germany and Asia countries.

  6. Recent Developments in Multiscale and Multiphase Modelling of the Hydraulic Fracturing Process

    Directory of Open Access Journals (Sweden)

    Yong Sheng

    2015-01-01

    Full Text Available Recently hydraulic fracturing of rocks has received much attention not only for its economic importance but also for its potential environmental impact. The hydraulically fracturing technique has been widely used in the oil (EOR and gas (EGR industries, especially in the USA, to extract more oil/gas through the deep rock formations. Also there have been increasing interests in utilising the hydraulic fracturing technique in geological storage of CO2 in recent years. In all cases, the design and implementation of the hydraulic fracturing process play a central role, highlighting the significance of research and development of this technique. However, the uncertainty behind the fracking mechanism has triggered public debates regarding the possible effect of this technique on human health and the environment. This has presented new challenges in the study of the hydraulic fracturing process. This paper describes the hydraulic fracturing mechanism and provides an overview of past and recent developments of the research performed towards better understandings of the hydraulic fracturing and its potential impacts, with particular emphasis on the development of modelling techniques and their implementation on the hydraulic fracturing.

  7. Addresing environmental challenges to shale gas and hydraulic fracturing

    Energy Technology Data Exchange (ETDEWEB)

    Vadillo Fernandez, L.; Rodriguez Gomez, V.; Fernadez Naranjo, F.J.

    2016-07-01

    This article reviews the main issues of unconventional gas extracted by hydraulic fracturing techniques. Topics such as technology, fracturing stages, flowback characterization and alternatives of disposal and reuse, water consumption, physicochemical features of the geological formations, development of the fractures performed by hydraulic fracturing, well flow decline, land use and occupation and induced seismicity are presented, as well as the scientific debate: the potential steps of methane gas and groundwater contamination. (Author)

  8. The Criteria for the Selection of Wells for Hydraulic Fracturing

    Directory of Open Access Journals (Sweden)

    O.V. Salimov

    2017-12-01

    Full Text Available Various methods of selection of wells for hydraulic fracturing are analyzed. It is established that all methods can be divided into three large groups: criteria in the table form of boundary values of parameters, statistical methods of pattern recognition, methods of engineering calculation. The complication or use of additional parameters only leads to a reduction in the number of wells at which hydraulic fracturing is possible. It is shown that the use of reservoir properties of rocks, which are already used by hydraulic fracturing simulators, is not practicable as selection criteria. It is required to include in the selection criteria only those additional factors on which the effectiveness of hydraulic fracturing depends directly.

  9. Characterisation of hydraulically-active fractures in a fractured ...

    African Journals Online (AJOL)

    2015-01-07

    Jan 7, 2015 ... injection and recovery tests were conducted for verification of the ... Keywords: self-potential method, hydraulically-conductive fractures, constant pressure injection and recovery ...... porous media 1: theory of the zeta potential.

  10. Analysis on the Initial Cracking Parameters of Cross-Measure Hydraulic Fracture in Underground Coal Mines

    Directory of Open Access Journals (Sweden)

    Yiyu Lu

    2015-07-01

    Full Text Available Initial cracking pressure and locations are important parameters in conducting cross-measure hydraulic fracturing to enhance coal seam permeability in underground coalmines, which are significantly influenced by in-situ stress and occurrence of coal seam. In this study, stress state around cross-measure fracturing boreholes was analyzed using in-situ stress coordinate transformation, then a mathematical model was developed to evaluate initial cracking parameters of borehole assuming the maximum tensile stress criterion. Subsequently, the influences of in-situ stress and occurrence of coal seams on initial cracking pressure and locations in underground coalmines were analyzed using the proposed model. Finally, the proposed model was verified with field test data. The results suggest that the initial cracking pressure increases with the depth cover and coal seam dip angle. However, it decreases with the increase in azimuth of major principle stress. The results also indicate that the initial cracking locations concentrated in the second and fourth quadrant in polar coordinate, and shifted direction to the strike of coal seam as coal seam dip angle and azimuth of maximum principle stress increase. Field investigation revealed consistent rule with the developed model that the initial cracking pressure increases with the coal seam dip angle. Therefore, the proposed mathematical model provides theoretical insight to analyze the initial cracking parameters during cross-measure hydraulic fracturing for underground coalmines.

  11. Streaming potential modeling in fractured rock: Insights into the identification of hydraulically active fractures

    Science.gov (United States)

    Roubinet, D.; Linde, N.; Jougnot, D.; Irving, J.

    2016-05-01

    Numerous field experiments suggest that the self-potential (SP) geophysical method may allow for the detection of hydraulically active fractures and provide information about fracture properties. However, a lack of suitable numerical tools for modeling streaming potentials in fractured media prevents quantitative interpretation and limits our understanding of how the SP method can be used in this regard. To address this issue, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid flow and associated self-potential problems in fractured rock. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

  12. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    International Nuclear Information System (INIS)

    Canamon, I.; Javier Elorza, F.; Ababou, R.

    2007-01-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB R , for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  13. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    Energy Technology Data Exchange (ETDEWEB)

    Canamon, I.; Javier Elorza, F. [Universidad Politecnica de Madrid, Dept. de Matematica Aplicada y Metodos Informaticas, ETSI Minas (UPM) (Spain); Ababou, R. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 (France)

    2007-07-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB{sup R}, for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  14. Interaction between Hydraulic Fracturing Process and Pre-existing Natural Fractures

    NARCIS (Netherlands)

    Meng, C.

    2010-01-01

    Hydraulic fracturing is employed as a stimulation treatment by the oil and gas industry to enhance the hydro-carbon recoveries. The rationale is that by creating fractures from the wellbore into the surrounding formations, the conductivity between the well and reservoir is significantly increased

  15. Correcting underestimation of optimal fracture length by modeling proppant conductivity variations in hydraulically fractured gas/condensate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Akram, A.H.; Samad, A. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Schlumberger, Houston, TX (United States)

    2006-07-01

    A study was conducted in which a newly developed numerical simulator was used to forecast the productivity of a hydraulically fractured well in a retrograde gas-condensate sandstone reservoir. The effect of condensate dropout was modeled in both the reservoir and the proppant pack. The type of proppant and the stress applied to it are among the factors that determine proppant conductivity in a single-phase flow. Other factors include the high velocity of gas and the presence of liquid in the proppant pack. It was concluded that apparent proppant permeability in a gas condensate reservoir varies along the length of the hydraulic fracture and depends on the distance from the wellbore. It will increase towards the tip of the fracture where liquid ratio and velocity are lower. Apparent proppant permeability also changes with time. Forecasting is most accurate when these conditions are considered in the simulation. There are 2 problems associated with the use of a constant proppant permeability in a gas condensate reservoir. The first relates to the fact that it is impossible to obtain a correct single number that will mimic the drawdown of the real fracture at a particular rate without going through the process of determining the proppant permeability profile in a numerical simulator. The second problem relates to the fact that constant proppant permeability yields an optimal fracture length that is too short. Analytical modeling does not account for these complexities. It was determined that the only way to accurately simulate the behaviour of a hydraulic fracture in a high rate well, is by advanced numerical modeling that considers varying apparent proppant permeability in terms of time and distance along the fracture length. 10 refs., 2 tabs., 16 figs., 1 appendix.

  16. Multiphase flow models for hydraulic fracturing technology

    Science.gov (United States)

    Osiptsov, Andrei A.

    2017-10-01

    The technology of hydraulic fracturing of a hydrocarbon-bearing formation is based on pumping a fluid with particles into a well to create fractures in porous medium. After the end of pumping, the fractures filled with closely packed proppant particles create highly conductive channels for hydrocarbon flow from far-field reservoir to the well to surface. The design of the hydraulic fracturing treatment is carried out with a simulator. Those simulators are based on mathematical models, which need to be accurate and close to physical reality. The entire process of fracture placement and flowback/cleanup can be conventionally split into the following four stages: (i) quasi-steady state effectively single-phase suspension flow down the wellbore, (ii) particle transport in an open vertical fracture, (iii) displacement of fracturing fluid by hydrocarbons from the closed fracture filled with a random close pack of proppant particles, and, finally, (iv) highly transient gas-liquid flow in a well during cleanup. The stage (i) is relatively well described by the existing hydralics models, while the models for the other three stages of the process need revisiting and considerable improvement, which was the focus of the author’s research presented in this review paper. For stage (ii), we consider the derivation of a multi-fluid model for suspension flow in a narrow vertical hydraulic fracture at moderate Re on the scale of fracture height and length and also the migration of particles across the flow on the scale of fracture width. At the stage of fracture cleanaup (iii), a novel multi-continua model for suspension filtration is developed. To provide closure relationships for permeability of proppant packings to be used in this model, a 3D direct numerical simulation of single phase flow is carried out using the lattice-Boltzmann method. For wellbore cleanup (iv), we present a combined 1D model for highly-transient gas-liquid flow based on the combination of multi-fluid and

  17. A Comparison between Deep and Shallow Stress Fields in Korea Using Earthquake Focal Mechanism Inversions and Hydraulic Fracturing Stress Measurements

    Science.gov (United States)

    Lee, Rayeon; Chang, Chandong; Hong, Tae-kyung; Lee, Junhyung; Bae, Seong-Ho; Park, Eui-Seob; Park, Chan

    2016-04-01

    We are characterizing stress fields in Korea using two types of stress data: earthquake focal mechanism inversions (FMF) and hydraulic fracturing stress measurements (HF). The earthquake focal mechanism inversion data represent stress conditions at 2-20 km depths, whereas the hydraulic fracturing stress measurements, mostly conducted for geotechnical purposes, have been carried out at depths shallower than 1 km. We classified individual stress data based on the World Stress Map quality ranking scheme. A total of 20 FMF data were classified into A-B quality, possibly representing tectonic stress fields. A total of 83 HF data out of compiled 226 data were classified into B-C quality, which we use for shallow stress field characterization. The tectonic stress, revealed from the FMF data, is characterized by a remarkable consistency in its maximum stress (σ1) directions in and around Korea (N79±2° E), indicating a quite uniform deep stress field throughout. On the other hand, the shallow stress field, represented by HF data, exhibits local variations in σ1 directions, possibly due to effects of topography and geologic structures such as faults. Nonetheless, there is a general similarity in σ1 directions between deep and shallow stress fields. To investigate the shallow stress field statistically, we follow 'the mean orientation and wavelength analysis' suggested by Reiter et al. (2014). After the stress pattern analysis, the resulting stress points distribute sporadically over the country, not covering the entire region evenly. In the western part of Korea, the shallow σ1directions are generally uniform with their search radius reaching 100 km, where the average stress direction agrees well with those of the deep tectonic stress. We note two noticeable differences between shallow and deep stresses in the eastern part of Korea. First, the shallow σ1 orientations are markedly non-uniform in the southeastern part of Korea with their search radius less than 25 km

  18. Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

    Science.gov (United States)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

    Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

  19. Hydraulic-fracture growth in dipping anisotropic strata as viewed through the surface deformation field

    International Nuclear Information System (INIS)

    Holzhausen, G.R.; Haase, C.S.; Stow, S.H.; Gazonas, G.

    1985-01-01

    In 1983 and 1984 Oak Rdige National Laboratory conducted a series of precision ground deformation measurements before, during, and after the generation of several large hydraulic fractures in a dipping member of the Cambrian Conasauga Shale. Each fracture was produced by the injection of approximately 500,000 L of slurry on a single day. Injection depth was 300 m. Leveling surveys were run several days before and several days after the injections. An array of eight high-precision borehole tiltmeters monitored ground deformations continuously for a period of several weeks. Analysis of the leveling and the tilt measurements revealed surface uplifts as great as 25 mm and tilts of tens of microradians during each injection. Furthermore, partial recovery (subsidence) of the ground took place during the days following an injection, accompanied by shifts in the position of maximum resultant uplift. Interpretation of the tilt measurements is consistent with stable widening and extension of hydraulic fractures with subhorizontal orientations. Comparison of the measured tilt patterns with fracture orientations established from logging of observation wells suggests that shearing parallel to the fracture planes accompanied fracture dilation. This interpretation is supported by measured tilts and ground uplifts that were as much as 100 percent greater than those expected from fracture dilation alone. Models of elastically anisotropic overburden rock do not explain the measured tilt patterns in the absence of shear stresses in the fracture planes. This work represents the first large-scale hydraulic-fracturing experiment in which the possible effects of material anisotropy and fracture-parallel shears have been measured and interpreted

  20. Hydraulic-fracture growth in dipping anisotropic strata as viewed through the surface deformation field

    International Nuclear Information System (INIS)

    Holzhausen, G.R.; Haase, C.S.; Stow, S.H.; Gazonas, G.

    1985-01-01

    In 1983 and 1984 Oak Ridge National Laboratory conducted a series of precision ground deformation measurements before, during, and after the generation of several large hydraulic fractures in a dipping member of the Cambrian Conassauga Shale. Each fracture was produced by the injection of approximately 500,000 liters of slurry on a single day. Injection depth was 300 m. Leveling surveys were run several days before and several days after the injections. An array of eight high-precision borehole tiltmeters monitored ground deformations continuously for a period of several weeks. Analysis of the leveling and the tilt measurements revealed surface uplifts as great as 25 mm and tilts of tens of microradians during each injection. Furthermore, partial recovery (subsidence) of the ground took place during the days following an injection, accompanied by shifts in the position of maximum resultant uplift. Interpretation of the tilt measurements is consistent with stable widening and extension of hydraulic fractures with subhorizontal orientations. Comparison of the measured tilt patterns with fracture orientations established from logging of observation wells suggests that shearing parallel to the fracture planes accompanied fracture dilation. This interpretation is supported by measured tilts and ground uplifts that were as much as 100 percent greater than those expected from fracture dilation alone. Models of elastically anisotropic overburden rock do not explain the measured tilt patterns in the absence of shear stresses in the fracture planes. This work represents the first large-scale hydraulic-fracturing experiment in which the possible effects of material anisotropy and fracture-parallel shears have been measured and interpreted

  1. Numerical investigation on hydraulic fracture cleanup and its impact on the productivity of a gas well with a non-Newtonian fluid model

    Energy Technology Data Exchange (ETDEWEB)

    Friedel, T. [Schlumberger Data and Consulting Services, Sugar Land, TX (United States)

    2006-07-01

    There are many damage mechanisms associated with hydraulically fractured gas wells. These include hydraulic damage caused by invading fluids during the treatment and damage due to the stresses exerted on the fracture face. Damage to the proppant pack can also reduce conductivity and non-Darcy flow. However, these are not the only impacts of impaired productivity in tight-gas reservoirs, which do not respond to hydraulic fracturing as expected. Some sustain a flat production profile or show only a slow increase in production rate for several weeks or months. This is due to poor rock quality, strong stress dependency in permeability, hydraulic and mechanical damage. Another reason for the poor performance is related to the cleanup of the cross-linked fracturing fluid with its non-Newtonian characteristics. This paper presented an improved 3-phase cleanup model for the investigation of polymer gel cleanup. Yield stress was considered according to the Herschel-Bulkley rheology model. The viscosity model is based on the exact analytical solution, including the plug flow zone. According to data in the published literature, half of the gel phase can be recovered. The gel saturation gradually increases towards the fracture tips, thereby lowering the fracture conductivities. The residing gel damages the permeability and porosity of the proppant pack or causes damage to the fracture face, thereby reducing production potential. These results are in agreement with field observations where fracture half-lengths, conductivities and productivity are also lower than expected. Preliminary results suggest that capillary forces and load-water recovery have little influence on gel cleanup. 16 refs., 2 tabs., 17 figs.

  2. Social costs from proximity to hydraulic fracturing in New York State

    International Nuclear Information System (INIS)

    Popkin, Jennifer H.; Duke, Joshua M.; Borchers, Allison M.; Ilvento, Thomas

    2013-01-01

    The study reports data from an economic choice experiment to determine the likely welfare impacts of hydraulic fracturing, in this case using natural gas extracted by hydraulic fracturing for household electricity. Data were collected from an Internet survey of 515 residents of New York State. The welfare analysis indicated that on average households incur a welfare loss from in-state hydraulic fracturing as the source of their electricity. The evidence suggests that households in shale counties bear more costs from HF electricity than households out of shale counties. The average welfare loss is substantive, estimated at 40–46% of average household electric bills in shale counties and 16–20% of bills in counties without shale. The evidence also suggests that relative proximity to HF well sites also increases cost borne by households. -- Highlights: •New York households were surveyed to determine impacts of hydraulic fracturing. •Households on average lose welfare if hydraulic fracturing gas provides their electricity. •The average welfare loss is estimated to be 16–46% of respondents’ electricity bill. •The welfare impacts were heterogeneous, with some predicted to have welfare gain. •Proximity to hydraulic fracturing wells decreases welfare, on average

  3. Insight into subdecimeter fracturing processes during hydraulic fracture experiment in Äspö hard rock laboratory, Sweden

    Science.gov (United States)

    Kwiatek, Grzegorz; Martínez-Garzón, Patricia; Plenkers, Katrin; Leonhardt, Maria; Zang, Arno; Dresen, Georg; Bohnhoff, Marco

    2017-04-01

    We analyze the nano- and picoseismicity recorded during a hydraulic fracturing in-situ experiment performed in Äspö Hard Rock Laboratory, Sweden. The fracturing experiment included six fracture stages driven by three different water injection schemes (continuous, progressive and pulse pressurization) and was performed inside a 28 m long, horizontal borehole located at 410 m depth. The fracturing process was monitored with two different seismic networks covering a wide frequency band between 0.01 Hz and 100000 Hz and included broadband seismometers, geophones, high-frequency accelerometers and acoustic emission sensors. The combined seismic network allowed for detection and detailed analysis of seismicity with moment magnitudes MW<-4 (source sizes approx. on cm scale) that occurred solely during the hydraulic fracturing and refracturing stages. We relocated the seismicity catalog using the double-difference technique and calculated the source parameters (seismic moment, source size, stress drop, focal mechanism and seismic moment tensors). The physical characteristics of induced seismicity are compared to the stimulation parameters and to the formation parameters of the site. The seismic activity varies significantly depending on stimulation strategy with conventional, continuous stimulation being the most seismogenic. We find a systematic spatio-temporal migration of microseismic events (propagation away and towards wellbore injection interval) and temporal transitions in source mechanisms (opening - shearing - collapse) both being controlled by changes in fluid injection pressure. The derived focal mechanism parameters are in accordance with the local stress field orientation, and signify the reactivation of pre-existing rock flaws. The seismicity follows statistical and source scaling relations observed at different scales elsewhere, however, at an extremely low level of seismic efficiency.

  4. Hydraulic Fracture Induced Seismicity During A Multi-Stage Pad Completion in Western Canada: Evidence of Activation of Multiple, Parallel Faults

    Science.gov (United States)

    Maxwell, S.; Garrett, D.; Huang, J.; Usher, P.; Mamer, P.

    2017-12-01

    Following reports of injection induced seismicity in the Western Canadian Sedimentary Basin, regulators have imposed seismic monitoring and traffic light protocols for fracturing operations in specific areas. Here we describe a case study in one of these reservoirs, the Montney Shale in NE British Columbia, where induced seismicity was monitored with a local array during multi-stage hydraulic fracture stimulations on several wells from a single drilling pad. Seismicity primarily occurred during the injection time periods, and correlated with periods of high injection rates and wellhead pressures above fracturing pressures. Sequential hydraulic fracture stages were found to progressively activate several parallel, critically-stressed faults, as illuminated by multiple linear hypocenter patterns in the range between Mw 1 and 3. Moment tensor inversion of larger events indicated a double-couple mechanism consistent with the regional strike-slip stress state and the hypocenter lineations. The critically-stressed faults obliquely cross the well paths which were purposely drilled parallel to the minimum principal stress direction. Seismicity on specific faults started and stopped when fracture initiation points of individual injection stages were proximal to the intersection of the fault and well. The distance ranges when the seismicity occurs is consistent with expected hydraulic fracture dimensions, suggesting that the induced fault slip only occurs when a hydraulic fracture grows directly into the fault and the faults are temporarily exposed to significantly elevated fracture pressures during the injection. Some faults crossed multiple wells and the seismicity was found to restart during injection of proximal stages on adjacent wells, progressively expanding the seismogenic zone of the fault. Progressive fault slip is therefore inferred from the seismicity migrating further along the faults during successive injection stages. An accelerometer was also deployed close

  5. Experience curve for natural gas production by hydraulic fracturing

    International Nuclear Information System (INIS)

    Fukui, Rokuhei; Greenfield, Carl; Pogue, Katie; Zwaan, Bob van der

    2017-01-01

    From 2007 to 2012 shale gas production in the US expanded at an astounding average growth rate of over 50%/yr, and thereby increased nearly tenfold over this short time period alone. Hydraulic fracturing technology, or “fracking”, as well as new directional drilling techniques, played key roles in this shale gas revolution, by allowing for extraction of natural gas from previously unviable shale resources. Although hydraulic fracturing technology had been around for decades, it only recently became commercially attractive for large-scale implementation. As the production of shale gas rapidly increased in the US over the past decade, the wellhead price of natural gas dropped substantially. In this paper we express the relationship between wellhead price and cumulative natural gas output in terms of an experience curve, and obtain a learning rate of 13% for the industry using hydraulic fracturing technology. This learning rate represents a measure for the know-how and skills accumulated thus far by the US shale gas industry. The use of experience curves for renewable energy options such as solar and wind power has allowed analysts, practitioners, and policy makers to assess potential price reductions, and underlying cost decreases, for these technologies in the future. The reasons for price reductions of hydraulic fracturing are fundamentally different from those behind renewable energy technologies – hence they cannot be directly compared – and hydraulic fracturing may soon reach, or maybe has already attained, a lower bound for further price reductions, for instance as a result of its water requirements or environmental footprint. Yet, understanding learning-by-doing phenomena as expressed by an industry-wide experience curve for shale gas production can be useful for strategic planning in the gas sector, as well as assist environmental policy design, and serve more broadly as input for projections of energy system developments. - Highlights: • Hydraulic

  6. Experimental Investigation of Crack Extension Patterns in Hydraulic Fracturing with Shale, Sandstone and Granite Cores

    Directory of Open Access Journals (Sweden)

    Jianming He

    2016-12-01

    Full Text Available Hydraulic fracturing is an important method of reservoir stimulation in the exploitation of geothermal resources, and conventional and unconventional oil and gas resources. In this article, hydraulic fracturing experiments with shale, sandstone cores (from southern Sichuan Basin, and granite cores (from Inner Mongolia were conducted to investigate the different hydraulic fracture extension patterns in these three reservoir rocks. The different reactions between reservoir lithology and pump pressure can be reflected by the pump pressure monitoring curves of hydraulic fracture experiments. An X-ray computer tomography (CT scanner was employed to obtain the spatial distribution of hydraulic fractures in fractured shale, sandstone, and granite cores. From the microscopic and macroscopic observation of hydraulic fractures, different extension patterns of the hydraulic fracture can be analyzed. In fractured sandstone, symmetrical hydraulic fracture morphology could be formed, while some micro cracks were also induced near the injection hole. Although the macroscopic cracks in fractured granite cores are barely observed by naked eye, the results of X-ray CT scanning obviously show the morphology of hydraulic fractures. It is indicated that the typical bedding planes well developed in shale formation play an important role in the propagation of hydraulic fractures in shale cores. The results also demonstrated that heterogeneity influenced the pathway of the hydraulic fracture in granite cores.

  7. Advanced hydraulic fracturing methods to create in situ reactive barriers

    International Nuclear Information System (INIS)

    Murdoch, L.

    1997-01-01

    This article describes the use of hydraulic fracturing to increase permeability in geologic formations where in-situ remedial action of contaminant plumes will be performed. Several in-situ treatment strategies are discussed including the use of hydraulic fracturing to create in situ redox zones for treatment of organics and inorganics. Hydraulic fracturing methods offer a mechanism for the in-situ treatment of gently dipping layers of reactive compounds. Specialized methods using real-time monitoring and a high-energy jet during fracturing allow the form of the fracture to be influenced, such as creation of assymmetric fractures beneath potential sources (i.e. tanks, pits, buildings) that should not be penetrated by boring. Some examples of field applications of this technique such as creating fractures filled with zero-valent iron to reductively dechlorinate halogenated hydrocarbons, and the use of granular activated carbon to adsorb compounds are discussed

  8. Characterizing hydraulic fractures in shale gas reservoirs using transient pressure tests

    Directory of Open Access Journals (Sweden)

    Cong Wang

    2015-06-01

    This work presents an unconventional gas reservoir simulator and its application to quantify hydraulic fractures in shale gas reservoirs using transient pressure data. The numerical model incorporates most known physical processes for gas production from unconventional reservoirs, including two-phase flow of liquid and gas, Klinkenberg effect, non-Darcy flow, and nonlinear adsorption. In addition, the model is able to handle various types and scales of fractures or heterogeneity using continuum, discrete or hybrid modeling approaches under different well production conditions of varying rate or pressure. Our modeling studies indicate that the most sensitive parameter of hydraulic fractures to early transient gas flow through extremely low permeability rock is actually the fracture-matrix contacting area, generated by fracturing stimulation. Based on this observation, it is possible to use transient pressure testing data to estimate the area of fractures generated from fracturing operations. We will conduct a series of modeling studies and present a methodology using typical transient pressure responses, simulated by the numerical model, to estimate fracture areas created or to quantity hydraulic fractures with traditional well testing technology. The type curves of pressure transients from this study can be used to quantify hydraulic fractures in field application.

  9. Database for hydraulically conductive fractures. Update 2009

    International Nuclear Information System (INIS)

    Palmen, J.; Tammisto, E.; Ahokas, H.

    2010-03-01

    Posiva flow logging (PFL) with a 0.5 m test interval and made in 10 cm steps can be used for the determination of the depth of hydraulically conductive fractures. Together with drillhole wall images and fracture data from core logging, PFL provides possibilities to detect individual conductive fractures. In this report, the results of PFL are combined with fracture data on drillholes OL-KR41 - OL-KR48, OL-KR41B - OLKR45B and pilot holes ONK-PH8 - ONK-PH10. In addition, HTU-data measured by 2 m section length and 2 m steps in holes OL-KR39 and OL-KR40 at depths 300-700 m were analyzed and combined with fracture data in a similar way. The conductive fractures were first recognised from PFL data and digital drillhole images and then the fractures from the core logging that correspond to the ones picked from the digital drillhole images were identified. The conductive fractures were primarily recognised in the images based on the openness of fractures or a visible flow in the image. In most of the cases, no tails of flow were seen in the image. In these cases the conductive fractures were recognised in the image based on the openness of fractures and a matching depth. On the basis of the results hydraulically conductive fractures/zones could in most cases be distinguished in the drillhole wall images. An important phase in the work is the calibration of the depth of the image, flow logging and the HTU logging with the sample length. In addition to results of PFL-correlation, Hydraulic Testing Unit (HTU) data measured by 2 m section length and 2 m steps was studied at selected depths for holes OL-KR39, OL-KR40, OL-KR42 and OL-KR45. Due to low HTU section depth accuracy the conducting fractures were successfully correlated with Fracture Data Base (FDB) fractures only in drillholes OL-KR39 and OL-KR40. HTU-data depth matching in these two drillholes was performed using geophysical Single Point Resistance (SPR) data both from geophysical and PFL measurements as a depth

  10. Theoretical and Experimental Investigation of Characteristics of Single Fracture Stress-Seepage Coupling considering Microroughness

    Directory of Open Access Journals (Sweden)

    Shengtong Di

    2017-01-01

    Full Text Available Based on the results of the test among the joint roughness coefficient (JRC of rock fracture, mechanical aperture, and hydraulic aperture proposed by Barton, this paper deduces and proposes a permeability coefficient formula of single fracture stress-seepage coupling considering microroughness by the introduction of effect variables considering the microparticle size and structural morphology of facture surface. Quasi-sandstone fracture of different particle size is made by the laboratory test, and the respective modification is made on the coupled shear-seepage test system of JAW-600 rock. Under this condition, the laboratory test of stress-seepage coupling of fracture of different particle size is carried out. The test results show that, for the different particle-sized fracture surface of the same JRC, the permeability coefficient is different, which means the smaller particle size, the smaller permeability coefficient, and the larger particle size, the larger permeability coefficient; with the increase of cranny hydraulic pressure, the permeability coefficient increases exponentially, and under the same cranny hydraulic pressure, there is relation of power function between the permeability coefficient and normal stress. Meanwhile, according to the theoretical formula, the microroughness coefficient of the fractures with different particle size is obtained by the calculation, and its accuracy and validity are verified by experiments. The theoretical verification values are in good agreement with the measured values.

  11. Evaluation of scale effects on hydraulic characteristics of fractured rock using fracture network model

    International Nuclear Information System (INIS)

    Ijiri, Yuji; Sawada, Atsushi; Uchida, Masahiro; Ishiguro, Katsuhiko; Umeki, Hiroyuki; Sakamoto, Kazuhiko; Ohnishi, Yuzo

    2001-01-01

    It is important to take into account scale effects on fracture geometry if the modeling scale is much larger than the in-situ observation scale. The scale effect on fracture trace length, which is the most scale dependent parameter, is investigated using fracture maps obtained at various scales in tunnel and dam sites. We found that the distribution of fracture trace length follows negative power law distribution in regardless of locations and rock types. The hydraulic characteristics of fractured rock is also investigated by numerical analysis of discrete fracture network (DFN) model where power law distribution of fracture radius is adopted. We found that as the exponent of power law distribution become larger, the hydraulic conductivity of DFN model increases and the travel time in DFN model decreases. (author)

  12. Massive hydraulic fracturing gas stimulation project

    International Nuclear Information System (INIS)

    Appledorn, C.R.; Mann, R.L.

    1977-01-01

    The Rio Blanco Massive Hydraulic Fracturing Project was fielded in 1974 as a joint Industry/ERDA demonstration to test the relative formations that were stimulated by the Rio Blanco Nuclear fracturing experiment. The project is a companion effort to and a continuation of the preceding nuclear stimulation project, which took place in May 1973. 8 figures

  13. The functional potential of microbial communities in hydraulic fracturing source water and produced water from natural gas extraction characterized by metagenomic sequencing.

    Directory of Open Access Journals (Sweden)

    Arvind Murali Mohan

    Full Text Available Microbial activity in produced water from hydraulic fracturing operations can lead to undesired environmental impacts and increase gas production costs. However, the metabolic profile of these microbial communities is not well understood. Here, for the first time, we present results from a shotgun metagenome of microbial communities in both hydraulic fracturing source water and wastewater produced by hydraulic fracturing. Taxonomic analyses showed an increase in anaerobic/facultative anaerobic classes related to Clostridia, Gammaproteobacteria, Bacteroidia and Epsilonproteobacteria in produced water as compared to predominantly aerobic Alphaproteobacteria in the fracturing source water. The metabolic profile revealed a relative increase in genes responsible for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. These results suggest that microbial communities in produced water have an increased genetic ability to handle stress, which has significant implications for produced water management, such as disinfection.

  14. Development of technical means for directional hydraulic fracturing with shearing loading of borehole walls

    Science.gov (United States)

    Rybalkin, LA; Patutin, AV; Patutin, DV

    2018-03-01

    During the process of mineral deposits’ mining one of the most important conditions for safe and economically profitable work of a mining enterprise is obtaining timely information on the stress state of the developed massif. One of the most common methods of remote study of the geomechanical state of the rock massif is hydraulic fracturing of the formation. Directional hydraulic fracturing is a type of the method employed to form cracks across production wells. This technology was most widely used in the gas industry to extract gas from shale formations. In mining, this technology is used to set up filtration screens, to integrate degassing, to soften the hard roof of coal seams. Possible practical appliance is the expansion of the application field of this technology to intensify the production of viscous oil, to leach non-ferrous metals, to create in the rock massif anti-filtration screens for various purposes, as well as to measure stresses acting along the wells.

  15. Laboratory tests of hydraulic fracturing and swell healing

    DEFF Research Database (Denmark)

    Thunbo, Christensen Claes; Foged, Christensen Helle; Foged, Niels

    1998-01-01

    New laboratory test set-ups and test procedures are described - for testing the formation of hydraulically induced fractures as well as the potential for subsequent fracture closurefrom the relase of a swelling potential. The main purpose with the tests is to provide information on fracturing str...

  16. Simulation of quasi-static hydraulic fracture propagation in porous media with XFEM

    Science.gov (United States)

    Juan-Lien Ramirez, Alina; Neuweiler, Insa; Löhnert, Stefan

    2015-04-01

    Hydraulic fracturing is the injection of a fracking fluid at high pressures into the underground. Its goal is to create and expand fracture networks to increase the rock permeability. It is a technique used, for example, for oil and gas recovery and for geothermal energy extraction, since higher rock permeability improves production. Many physical processes take place when it comes to fracking; rock deformation, fluid flow within the fractures, as well as into and through the porous rock. All these processes are strongly coupled, what makes its numerical simulation rather challenging. We present a 2D numerical model that simulates the hydraulic propagation of an embedded fracture quasi-statically in a poroelastic, fully saturated material. Fluid flow within the porous rock is described by Darcy's law and the flow within the fracture is approximated by a parallel plate model. Additionally, the effect of leak-off is taken into consideration. The solid component of the porous medium is assumed to be linear elastic and the propagation criteria are given by the energy release rate and the stress intensity factors [1]. The used numerical method for the spatial discretization is the eXtended Finite Element Method (XFEM) [2]. It is based on the standard Finite Element Method, but introduces additional degrees of freedom and enrichment functions to describe discontinuities locally in a system. Through them the geometry of the discontinuity (e.g. a fracture) becomes independent of the mesh allowing it to move freely through the domain without a mesh-adapting step. With this numerical model we are able to simulate hydraulic fracture propagation with different initial fracture geometries and material parameters. Results from these simulations will also be presented. References [1] D. Gross and T. Seelig. Fracture Mechanics with an Introduction to Micromechanics. Springer, 2nd edition, (2011) [2] T. Belytschko and T. Black. Elastic crack growth in finite elements with minimal

  17. Advanced Hydraulic Fracturing Technology for Unconventional Tight Gas Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; A. Daniel Hill; D. Zhu

    2007-06-19

    The objectives of this project are to develop and test new techniques for creating extensive, conductive hydraulic fractures in unconventional tight gas reservoirs by statistically assessing the productivity achieved in hundreds of field treatments with a variety of current fracturing practices ranging from 'water fracs' to conventional gel fracture treatments; by laboratory measurements of the conductivity created with high rate proppant fracturing using an entirely new conductivity test - the 'dynamic fracture conductivity test'; and by developing design models to implement the optimal fracture treatments determined from the field assessment and the laboratory measurements. One of the tasks of this project is to create an 'advisor' or expert system for completion, production and stimulation of tight gas reservoirs. A central part of this study is an extensive survey of the productivity of hundreds of tight gas wells that have been hydraulically fractured. We have been doing an extensive literature search of the SPE eLibrary, DOE, Gas Technology Institute (GTI), Bureau of Economic Geology and IHS Energy, for publicly available technical reports about procedures of drilling, completion and production of the tight gas wells. We have downloaded numerous papers and read and summarized the information to build a database that will contain field treatment data, organized by geographic location, and hydraulic fracture treatment design data, organized by the treatment type. We have conducted experimental study on 'dynamic fracture conductivity' created when proppant slurries are pumped into hydraulic fractures in tight gas sands. Unlike conventional fracture conductivity tests in which proppant is loaded into the fracture artificially; we pump proppant/frac fluid slurries into a fracture cell, dynamically placing the proppant just as it occurs in the field. From such tests, we expect to gain new insights into some of the critical

  18. Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

    Science.gov (United States)

    Yushi, Zou; Xinfang, Ma; Tong, Zhou; Ning, Li; Ming, Chen; Sihai, Li; Yinuo, Zhang; Han, Li

    2017-09-01

    Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

  19. Understanding hydraulic fracturing: a multi-scale problem

    Science.gov (United States)

    Hyman, J. D.; Jiménez-Martínez, J.; Viswanathan, H. S.; Carey, J. W.; Porter, M. L.; Rougier, E.; Karra, S.; Kang, Q.; Frash, L.; Chen, L.; Lei, Z.; O’Malley, D.; Makedonska, N.

    2016-01-01

    Despite the impact that hydraulic fracturing has had on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nanometres to kilometres. We characterize flow and transport in shale formations across and between these scales using integrated computational, theoretical and experimental efforts/methods. At the field scale, we use discrete fracture network modelling to simulate production of a hydraulically fractured well from a fracture network that is based on the site characterization of a shale gas reservoir. At the core scale, we use triaxial fracture experiments and a finite-discrete element model to study dynamic fracture/crack propagation in low permeability shale. We use lattice Boltzmann pore-scale simulations and microfluidic experiments in both synthetic and shale rock micromodels to study pore-scale flow and transport phenomena, including multi-phase flow and fluids mixing. A mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs. Finally, we discuss the potential of CO2 as an alternative working fluid, both in fracturing and re-stimulating activities, beyond its environmental advantages. This article is part of the themed issue ‘Energy and the subsurface’. PMID:27597789

  20. Percolation Theory and Modern Hydraulic Fracturing

    Science.gov (United States)

    Norris, J. Q.; Turcotte, D. L.; Rundle, J. B.

    2015-12-01

    During the past few years, we have been developing a percolation model for fracking. This model provides a powerful tool for understanding the growth and properties of the complex fracture networks generated during a modern high volume hydraulic fracture stimulations of tight shale reservoirs. The model can also be used to understand the interaction between the growing fracture network and natural reservoir features such as joint sets and faults. Additionally, the model produces a power-law distribution of bursts which can easily be compared to observed microseismicity.

  1. Source Characterization and Seismic Hazard Considerations for Hydraulic Fracture Induced Seismicity

    Science.gov (United States)

    Bosman, K.; Viegas, G. F.; Baig, A. M.; Urbancic, T.

    2015-12-01

    Large microseismic events (M>0) have been shown to be generated during hydraulic fracture treatments relatively frequently. These events are a concern both from public safety and engineering viewpoints. Recent microseismic monitoring projects in the Horn River Basin have utilized both downhole and surface sensors to record events associated with hydraulic fracturing. The resulting hybrid monitoring system has produced a large dataset with two distinct groups of events: large events recorded by the surface network (0structures; small events are concentrated at reservoir depth. Differences in behavior have been observed between these two datasets, leading to conclusions of different underlying processes responsible for the recorded activity. Both datasets show very low seismic efficiency, implying slip weakening and possibly the presence of fluids in the source region. Reservoir events have shear-tensile source mechanisms ranging between tensile opening and tensile closing, and fracture orientations dominated by the rock fabric which are not always optimally oriented to the regional stress field. The observed source characteristics are expected for events driven by increased pore pressure and reduced friction due to lubrication. On average, deep events show higher stress drop, apparent stress, and rupture velocity than reservoir events. This reflects higher confining stresses with depth, and possibly the release of stored energy in the existing zone of weakness. Deep events are dominated by shear failures, but source characteristics are smaller than for naturally occurring tectonic earthquakes of similar magnitude. Most importantly from a seismic hazard perspective, large earthquakes associated with hydrofracing have lower stress drops than tectonic earthquakes, and thus produce smaller peak ground acceleration and less damage on surface. The largest event recorded in this dataset has a moment magnitude of +2.9 and was felt by field crews in the area. The response

  2. Monitoring hydraulic fractures: state estimation using an extended Kalman filter

    International Nuclear Information System (INIS)

    Rochinha, Fernando Alves; Peirce, Anthony

    2010-01-01

    There is considerable interest in using remote elastostatic deformations to identify the evolving geometry of underground fractures that are forced to propagate by the injection of high pressure viscous fluids. These so-called hydraulic fractures are used to increase the permeability in oil and gas reservoirs as well as to pre-fracture ore-bodies for enhanced mineral extraction. The undesirable intrusion of these hydraulic fractures into environmentally sensitive areas or into regions in mines which might pose safety hazards has stimulated the search for techniques to enable the evolving hydraulic fracture geometries to be monitored. Previous approaches to this problem have involved the inversion of the elastostatic data at isolated time steps in the time series provided by tiltmeter measurements of the displacement gradient field at selected points in the elastic medium. At each time step, parameters in simple static models of the fracture (e.g. a single displacement discontinuity) are identified. The approach adopted in this paper is not to regard the sequence of sampled elastostatic data as independent, but rather to treat the data as linked by the coupled elastic-lubrication equations that govern the propagation of the evolving hydraulic fracture. We combine the Extended Kalman Filter (EKF) with features of a recently developed implicit numerical scheme to solve the coupled free boundary problem in order to form a novel algorithm to identify the evolving fracture geometry. Numerical experiments demonstrate that, despite excluding significant physical processes in the forward numerical model, the EKF-numerical algorithm is able to compensate for the un-modeled dynamics by using the information fed back from tiltmeter data. Indeed the proposed algorithm is able to provide reasonably faithful estimates of the fracture geometry, which are shown to converge to the actual hydraulic fracture geometry as the number of tiltmeters is increased. Since the location of

  3. Legal aspects of the hydraulic fracturing method

    Directory of Open Access Journals (Sweden)

    Marta Duraj

    2011-12-01

    Full Text Available In recent months the possibility of extracting shale gas by way of the hydraulic fracturing method in Poland as well as across EU territory has been widely discussed. The European Parliament is to decide whether to ban this method. There are various legal, ecological and economical aspects influencing European legislators. It is hard not to notice how strongly the anti- and pro- hydraulic fracturing lobbies are connected with business. At the moment there are no specific regulations that relate directly to this extraction method, neither in the EU as a whole nor in Poland. However, in Poland a new Geological and Mining Act is supposed to come into force on 1st January 2012, which will regulate natural gas extraction with a view to ensure proper extraction of shale gas in the near future. This article is aimed at showing Polish regulations, both planned and currently in force, as well as the relevant EU law in respect of shale gas extraction. The author would like to emphasize the need to create one coherent legislative regime which would enable entrepreneurs to commence extraction by way of hydraulic fracturing without creating a danger for the environment.

  4. Hydraulic Fracturing and the Environment

    Science.gov (United States)

    Ayatollahy Tafti, T.; Aminzadeh, F.; Jafarpour, B.; de Barros, F.

    2013-12-01

    In this presentation, we highlight two key environmental concerns of hydraulic fracturing (HF), namely induced seismicity and groundwater contamination (GC). We examine the induced seismicity (IS) associated with different subsurface fluid injection and production (SFIP) operations and the key operational parameters of SFIP impacting it. In addition we review the key potential sources for possible water contamination. Both in the case of IS and GC we propose modeling and data analysis methods to quantify the risk factors to be used for monitoring and risk reduction. SFIP include presents a risk in hydraulic fracturing, waste water injection, enhanced oil recovery as well as geothermal energy operations. Although a recent report (NRC 2012) documents that HF is not responsible for most of the induced seismicities, we primarily focus on HF here. We look into vaious operational parameters such as volume and rate of water injection, the direction of the well versus the natural fracture network, the depth of the target and the local stress field and fault system, as well as other geological features. The latter would determine the potential for triggering tectonic related events by small induced seismicity events. We provide the building blocks for IS risk assessment and monitoring. The system we propose will involve adequate layers of complexity based on mapped seismic attributes as well as results from ANN and probabilistic predictive modeling workflows. This leads to a set of guidelines which further defines 'safe operating conditions' and 'safe operating zones' which will be a valuable reference for future SFIP operations. We also illustrate how HF can lead to groundwater aquifer contamination. The source of aquifer contamination can be the hydrocarbon gas or the chemicals used in the injected liquid in the formation. We explore possible pathways of contamination within and discuss the likelihood of contamination from each source. Many of the chemical compounds used

  5. Increasing the production efficiency and reducing the environmental impacts of hydraulic fracturing

    Science.gov (United States)

    Viswanathan, H. S.

    2016-12-01

    Shale gas is an unconventional fossil energy resource profoundly impacting US energy independence and is projected to last for at least 100 years. Production of methane and other hydrocarbons from low permeability shale involves hydraulic fracturing of rock, establishing fracture connectivity, and multiphase fluid-flow and reaction processes all of which are poorly understood. The result is inefficient extraction with many environmental concerns. A science-based capability is required to quantify the governing mesoscale fluid-solid interactions, including microstructural control of fracture patterns and the interaction of engineered fluids with hydrocarbon flow. These interactions depend on coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Determining the key mechanisms in subsurface THMC systems has been impeded due to the lack of sophisticated experimental methods to measure fracture aperture and connectivity, multiphase permeability, and chemical exchange capacities at the high temperature, pressure, and stresses present in the subsurface. In this study, we developed and prototyped the microfluidic and triaxial core flood experiments required to reveal the fundamental dynamics of fracture-fluid interactions. The goal is transformation of hydraulic fracturing from present ad hoc approaches to science-based strategies while safely enhancing production. Specifically, we have demonstrated an integrated experimental/modeling approach that allows for a comprehensive characterization of fluid-solid interactions and develop models that can be used to determine the reservoir operating conditions necessary to gain a degree of control over fracture generation, fluid flow, and interfacial processes over a range of subsurface conditions.

  6. Stress Fractures

    Science.gov (United States)

    Stress fractures Overview Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of ...

  7. Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production (Part I)

    Science.gov (United States)

    Fernandez, C. A.; Jung, H. B.; Shao, H.; Bonneville, A.; Heldebrant, D.; Hoyt, D.; Zhong, L.; Holladay, J.

    2014-12-01

    Cost-effective yet safe creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the viability of enhanced geothermal systems and unconventional oil/gas recovery. Current reservoir stimulation processes utilize brute force (hydraulic pressures in the order of hundreds of bar) to create/propagate fractures in the bedrock. Such stimulation processes entail substantial economic costs ($3.3 million per reservoir as of 2011). Furthermore, the environmental impacts of reservoir stimulation are only recently being determined. Widespread concerns about the environmental contamination have resulted in a number of regulations for fracturing fluids advocating for greener fracturing processes. To reduce the costs and environmental impact of reservoir stimulation, we developed an environmentally friendly and recyclable hydraulic fracturing fluid that undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at temperatures relevant for reservoir stimulation in Enhanced Geothermal System (EGS). The volume expansion, which will specifically occurs at EGS depths of interest, generates an exceptionally large mechanical stress in fracture networks of highly impermeable rock propagating fractures at effective stress an order of magnitude lower than current technology. This paper will concentrate on the presentation of this CO2-triggered expanding hydrogel formed from diluted aqueous solutions of polyallylamine (PAA). Aqueous PAA-CO2 mixtures also show significantly higher viscosities than conventional rheology modifiers at similar pressures and temperatures due to the cross-linking reaction of PAA with CO2, which was demonstrated by chemical speciation studies using in situ HP-HT 13C MAS-NMR. In addtion, PAA shows shear-thinning behavior, a critical advantage for the use of this fluid system in EGS reservoir stimulation. The high pressure/temperature experiments and their results as well

  8. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Science.gov (United States)

    2010-07-01

    ... Fracturing of Coal Beds. 147.52 Section 147.52 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the program...

  9. Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

    Science.gov (United States)

    Langenbruch, C.; Shapiro, S. A.

    2014-12-01

    For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

  10. Estimation of In Situ Stresses with Hydro-Fracturing Tests and a Statistical Method

    Science.gov (United States)

    Lee, Hikweon; Ong, See Hong

    2018-03-01

    At great depths, where borehole-based field stress measurements such as hydraulic fracturing are challenging due to difficult downhole conditions or prohibitive costs, in situ stresses can be indirectly estimated using wellbore failures such as borehole breakouts and/or drilling-induced tensile failures detected by an image log. As part of such efforts, a statistical method has been developed in which borehole breakouts detected on an image log are used for this purpose (Song et al. in Proceedings on the 7th international symposium on in situ rock stress, 2016; Song and Chang in J Geophys Res Solid Earth 122:4033-4052, 2017). The method employs a grid-searching algorithm in which the least and maximum horizontal principal stresses ( S h and S H) are varied, and the corresponding simulated depth-related breakout width distribution as a function of the breakout angle ( θ B = 90° - half of breakout width) is compared to that observed along the borehole to determine a set of S h and S H having the lowest misfit between them. An important advantage of the method is that S h and S H can be estimated simultaneously in vertical wells. To validate the statistical approach, the method is applied to a vertical hole where a set of field hydraulic fracturing tests have been carried out. The stress estimations using the proposed method were found to be in good agreement with the results interpreted from the hydraulic fracturing test measurements.

  11. Water Stress from High-Volume Hydraulic Fracturing Potentially Threatens Aquatic Biodiversity and Ecosystem Services in Arkansas, United States.

    Science.gov (United States)

    Entrekin, Sally; Trainor, Anne; Saiers, James; Patterson, Lauren; Maloney, Kelly; Fargione, Joseph; Kiesecker, Joseph; Baruch-Mordo, Sharon; Konschnik, Katherine; Wiseman, Hannah; Nicot, Jean-Philippe; Ryan, Joseph N

    2018-02-20

    Demand for high-volume, short duration water withdrawals could create water stress to aquatic organisms in Fayetteville Shale streams sourced for hydraulic fracturing fluids. We estimated potential water stress using permitted water withdrawal volumes and actual water withdrawals compared to monthly median, low, and high streamflows. Risk for biological stress was considered at 20% of long-term median and 10% of high- and low-flow thresholds. Future well build-out projections estimated potential for continued stress. Most water was permitted from small, free-flowing streams and "frack" ponds (dammed streams). Permitted 12-h pumping volumes exceeded median streamflow at 50% of withdrawal sites in June, when flows were low. Daily water usage, from operator disclosures, compared to median streamflow showed possible water stress in 7-51% of catchments from June-November, respectively. If 100% of produced water was recycled, per-well water use declined by 25%, reducing threshold exceedance by 10%. Future water stress was predicted to occur in fewer catchments important for drinking water and species of conservation concern due to the decline in new well installations and increased use of recycled water. Accessible and precise withdrawal and streamflow data are critical moving forward to assess and mitigate water stress in streams that experience high-volume withdrawals.

  12. Water stress from high-volume hydraulic fracturing potentially threatens aquatic biodiversity and ecosystem services in Arkansas, United States

    Science.gov (United States)

    Entrekin, Sally; Trainor, Anne; Saiers, James; Patterson, Lauren; Maloney, Kelly O.; Fargione, Joseph; Kiesecker, Joseph M.; Baruch-Mordo, Sharon; Konschnik, Katherine E.; Wiseman, Hannah; Nicot, Jean-Philippe; Ryan, Joseph N.

    2018-01-01

    Demand for high-volume, short duration water withdrawals could create water stress to aquatic organisms in Fayetteville Shale streams sourced for hydraulic fracturing fluids. We estimated potential water stress using permitted water withdrawal volumes and actual water withdrawals compared to monthly median, low, and high streamflows. Risk for biological stress was considered at 20% of long-term median and 10% of high- and low-flow thresholds. Future well build-out projections estimated potential for continued stress. Most water was permitted from small, free-flowing streams and “frack” ponds (dammed streams). Permitted 12-h pumping volumes exceeded median streamflow at 50% of withdrawal sites in June, when flows were low. Daily water usage, from operator disclosures, compared to median streamflow showed possible water stress in 7–51% of catchments from June–November, respectively. If 100% of produced water was recycled, per-well water use declined by 25%, reducing threshold exceedance by 10%. Future water stress was predicted to occur in fewer catchments important for drinking water and species of conservation concern due to the decline in new well installations and increased use of recycled water. Accessible and precise withdrawal and streamflow data are critical moving forward to assess and mitigate water stress in streams that experience high-volume withdrawals.

  13. Application of Phase-Field Techniques to Hydraulically- and Deformation-Induced Fracture.

    Energy Technology Data Exchange (ETDEWEB)

    Culp, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Miller, Nathan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schweizer, Laura [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-08-01

    Phase-field techniques provide an alternative approach to fracture problems which mitigate some of the computational expense associated with tracking the crack interface and the coalescence of individual fractures. The technique is extended to apply to hydraulically driven fracture such as would occur during fracking or CO2 sequestration. Additionally, the technique is applied to a stainless steel specimen used in the Sandia Fracture Challenge. It was found that the phase-field model performs very well, at least qualitatively, in both deformation-induced fracture and hydraulically-induced fracture, though spurious hourglassing modes were observed during coupled hydralically-induced fracture. Future work would include performing additional quantitative benchmark tests and updating the model as needed.

  14. Hydraulic fracture monitoring in hard rock at 410 m depth with an advanced fluid-injection protocol and extensive sensor array

    Science.gov (United States)

    Zang, Arno; Stephansson, Ove; Stenberg, Leif; Plenkers, Katrin; Specht, Sebastian; Milkereit, Claus; Schill, Eva; Kwiatek, Grzegorz; Dresen, Georg; Zimmermann, Günter; Dahm, Torsten; Weber, Michael

    2017-02-01

    In this paper, an underground experiment at the Äspö Hard Rock Laboratory (HRL) is described. Main goal is optimizing geothermal heat exchange in crystalline rock mass at depth by multistage hydraulic fracturing with minimal impact on the environment, that is, seismic events. For this, three arrays with acoustic emission, microseismicity and electromagnetic sensors are installed mapping hydraulic fracture initiation and growth. Fractures are driven by three different water injection schemes (continuous, progressive and pulse pressurization). After a brief review of hydraulic fracture operations in crystalline rock mass at mine scale, the site geology and the stress conditions at Äspö HRL are described. Then, the continuous, single-flow rate and alternative, multiple-flow rate fracture breakdown tests in a horizontal borehole at depth level 410 m are described together with the monitoring networks and sensitivity. Monitoring results include the primary catalogue of acoustic emission hypocentres obtained from four hydraulic fractures with the in situ trigger and localizing network. The continuous versus alternative water injection schemes are discussed in terms of the fracture breakdown pressure, the fracture pattern from impression packer result and the monitoring at the arrays. An example of multistage hydraulic fracturing with several phases of opening and closing of fracture walls is evaluated using data from acoustic emissions, seismic broad-band recordings and electromagnetic signal response. Based on our limited amount of in situ tests (six) and evaluation of three tests in Ävrö granodiorite, in the multiple-flow rate test with progressively increasing target pressure, the acoustic emission activity starts at a later stage in the fracturing process compared to the conventional fracturing case with continuous water injection. In tendency, also the total number and magnitude of acoustic events are found to be smaller in the progressive treatment with

  15. Toxicity Assessment for EPA's Hydraulic Fracturing Study

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset contains data used to develop multiple manuscripts on the toxicity of chemicals associated with the hydraulic fracturing industry. These manuscripts...

  16. Hydraulic Fracturing for Oil and Gas: Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States (Final Report)

    Science.gov (United States)

    This final report provides a review and synthesis of available scientific information concerning the relationship between hydraulic fracturing activities and drinking water resources in the United States. The report is organized around activities in the hydraulic...

  17. Simulating Hydraulic Fracturing: Failure in soft versus hard rocks

    Science.gov (United States)

    Aleksans, J.; Koehn, D.; Toussaint, R.

    2017-12-01

    In this contribution we discuss the dynamic development of hydraulic fractures, their evolution and the resulting seismicity during fluid injection in a coupled numerical model. The model describes coupling between a solid that can fracture dynamically and a compressible fluid that can push back at the rock and open fractures. With a series of numerical simulations we show how the fracture pattern and seismicity change depending on changes in depth, injection rate, Young's Modulus and breaking strength. Our simulations indicate that the Young's Modulus has the largest influence on the fracture dynamics and also the related seismicity. Simulations of rocks with a Young's modulus smaller than 10 GPa show dominant mode I failure and a growth of fracture aperture with a decrease in Young's modulus. Simulations of rocks with a higher Young's modulus than 10 GPa show fractures with a constant aperture and fracture growth that is mainly governed by a growth in crack length and an increasing amount of mode II failure. We propose that two distinct failure regimes are observed in the simulations, above 10 GPa rocks break with a constant critical stress intensity factor whereas below 10 GPa they break reaching a critical cohesion, i.e. a critical tensile strength. These results are very important for the prediction of fracture dynamics and seismicity during fluid injection, especially since we see a transition from one failure regime to another at around 10 GPa, a Young's modulus that lies in the middle of possible values for natural shale rocks.

  18. Hydraulic conductivities of fractures and matrix in Slovenian carbonate aquifers

    Directory of Open Access Journals (Sweden)

    Timotej Verbovšek

    2008-12-01

    Full Text Available Hydraulic conductivities and specific storage coefficients of fractures and matrix in Slovenian carbonate aquifers were determined by Barker’s method for pumping test analysis, based on fractional flow dimension. Values are presented for limestones and mainly for dolomites, and additionally for separate aquifers, divided by age andlithology in several groups. Data was obtained from hydrogeological reports for 397 water wells, and among these, 79 pumping tests were reinterpreted. Hydraulic conductivities of fractures are higher than the hydraulic conductivities of matrix, and the differences are highly statistically significant. Likewise, differences are significant for specific storage, and the values of these coefficients are higher in the matrix. Values of all coefficients vary in separate aquifers, and the differences can be explained by diagenetic effects, crystal size, degree of fracturing, andcarbonate purity. Comparison of the methods, used in the reports, and the Barker’s method (being more suitable for karstic and fractured aquifers, shows that the latter fits real data better.

  19. Study of pore pressure reaction on hydraulic fracturing

    Science.gov (United States)

    Trimonova, Mariia; Baryshnikov, Nikolay; Turuntaev, Sergey; Zenchenko, Evgeniy; Zenchenko, Petr

    2017-04-01

    We represent the results of the experimental study of the hydraulic fracture propagation influence on the fluid pore pressure. Initial pore pressure was induced by injection and production wells. The experiments were carried out according to scaling analysis based on the radial model of the fracture. All required geomechanical and hydrodynamical properties of a sample were derived from the scaling laws. So, gypsum was chosen as a sample material and vacuum oil as a fracturing fluid. The laboratory setup allows us to investigate the samples of cylindrical shape. It can be considered as an advantage in comparison with standard cubic samples, because we shouldn't consider the stress field inhomogeneity induced by the corners. Moreover, we can set 3D-loading by this setting. Also the sample diameter is big enough (43cm) for placing several wells: the fracturing well in the center and injection and production wells on two opposite sides of the central well. The experiment consisted of several stages: a) applying the horizontal pressure; b) applying the vertical pressure; c) water solution injection in the injection well with a constant pressure; d) the steady state obtaining; e) the oil injection in the central well with a constant rate. The pore pressure was recorded in the 15 points along bottom side of the sample during the whole experiment. We observe the pore pressure change during all the time of the experiment. First, the pore pressure changed due to water injection. Then we began to inject oil in the central well. We compared the obtained experimental data on the pore pressure changes with the solution of the 2D single-phase equation of pore-elasticity, and we found significant difference. The variation of the equation parameters couldn't help to resolve the discrepancy. After the experiment, we found that oil penetrated into the sample before and after the fracture initiation. This fact encouraged us to consider another physical process - the oil

  20. The successful use of transverse hydraulic fractures from horizontal wellbores

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, D. G.; Yang, Z.; Rahman, S. S. [New South Wales Univ., NSW (Australia)

    1998-12-31

    Since a significant proportion of the world`s recoverable hydrocarbon resources exist in reservoirs possessing permeabilities of less than one milli-Darcy (mD), some form of permeability enhancement or stimulation is necessary if the hydrocarbons are to be exploited economically. Multi-stage, transversely fractured horizontal wellbores are shown to have the potential to greatly increase production from low permeability formations. To overcome the problems caused by near-wellbore tortuosity, common to wells with multiple fracturing from the same perforated interval, a criterion was devised which predicts the wellbore pressures to initiate secondary multiple transverse hydraulic fractures in close proximity to primary fractures. The criterion, confirmed by laboratory experiments, demonstrates that transversely fractured horizontal wellbores have limited capacities to resist the initiation of multiple fractures from adjacent perforations. This characteristic can be used in designing hydraulic fracture treatments to establish injection pressure limits or threshold pressures, above which additional multiple fractures will initiate and propagate from the wellbore. 23 refs., 1 tab., 10 figs.

  1. Impacts of bedding directions of shale gas reservoirs on hydraulically induced crack propagation

    Directory of Open Access Journals (Sweden)

    Keming Sun

    2016-03-01

    Full Text Available Shale gas reservoirs are different from conventional ones in terms of their bedding architectures, so their hydraulic fracturing rules are somewhat different. In this paper, shale hydraulic fracturing tests were carried out by using the triaxial hydraulic fracturing test system to identify the effects of natural bedding directions on the crack propagation in the process of hydraulic fracturing. Then, the fracture initiation criterion of hydraulic fracturing was prepared using the extended finite element method. On this basis, a 3D hydraulic fracturing computation model was established for shale gas reservoirs. And finally, a series of studies were performed about the effects of bedding directions on the crack propagation created by hydraulic fracturing in shale reservoirs. It is shown that the propagation rules of hydraulically induced fractures in shale gas reservoirs are jointly controlled by the in-situ stress and the bedding plane architecture and strength, with the bedding direction as the main factor controlling the crack propagation directions. If the normal tensile stress of bedding surface reaches its tensile strength after the fracturing, cracks will propagate along the bedding direction, and otherwise vertical to the minimum in-situ stress direction. With the propagating of cracks along bedding surfaces, the included angle between the bedding normal direction and the minimum in-situ stress direction increases, the fracture initiation and propagation pressures increase and the crack areas decrease. Generally, cracks propagate in the form of non-plane ellipsoids. With the injection of fracturing fluids, crack areas and total formation filtration increase and crack propagation velocity decreases. The test results agree well with the calculated crack propagation rules, which demonstrate the validity of the above-mentioned model.

  2. Hydraulic fracturing in well ONM 15, Hassi-Messaoud field

    Energy Technology Data Exchange (ETDEWEB)

    Kerbouc, P

    1968-01-01

    In the Hassi-Messaoud field, hydraulic fracturing has been an extremely difficult problem because of the difficult conditions, and numerous tests run with conventional techniques which have had good results elswhere in the Sahara and worldwide, have given poor results. In Dec. 1967, the CFP(A) succeeded in an experimental fracturing operation on the ONM 15 well, increasing the production from 1 to 11 mU3D/hr. The principal results were: (1) in the sandstone reservoir of Hassi-Messaoud, the fracture was successfully propped with high-strength glass beads; (2) the orientation of the fracture was vertical; and (3) in certain favorable cases, such as wells that were mudded off or had a permeability barrier close to the well, the productivity can be increased by a factor of 10. However, it can still not be stated that hydraulic fracturing will be an economic stimulation method for the Hassi-Messaoud reservoir.

  3. Hydraulic Fracturing and Production Optimization in Eagle Ford Shale Using Coupled Geomechanics and Fluid Flow Model

    Science.gov (United States)

    Suppachoknirun, Theerapat; Tutuncu, Azra N.

    2017-12-01

    With increasing production from shale gas and tight oil reservoirs, horizontal drilling and multistage hydraulic fracturing processes have become a routine procedure in unconventional field development efforts. Natural fractures play a critical role in hydraulic fracture growth, subsequently affecting stimulated reservoir volume and the production efficiency. Moreover, the existing fractures can also contribute to the pressure-dependent fluid leak-off during the operations. Hence, a reliable identification of the discrete fracture network covering the zone of interest prior to the hydraulic fracturing design needs to be incorporated into the hydraulic fracturing and reservoir simulations for realistic representation of the in situ reservoir conditions. In this research study, an integrated 3-D fracture and fluid flow model have been developed using a new approach to simulate the fluid flow and deliver reliable production forecasting in naturally fractured and hydraulically stimulated tight reservoirs. The model was created with three key modules. A complex 3-D discrete fracture network model introduces realistic natural fracture geometry with the associated fractured reservoir characteristics. A hydraulic fracturing model is created utilizing the discrete fracture network for simulation of the hydraulic fracture and flow in the complex discrete fracture network. Finally, a reservoir model with the production grid system is used allowing the user to efficiently perform the fluid flow simulation in tight formations with complex fracture networks. The complex discrete natural fracture model, the integrated discrete fracture model for the hydraulic fracturing, the fluid flow model, and the input dataset have been validated against microseismic fracture mapping and commingled production data obtained from a well pad with three horizontal production wells located in the Eagle Ford oil window in south Texas. Two other fracturing geometries were also evaluated to optimize

  4. Experimental insights into geochemical changes in hydraulically fractured Marcellus Shale

    International Nuclear Information System (INIS)

    Marcon, Virginia; Joseph, Craig; Carter, Kimberly E.; Hedges, Sheila W.; Lopano, Christina L.; Guthrie, George D.; Hakala, J. Alexandra

    2017-01-01

    Hydraulic fracturing applied to organic-rich shales has significantly increased the recoverable volume of methane available for U.S. energy consumption. Fluid-shale reactions in the reservoir may affect long-term reservoir productivity and waste management needs through changes to fracture mineral composition and produced fluid chemical composition. We performed laboratory experiments with Marcellus Shale and lab-generated hydraulic fracturing fluid at elevated pressures and temperatures to evaluate mineral reactions and the release of trace elements into solution. Results from the experiment containing fracturing chemicals show evidence for clay and carbonate dissolution, secondary clay and anhydrite precipitation, and early-stage (24–48 h) fluid enrichment of certain elements followed by depletion in later stages (i.e. Al, Cd, Co, Cr, Cu, Ni, Sc, Zn). Other elements such as As, Fe, Mn, Sr, and Y increased in concentration and remained elevated throughout the duration of the experiment with fracturing fluid. Geochemical modeling of experimental fluid data indicates primary clay dissolution, and secondary formation of smectites and barite, after reaction with fracturing fluid. Changes in aqueous organic composition were observed, indicating organic additives may be chemically transformed or sequestered by the formation after hydraulic fracturing. The NaCl concentrations in our fluids are similar to measured concentrations in Marcellus Shale produced waters, showing that these experiments are representative of reservoir fluid chemistries and can provide insight on geochemical reactions that occur in the field. These results can be applied towards evaluating the evolution of hydraulically-fractured reservoirs, and towards understanding geochemical processes that control the composition of produced water from unconventional shales. - Highlights: • Metal concentrations could be at their peak in produced waters recovered 24–48 after fracturing. • Carbonate

  5. Numerical Study of Critical Role of Rock Heterogeneity in Hydraulic Fracture Propagation

    Energy Technology Data Exchange (ETDEWEB)

    J. Zhou; H. Huang; M. Deo

    2016-03-01

    Log and seismic data indicate that most shale formations have strong heterogeneity. Conventional analytical and semi-analytical fracture models are not enough to simulate the complex fracture propagation in these highly heterogeneous formation. Without considering the intrinsic heterogeneity, predicted morphology of hydraulic fracture may be biased and misleading in optimizing the completion strategy. In this paper, a fully coupling fluid flow and geomechanics hydraulic fracture simulator based on dual-lattice Discrete Element Method (DEM) is used to predict the hydraulic fracture propagation in heterogeneous reservoir. The heterogeneity of rock is simulated by assigning different material force constant and critical strain to different particles and is adjusted by conditioning to the measured data and observed geological features. Based on proposed model, the effects of heterogeneity at different scale on micromechanical behavior and induced macroscopic fractures are examined. From the numerical results, the microcrack will be more inclined to form at the grain weaker interface. The conventional simulator with homogeneous assumption is not applicable for highly heterogeneous shale formation.

  6. Hydraulic Shearing and Hydraulic Jacking Observed during Hydraulic Stimulations in Fractured Geothermal Reservoir in Pohang, Korea

    Science.gov (United States)

    Min, K. B.; Park, S.; Xie, L.; Kim, K. I.; Yoo, H.; Kim, K. Y.; Choi, J.; Yoon, K. S.; Yoon, W. S.; Lee, T. J.; Song, Y.

    2017-12-01

    Enhanced Geothermal System (EGS) relies on sufficient and irreversible enhancement of reservoir permeability through hydraulic stimulation and possibility of such desirable change of permeability is an open question that can undermine the universality of EGS concept. We report results of first hydraulic stimulation campaign conducted in two deep boreholes in fractured granodiorite geothermal reservoir in Pohang, Korea. Borehole PX-1, located at 4.22 km, was subjected to the injection of 3,907 m3 with flow rate of up to 18 kg/s followed by bleeding off of 1,207 m3. The borehole PX-2, located at 4.35 km, was subjected to the injection of 1,970 m3 with flow rate of up to 46 kg/sIn PX-1, a sharp distinct decline of wellhead pressure was observed at around 16 MPa of wellhead pressure which was similar to the predicted injection pressure to induce hydraulic shearing. Injectivity interpretation before and after the hydraulic shearing indicates that permanent increase of permeability was achieved by a factor of a few. In PX-2, however, injectivity was very small and hydraulic shearing was not observed due possibly to the near wellbore damage made by the remedying process of lost circulation such as using lost circulation material during drilling. Flow rate of larger than 40 kg/s was achieved at very high well head pressure of nearly 90 MPa. Hydraulic jacking, that is reversible opening and closure of fracture with change of injection pressure, was clearly observed. Although sharp increase of permeability due to fracture opening was achieved with elevated injection pressure, the increased permeability was reversed with decreased injection pressure.Two contrasting response observed in the same reservoir at two different boreholes which is apart only 600 m apart provide important implication that can be used for the stimulation strategy for EGS.This work was supported by the New and Renewable Energy Technology Development Program of the Korea Institute of Energy Technology

  7. Rio Blanco massive hydraulic fracture: project definition

    International Nuclear Information System (INIS)

    1976-01-01

    A recent Federal Power Commission feasibility study assessed the possibility of economically producing gas from three Rocky Mountain basins. These basins have potentially productive horizons 2,000 to 4,000 feet thick containing an estimated total of 600 trillion cubic feet of gas in place. However, the producing sands are of such low permeability and heterogeneity that conventional methods have failed to develop these basins economically. The Natural Gas Technology Task Force, responsible for preparing the referenced feasibility study, determined that, if effective well stimulation methods for these basins can be developed, it might be possible to recover 40 to 50 percent of the gas in place. The Task Force pointed out two possible underground fracturing methods: Nuclear explosive fracturing, and massive hydraulic fracturing. They argued that once technical viability has been demonstrated, and with adequate economic incentives, there should be no reason why one or even both of these approaches could not be employed, thus making a major contribution toward correcting the energy deficiency of the Nation. A joint Government-industry demonstration program has been proposed to test the relative effectiveness of massive hydraulic fracturing of the same formation and producing horizons that were stimulated by the Rio Blanco nuclear project

  8. The impact of in-situ stress and outcrop-based fracture geometry on hydraulic aperture and upscaled permeability in fractured reservoirs

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    explicitly, we quantify equivalent permeability, i.e. combined matrix and stress-dependent fracture flow. Fracture networks extracted from a large outcropping pavement form the basis of these models. The results show that the angle between fracture strike and σ 1 has a controlling impact on aperture...

  9. The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    Predicting equivalent permeability in fractured reservoirs requires an understanding of the fracture network geometry and apertures. There are different methods for defining aperture, based on outcrop observations (power law scaling), fundamental mechanics (sublinear length-aperture scaling...... in the fraction of open fractures. For the applied stress conditions, Coulomb predicts that 50% of the network is critically stressed, compared to 80% for Barton-Bandis peak shear. The impact of the fracture network on equivalent permeability depends on the matrix hydraulic properties, as in a low...

  10. Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback and Produced Waters

    Science.gov (United States)

    as part of EPA's Hydraulic Fracturing Drinking Water Assessment, EPA is summarizing existing toxicity data for chemicals reported to be used in hydraulic fracturing fluids and/or found in flowback or produced waters from hydraulically fractured wells

  11. An Experimental Investigation of Hydraulic Fracturing in Shale Considering Anisotropy and Using Freshwater and Supercritical CO2

    Directory of Open Access Journals (Sweden)

    Jianming He

    2018-03-01

    Full Text Available The process of hydraulic fracturing makes use of a liquid to fracture reservoir rocks for the exploitation of unconventional resources. Hence, it is vital to understand the processes that produce the fracture networks that occur during hydraulic fracturing. A shale reservoir is one of the largest unconventional resources and it displays obvious anisotropic characteristics due to its inherent sedimentary structures. The viscosity and flow ability of the fracturing fluid plays an important role in this process. We conducted a series of hydraulic fracturing tests on shale cores (from the southern Sichuan Basin using freshwater and supercritical CO2 (SCO2 as fracturing fluids to investigate the different modes of fracture propagation. The pump pressure curves that we obtained during the fracturing experiment show how the shale responded to each of the fracturing fluids. We examined the influence of the anisotropic characteristics on the propagation of hydraulic fractures by conducting a series of hydraulic fracturing experiments on the shale cores using different bedding orientations. The bedding orientation of the shale had a profound influence on the fracture propagation when using either freshwater or a SCO2 fluid. The breakdown pressure of the shale core was affected not only by the bedding orientation but also by the fracturing fluid. A macroscopic observation of the fractures revealed different fracture geometries and propagation patterns. The results demonstrated that the anisotropic structures and the fracturing fluids could influence the path of the hydraulic fracture.

  12. Estimating the hydraulic conductivity of two-dimensional fracture networks

    Science.gov (United States)

    Leung, C. T.; Zimmerman, R. W.

    2010-12-01

    Most oil and gas reservoirs, as well as most potential sites for nuclear waste disposal, are naturally fractured. In these sites, the network of fractures will provide the main path for fluid to flow through the rock mass. In many cases, the fracture density is so high as to make it impractical to model it with a discrete fracture network (DFN) approach. For such rock masses, it would be useful to have recourse to analytical, or semi-analytical, methods to estimate the macroscopic hydraulic conductivity of the fracture network. We have investigated single-phase fluid flow through stochastically generated two-dimensional fracture networks. The centres and orientations of the fractures are uniformly distributed, whereas their lengths follow either a lognormal distribution or a power law distribution. We have considered the case where the fractures in the network each have the same aperture, as well as the case where the aperture of each fracture is directly proportional to the fracture length. The discrete fracture network flow and transport simulator NAPSAC, developed by Serco (Didcot, UK), is used to establish the “true” macroscopic hydraulic conductivity of the network. We then attempt to match this conductivity using a simple estimation method that does not require extensive computation. For our calculations, fracture networks are represented as networks composed of conducting segments (bonds) between nodes. Each bond represents the region of a single fracture between two adjacent intersections with other fractures. We assume that the bonds are arranged on a kagome lattice, with some fraction of the bonds randomly missing. The conductance of each bond is then replaced with some effective conductance, Ceff, which we take to be the arithmetic mean of the individual conductances, averaged over each bond, rather than over each fracture. This is in contrast to the usual approximation used in effective medium theories, wherein the geometric mean is used. Our

  13. Advances in coalbed methane reservoirs using integrated reservoir characterization and hydraulic fracturing in Karaganda coal basin, Kazakhstan

    Science.gov (United States)

    Ivakhnenko, Aleksandr; Aimukhan, Adina; Kenshimova, Aida; Mullagaliyev, Fandus; Akbarov, Erlan; Mullagaliyeva, Lylia; Kabirova, Svetlana; Almukhametov, Azamat

    2017-04-01

    Coalbed methane from Karaganda coal basin is considered to be an unconventional source of energy for the Central and Eastern parts of Kazakhstan. These regions are situated far away from the main traditional sources of oil and gas related to Precaspian petroleum basin. Coalbed methane fields in Karaganda coal basin are characterized by geological and structural complexity. Majority of production zones were characterized by high methane content and extremely low coal permeability. The coal reservoirs also contained a considerable natural system of primary, secondary, and tertiary fractures that were usually capable to accommodate passing fluid during hydraulic fracturing process. However, after closing was often observed coal formation damage including the loss of fluids, migration of fines and higher pressures required to treat formation than were expected. Unusual or less expected reservoir characteristics and values of properties of the coal reservoir might be the cause of the unusual occurred patterns in obtained fracturing, such as lithological peculiarities, rock mechanical properties and previous natural fracture systems in the coals. Based on these properties we found that during the drilling and fracturing of the coal-induced fractures have great sensitivity to complex reservoir lithology and stress profiles, as well as changes of those stresses. In order to have a successful program of hydraulic fracturing and avoid unnecessary fracturing anomalies we applied integrated reservoir characterization to monitor key parameters. In addition to logging data, core sample analysis was applied for coalbed methane reservoirs to observe dependence tiny lithological variations through the magnetic susceptibility values and their relation to permeability together with expected principal stress. The values of magnetic susceptibility were measured by the core logging sensor, which is equipped with the probe that provides volume magnetic susceptibility parameters

  14. Fracture Propagation, Fluid Flow, and Geomechanics of Water-Based Hydraulic Fracturing in Shale Gas Systems and Electromagnetic Geophysical Monitoring of Fluid Migration

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Um, Evan; Moridis, George

    2014-12-01

    We investigate fracture propagation induced by hydraulic fracturing with water injection, using numerical simulation. For rigorous, full 3D modeling, we employ a numerical method that can model failure resulting from tensile and shear stresses, dynamic nonlinear permeability, leak-off in all directions, and thermo-poro-mechanical effects with the double porosity approach. Our numerical results indicate that fracture propagation is not the same as propagation of the water front, because fracturing is governed by geomechanics, whereas water saturation is determined by fluid flow. At early times, the water saturation front is almost identical to the fracture tip, suggesting that the fracture is mostly filled with injected water. However, at late times, advance of the water front is retarded compared to fracture propagation, yielding a significant gap between the water front and the fracture top, which is filled with reservoir gas. We also find considerable leak-off of water to the reservoir. The inconsistency between the fracture volume and the volume of injected water cannot properly calculate the fracture length, when it is estimated based on the simple assumption that the fracture is fully saturated with injected water. As an example of flow-geomechanical responses, we identify pressure fluctuation under constant water injection, because hydraulic fracturing is itself a set of many failure processes, in which pressure consistently drops when failure occurs, but fluctuation decreases as the fracture length grows. We also study application of electromagnetic (EM) geophysical methods, because these methods are highly sensitive to changes in porosity and pore-fluid properties due to water injection into gas reservoirs. Employing a 3D finite-element EM geophysical simulator, we evaluate the sensitivity of the crosswell EM method for monitoring fluid movements in shaly reservoirs. For this sensitivity evaluation, reservoir models are generated through the coupled flow

  15. Laboratory investigation of shale rock to identify fracture propagation in vertical direction to bedding

    Science.gov (United States)

    Peng, Tan; Yan, Jin; Bing, Hou; Yingcao, Zhou; Ruxin, Zhang; Zhi, Chang; Meng, Fan

    2018-06-01

    Affected by beddings and natural fractures, fracture geometry in the vertical plane is complex in shale formation, which differs from a simple fracture in homogeneous sandstone reservoirs. However, the propagation mechanism of a hydraulic fracture in the vertical plane has not been well understood. In this paper, a true tri-axial pressure machine was deployed for shale horizontal well fracturing simulation experiments of shale outcrops. The effects of multiple factors on hydraulic fracture vertical propagation were studied. The results revealed that hydraulic fracture initiation and propagation displayed four basic patterns in the vertical plane of laminated shale formation. A hydraulic fracture would cross the beddings under the high vertical stress difference between a vertical stress and horizontal minimum stress of 12 MPa, while a hydraulic fracture propagates along the beddings under a low vertical stress difference of 3 MPa. Four kinds of fracture geometry, including a single main fracture, a nonplanar fracture, a complex fracture, and a complex fracture network, were observed due to the combined effects of flow rate and viscosity. Due to the influence of binding strength (or cementing strength) on the fracture communication effects between a hydraulic fracture and the beddings, the opening region of the beddings takes the shape of an ellipse.

  16. An unusual stress fracture: Bilateral posterior longitudinal stress fracture of tibia.

    Science.gov (United States)

    Malkoc, Melih; Korkmaz, Ozgur; Ormeci, Tugrul; Oltulu, Ismail; Isyar, Mehmet; Mahirogulları, Mahir

    2014-01-01

    Stress fractures (SF) occur when healthy bone is subjected to cyclic loading, which the normal carrying range capacity is exceeded. Usually, stress fractures occur at the metatarsal bones, calcaneus, proximal or distal tibia and tends to be unilateral. This article presents a 58-year-old male patient with bilateral posterior longitudinal tibial stress fractures. A 58 years old male suffering for persistent left calf pain and decreased walking distance for last one month and after imaging studies posterior longitudinal tibial stress fracture was detected on his left tibia. After six months the patient was admitted to our clinic with the same type of complaints in his right leg. All imaging modalities and blood counts were performed and as a result longitudinal posterior tibial stress fractures were detected on his right tibia. Treatment of tibial stress fracture includes rest and modified activity, followed by a graded return to activity commensurate with bony healing. We have applied the same treatment protocol and our results were acceptable but our follow up time short for this reason our study is restricted for separate stress fractures of the posterior tibia. Although the main localization of tibial stress fractures were unilateral, anterior and transverse pattern, rarely, like in our case, the unusual bilateral posterior localization and longitudinal pattern can be seen. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Coupled Fracture and Flow in Shale in Hydraulic Fracturing

    Science.gov (United States)

    Carey, J. W.; Mori, H.; Viswanathan, H.

    2014-12-01

    Production of hydrocarbon from shale requires creation and maintenance of fracture permeability in an otherwise impermeable shale matrix. In this study, we use a combination of triaxial coreflood experiments and x-ray tomography characterization to investigate the fracture-permeability behavior of Utica shale at in situ reservoir conditions (25-50 oC and 35-120 bars). Initially impermeable shale core was placed between flat anvils (compression) or between split anvils (pure shear) and loaded until failure in the triaxial device. Permeability was monitored continuously during this process. Significant deformation (>1%) was required to generate a transmissive fracture system. Permeability generally peaked at the point of a distinct failure event and then dropped by a factor of 2-6 when the system returned to hydrostatic failure. Permeability was very small in compression experiments (fashion as pressure increased. We also observed that permeability decreased with increasing fluid flow rate indicating that flow did not follow Darcy's Law, possibly due to non-laminar flow conditions, and conformed to Forscheimer's law. The coupled deformation and flow behavior of Utica shale, particularly the large deformation required to initiate flow, indicates the probable importance of activation of existing fractures in hydraulic fracturing and that these fractures can have adequate permeability for the production of hydrocarbon.

  18. Literature survey: Relations between stress change, deformation and transmissivity for fractures and deformation zones based on in situ investigations

    Energy Technology Data Exchange (ETDEWEB)

    Fransson, Aasa (Chalmers Univ. of Technology, Goeteborg (Sweden))

    2009-02-15

    This literature survey is focused upon relations between stress change, deformation and transmissivity for fractures and deformation zones and aims at compiling and commenting on relevant information and references with focus on data from in situ investigations. Main issues to investigate are: - Impact of normal stress change and deformation on transmissivity, for fractures and deformation zones. - Impact of shear stress and displacement on transmissivity, for fractures and deformation zones for different normal load conditions. Considering the line of research within the area, the following steps in the development can be identified. During the 1970's and 1980's, the fundamentals of rock joint deformation were investigated and identification and description of mechanisms were made in the laboratory. In the 1990's, coupling of stress-flow properties of rock joints were made using hydraulic testing to identify and describe the mechanisms in the field. Both individual fractures and deformation zones were of interest. In situ investigations have also been the topic of interest the last ten years. Further identification and description of mechanisms in the field have been made including investigation and description of system of fractures, different types of fractures (interlocked/mated or mismatched/unmated) and how this is coupled to the hydromechanical behavior. In this report, data from in situ investigations are compiled and the parameters considered to be important to link fracture deformation and transmissivity are normal stiffness, k{sub n} and hydraulic aperture, b{sub h}. All data except for those from one site originate from investigations performed in granitic rock. Normal stiffness, k{sub n}, and hydraulic aperture, b{sub h}, are correlated, even though data are scattered. In general, the largest variation is seen for small hydraulic apertures and high normal stiffness. The increasing number of contact points (areas) and fracture filling are

  19. Monitoring Hydraulic Fracturing Using Ground-Based Controlled Source Electromagnetics

    Science.gov (United States)

    Hickey, M. S.; Trevino, S., III; Everett, M. E.

    2017-12-01

    Hydraulic fracturing allows hydrocarbon production in low permeability formations. Imaging the distribution of fluid used to create a hydraulic fracture can aid in the characterization of fracture properties such as extent of plume penetration as well as fracture azimuth and symmetry. This could contribute to improving the efficiency of an operation, for example, in helping to determine ideal well spacing or the need to refracture a zone. A ground-based controlled-source electromagnetics (CSEM) technique is ideal for imaging the fluid due to the change in field caused by the difference in the conductive properties of the fluid when compared to the background. With advances in high signal to noise recording equipment, coupled with a high-power, broadband transmitter we can show hydraulic fracture extent and azimuth with minimal processing. A 3D finite element code is used to model the complete well casing along with the layered subsurface. This forward model is used to optimize the survey design and isolate the band of frequencies with the best response. In the field, the results of the modeling are also used to create a custom pseudorandom numeric (PRN) code to control the frequencies transmitted through a grounded dipole source. The receivers record the surface voltage across two grounded dipoles, one parallel and one perpendicular to the transmitter. The data are presented as the displays of amplitude ratios across several frequencies with the associated spatial information. In this presentation, we show multiple field results in multiple basins in the United States along with the CSEM theory used to create the survey designs.

  20. Single and multiple transverse fracture initiation from horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, D.G.; Rahman, M.M.; Rahman, M.K.; Rahman, S.S. [School of Petroleum Engineering, The University of New South Wales, 2052 Sydney (Australia)

    2002-08-01

    The results of an analytical and experimental study of the initiation of transverse fractures from horizontal wells are presented. Analytical criteria for the initiation of single hydraulic fracture are reviewed, and criterion for initiation of multiple hydraulic fractures was developed by modification of the existing Drucker and Prager criterion for single hydraulic fracture initiation. The developed criterion for multiple fracture initiation was validated by comparisons with actual hydraulic fracture initiation pressures, which were obtained from scaled laboratory experiments and numerical results from boundary element analysis. Other criteria are assessed against the experimental results. Experimentally obtained transverse fracture initiation pressures were found close to longitudinal fracture initiation pressures estimated from maximum tensile stress criterion and Hoek and Brown criterion. One possible explanation of this finding is presented. Results from Drucker and Prager criteria for single and multiple fracture initiation were, however, found closer to experimental values. Therefore, these criteria could be useful to engineers involved with hydraulic fracturing for predicting transverse fracture initiation pressures from horizontal wells drilled parallel to the minimum horizontal in-situ stress.

  1. Effect of Poroelasticity on Hydraulic Fracture Interactions

    DEFF Research Database (Denmark)

    Usui, Tomoya; Salimzadeh, Saeed; Paluszny, Adriana

    2017-01-01

    This study investigates, by performing finite element-based simulations, the influence of fluid leak-off and poroelasticity on growth of multiple hydraulic fractures that initiate from a single horizontal well. In this research, poroelastic deformation of the matrix is coupled with fluid flow in ...

  2. Hydraulic fracturing in anisotropic and heterogeneous rocks

    NARCIS (Netherlands)

    Valliappan, V.; Remmers, J.J.C.; Barnhoorn, A.; Smeulders, D.M.J.

    2017-01-01

    In this paper, we present a two dimensional model for modelling the hydraulic fracture process in anisotropic and heterogeneous rocks. The model is formulated using extended finite elements (XFEM) in combination with Newton-Raphson method for spatial and Euler's implicit scheme for time. The

  3. The disposal of intermediate-level radioactive liquid waste by hydraulic fracturing process

    International Nuclear Information System (INIS)

    Chen Ruilin; Zhou Hanchen; Gao Yuzhu; Qiao Wen; Wang Wentao

    1993-01-01

    The hydraulic fracturing process is characterized by combination of the treatment with the disposal of ILLW (intermediate-level liquid waste). It is of cement solidification in deep geology stratum. First of all, it is necessary to select a suitable disposal site with detailed information on geology and hydrogeology. The process has such advantages as simple, low cost, large capacity of disposal, safe and reliable in technology. It is an attractive process of ILLW. Since 1980's, the research and the concept design of the hydraulic fracturing process have been initiated for disposal of ILLW. It is demonstrated by the field tests. The authors considered that the geological structure near Sichuan Nuclear Fuel Plant fits the disposal of ILLW by the hydraulic fracturing process

  4. The disposal of intermediate-level radioactive liquid waste by hydraulic fracturing process

    Energy Technology Data Exchange (ETDEWEB)

    Ruilin, Chen; Hanchen, Zhou; Yuzhu, Gao; Wen, Qiao; Wentao, Wang [Beijing Inst. of Nuclear Engineering (China)

    1994-12-31

    The hydraulic fracturing process is characterized by combination of the treatment with the disposal of ILLW (intermediate-level liquid waste). It is of cement solidification in deep geology stratum. First of all, it is necessary to select a suitable disposal site with detailed information on geology and hydrogeology. The process has such advantages as simple, low cost, large capacity of disposal, safe and reliable in technology. It is an attractive process of ILLW. Since 1980`s, the research and the concept design of the hydraulic fracturing process have been initiated for disposal of ILLW. It is demonstrated by the field tests. The authors considered that the geological structure near Sichuan Nuclear Fuel Plant fits the disposal of ILLW by the hydraulic fracturing process.

  5. Disposal of waste by hydraulic fracturing

    International Nuclear Information System (INIS)

    Tamura, T.; Weeren, H.

    1984-01-01

    Liquid radioactive waste solutions at the Oak Ridge National Laboratory (ORNL) have been disposed of for nearly 20 years by preparing a slurry, injecting it into bedding plane fractures formed in low-permeability shale, and allowing the slurry to set into a solid. Three major considerations are required for this method: a rock formation that forms horizontal or bedding plane fractures and is highly impermeable, a plant facility that can develop sufficient hydraulic pressure to fracture the rock and to inject the slurry, and a slurry that can be pumped into the fracture and that will set, preferably, into a low-leaching solid. The requirements and desirable conditions of the formation, the process and facility as used for radioactive waste disposal, and the mix formulation and slurry properties that were required for injection and solidification are described. The intent of this paper is to stimulate interest in this technique for possible application to nonnuclear wastes

  6. Review of possible correlations between in situ stress and PFL fracture transmissivity data at Forsmark

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Derek (University of Alberta (United States)); Follin, Sven (SF GeoLogic AB (Sweden))

    2011-11-15

    In laboratory samples, the fracture transmissivity decreases significantly as the confining stress increases. While these experimental relationships are widely accepted and validated on laboratory samples, it is unknown if such relationships exist in situ or if these relationships can be scaled from the centimetre-scale laboratory tests to the metre-scale of in situ fractures. The purpose of this work is to assess the relationship between the structural-hydraulic data gathered in deep, cored boreholes at Forsmark and the in situ stress state acting on the these fractures. In conclusion, there does not appear to be sufficient evidence from these analyses to support the notion that the magnitude of the flow along the fractures at Forsmark is solely controlled by the in situ stress acting on the fracture. This should not be surprising because the majority of the fractures formed more than 1 billion years ago and the current in situ stress state has only been active for the past 12 million years. It is more likely that the transmissivity values are controlled by fracture roughness, open channels within the fracture, fracture stiffness and fracture infilling material

  7. Epidemiology of metatarsal stress fractures versus tibial and femoral stress fractures during elite training.

    Science.gov (United States)

    Finestone, Aharon; Milgrom, Charles; Wolf, Omer; Petrov, Kaloyan; Evans, Rachel; Moran, Daniel

    2011-01-01

    The training of elite infantry recruits takes a year or more. Stress fractures are known to be endemic in their basic training and the clinical presentation of tibial, femoral, and metatarsal stress fractures are different. Stress fracture incidence during the subsequent progressively more demanding training is not known. The study hypothesis was that after an adaptation period, the incidence of stress fractures during the course of 1 year of elite infantry training would fall in spite of the increasingly demanding training. Seventy-six male elite infantry recruits were followed for the development of stress fractures during a progressively more difficult training program composed of basic training (1 to 14 weeks), advanced training (14 to 26 weeks), and unit training (26 to 52 weeks). Subjects were reviewed regularly and those with clinical suspicion of stress fracture were assessed using bone scan and X-rays. The incidence of stress fractures was 20% during basic training, 14% during advanced training and 23% during unit training. There was a statistically significant difference in the incidence of tibial and femoral stress fractures versus metatarsal stress fractures before and after the completion of phase II training at week 26 (p=0.0001). Seventy-eight percent of the stress fractures during phases I and II training were either tibial or femoral, while 91% of the stress fractures in phase III training were metatarsal. Prior participation in ball sports (p=0.02) and greater tibial length (p=0.05) were protective factors for stress fracture. The study hypothesis that after a period of soldier adaptation, the incidence of stress fractures would decrease in spite of the increasingly demanding elite infantry training was found to be true for tibial and femoral fractures after 6 months of training but not for metatarsal stress fractures. Further studies are required to understand the mechanism of this difference but physicians and others treating stress fractures

  8. Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

    Directory of Open Access Journals (Sweden)

    Zhaohui Chong

    2017-07-01

    Full Text Available Hydraulic fracturing is an important method to enhance permeability in oil and gas exploitation projects and weaken hard roofs of coal seams to reduce dynamic disasters, for example, rock burst. It is necessary to fully understand the mechanism of the initiation, propagation, and coalescence of hydraulic fracture network (HFN caused by fluid flow in rock formations. In this study, a coupled hydro-mechanical model was built based on synthetic rock mass (SRM method to investigate the effects of natural fracture (NF density on HFN propagation. Firstly, the geometrical structures of NF obtained from borehole images at the field scale were applied to the model. Secondly, the micro-parameters of the proposed model were validated against the interaction between NF and hydraulic fracture (HF in physical experiments. Finally, a series of numerical simulations were performed to study the mechanism of HFN propagation. In addition, confining pressure ratio (CPR and injection rate were also taken into consideration. The results suggested that the increase of NF density drives the growth of stimulated reservoir volume (SRV, concentration area of injection pressure (CAIP, and the number of cracks caused by NF. The number of tensile cracks caused by rock matrix decrease gradually with the increase of NF density, and the number of shear cracks caused by rock matrix are almost immune to the change of NF density. The propagation orientation of HFN and the breakdown pressure in rock formations are mainly controlled by CPR. Different injection rates would result in a relatively big difference in the gradient of injection pressure, but this difference would be gradually narrowed with the increase of NF density. Natural fracture density is the key factor that influences the percentages of different crack types in HFN, regardless of the value of CPR and injection rate. The proposed model may help predict HFN propagation and optimize fracturing treatment designs in

  9. Executive Summary, Hydraulic Fracturing Study - Draft Assessment 2015

    Science.gov (United States)

    In this Executive Summary of the HF Draft report, EPA highlights the reviews of scientific literature to assess the potential for hydraulic fracturing for oil and gas to change the quality or quantity of drinking water resources.

  10. Assessment of the Impacts of Hydraulic Fracturing at Bakken on Regional Water Resources

    Science.gov (United States)

    Lin, Z.; Lin, T.; Lim, S.; Borders, M.

    2015-12-01

    Unconventional oil production at the Bakken Shale of western North Dakota increased more than ten-fold from 2008 to 2014. Although unconventional oil production uses less water than conventional oil production per unit of energy, the cumulative water needs for unconventional oil production due to multiple drilling and fracturing operations may be locally or temporally significant. We collected and analyzed the data for a total of 8453 horizontal wells developed at Bakken in western North Dakota during 2007-2014. The hydraulic fracturing activities mainly occurred in a core area of four counties, including Dunn, McKenzie, Mountrail, and Williams. The annual total water used for hydraulic fracking in western North Dakota increased from 302 ac-ft in 2007 to 21,605 ac-ft in 2014, by more than 70 times in 8 years. The four-county core area accounted for about 90% of total hydraulic fracturing water use in western North Dakota. Compared to the total water uses of all types, hydraulic fracturing water use in the four-county core area accounted for 0.7% in 2007 and 43.1% in 2014. Statewide, this percentage increased from 0.1% to 6.1% in the same time period. As horizontal drilling and hydraulic fracturing technologies matured for unconventional oil development at Bakken, the total depth and the total length of laterals per well seemed to reach an optimal value in the last four years (2011-2014). However, the number of fracturing stages and the volume of fracking water used per completion are still on the rise. The average water use per well increased from about 1.7 ac-ft in 2007 to 11.4 ac-ft in 2014. Correspondingly, the water intensity (volume of fracking water used per foot of laterals) increased from 67 gallon/ft in 2007 to about 372 gallon/ft 2014. The results helped us better understand the environmental impacts of hydraulic fracturing at Bakken and better manage the water resources in the region.

  11. Test plan: Hydraulic fracturing and hydrologic tests in Marker Beds 139 and 140

    International Nuclear Information System (INIS)

    Wawersik, W.R.; Beauheim, R.L.

    1991-03-01

    Combined hydraulic fracturing and hydrological measurements in this test plan are designed to evaluate the potential influence of fracture formation in anhydrite Marker Beds 139 and 140 on gas pressure in and gas flow from the disposal rooms in the Waste Isolation Pilot Plant with time. The tests have the further purpose of providing comparisons of permeabilities of anhydrite interbeds in an undisturbed (virgin) state and after fracture development and/or opening and dilation of preexisting partially healed fractures. Three sets of combined hydraulic fracturing and hydrological measurements are planned. A set of trial measurements is expected to last four to six weeks. The duration of each subsequent experiment is anticipated to be six to eight weeks

  12. Characterization of the Oriskany and Berea Sandstones: Evaluating Biogeochemical Reactions of Potential Sandstone–Hydraulic Fracturing Fluid Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Verba, Circe [National Energy Technology Lab. (NETL), Albany, OR (United States); Harris, Aubrey [National Energy Technology Lab. (NETL), Albany, OR (United States)

    2016-07-07

    The Marcellus shale, located in the mid-Atlantic Appalachian Basin, has been identified as a source for natural gas and targeted for hydraulic fracturing recovery methods. Hydraulic fracturing is a technique used by the oil and gas industry to access petroleum reserves in geologic formations that cannot be accessed with conventional drilling techniques (Capo et al., 2014). This unconventional technique fractures rock formations that have low permeability by pumping pressurized hydraulic fracturing fluids into the subsurface. Although the major components of hydraulic fracturing fluid are water and sand, chemicals, such as recalcitrant biocides and polyacrylamide, are also used (Frac Focus, 2015). There is domestic concern that the chemicals could reach groundwater or surface water during transport, storage, or the fracturing process (Chapman et al., 2012). In the event of a surface spill, understanding the natural attenuation of the chemicals in hydraulic fracturing fluid, as well as the physical and chemical properties of the aquifers surrounding the spill site, will help mitigate potential dangers to drinking water. However, reports on the degradation pathways of these chemicals are limited in existing literature. The Appalachian Basin Marcellus shale and its surrounding sandstones host diverse mineralogical suites. During the hydraulic fracturing process, the hydraulic fracturing fluids come into contact with variable mineral compositions. The reactions between the fracturing fluid chemicals and the minerals are very diverse. This report: 1) describes common minerals (e.g. quartz, clay, pyrite, and carbonates) present in the Marcellus shale, as well as the Oriskany and Berea sandstones, which are located stratigraphically below and above the Marcellus shale; 2) summarizes the existing literature of the degradation pathways for common hydraulic fracturing fluid chemicals [polyacrylamide, ethylene glycol, poly(diallyldimethylammonium chloride), glutaraldehyde

  13. An integrated extended Kalman filter–implicit level set algorithm for monitoring planar hydraulic fractures

    International Nuclear Information System (INIS)

    Peirce, A; Rochinha, F

    2012-01-01

    We describe a novel approach to the inversion of elasto-static tiltmeter measurements to monitor planar hydraulic fractures propagating within three-dimensional elastic media. The technique combines the extended Kalman filter (EKF), which predicts and updates state estimates using tiltmeter measurement time-series, with a novel implicit level set algorithm (ILSA), which solves the coupled elasto-hydrodynamic equations. The EKF and ILSA are integrated to produce an algorithm to locate the unknown fracture-free boundary. A scaling argument is used to derive a strategy to tune the algorithm parameters to enable measurement information to compensate for unmodeled dynamics. Synthetic tiltmeter data for three numerical experiments are generated by introducing significant changes to the fracture geometry by altering the confining geological stress field. Even though there is no confining stress field in the dynamic model used by the new EKF-ILSA scheme, it is able to use synthetic data to arrive at remarkably accurate predictions of the fracture widths and footprints. These experiments also explore the robustness of the algorithm to noise and to placement of tiltmeter arrays operating in the near-field and far-field regimes. In these experiments, the appropriate parameter choices and strategies to improve the robustness of the algorithm to significant measurement noise are explored. (paper)

  14. An Improved Rate-Transient Analysis Model of Multi-Fractured Horizontal Wells with Non-Uniform Hydraulic Fracture Properties

    Directory of Open Access Journals (Sweden)

    Youwei He

    2018-02-01

    Full Text Available Although technical advances in hydraulically fracturing and drilling enable commercial production from tight reservoirs, oil/gas recovery remains at a low level. Due to the technical and economic limitations of well-testing operations in tight reservoirs, rate-transient analysis (RTA has become a more attractive option. However, current RTA models hardly consider the effect of the non-uniform production on rate decline behaviors. In fact, PLT results demonstrate that production profile is non-uniform. To fill this gap, this paper presents an improved RTA model of multi-fractured horizontal wells (MFHWs to investigate the effects of non-uniform properties of hydraulic fractures (production of fractures, fracture half-length, number of fractures, fracture conductivity, and vertical permeability on rate transient behaviors through the diagnostic type curves. Results indicate obvious differences on the rate decline curves among the type curves of uniform properties of fractures (UPF and non-uniform properties of fractures (NPF. The use of dimensionless production integral derivative curve magnifies the differences so that we can diagnose the phenomenon of non-uniform production. Therefore, it’s significant to incorporate the effects of NPF into the RDA models of MFHWs, and the model proposed in this paper enables us to better evaluate well performance based on long-term production data.

  15. An unusual stress fracture: Bilateral posterior longitudinal stress fracture of tibia

    OpenAIRE

    Malkoc, Melih; Korkmaz, Ozgur; Ormeci, Tugrul; Oltulu, Ismail; Isyar, Mehmet; Mahirogulları, Mahir

    2014-01-01

    INTRODUCTION Stress fractures (SF) occur when healthy bone is subjected to cyclic loading, which the normal carrying range capacity is exceeded. Usually, stress fractures occur at the metatarsal bones, calcaneus, proximal or distal tibia and tends to be unilateral. PRESENTATION OF CASE This article presents a 58-year-old male patient with bilateral posterior longitudinal tibial stress fractures. A 58 years old male suffering for persistent left calf pain and decreased walking distance for las...

  16. Shallow Aquifer Vulnerability From Subsurface Fluid Injection at a Proposed Shale Gas Hydraulic Fracturing Site

    Science.gov (United States)

    Wilson, M. P.; Worrall, F.; Davies, R. J.; Hart, A.

    2017-11-01

    Groundwater flow resulting from a proposed hydraulic fracturing (fracking) operation was numerically modeled using 91 scenarios. Scenarios were chosen to be a combination of hydrogeological factors that a priori would control the long-term migration of fracking fluids to the shallow subsurface. These factors were induced fracture extent, cross-basin groundwater flow, deep low hydraulic conductivity strata, deep high hydraulic conductivity strata, fault hydraulic conductivity, and overpressure. The study considered the Bowland Basin, northwest England, with fracking of the Bowland Shale at ˜2,000 m depth and the shallow aquifer being the Sherwood Sandstone at ˜300-500 m depth. Of the 91 scenarios, 73 scenarios resulted in tracked particles not reaching the shallow aquifer within 10,000 years and 18 resulted in travel times less than 10,000 years. Four factors proved to have a statistically significant impact on reducing travel time to the aquifer: increased induced fracture extent, absence of deep high hydraulic conductivity strata, relatively low fault hydraulic conductivity, and magnitude of overpressure. Modeling suggests that high hydraulic conductivity formations can be more effective barriers to vertical flow than low hydraulic conductivity formations. Furthermore, low hydraulic conductivity faults can result in subsurface pressure compartmentalization, reducing horizontal groundwater flow, and encouraging vertical fluid migration. The modeled worst-case scenario, using unlikely geology and induced fracture lengths, maximum values for strata hydraulic conductivity and with conservative tracer behavior had a particle travel time of 130 years to the base of the shallow aquifer. This study has identified hydrogeological factors which lead to aquifer vulnerability from shale exploitation.

  17. Fully Coupled Geomechanics and Discrete Flow Network Modeling of Hydraulic Fracturing for Geothermal Applications

    Energy Technology Data Exchange (ETDEWEB)

    Fu, P; Johnson, S M; Hao, Y; Carrigan, C R

    2011-01-18

    The primary objective of our current research is to develop a computational test bed for evaluating borehole techniques to enhance fluid flow and heat transfer in enhanced geothermal systems (EGS). Simulating processes resulting in hydraulic fracturing and/or the remobilization of existing fractures, especially the interaction between propagating fractures and existing fractures, represents a critical goal of our project. To this end, we are continuing to develop a hydraulic fracturing simulation capability within the Livermore Distinct Element Code (LDEC), a combined FEM/DEM analysis code with explicit solid-fluid mechanics coupling. LDEC simulations start from an initial fracture distribution which can be stochastically generated or upscaled from the statistics of an actual fracture distribution. During the hydraulic stimulation process, LDEC tracks the propagation of fractures and other modifications to the fracture system. The output is transferred to the Non-isothermal Unsaturated Flow and Transport (NUFT) code to capture heat transfer and flow at the reservoir scale. This approach is intended to offer flexibility in the types of analyses we can perform, including evaluating the effects of different system heterogeneities on the heat extraction rate as well as seismicity associated with geothermal operations. This paper details the basic methodology of our approach. Two numerical examples showing the capability and effectiveness of our simulator are also presented.

  18. Results and conclusions of stress measurements at Stripa

    International Nuclear Information System (INIS)

    Doe, T.W.; Hustrulid, W.A.; Leijon, B.; Ingevald, K.; Strindell, L.; Carlsson, H.

    1982-10-01

    This paper describes the results of stress measurements at Stripa, compares the results obtained by different techniques, and recommends a stress measurement program for a hard rock repository site. The state of stress at the Stripa Mine has been measured both in a 381-m-deep hole drilled from the surface and in holes drilled from the drifts underground. Hydraulic fracturing and several overcoring methods have been used (Lulea triaxial gauge, CSIRO gauge, USBM gauge, Swedish State Power Board deep-hole Leeman triaxial gauge). The results of overcoring and hydraulic fracturing agree well, particularly for the magnitude and orientation of the greatest stress. A recommended program for stress measurement at a repository site would include hydraulic fracturing and deep-hole overcoring in a deep hole drilled from surface, and overcoring (Lulea gauge and USBM gauge) and hydraulic fracturing from holes drilled from underground openings when access is available. Propagation of the hydraulic fractures should be monitored acoustically to determine their location and orientation

  19. Dependence of fracture mechanical and fluid flow properties on fracture roughness and sample size

    International Nuclear Information System (INIS)

    Tsang, Y.W.; Witherspoon, P.A.

    1983-01-01

    A parameter study has been carried out to investigate the interdependence of mechanical and fluid flow properties of fractures with fracture roughness and sample size. A rough fracture can be defined mathematically in terms of its aperture density distribution. Correlations were found between the shapes of the aperture density distribution function and the specific fractures of the stress-strain behavior and fluid flow characteristics. Well-matched fractures had peaked aperture distributions that resulted in very nonlinear stress-strain behavior. With an increasing degree of mismatching between the top and bottom of a fracture, the aperture density distribution broadened and the nonlinearity of the stress-strain behavior became less accentuated. The different aperture density distributions also gave rise to qualitatively different fluid flow behavior. Findings from this investigation make it possible to estimate the stress-strain and fluid flow behavior when the roughness characteristics of the fracture are known and, conversely, to estimate the fracture roughness from an examination of the hydraulic and mechanical data. Results from this study showed that both the mechanical and hydraulic properties of the fracture are controlled by the large-scale roughness of the joint surface. This suggests that when the stress-flow behavior of a fracture is being investigated, the size of the rock sample should be larger than the typical wave length of the roughness undulations

  20. The hydraulic properties of fracture zones and tracer tests with non-reactive elements in Studsvik

    International Nuclear Information System (INIS)

    Klockars, C.-E.; Persson, O.; Landstroem, O.

    1982-04-01

    Tracer technique was applied in a rock formation within the Studsvik Energiteknik area in order to study hydrodynamic properties of discrete fracture zones between boreholes. The two hole method was applied in these studies; a nonreactive tracer is injected in one hole into a fracture zone which is in hydraulic contact with a central pump hole (observation hole). Hydraulic tests and TV inspection were carried out in the fracture zones. Chemical composition of the groundwater was determined. In summary, the following hydraulic properties were found for the fracture zones between the boreholes B1N-B6N and B5N-B6N respectively, under the prevailing conditions: 1) The fracture zones studied consists of a number of transport pathways with different mean transit times, varying from 100 to 1200 hours. 2) The fracture zone between boreholes B1N and B6N has a mean hydraulic conductivity of 6-7 x 10 -5 m/s and the fracture zone between boreholes B5N and B6N, 2 x 10 -4 m/s. 3) The kinematic porosity of the fracture zones studied, calculated as the ratio between the hydraulic conductivity of the rock mass and that of the fracture zone, is 2 x 10 -3 and 5 x 10 -3 , respectively. 4) The roughness factor β, which expresses the ratio between measured and theoretically calculated (plane-parallel) fracture conductivity for the fracture zones studied, is approximately 0.04 and 0.06, respectively. 5) Dispersivity for the flow channels within the fracture zones is of the order of 0.3-0.8 m. 6) The groundwater encountered is a nearly neutral, probably reducing, Na-Ca-HCO 3 water. The results of the tracer tests reveal the following: I-131 is a suitable nonreactive tracer for the test area. A test with simultaneous injection of I-131 and T (tritium) gave comparable breakthrough curves. (Author)

  1. Stress fracture of the femoral neck in a child (stress fracture)

    International Nuclear Information System (INIS)

    Coldwell, D.; Gross, G.W.; Boal, D.K.

    1984-01-01

    Femoral neck stress fracture is extremely rare in childhood. We report a case of femoral neck stress fracture in an 11-year-old girl. Differentials diagnosis and a brief review of the literature follow. (orig.)

  2. EPA Published Research Related to the Hydraulic Fracturing Study

    Science.gov (United States)

    A list of publications that will support the draft assessment report on the potential impacts of hydraulic fracturing on drinking water resources. These publications have undergone peer review through the journal where the paper has been published.

  3. Prediction of tectonic stresses and fracture networks with geomechanical reservoir models

    International Nuclear Information System (INIS)

    Henk, A.; Fischer, K.

    2014-09-01

    This project evaluates the potential of geomechanical Finite Element (FE) models for the prediction of in situ stresses and fracture networks in faulted reservoirs. Modeling focuses on spatial variations of the in situ stress distribution resulting from faults and contrasts in mechanical rock properties. In a first methodological part, a workflow is developed for building such geomechanical reservoir models and calibrating them to field data. In the second part, this workflow was applied successfully to an intensively faulted gas reservoir in the North German Basin. A truly field-scale geomechanical model covering more than 400km 2 was built and calibrated. It includes a mechanical stratigraphy as well as a network of 86 faults. The latter are implemented as distinct planes of weakness and allow the fault-specific evaluation of shear and normal stresses. A so-called static model describes the recent state of the reservoir and, thus, after calibration its results reveal the present-day in situ stress distribution. Further geodynamic modeling work considers the major stages in the tectonic history of the reservoir and provides insights in the paleo stress distribution. These results are compared to fracture data and hydraulic fault behavior observed today. The outcome of this project confirms the potential of geomechanical FE models for robust stress and fracture predictions. The workflow is generally applicable and can be used for modeling of any stress-sensitive reservoir.

  4. Prediction of tectonic stresses and fracture networks with geomechanical reservoir models

    Energy Technology Data Exchange (ETDEWEB)

    Henk, A.; Fischer, K. [TU Darmstadt (Germany). Inst. fuer Angewandte Geowissenschaften

    2014-09-15

    This project evaluates the potential of geomechanical Finite Element (FE) models for the prediction of in situ stresses and fracture networks in faulted reservoirs. Modeling focuses on spatial variations of the in situ stress distribution resulting from faults and contrasts in mechanical rock properties. In a first methodological part, a workflow is developed for building such geomechanical reservoir models and calibrating them to field data. In the second part, this workflow was applied successfully to an intensively faulted gas reservoir in the North German Basin. A truly field-scale geomechanical model covering more than 400km{sup 2} was built and calibrated. It includes a mechanical stratigraphy as well as a network of 86 faults. The latter are implemented as distinct planes of weakness and allow the fault-specific evaluation of shear and normal stresses. A so-called static model describes the recent state of the reservoir and, thus, after calibration its results reveal the present-day in situ stress distribution. Further geodynamic modeling work considers the major stages in the tectonic history of the reservoir and provides insights in the paleo stress distribution. These results are compared to fracture data and hydraulic fault behavior observed today. The outcome of this project confirms the potential of geomechanical FE models for robust stress and fracture predictions. The workflow is generally applicable and can be used for modeling of any stress-sensitive reservoir.

  5. Stress fractures

    International Nuclear Information System (INIS)

    Berquist, T.H.; Cooper, K.L.; Pritchard, D.J.

    1985-01-01

    The diagnosis of a stress fracture should be considered in patients presented with pain after a change in activity, especially if the activity is strenuous and the pain is in the lower extremities. Since evidence of the stress fracture may not be apparent for weeks on routine radiographs, proper use of other imaging techniques will allow an earlier diagnosis. Prompt diagnosis is especially important in the femur, where displacement may occur

  6. Results and conclusions of stress measurements at Stripa

    International Nuclear Information System (INIS)

    Doe, T.W.; Hustrulid, W.A.; Leijon, B.; Ingevald, K.; Strindell, L.; Carlsson, Hans

    1983-01-01

    This paper describes the results of stress measurements at Stripa, compares the results obtained by different techniques, and recommends a stress measurement program for a hard rock repository site. The state of stress at the Stripa Mine has been measured both in a 381m deep hole drilled from the surface and in holes drilled from the drifts underground. The results of overcoring and hydraulic fracturing agree well, particularly for the magnitude and orientation of the greatest stress. A recommended program for stress measurement at a repository site would include hydraulic fracturing and deep-hole overcoring in a deep hole drilled from surface, and ovecoring and hydraulic fracturing from holes drilled from underground openings when access is available. Propagation of the hydraulic fractures should be monitored acoustically to determine their location and orientation

  7. Invasion-Flowback Processes During Hydraulic Fracturing Well Interference

    Science.gov (United States)

    Kenzhekhanov, Shaken; He, Kai; Xu, Liang; Lord, Paul; Lozano, Martin; Neeves, Keith; Yin, Xiaolong

    2017-11-01

    Drainage-imbibition cycles that simulate hydraulic fracturing fluid's invasion and flowback during well interference were investigated using NOA81 microfluidic micromodels. Well interference is quite common in unconventional oil and gas fields. It is not unusual for the fracturing fluid injected into a well to be discovered in a nearby well. Normally, the effect of such interference is considered to be negative, as fracturing fluid will be imbibed into the porous rock and block the flow path of hydrocarbons. However, field data show that some interferences are beneficial, and microfluidic experiments presented in this study show that surfactant in the fracturing fluid may be a reason for the observed positive interference. Two fluid drainage-imbibition cycles were conducted in micromodels. The first cycle simulates fracturing of the old well and the second cycle simulates fluid invasion from the new well into the old well's fracture network. The experimental data show that while most such interferences indeed can cause production loss, when the old well's fracturing fluid does not contain surfactant yet the new well's fracturing fluid does, interference can be positive, as the residual water saturation in the porous medium is effectively reduced by surfactants.

  8. Elucidating hydraulic fracturing impacts on groundwater quality using a regional geospatial statistical modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Burton, Taylour G., E-mail: tgburton@uh.edu [Civil and Environmental Engineering, University of Houston, W455 Engineering Bldg. 2, Houston, TX 77204-4003 (United States); Rifai, Hanadi S., E-mail: rifai@uh.edu [Civil and Environmental Engineering, University of Houston, N138 Engineering Bldg. 1, Houston, TX 77204-4003 (United States); Hildenbrand, Zacariah L., E-mail: zac@informenv.com [Inform Environmental, LLC, Dallas, TX 75206 (United States); Collaborative Laboratories for Environmental Analysis and Remediation, University of Texas at Arlington, Arlington, TX 76019 (United States); Carlton, Doug D., E-mail: doug.carlton@mavs.uta.edu [Collaborative Laboratories for Environmental Analysis and Remediation, University of Texas at Arlington, Arlington, TX 76019 (United States); Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, TX (United States); Fontenot, Brian E., E-mail: brian.fonteno@mavs.uta.edu [Collaborative Laboratories for Environmental Analysis and Remediation, University of Texas at Arlington, Arlington, TX 76019 (United States); Schug, Kevin A., E-mail: kschug@uta.edu [Collaborative Laboratories for Environmental Analysis and Remediation, University of Texas at Arlington, Arlington, TX 76019 (United States); Department of Chemistry & Biochemistry, The University of Texas at Arlington, Arlington, TX (United States)

    2016-03-01

    Hydraulic fracturing operations have been viewed as the cause of certain environmental issues including groundwater contamination. The potential for hydraulic fracturing to induce contaminant pathways in groundwater is not well understood since gas wells are completed while isolating the water table and the gas-bearing reservoirs lay thousands of feet below the water table. Recent studies have attributed ground water contamination to poor well construction and leaks in the wellbore annulus due to ruptured wellbore casings. In this paper, a geospatial model of the Barnett Shale region was created using ArcGIS. The model was used for spatial analysis of groundwater quality data in order to determine if regional variations in groundwater quality, as indicated by various groundwater constituent concentrations, may be associated with the presence of hydraulically fractured gas wells in the region. The Barnett Shale reservoir pressure, completions data, and fracture treatment data were evaluated as predictors of groundwater quality change. Results indicated that elevated concentrations of certain groundwater constituents are likely related to natural gas production in the study area and that beryllium, in this formation, could be used as an indicator variable for evaluating fracturing impacts on regional groundwater quality. Results also indicated that gas well density and formation pressures correlate to change in regional water quality whereas proximity to gas wells, by itself, does not. The results also provided indirect evidence supporting the possibility that micro annular fissures serve as a pathway transporting fluids and chemicals from the fractured wellbore to the overlying groundwater aquifers. - Graphical abstract: A relative increase in beryllium concentrations in groundwater for the Barnett Shale region from 2001 to 2011 was visually correlated with the locations of gas wells in the region that have been hydraulically fractured over the same time period

  9. Elucidating hydraulic fracturing impacts on groundwater quality using a regional geospatial statistical modeling approach

    International Nuclear Information System (INIS)

    Burton, Taylour G.; Rifai, Hanadi S.; Hildenbrand, Zacariah L.; Carlton, Doug D.; Fontenot, Brian E.; Schug, Kevin A.

    2016-01-01

    Hydraulic fracturing operations have been viewed as the cause of certain environmental issues including groundwater contamination. The potential for hydraulic fracturing to induce contaminant pathways in groundwater is not well understood since gas wells are completed while isolating the water table and the gas-bearing reservoirs lay thousands of feet below the water table. Recent studies have attributed ground water contamination to poor well construction and leaks in the wellbore annulus due to ruptured wellbore casings. In this paper, a geospatial model of the Barnett Shale region was created using ArcGIS. The model was used for spatial analysis of groundwater quality data in order to determine if regional variations in groundwater quality, as indicated by various groundwater constituent concentrations, may be associated with the presence of hydraulically fractured gas wells in the region. The Barnett Shale reservoir pressure, completions data, and fracture treatment data were evaluated as predictors of groundwater quality change. Results indicated that elevated concentrations of certain groundwater constituents are likely related to natural gas production in the study area and that beryllium, in this formation, could be used as an indicator variable for evaluating fracturing impacts on regional groundwater quality. Results also indicated that gas well density and formation pressures correlate to change in regional water quality whereas proximity to gas wells, by itself, does not. The results also provided indirect evidence supporting the possibility that micro annular fissures serve as a pathway transporting fluids and chemicals from the fractured wellbore to the overlying groundwater aquifers. - Graphical abstract: A relative increase in beryllium concentrations in groundwater for the Barnett Shale region from 2001 to 2011 was visually correlated with the locations of gas wells in the region that have been hydraulically fractured over the same time period

  10. Coupled Thermo-Hydro-Mechanical-Chemical Modeling of Water Leak-Off Process during Hydraulic Fracturing in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-11-01

    Full Text Available The water leak-off during hydraulic fracturing in shale gas reservoirs is a complicated transport behavior involving thermal (T, hydrodynamic (H, mechanical (M and chemical (C processes. Although many leak-off models have been published, none of the models fully coupled the transient fluid flow modeling with heat transfer, chemical-potential equilibrium and natural-fracture dilation phenomena. In this paper, a coupled thermo-hydro-mechanical-chemical (THMC model based on non-equilibrium thermodynamics, hydrodynamics, thermo-poroelastic rock mechanics, and non-isothermal chemical-potential equations is presented to simulate the water leak-off process in shale gas reservoirs. The THMC model takes into account a triple-porosity medium, which includes hydraulic fractures, natural fractures and shale matrix. The leak-off simulation with the THMC model involves all the important processes in this triple-porosity medium, including: (1 water transport driven by hydraulic, capillary, chemical and thermal osmotic convections; (2 gas transport induced by both hydraulic pressure driven convection and adsorption; (3 heat transport driven by thermal convection and conduction; and (4 natural-fracture dilation considered as a thermo-poroelastic rock deformation. The fluid and heat transport, coupled with rock deformation, are described by a set of partial differential equations resulting from the conservation of mass, momentum, and energy. The semi-implicit finite-difference algorithm is proposed to solve these equations. The evolution of pressure, temperature, saturation and salinity profiles of hydraulic fractures, natural fractures and matrix is calculated, revealing the multi-field coupled water leak-off process in shale gas reservoirs. The influences of hydraulic pressure, natural-fracture dilation, chemical osmosis and thermal osmosis on water leak-off are investigated. Results from this study are expected to provide a better understanding of the

  11. Estimating Hydraulic Conductivities in a Fractured Shale Formation from Pressure Pulse Testing and 3d Modeling

    Science.gov (United States)

    Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.

    2013-12-01

    logging, porosity varies by a factor of 2.5 whilst hydraulic conductivity varies by 2 to 3 orders of magnitude. In addition, a 3D numerical reconstruction of the internal structure of the fault zone inferred from borehole imagery has been built to estimate the permeability tensor variations. First results indicate that hydraulic conductivity values calculated for this structure are 2 to 3 orders of magnitude above those measured in situ. Such high values are due to the imaging method that only takes in to account open fractures of simple geometry (sine waves). Even though improvements are needed to handle more complex geometry, outcomes are promising as the fault damaged zone clearly appears as the highest permeability zone, where stress analysis show that the actual stress state may favor tensile reopening of fractures. Using shale samples cored from the different internal structures of the fault zone, we aim now to characterize the advection and diffusion using laboratory petrophysical tests combined with radial and through-diffusion experiments.

  12. Characterization of the chemicals used in hydraulic fracturing fluids for wells located in the Marcellus Shale Play.

    Science.gov (United States)

    Chen, Huan; Carter, Kimberly E

    2017-09-15

    Hydraulic fracturing, coupled with the advances in horizontal drilling, has been used for recovering oil and natural gas from shale formations and has aided in increasing the production of these energy resources. The large volumes of hydraulic fracturing fluids used in this technology contain chemical additives, which may be toxic organics or produce toxic degradation byproducts. This paper investigated the chemicals introduced into the hydraulic fracturing fluids for completed wells located in Pennsylvania and West Virginia from data provided by the well operators. The results showed a total of 5071 wells, with average water volumes of 5,383,743 ± 2,789,077 gal (mean ± standard deviation). A total of 517 chemicals was introduced into the formulated hydraulic fracturing fluids. Of the 517 chemicals listed by the operators, 96 were inorganic compounds, 358 chemicals were organic species, and the remaining 63 cannot be identified. Many toxic organics were used in the hydraulic fracturing fluids. Some of them are carcinogenic, including formaldehyde, naphthalene, and acrylamide. The degradation of alkylphenol ethoxylates would produce more toxic, persistent, and estrogenic intermediates. Acrylamide monomer as a primary degradation intermediate of polyacrylamides is carcinogenic. Most of the chemicals appearing in the hydraulic fracturing fluids can be removed when adopting the appropriate treatments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. First successful multistage hydraulic fracture monitoring for a horizontal well in Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, Guillermo; Rios, Austreberto; Riano, Juan M. [PEMEX, Mexico, DF (Mexico); Sanchez, Adrian; Bustos, Tomas [Schlumberger, Mexico DF (Mexico)

    2008-07-01

    In their constant effort to increase the production from Chicontepec, PEMEX drilled a multilateral well with three horizontal lateral sections; the intention was to increase the production in comparison with vertical wells. In the second arm of this well four intervals were identified to be fractured, this was a new approach since it was the first occasion that multiple fractures were planned in a horizontal well. An important part of the project was the evaluation of the effectiveness of the hydraulic fracturing. This evaluation was performed by micro seismic monitoring during the treatment. This technology allows the detection of events generated during the fluid injection in the reservoir, with receivers located in a nearby monitoring well. The interpretation of this data allows the identification in 3 D space of the fracture locations. This information is valuable for optimization of subsequent treatments and for planning the field development. The data is recorded in real time and can be used to make decisions during the fracturing operation. In this paper we describe the results of the hydraulic fracturing monitoring performed in four intervals in a horizontal well showing the geometry and direction of each one of the fractures. (author)

  14. QAPP for Hydraulic Fracturing (HF) Surface Spills Data Analysis

    Science.gov (United States)

    This QAPP provides information concerning the analysis of spills associated with hydraulic fracturing. This project is relevant to both the chemical mixing and flowback and produced water stages of the HF water cycle as found in the HF Study Plan.

  15. Assessing the monitoring performance using a synthetic microseismic catalogue for hydraulic fracturing

    Science.gov (United States)

    Ángel López Comino, José; Kriegerowski, Marius; Cesca, Simone; Dahm, Torsten; Mirek, Janusz; Lasocki, Stanislaw

    2016-04-01

    Hydraulic fracturing is considered among the human operations which could induce or trigger seismicity or microseismic activity. The influence of hydraulic fracturing operations is typically expected in terms of weak magnitude events. However, the sensitivity of the rock mass to trigger seismicity varies significantly for different sites and cannot be easily predicted prior to operations. In order to assess the sensitivity of microseismity to hydraulic fracturing operations, we perform a seismic monitoring at a shale gas exploration/exploitation site in the central-western part of the Peribaltic synclise at Pomerania (Poland). The monitoring will be continued before, during and after the termination of hydraulic fracturing operations. The fracking operations are planned in April 2016 at a depth 4000 m. A specific network setup has been installed since summer 2015, including a distributed network of broadband stations and three small-scale arrays. The network covers a region of 60 km2. The aperture of small scale arrays is between 450 and 950 m. So far no fracturing operations have been performed, but seismic data can already be used to assess the seismic noise and background microseismicity, and to investigate and assess the detection performance of our monitoring setup. Here we adopt a recently developed tool to generate a synthetic catalogue and waveform dataset, which realistically account for the expected microseismicity. Synthetic waveforms are generated for a local crustal model, considering a realistic distribution of hypocenters, magnitudes, moment tensors, and source durations. Noise free synthetic seismograms are superposed to real noise traces, to reproduce true monitoring conditions at the different station locations. We estimate the detection probability for different magnitudes, source-receiver distances, and noise conditions. This information is used to estimate the magnitude of completeness at the depth of the hydraulic fracturing horizontal wells

  16. The Multi-Porosity Multi-Permeability and Electrokinetic Natures of Shales and Their Effects in Hydraulic Fracturing of Unconventional Shale Reservoirs

    Science.gov (United States)

    Liu, C.; Hoang, S. K.; Tran, M. H.; Abousleiman, Y. N.

    2013-12-01

    Imaging studies of unconventional shale reservoir rocks have recently revealed the multi-porosity multi-permeability nature of these intricate formations. In particular, the porosity spectrum of shale reservoir rocks often comprises of the nano-porosity in the organic matters, the inter-particle micro-porosity, and the macroscopic porosity of the natural fracture network. Shale is also well-known for its chemically active behaviors, especially shrinking and swelling when exposed to aqueous solutions, as the results of pore fluid exchange with external environment due to the difference in electro-chemical potentials. In this work, the effects of natural fractures and electrokinetic nature of shale on the formation responses during hydraulic fracturing are examined using the dual-poro-chemo-electro-elasticity approach which is a generalization of the classical Biot's poroelastic formulation. The analyses show that the presence of natural fractures can substantially increase the leak-off rate of fracturing fluid into the formation and create a larger region of high pore pressure near the fracture face as shown in Fig.1a. Due to the additional fluid invasion, the naturally fractured shale swells up more and the fracture aperture closes faster compared to an intrinsically low permeability non-fractured shale formation as shown in Fig.1b. Since naturally fractured zones are commonly targeted as pay zones, it is important to account for the faster fracture closing rate in fractured shales in hydraulic fracturing design. Our results also show that the presence of negative fixed charges on the surface of clay minerals creates an osmotic pressure at the interface of the shale and the external fluid as shown in Fig.1c. This additional Donnan-induced pore pressure can result in significant tensile effective stresses and tensile damage in the shale as shown in Fig.1d. The induced tensile damage can exacerbate the problem of proppant embedment resulting in more fracture closure

  17. 77 FR 40354 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft

    Science.gov (United States)

    2012-07-09

    ... through the UIC Class II Program, the well class for oil and gas activities. Geothermal activities are not... inject diesel fuels during hydraulic fracturing related to oil, gas, or geothermal operations must obtain... geothermal activities, the draft guidance only covers hydraulic fracturing using diesel fuels related to oil...

  18. Regulating hydraulic fracturing in shale gas plays: The case of Texas

    International Nuclear Information System (INIS)

    Rahm, Dianne

    2011-01-01

    The ability to economically produce natural gas from unconventional shale gas reservoirs has been made possible recently through the application of horizontal drilling and hydraulic fracturing. This new technique has radically changed the energy future of the United States. The U.S. has shifted from a waning producer of natural gas to a growing producer. The Energy Information Administration forecasts that by 2035 nearly half of U.S. natural gas will come from shale gas. Texas is a major player in these developments. Of the eight states and coastal areas that account for the bulk of U.S. gas, Texas has the largest proved reserves. Texas' Barnett Shale already produces six percent of the continental U.S.' gas and exploration of Texas' other shale gas regions is just beginning. Shale gas production is highly controversial, in part because of environmental concerns. Some U.S. states have put hydraulic fracturing moratoriums in place because of fear of drinking water contamination. The federal government has gotten involved and some states, like Texas, have accused it of overreaching. The contention over shale gas drilling in the U.S. may be a bellwether for other parts of the world that are now moving forward with their own shale gas production. - Highlights: → Shale gas production through hydraulic fracturing and horizontal drilling techniques has transformed natural gas production in the United States and portents to do so for the world. → Hydraulic fracturing is highly controversial in part because of fears of environmental impacts particularly on drinking water resources. → The boom in shale gas production is not likely to be stopped because of the amount of resource available, the need for the resource, and the amount of money to be made from production.

  19. Discourse over a contested technology on Twitter: A case study of hydraulic fracturing.

    Science.gov (United States)

    Hopke, Jill E; Simis, Molly

    2015-10-04

    High-volume hydraulic fracturing, a drilling simulation technique commonly referred to as "fracking," is a contested technology. In this article, we explore discourse over hydraulic fracturing and the shale industry on the social media platform Twitter during a period of heightened public contention regarding the application of the technology. We study the relative prominence of negative messaging about shale development in relation to pro-shale messaging on Twitter across five hashtags (#fracking, #globalfrackdown, #natgas, #shale, and #shalegas). We analyze the top actors tweeting using the #fracking hashtag and receiving @mentions with the hashtag. Results show statistically significant differences in the sentiment about hydraulic fracturing and shale development across the five hashtags. In addition, results show that the discourse on the main contested hashtag #fracking is dominated by activists, both individual activists and organizations. The highest proportion of tweeters, those posting messages using the hashtag #fracking, were individual activists, while the highest proportion of @mention references went to activist organizations. © The Author(s) 2015.

  20. INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    David S. Schechter

    2005-04-27

    This report describes the work performed during the fourth year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificially fractured cores (AFCs) and X-ray CT scanner to examine the physical mechanisms of bypassing in hydraulically fractured reservoirs (HFR) and naturally fractured reservoirs (NFR) that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. In Chapter 1, we worked with DOE-RMOTC to investigate fracture properties in the Tensleep Formation at Teapot Dome Naval Reserve as part of their CO{sub 2} sequestration project. In Chapter 2, we continue our investigation to determine the primary oil recovery mechanism in a short vertically fractured core. Finally in Chapter 3, we report our numerical modeling efforts to develop compositional simulator with irregular grid blocks.

  1. Reducing the environmental impact of hydraulic fracturing through design optimisation of positive displacement pumps

    International Nuclear Information System (INIS)

    Josifovic, Aleksandar; Roberts, Jennifer J.; Corney, Jonathan; Davies, Bruce; Shipton, Zoe K.

    2016-01-01

    The current approach to hydraulic fracturing requires large amounts of industrial hardware to be transported, installed and operated in temporary locations. A significant proportion of this equipment is comprised of the fleet of pumps required to provide the high pressures and flows necessary for well stimulation. Studies have shown that over 90% of the emissions of CO_2 and other pollutants that occur during a hydraulic fracturing operation are associated with these pumps. Pollution and transport concerns are of paramount importance for the emerging hydraulic fracturing industry in Europe, and so it is timely to consider these factors when assessing the design of high pressure pumps for the European resources. This paper gives an overview of the industrial plant required to carry out a hydraulic fracturing operation. This is followed by an analysis of the pump's design space that could result in improved pump efficiency. We find that reducing the plunger diameter and running the pump at higher speeds can increase the overall pump efficiency by up to 4.6%. Such changes to the pump's parameters would results in several environmental benefits beyond the obvious economic gains of lower fuel consumption. The paper concludes with a case study that quantifies these benefits. - Highlights: • We develop a parameterized model of hydraulic fracturing pumps. • We explore performance variation to optimise pump efficiency and performance. • New design could increase pump energy efficiency up to 4.6% and improve reliability. • The new design could also reduce environmental and social impacts of pumping. • This illustrates how optimised mechanical design can lower impacts and cost.

  2. Study of gas production from shale reservoirs with multi-stage hydraulic fracturing horizontal well considering multiple transport mechanisms

    Science.gov (United States)

    Wei, Mingzhen; Liu, Hong

    2018-01-01

    Development of unconventional shale gas reservoirs (SGRs) has been boosted by the advancements in two key technologies: horizontal drilling and multi-stage hydraulic fracturing. A large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in SGRs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the SGRs with MsFHW is influenced by both reservoir conditions and hydraulic fracture properties. However, rare simulation work has been conducted for multi-stage hydraulic fractured SGRs. Most of them use well testing methods, which have too many unrealistic simplifications and assumptions. Also, no systematical work has been conducted considering all reasonable transport mechanisms. And there are very few works on sensitivity studies of uncertain parameters using real parameter ranges. Hence, a detailed and systematic study of reservoir simulation with MsFHW is still necessary. In this paper, a dual porosity model was constructed to estimate the effect of parameters on shale gas production with MsFHW. The simulation model was verified with the available field data from the Barnett Shale. The following mechanisms have been considered in this model: viscous flow, slip flow, Knudsen diffusion, and gas desorption. Langmuir isotherm was used to simulate the gas desorption process. Sensitivity analysis on SGRs’ production performance with MsFHW has been conducted. Parameters influencing shale gas production were classified into two categories: reservoir parameters including matrix permeability, matrix porosity; and hydraulic fracture parameters including hydraulic fracture spacing, and fracture half-length. Typical ranges of matrix parameters have been reviewed. Sensitivity analysis have been conducted to analyze the effect of the above factors on the production performance of SGRs. Through comparison, it can be found that hydraulic fracture

  3. Hydraulic Parameter Generation Technique Using a Discrete Fracture Network with Bedrock Heterogeneity in Korea

    Directory of Open Access Journals (Sweden)

    Jae-Yeol Cheong

    2017-12-01

    Full Text Available In instances of damage to engineered barriers containing nuclear waste material, surrounding bedrock is a natural barrier that retards radionuclide movement by way of adsorption and delay due to groundwater flow through highly tortuous fractured rock pathways. At the Gyeongju nuclear waste disposal site, groundwater mainly flows through granitic and sedimentary rock fractures. Therefore, to understand the nuclide migration path, it is necessary to understand discrete fracture networks based on heterogeneous fracture orientations, densities, and size characteristics. In this study, detailed heterogeneous fracture distribution, including the density and orientation of the fractures, was considered for a region that has undergone long periods of change from various geological activities at and around the Gyeongju site. A site-scale discrete fracture network (DFN model was constructed taking into account: (i regional fracture heterogeneity constrained by a multiple linear regression analysis of fracture intensity on faults and electrical resistivity; and (ii the connectivity of conductive fractures having fracture hydraulic parameters, using transient flow simulation. Geometric and hydraulic heterogeneity of the DFN was upscaled into equivalent porous media for flow and transport simulation for a large-scale model.

  4. Approaching a universal scaling relationship between fracture stiffness and fluid flow

    Science.gov (United States)

    Pyrak-Nolte, Laura J.; Nolte, David D.

    2016-02-01

    A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites.

  5. Experience curve for natural gas production by hydraulic fracturing

    NARCIS (Netherlands)

    Fukui, R.; Greenfield, C.; Pogue, K.; van der Zwaan, B.

    From 2007 to 2012 shale gas production in the US expanded at an astounding average growth rate of over 50yr, and thereby increased nearly tenfold over this short time period alone. Hydraulic fracturing technology, or ``fracking'', as well as new directional drilling techniques, played key roles in

  6. Interwell tracer analyses of a hydraulically fractured granitic geothermal reservoir

    International Nuclear Information System (INIS)

    Tester, J.W.; Potter, R.M.; Bivins, R.L.

    1979-01-01

    Field experiments using fluorescent dye and radioactive tracers (Br 82 and I 131 ) have been employed to characterize a hot, low-matrix permeability, hydraulically-fractured granitic reservoir at depths of 2440 to 2960 m (8000 to 9700 ft). Tracer profiles and residence time distributions have been used to delineate changes in the fracture system, particularly in diagnosing pathological flow patterns and in identifying new injection and production zones. The effectiveness of one- and two-dimensional theoretical dispersion models utilizing single and multiple porous, fractured zones with velocity and formation dependent effects are discussed with respect to actual field data

  7. Coupled hydro-thermo-mechanical modeling of hydraulic fracturing in quasi-brittle rocks using BPM-DEM

    Directory of Open Access Journals (Sweden)

    Ingrid Tomac

    2017-02-01

    Full Text Available This paper presents an improved understanding of coupled hydro-thermo-mechanical (HTM hydraulic fracturing of quasi-brittle rock using the bonded particle model (BPM within the discrete element method (DEM. BPM has been recently extended by the authors to account for coupled convective–conductive heat flow and transport, and to enable full hydro-thermal fluid–solid coupled modeling. The application of the work is on enhanced geothermal systems (EGSs, and hydraulic fracturing of hot dry rock (HDR is studied in terms of the impact of temperature difference between rock and a flowing fracturing fluid. Micro-mechanical investigation of temperature and fracturing fluid effects on hydraulic fracturing damage in rocks is presented. It was found that fracture is shorter with pronounced secondary microcracking along the main fracture for the case when the convective–conductive thermal heat exchange is considered. First, the convection heat exchange during low-viscosity fluid infiltration in permeable rock around the wellbore causes significant rock cooling, where a finger-like fluid infiltration was observed. Second, fluid infiltration inhibits pressure rise during pumping and delays fracture initiation and propagation. Additionally, thermal damage occurs in the whole area around the wellbore due to rock cooling and cold fluid infiltration. The size of a damaged area around the wellbore increases with decreasing fluid dynamic viscosity. Fluid and rock compressibility ratio was found to have significant effect on the fracture propagation velocity.

  8. Ambient Seismic Imaging of Hydraulically Active Fractures at km Depths

    Science.gov (United States)

    Malin, P. E.; Sicking, C.

    2017-12-01

    Streaming Depth Images of ambient seismic signals using numerous, densely-distributed, receivers have revealed their connection to hydraulically active fractures at 0.5 to 5 km depths. Key for this type of imaging is very high-fold stacking over both multiple receives and periods of a few hours. Also important is suppression of waveforms from fixed, repeating sources such as pumps, generators, and traffic. A typical surface-based ambient SDI survey would use a 3D seismic receiver grid. It would have 1,000 to 4,000 uniformly distributed receivers at a density of 50/km2over the target. If acquired by borehole receivers buried 100 m deep, the density can be dropped by an order of magnitude. We show examples of the acquisition and signal processing scenarios used to produce the ambient images. (Sicking et al., SEG Interpretation, Nov 2017.) While the fracture-fluid source connection of SDI has been verified by drilling and various types of hydraulic tests, the precise nature of the signal's origin is not clear. At the current level of observation, the signals do not have identifiable phases, but can be focused using P wave velocities. Suggested sources are resonances of pressures fluctuations in the fractures, or small, continuous, slips on fractures surfaces. In either case, it appears that the driving mechanism is tectonic strain in an inherently unstable crust. Solid earth tides may enhance these strains. We illustrate the value of the ambient SDI method in its industrial application by showing case histories from energy industry and carbon-capture-sequestration projects. These include ambient images taken before, during, and after hydraulic treatments in un-conventional reservoirs. The results show not only locations of active fractures, but also their time responses to stimulation and production. Time-lapse ambient imaging can forecast and track events such as well interferences and production changes that can result from nearby treatments.

  9. Numerical simulation of hydraulic fracturing and associated microseismicity using finite-discrete element method

    Directory of Open Access Journals (Sweden)

    Qi Zhao

    2014-12-01

    Full Text Available Hydraulic fracturing (HF technique has been extensively used for the exploitation of unconventional oil and gas reservoirs. HF enhances the connectivity of less permeable oil and gas-bearing rock formations by fluid injection, which creates an interconnected fracture network and increases the hydrocarbon production. Meanwhile, microseismic (MS monitoring is one of the most effective approaches to evaluate such stimulation process. In this paper, the combined finite-discrete element method (FDEM is adopted to numerically simulate HF and associated MS. Several post-processing tools, including frequency-magnitude distribution (b-value, fractal dimension (D-value, and seismic events clustering, are utilized to interpret numerical results. A non-parametric clustering algorithm designed specifically for FDEM is used to reduce the mesh dependency and extract more realistic seismic information. Simulation results indicated that at the local scale, the HF process tends to propagate following the rock mass discontinuities; while at the reservoir scale, it tends to develop in the direction parallel to the maximum in-situ stress.

  10. FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS

    Science.gov (United States)

    Hydraulic fracturing, a method of increasing fluid flow within the subsurface, should improve the effectiveness of several remedial techniques, including pump and treat, vapor extraction, bio-remediation, and soil-flushing. he technique is widely used to increase the yields of oi...

  11. Stress fractures in athletes

    International Nuclear Information System (INIS)

    Kirschberger, R.; Henning, A.; Graff, K.H.

    1984-01-01

    The early exclusion of the presence of a stress fracture may be decisive for the success of an athlete. Scintigraphy with a bone-seeking radiopharmaceutical is suitable for the early detection of stress lesions. Of 30 athletes, fractures were demonstrated in 17 whereas in 6 they were excluded. We found most fractures in the tarsal bones such as os naviculare pedis, ossa cuneiformia and talus. The type of sport engaged in appears to be an important factor in determining the location of the fracture. Scintiphotos were taken in several views using region of interest techniques and two phase-scintigraphy. This method is considered to be useful for localization and follow-up of skeletal stress lesions as well as for differential diagnosis. (orig.) [de

  12. Stress fractures in athletes

    Energy Technology Data Exchange (ETDEWEB)

    Kirschberger, R; Henning, A; Graff, K H

    1984-12-01

    The early exclusion of the presence of a stress fracture may be decisive for the success of an athlete. Scintigraphy with a bone-seeking radiopharmaceutical is suitable for the early detection of stress lesions. Of 30 athletes, fractures were demonstrated in 17 whereas in 6 they were excluded. We found most fractures in the tarsal bones such as os naviculare pedis, ossa cuneiformia and talus. The type of sport engaged in appears to be an important factor in determining the location of the fracture. Scintiphotos were taken in several views using region of interest techniques and two phase-scintigraphy. This method is considered to be useful for localization and follow-up of skeletal stress lesions as well as for differential diagnosis.

  13. Observation of ground deformation associated with hydraulic fracturing and seismicity in the Western Canadian Sedimentary Basin

    Science.gov (United States)

    Kubanek, J.; Liu, Y.; Harrington, R. M.; Samsonov, S.

    2017-12-01

    In North America, the number of induced earthquakes related to fluid injection due to the unconventional recovery of oil and gas resources has increased significantly within the last five years. Recent studies demonstrate that InSAR is an effective tool to study surface deformation due to large-scale wastewater injection, and highlight the value of surface deformation monitoring with respect to understanding evolution of pore pressure and stress at depth - vital parameters to forecast fault reactivation, and thus, induced earthquakes. In contrast to earthquakes related to the injection of large amounts of wastewater, seismic activity related to the hydraulic fracturing procedure itself was, until recently, considered to play a minor role without significant hazard. In the Western Canadian Sedimentary Basin (WCSB), however, Mw>4 earthquakes have recently led to temporary shutdown of industrial injection activity, causing multi-million dollar losses to operators and raising safety concerns with the local population. Recent studies successfully utilize seismic data and modeling to link seismic activity with hydraulic fracturing in the WCSB. Although the study of surface deformation is likely the most promising tool for monitoring integrity of a well and to derive potential signatures prior to moderate or large induced events, InSAR has, to date, not been utilized to detect surface deformation related to hydraulic fracturing and seismicity. We therefore plan to analyze time-series of SAR data acquired between 1991 to present over two target sites in the WCSB that will enable the study of long- and short-term deformation. Since the conditions for InSAR are expected to be challenging due to spatial and temporal decorrelation, we have designed corner reflectors that will be installed at one target site to improve interferometric performance. The corner reflectors will be collocated with broadband seismometers and Trimble SeismoGeodetic Systems that simultaneously measure

  14. Influence of Concentration and Salinity on the Biodegradability of Organic Additives in Hydraulic Fracturing Fluid

    Science.gov (United States)

    Mouser, P. J.; Kekacs, D.

    2014-12-01

    One of the risks associated with the use of hydraulic fracturing technologies for energy development is the potential release of hydraulic fracturing-related fluids into surface waters or shallow aquifers. Many of the organic additives used in hydraulic fracturing fluids are individually biodegradable, but little is know on how they will attenuate within a complex organic fluid in the natural environment. We developed a synthetic hydraulic fracturing fluid based on disclosed recipes used by Marcellus shale operators to evaluate the biodegradation potential of organic additives across a concentration (25 to 200 mg/L DOC) and salinity gradient (0 to 60 g/L) similar to Marcellus shale injected fluids. In aerobic aqueous solutions, microorganisms removed 91% of bulk DOC from low SFF solutions and 57% DOC in solutions having field-used SFF concentrations within 7 days. Under high SFF concentrations, salinity in excess of 20 g/L inhibited organic compound biodegradation for several weeks, after which time the majority (57% to 75%) of DOC remained in solution. After SFF amendment, the initially biodiverse lake or sludge microbial communities were quickly dominated (>79%) by Pseudomonas spp. Approximately 20% of added carbon was converted to biomass while the remainder was respired to CO2 or other metabolites. Two alcohols, isopropanol and octanol, together accounted for 2-4% of the initial DOC, with both compounds decreasing to below detection limits within 7 days. Alcohol degradation was associated with an increase in acetone at mg/L concentrations. These data help to constrain the biodegradation potential of organic additives in hydraulic fracturing fluids and guide our understanding of the microbial communities that may contribute to attenuation in surface waters.

  15. Bone stress in runners with tibial stress fracture.

    Science.gov (United States)

    Meardon, Stacey A; Willson, John D; Gries, Samantha R; Kernozek, Thomas W; Derrick, Timothy R

    2015-11-01

    Combinations of smaller bone geometry and greater applied loads may contribute to tibial stress fracture. We examined tibial bone stress, accounting for geometry and applied loads, in runners with stress fracture. 23 runners with a history of tibial stress fracture & 23 matched controls ran over a force platform while 3-D kinematic and kinetic data were collected. An elliptical model of the distal 1/3 tibia cross section was used to estimate stress at 4 locations (anterior, posterior, medial and lateral). Inner and outer radii for the model were obtained from 2 planar x-ray images. Bone stress differences were assessed using two-factor ANOVA (α=0.05). Key contributors to observed stress differences between groups were examined using stepwise regression. Runners with tibial stress fracture experienced greater anterior tension and posterior compression at the distal tibia. Location, but not group, differences in shear stress were observed. Stepwise regression revealed that anterior-posterior outer diameter of the tibia and the sagittal plane bending moment explained >80% of the variance in anterior and posterior bone stress. Runners with tibial stress fracture displayed greater stress anteriorly and posteriorly at the distal tibia. Elevated tibial stress was associated with smaller bone geometry and greater bending moments about the medial-lateral axis of the tibia. Future research needs to identify key running mechanics associated with the sagittal plane bending moment at the distal tibia as well as to identify ways to improve bone geometry in runners in order to better guide preventative and rehabilitative efforts. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Development of Chelating Agent-Based Polymeric Gel System for Hydraulic Fracturing

    Directory of Open Access Journals (Sweden)

    Muhammad Shahzad Kamal

    2018-06-01

    Full Text Available Hydraulic Fracturing is considered to be one of the most important stimulation methods. Hydraulic Fracturing is carried out by inducing fractures in the formation to create conductive pathways for the flow of hydrocarbon. The pathways are kept open either by using proppant or by etching the fracture surface using acids. A typical fracturing fluid usually consists of a gelling agent (polymers, cross-linkers, buffers, clay stabilizers, gel stabilizers, biocide, surfactants, and breakers mixed with fresh water. The numerous additives are used to prevent damage resulting from such operations, or better yet, enhancing it beyond just the aim of a fracturing operation. This study introduces a new smart fracturing fluid system that can be either used for proppant fracturing (high pH or acid fracturing (low pH operations in sandstone formations. The fluid system consists of glutamic acid diacetic acid (GLDA that can replace several additives, such as cross-linker, breaker, biocide, and clay stabilizer. GLDA is also a surface-active fluid that will reduce the interfacial tension eliminating the water-blockage effect. GLDA is compatible and stable with sea water, which is advantageous over the typical fracturing fluid. It is also stable in high temperature reservoirs (up to 300 °F and it is also environmentally friendly and readily biodegradable. The new fracturing fluid formulation can withstand up to 300 °F of formation temperature and is stable for about 6 h under high shearing rates (511 s−1. The new fracturing fluid formulation breaks on its own and the delay time or the breaking time can be controlled with the concentrations of the constituents of the fluid (GLDA or polymer. Coreflooding experiments were conducted using Scioto and Berea sandstone cores to evaluate the effectiveness of the developed fluid. The flooding experiments were in reasonable conformance with the rheological properties of the developed fluid regarding the thickening and

  17. SIMULATION AND OPTIMIZATION OF THE HYDRAULIC FRACTURING OPERATION IN A HEAVY OIL RESERVOIR IN SOUTHERN IRAN

    Directory of Open Access Journals (Sweden)

    REZA MASOOMI

    2017-01-01

    Full Text Available Extraction of oil from some Iranian reservoirs due to high viscosity of their oil or reducing the formation permeability due to asphaltene precipitation or other problems is not satisfactory. Hydraulic fracturing method increases production in the viscous oil reservoirs that the production rate is low. So this is very important for some Iranian reservoirs that contain these characteristics. In this study, hydraulic fracturing method has been compositionally simulated in a heavy oil reservoir in southern Iran. In this study, the parameters of the fracture half length, the propagation direction of the cracks and the depth of fracturing have been considered in this oil reservoir. The aim of this study is to find the best scenario which has the highest recovery factor in this oil reservoir. For this purpose the parameters of the length, propagation direction and depth of fracturing have been optimized in this reservoir. Through this study the cumulative oil production has been evaluated with the compositional simulation for the next 10 years in this reservoir. Also at the end of this paper, increasing the final production of this oil reservoir caused by optimized hydraulic fracturing has been evaluated.

  18. Stress fractures and bone pain

    International Nuclear Information System (INIS)

    Groshar, D.; Even-Sapir, E.; Lam, M.; Israel, O.; Front, D.

    1984-01-01

    Stress fractures result from an unusual repetitive physical activity causing absorption of bone in excess of repair and bone formation. This leads to the weakening of the bone and subsequently to a fracture. It is a benign condition that if recognized in time does not need any treatment besides rest. However, if diagnosis is not made and physical activity continues it may result in severe injury to the bone and a frank fracture may result. Pain is the typical clinical feature and bone scintigraphy, being more sensitive than radiography, is done to establish early diagnosis. The presence of asymptomatic sites of abnormal bone uptake typical of stress fracture in which pain appeared only about 2 weeks after scintigraphy, drew the authors' attention to the question of how close is the relationship between stress fractures and bone pain. Sixty-four military recruits diagnosed as suffering from stress fracture were investigated in order to correlate sites with abnormal uptake of Tc-99m MDP on bone scintigraphy with sites of local pain. In 37 (58%) subjects multiple sites of abnormal uptake were recognised. Of 123 sites of abnormal uptake, 31 (25%) were asymptomatic. In three patients bone pain appeared at the site of the abnormal uptake two weeks after scintigraphy. Bone scintigraphy appears to be more sensitive than bone pain in the diagnosis of stress fractures. The osteoblastic activity which manifests itself by abnormal uptake appears in some cases earlier than the pain caused by the fracture. Present findings may suggest that under certain circumstances, in a population prone to stress fracture, bone scan should be considered as a screening method

  19. Distinguishing stress fractures from pathologic fractures: a multimodality approach

    International Nuclear Information System (INIS)

    Fayad, Laura M.; Kamel, Ihab R.; Kawamoto, Satomi; Bluemke, David A.; Fishman, Elliot K.; Frassica, Frank J.

    2005-01-01

    Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount. (orig.)

  20. Hydraulic fracturing as an interpretive policy problem: lessons on energy controversies in Europe and the U.S.A.

    NARCIS (Netherlands)

    Dodge, Jennifer; Metze, Tamara

    2017-01-01

    This special issue addresses hydraulic fracturing for shale gas extraction as an interpretive policy problem. Bringing together empirical cases from the U.S.A., the Netherlands, the U.K., Poland, and Germany, we identify three approaches to the interpretation of hydraulic fracturing in the article:

  1. On the possibility of magnetic nano-markers use for hydraulic fracturing in shale gas mining

    Science.gov (United States)

    Zawadzki, Jaroslaw; Bogacki, Jan

    2016-04-01

    Recently shale gas production became essential for the global economy, thanks to fast advances in shale fracturing technology. Shale gas extraction can be achieved by drilling techniques coupled with hydraulic fracturing. Further increasing of shale gas production is possible by improving the efficiency of hydraulic fracturing and assessing the spatial distribution of fractures in shale deposits. The latter can be achieved by adding magnetic markers to fracturing fluid or directly to proppant, which keeps the fracture pathways open. After that, the range of hydraulic fracturing can be assessed by measurement of vertical and horizontal component of earth's magnetic field before and after fracturing. The difference in these components caused by the presence of magnetic marker particles may allow to delineate spatial distribution of fractures. Due to the fact, that subterranean geological formations may contain minerals with significant magnetic properties, it is important to provide to the markers excellent magnetic properties which should be also, independent of harsh chemical and geological conditions. On the other hand it is of great significance to produce magnetic markers at an affordable price because of the large quantities of fracturing fluids or proppants used during shale fracturing. Examining the properties of nano-materials, it was found, that they possess clearly superior magnetic properties, as compared to the same structure but having a larger particle size. It should be then possible, to use lower amount of magnetic marker, to obtain the same effect. Although a research on properties of new magnetic nano-materials is very intensive, cheap magnetic nano-materials are not yet produced on a scale appropriate for shale gas mining. In this work we overview, in detail, geological, technological and economic aspects of using magnetic nano-markers in shale gas mining. Acknowledgment This work was supported by the NCBiR under Grant "Electromagnetic method to

  2. Three-Dimensional poroelastic effects during hydraulic fracturing in permeable rocks

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Paluszny, Adriana; Zimmerman, Robert W.

    2017-01-01

    A fully coupled three-dimensional finite-element model for hydraulic fractures in permeable rocks is presented, and used to investigate the ranges of applicability of the classical analytical solutions that are known to be valid in limiting cases. This model simultaneously accounts for fluid flow...

  3. Hydraulic fracturing, energy transition and political engagement in the Netherlands

    NARCIS (Netherlands)

    Rasch, Elisabet Dueholm; Köhne, Michiel

    2016-01-01

    This paper analyses how citizens (re)define their relation to the state in the contestation of hydraulic fracturing in the Noordoostpolder (the Netherlands) in the context of energy transition. It approaches citizenship as the negotiations between governments and citizens about in-and exclusion

  4. Hydrogeological study of single water conducting fracture using a crosshole hydraulic test apparatus

    International Nuclear Information System (INIS)

    Yamamoto, Hajime; Shimo, Michito; Yamamoto, Takuya

    1998-03-01

    The Crosshole Injection Test Apparatus has been constructed to evaluate the hydraulic properties and conditions, such as hydraulic conductivity and its anisotropy, storage coefficient, pore pressure etc. within a rock near a drift. The construction started in FY93 and completed on August FY96 as a set of equipments for the use of crosshole hydraulic test, which is composed of one injection borehole instrument, one observation borehole instrument and a set of on-ground instrument. In FY96, in-situ feasibility test was conducted at a 550 m level drift in Kamaishi In Situ Test Site which has been operated by PNC, and the performance of the equipment and its applicability to various types of injection method were confirmed. In this year, a hydrogeological investigation on the single water conducting fracture was conducted at a 250 m level drift in Kamaishi In Situ Test Site, using two boreholes, KCH-3 and KCH-4, both of which are 30 m depth and inclined by 45 degrees from the surface. Pressure responses at the KCH-3 borehole during the drilling of KCH-4 borehole, the results of Borehole TV logging and core observation indicated that a major conductive single-fracture was successfully isolated by the packers. As a result of a series of the single-hole and the crosshole tests (sinusoidal and constant flowrate test), the hydraulic parameters of the single-fracture (such as hydraulic conductivity and storage coefficient) were determined. This report shows all the test result, analysed data, and also describes the hydro-geological structure near the drift. (author)

  5. On the link between stress field and small-scale hydraulic fracture growth in anisotropic rock derived from microseismicity

    Science.gov (United States)

    Gischig, Valentin Samuel; Doetsch, Joseph; Maurer, Hansruedi; Krietsch, Hannes; Amann, Florian; Evans, Keith Frederick; Nejati, Morteza; Jalali, Mohammadreza; Valley, Benoît; Obermann, Anne Christine; Wiemer, Stefan; Giardini, Domenico

    2018-01-01

    To characterize the stress field at the Grimsel Test Site (GTS) underground rock laboratory, a series of hydrofracturing and overcoring tests were performed. Hydrofracturing was accompanied by seismic monitoring using a network of highly sensitive piezosensors and accelerometers that were able to record small seismic events associated with metre-sized fractures. Due to potential discrepancies between the hydrofracture orientation and stress field estimates from overcoring, it was essential to obtain high-precision hypocentre locations that reliably illuminate fracture growth. Absolute locations were improved using a transverse isotropic P-wave velocity model and by applying joint hypocentre determination that allowed for the computation of station corrections. We further exploited the high degree of waveform similarity of events by applying cluster analysis and relative relocation. Resulting clouds of absolute and relative located seismicity showed a consistent east-west strike and 70° dip for all hydrofractures. The fracture growth direction from microseismicity is consistent with the principal stress orientations from the overcoring stress tests, provided that an anisotropic elastic model for the rock mass is used in the data inversions. The σ1 stress is significantly larger than the other two principal stresses and has a reasonably well-defined orientation that is subparallel to the fracture plane; σ2 and σ3 are almost equal in magnitude and thus lie on a circle defined by the standard errors of the solutions. The poles of the microseismicity planes also lie on this circle towards the north. Analysis of P-wave polarizations suggested double-couple focal mechanisms with both thrust and normal faulting mechanisms present, whereas strike-slip and thrust mechanisms would be expected from the overcoring-derived stress solution. The reasons for these discrepancies can be explained by pressure leak-off, but possibly may also involve stress field rotation around the

  6. Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales

    Energy Technology Data Exchange (ETDEWEB)

    Daly, Rebecca A.; Borton, Mikayla A.; Wilkins, Michael J.; Hoyt, David W.; Kountz, Duncan J.; Wolfe, Richard A.; Welch, Susan A.; Marcus, Daniel N.; Trexler, Ryan V.; MacRae, Jean D.; Krzycki, Joseph A.; Cole, David R.; Mouser, Paula J.; Wrighton, Kelly C.

    2016-09-05

    Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that methylamine cycling supports methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while sulfide generation from thiosulfate represents a poorly recognized corrosion mechanism in shales. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.

  7. Fracture criteria of reactor graphite under multiaxial stresses

    International Nuclear Information System (INIS)

    Sato, S.; Kawamata, K.; Kurumada, A.; Oku, T.

    1987-01-01

    New fracture criteria for graphite under multiaxial stresses are presented for designing core and support materials of a high temperature gas cooled reactor. Different kinds of fracture strength tests are carried out for a near isotropic graphite IG-11. Results show that, under the stress state in which tensile stresses are predominant, the maximum principal stress theory is seen as applicable for brittle fracture. Under the stress state in which compressive stresses are predominant there may be two fracture modes for brittle fracture, namely, slipping fracture and mode II fracture. For the former fracture mode the maximum shear stress criterion is suitable, but for the latter fracture mode a new mode II fracture criterion including a restraint effect for cracks is verified to be applicable. Also a statistical correction for brittle fracture criteria under multiaxial stresses is discussed. By considering the allowable stress values for safe design, the specified minimum ultimate strengths corresponding to a survival probability of 99% at the 95% confidence level are presented. (orig./HP)

  8. Streaming Potential Modeling to Understand the Identification of Hydraulically Active Fractures and Fracture-Matrix Fluid Interactions Using the Self-Potential Method

    Science.gov (United States)

    Jougnot, D.; Roubinet, D.; Linde, N.; Irving, J.

    2016-12-01

    Quantifying fluid flow in fractured media is a critical challenge in a wide variety of research fields and applications. To this end, geophysics offers a variety of tools that can provide important information on subsurface physical properties in a noninvasive manner. Most geophysical techniques infer fluid flow by data or model differencing in time or space (i.e., they are not directly sensitive to flow occurring at the time of the measurements). An exception is the self-potential (SP) method. When water flows in the subsurface, an excess of charge in the pore water that counterbalances electric charges at the mineral-pore water interface gives rise to a streaming current and an associated streaming potential. The latter can be measured with the SP technique, meaning that the method is directly sensitive to fluid flow. Whereas numerous field experiments suggest that the SP method may allow for the detection of hydraulically active fractures, suitable tools for numerically modeling streaming potentials in fractured media do not exist. Here, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid-flow and associated self-potential problems in fractured domains. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods due to computational limitations. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

  9. Risk factors for stress fractures.

    Science.gov (United States)

    Bennell, K; Matheson, G; Meeuwisse, W; Brukner, P

    1999-08-01

    Preventing stress fractures requires knowledge of the risk factors that predispose to this injury. The aetiology of stress fractures is multifactorial, but methodological limitations and expediency often lead to research study designs that evaluate individual risk factors. Intrinsic risk factors include mechanical factors such as bone density, skeletal alignment and body size and composition, physiological factors such as bone turnover rate, flexibility, and muscular strength and endurance, as well as hormonal and nutritional factors. Extrinsic risk factors include mechanical factors such as surface, footwear and external loading as well as physical training parameters. Psychological traits may also play a role in increasing stress fracture risk. Equally important to these types of analyses of individual risk factors is the integration of information to produce a composite picture of risk. The purpose of this paper is to critically appraise the existing literature by evaluating study design and quality, in order to provide a current synopsis of the known scientific information related to stress fracture risk factors. The literature is not fully complete with well conducted studies on this topic, but a great deal of information has accumulated over the past 20 years. Although stress fractures result from repeated loading, the exact contribution of training factors (volume, intensity, surface) has not been clearly established. From what we do know, menstrual disturbances, caloric restriction, lower bone density, muscle weakness and leg length differences are risk factors for stress fracture. Other time-honoured risk factors such as lower extremity alignment have not been shown to be causative even though anecdotal evidence indicates they are likely to play an important role in stress fracture pathogenesis.

  10. Modeling of Hydraulic Fracture Propagation at the kISMET Site Using a Fully Coupled 3D Network-Flow and Quasi- Static Discrete Element Model

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jing [Idaho National Lab. (INL), Idaho Falls, ID (United States); Huang, Hai [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mattson, Earl [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wang, Herb F. [Univ. of Wisconsin, Madison, WI (United States); Haimson, Bezalel C. [Univ. of Wisconsin, Madison, WI (United States); Doe, Thomas W. [Golder Associates Inc., Redmond, VA (United States); Oldenburg, Curtis M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Dobson, Patrick F. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-02-01

    Aimed at supporting the design of hydraulic fracturing experiments at the kISMET site, ~1500 m below ground in a deep mine, we performed pre-experimental hydraulic fracturing simulations in order to estimate the breakdown pressure, propagation pressure, fracture geometry, and the magnitude of induced seismicity using a newly developed fully coupled three-dimensional (3D) network flow and quasi-static discrete element model (DEM). The quasi-static DEM model, which is constructed by Delaunay tessellation of the rock volume, considers rock fabric heterogeneities by using the “disordered” DEM mesh and adding random perturbations to the stiffness and tensile/shear strengths of individual DEM elements and the elastic beams between them. A conjugate 3D flow network based on the DEM lattice is constructed to calculate the fluid flow in both the fracture and porous matrix. One distinctive advantage of the model is that fracturing is naturally described by the breakage of elastic beams between DEM elements. It is also extremely convenient to introduce mechanical anisotropy into the model by simply assigning orientation-dependent tensile/shear strengths to the elastic beams. In this paper, the 3D hydraulic fracturing model was verified against the analytic solution for a penny-shaped crack model. We applied the model to simulate fracture propagation from a vertical open borehole based on initial estimates of rock mechanical properties and in-situ stress conditions. The breakdown pressure and propagation pressure are directly obtained from the simulation. In addition, the released elastic strain energies of individual fracturing events were calculated and used as a conservative estimate for the magnitudes of the potential induced seismic activities associated with fracturing. The comparisons between model predictions and experimental results are still ongoing.

  11. Risks to Water Resources from Shale Gas Development and Hydraulic Fracturing in the United States

    Science.gov (United States)

    Vengosh, Avner; Jackson, Robert B.; Warner, Nathaniel; Darrah, Thomas H.; Kondash, Andrew

    2014-05-01

    The rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded oil and gas exploration in the USA. The rapid rate of shale gas exploration has triggered an intense public debate regarding the potential environmental and human health effects. A review of the updated literature has identified four potential risks for impacts on water resources: (1) stray gas contamination of shallow aquifers near shale gas sites; (2) contamination of surface water and shallow groundwater from spills, leaks, and disposal of inadequately treated wastewater or hydraulic fracturing fluids; (3) accumulation of toxic and radioactive residues in soil or stream sediments near disposal or spill sites; and (4) over-extraction of water resources for drilling and hydraulic fracturing that could induce water shortages and conflicts with other water users, particularly in water-scarce areas. As part of a long-term research on the potential water contamination associated with shale gas development, new geochemical and isotopic techniques have been developed for delineating the origin of gases and contaminants in water resource. In particular, multiple geochemical and isotopic (carbon isotopes in hydrocarbons, noble gas, strontium, boron, radium isotopes) tracers have been utilized to distinguish between naturally occurring dissolved gas and salts in water and contamination directly induced from shale gas drilling and hydraulic fracturing operations.

  12. Stress fractures in athletes

    International Nuclear Information System (INIS)

    Steingruber, I.E.; Wolf, C.; Gruber, H.; Czermak, B.V.; Mallouhi, A.; Jaschke, W.; Gabriel, M.

    2002-01-01

    Stress fractures may pose a diagnostic dilemma for radiologists since they are sometimes difficult to demonstrate on plain films and may simulate a tumour. They were first described in military personnel and professional athletes. Recently, there is an increasing incidence in the general population due to increasing sportive activities. Stress fractures occur most often in the lower extremities, especially in the tibia, the tarsal bone, the metatarsal bone, the femur and the fibula. In the upper extremities, they are commonly found in the humerus, the radius and the ulna. Some fractures of the lower extremities appear to be specific for particular sports, for example, fractures of the tibia affect mostly distance runners. Whereas stress fractures of the upper extremities are generally associated with upper limb-dominated sports. A correct diagnosis requires a careful clinical evaluation. The initial plain radiography may be normal. Further radiological evaluation could be performed by means of computerised tomography, magnetic resonance imaging and bone scanning. The latter two techniques are especially helpful for establishing a correct initial diagnosis. (orig.) [de

  13. Metatarsal stress fractures - aftercare

    Science.gov (United States)

    ... Metatarsal stress fracture. In: Safran MR, Zachazewski J, Stone DA, eds. Instructions for Sports Medicine Patients . 2nd ed. Elsevier Saunders; 2012:648-652. Smith MS. Metatarsal fractures. In: Eiff PM, Hatch R, eds. Fracture Management for Primary Care . 3rd ed. ...

  14. Stress fractures in elite cross-country athletes.

    Science.gov (United States)

    Laker, Scott R; Saint-Phard, Deborah; Tyburski, Mark; Van Dorsten, Brent

    2007-04-01

    This retrospective and comparative survey investigates an unusual number of stress fractures seen within a Division I college cross-country team. An anonymous questionnaire-designed to observe factors known to increase stress fracture incidence-was distributed to members of the current and previous seasons' teams. Running surface, sleep hours, intake of calcium, and shoe type were among the factors investigated. Eleven lower extremity stress fractures were found in nine athletes. Athletes with stress fractures reported significantly fewer workouts per week on the new track. All other study parameters had no statistically significant effect on stress fractures in these athletes.

  15. Increasing the effectiveness of the hydraulic fracturing of seams with the use of the pattern recognition method

    Energy Technology Data Exchange (ETDEWEB)

    Rasizade, Ya M; Nagiev, T M; Kuznetsov, V I; Mikerin, B P

    1977-08-01

    An examination is made of using a sequential diagnostic procedure for increasing the effectiveness of the hydraulic fracturing of seams in boreholes of the gas and oil drilling administration of the Khadyzhenneft' association. The use of the pattern recognition method was shown to make it possible to increase the effectiveness of hydraulic fracturing by up to 80%. 4 references, 1 figure, 3 tables.

  16. “Fracking” controversy and communication: Using national survey data to understand public perceptions of hydraulic fracturing

    International Nuclear Information System (INIS)

    Boudet, Hilary; Clarke, Christopher; Bugden, Dylan; Maibach, Edward; Roser-Renouf, Connie; Leiserowitz, Anthony

    2014-01-01

    The recent push to develop unconventional sources of oil and gas both in the U.S. and abroad via hydraulic fracturing (“fracking”) has generated a great deal of controversy. Effectively engaging stakeholders and setting appropriate policies requires insights into current public perceptions of this issue. Using a nationally representative U.S. sample (N=1061), we examine public perceptions of hydraulic fracturing including: “top of mind” associations; familiarity with the issue; levels of support/opposition; and predictors of such judgments. Similar to findings on other emerging technologies, our results suggest limited familiarity with the process and its potential impacts and considerable uncertainty about whether to support it. Multiple regression analysis (r 2 =.49) finds that women, those holding egalitarian worldviews, those who read newspapers more than once a week, those more familiar with hydraulic fracturing, and those who associate the process with environmental impacts are more likely to oppose fracking. In contrast, people more likely to support fracking tend to be older, hold a bachelor's degree or higher, politically conservative, watch TV news more than once a week, and associate the process with positive economic or energy supply outcomes. Based on these findings, we discuss recommendations for future research, risk communication, and energy policy. - Highlights: • We conducted a survey of Americans' views on hydraulic fracturing in September 2012. • A majority of Americans have heard little or nothing about hydraulic fracturing. • Many Americans do not know if they support/oppose it or are undecided. • Those who have made a decision are evenly split between support and opposition. • Predictors of support include education, media use and top of mind associations

  17. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    International Nuclear Information System (INIS)

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress

  18. Experience in North America Tight Oil Reserves Development. Horizontal Wells and Multistage Hydraulic Fracturing

    Directory of Open Access Journals (Sweden)

    R.R. Ibatullin

    2017-09-01

    Full Text Available The accelerated development of horizontal drilling technology in combination with the multistage hydraulic fracturing of the reservoir has expanded the geological conditions for commercial oil production from tight reservoirs in North America. Geological and physical characteristics of tight reservoirs in North America are presented, as well as a comparison of the geological and physical properties of the reservoirs of the Western Canadian Sedimentary Basin and the Volga-Ural oil and gas province, in particular, in the territory of Tatarstan. The similarity of these basins is shown in terms of formation and deposition. New drilling technologies for horizontal wells (HW and multistage hydraulic fracturing are considered. The drilling in tight reservoirs is carried out exclusively on hydrocarbon-based muds The multi-stage fracturing technology with the use of sliding sleeves, and also slick water – a low-viscous carrier for proppant is the most effective solution for conditions similar to tight reservoirs in the Devonian formation of Tatarstan. Tax incentives which are actively used for the development of HW and multistage fracturing technologies in Canada are described. wells, multistage fracturing

  19. Chemical Interactions of Hydraulic Fracturing Biocides with Natural Pyrite

    Science.gov (United States)

    Consolazio, Nizette A.

    In conjunction with horizontal drilling, hydraulic fracturing or fracking has enabled the recovery of natural gas from low permeable shale formations. In addition to water, these fracking fluids employ proppants and up to 38 different chemical additives to improve the efficiency of the process. One important class of additives used in hydraulic fracturing is biocides. When applied appropriately, they limit the growth of harmful microorganisms within the well, saving energy producers 4.5 billion dollars each year. However, biocides or their harmful daughter products may return to the surface in produced water, which must then be appropriately stored, treated and disposed of. Little is known about the effect of mineral-fluid interactions on the fate of the biocides employed in hydraulic fracturing. In this study, we employed laboratory experiments to determine changes in the persistence and products of these biocides under controlled environments. While many minerals are present in shale formations, pyrite, FeS2(s) is particularly interesting because of its prevalence and reactivity. The FeII groups on the face of pyrite may be oxidized to form FeIII phases. Both of these surfaces have been shown to be reactive with organic compounds. Chlorinated compounds undergo redox reactions at the pyrite-fluid interface, and sulfur-containing compounds undergo exceptionally strong sorption to both pristine and oxidized pyrite. This mineral may significantly influence the degradation of biocides in the Marcellus Shale. Thus, the overall goal of this study was to understand the effect of pyrite on biocide reactivity in hydraulic fracturing, focusing on the influence of pyrite on specific functional groups. The first specific objective was to demonstrate the effect of pyrite and pyrite reaction products on the degradation of the bromine-containing biocide, DBNPA. On the addition of pyrite to DBNPA, degradation rates of the doubly brominated compound were found to increase

  20. Source Mechanisms of Low Frequency Seismicity in a Hydraulic Fracturing Context

    Science.gov (United States)

    Zecevic, M.; Daniel, G.; Hubans, F.; Gouedard, P.

    2014-12-01

    In recent years, long-period long-duration (LPLD) events have been observed during hydraulic fracturing of hydrocarbon reservoirs (Das & Zoback, 2013). LPLDs are low-amplitude signals lasting from tens of seconds to minutes. Their source mechanisms are not fully understood. However, as they are remarkably similar in character to tectonic tremors it has been suggested that they may also have comparable source models. Current models suggest that a tectonic tremor consists of numerous slow-slip earthquakes superposed on each other to form continuous waveforms (Shelley et al., 2007). These slow-slip earthquakes are thought to be a result of shear slip on faults close to failure with low confining pressure, most likely due to the presence of fluid with pore pressures close to lithostatic pressures (Peng & Gomberg, 2010). This study aims to further understand the source mechanism of LPLDs. A hydraulic fracturing dataset containing thousands of located microseismic earthquakes (MEQs) and numerous LPLDs is presented. The MEQs are located around the injection stages whereas the LPLDs are clustered in a limited region within the reservoir. This clustering suggests that LPLDs can only be generated where the conditions in the reservoir are favorable. These results correspond with the possibility that LPLDs are manifestations of slow-slip, with the source locations confined by variations in the mechanical properties of the reservoir. To test this hypothesis a further understanding of the mechanisms of LPLDs and the stress field in which they occur is needed. However, calculating focal mechanisms for LPLDs is difficult due to their emergent onset and lack of clear phases. Consequently, LPLDs must be put into context with the observed MEQs. We will present the spatial distribution of the focal mechanisms of the MEQs and analyze our findings with respect to the occurrence of the LPLD events.

  1. Geophysical Properties of Hard Rock for Investigation of Stress Fields in Deep Mines

    Science.gov (United States)

    Tibbo, M.; Young, R. P.; Schmitt, D. R.; Milkereit, B.

    2014-12-01

    A complication in geophysical monitoring of deep mines is the high-stress dependency of the physical properties of hard rocks. In-mine observations show anisotropic variability of the in situ P- and S-wave velocities and resistivity of the hard rocks that are likely related to stress field changes. As part of a comprehensive study in a deep, highly stressed mine located in Sudbury, Ontario, Canada, data from in situ monitoring of the seismicity, conductivity, stress, and stress dependent physical properties has been obtain. In-laboratory experiments are also being performed on borehole cores from the Sudbury mines. These experiments will measure the Norite borehole core's properties including elastic modulus, bulk modulus, P- and S-wave velocities, and density. Hydraulic fracturing has been successfully implemented in industries such as oil and gas and enhanced geothermal systems, and is currently being investigated as a potential method for preconditioning in mining. However, further research is required to quantify how hydraulic fractures propagate through hard, unfractured rock as well as naturally fractured rock typically found in mines. These in laboratory experiments will contribute to a hydraulic fracturing project evaluating the feasibility and effectiveness of hydraulic fracturing as a method of de-stressing hard rock mines. A tri-axial deformation cell equipped with 18 Acoustic Emission (AE) sensors will be used to bring the borehole cores to a tri-axial state of stress. The cores will then be injected with fluid until the the hydraulic fracture has propagated to the edge of the core, while AE waveforms will be digitized continuously at 10 MHz and 12-bit resolution for the duration of each experiment. These laboratory hydraulic fracture experiments will contribute to understanding how parameters including stress ratio, fluid injection rate, and viscosity, affect the fracturing process.

  2. The Potential Impacts of Hydraulic Fracturing on Agriculture

    OpenAIRE

    Beng Ong

    2014-01-01

    Hydraulic fracturing (or “fracking”) is a method of extracting oil and natural gas trapped in deep rock layers underground by pumping water, sand, and other chemicals/additives at high pressures into a well drilled vertically, and then horizontally into the rocks.Advocates of fracking in U.S. have skillfully positioned domestic natural gas as a sensible alternative energy to the country’s goals of reducing carbon emissions and dependence on foreign oil, while simultaneously creating jobs loca...

  3. Response to 'Word choice as political speech': Hydraulic fracturing is a partisan issue.

    Science.gov (United States)

    Hopke, Jill E; Simis, Molly

    2016-04-28

    In 2015, Hopke & Simis published an analysis of social media discourse around hydraulic fracturing. Grubert (2016) offered a commentary on the research, highlighting the politicization of terminology used in the discourse on this topic. The present article is a response to Grubert (2016)'s commentary, in which we elaborate on the distinctions between terminology used in social media discourse around hydraulic fracturing (namely, 'frack,' 'fracking,' 'frac,' and 'fracing'). Additionally preliminary analysis supports the claim that industry-preferred terminology is severely limited in its reach. When industry actors opt-out of the discourse, the conversation followed by the majority of lay audiences is dominated by activists. exacerbating the political schism on the issue. © The Author(s) 2016.

  4. Simulation of complex fracture networks influenced by natural fractures in shale gas reservoir

    Directory of Open Access Journals (Sweden)

    Zhao Jinzhou

    2014-10-01

    Full Text Available When hydraulic fractures intersect with natural fractures, the geometry and complexity of a fracture network are determined by the initiation and propagation pattern which is affected by a number of factors. Based on the fracture mechanics, the criterion for initiation and propagation of a fracture was introduced to analyze the tendency of a propagating angle and factors affecting propagating pressure. On this basis, a mathematic model with a complex fracture network was established to investigate how the fracture network form changes with different parameters, including rock mechanics, in-situ stress distribution, fracture properties, and frac treatment parameters. The solving process of this model was accelerated by classifying the calculation nodes on the extending direction of the fracture by equal pressure gradients, and solving the geometrical parameters prior to the iteration fitting flow distribution. With the initiation and propagation criterion as the bases for the propagation of branch fractures, this method decreased the iteration times through eliminating the fitting of the fracture length in conventional 3D fracture simulation. The simulation results indicated that the formation with abundant natural fractures and smaller in-situ stress difference is sufficient conditions for fracture network development. If the pressure in the hydraulic fractures can be kept at a high level by temporary sealing or diversion, the branch fractures will propagate further with minor curvature radius, thus enlarging the reservoir stimulation area. The simulated shape of fracture network can be well matched with the field microseismic mapping in data point range and distribution density, validating the accuracy of this model.

  5. 2016-2017 Update of Hydraulic Fracturing Induced Earthquakes near Fox Creek, Alberta

    Science.gov (United States)

    Wang, R.; Gu, Y. J.; Zhang, M.

    2017-12-01

    With a reported Richter magnitude (ML) of 4.8, the January 12, 2016 earthquake near Fox Creek is the largest event in Alberta during the past decade. This event led to the suspension of a nearby hydraulic fracturing well, in compliance with the provincial "traffic-light" protocol. In previous study, we examine the hypocenter location and focal mechanism of this earthquake, and the results support an anthropogenic origin. Since then (until August 2017), no event reached ML=4, while several ML>3 events occurred in the Fox Creek area. Their focal mechanisms are consistent with the ones from previous events that were induced by hydraulic fracturing, suggesting a strike-slip mechanism with either N-S or E-W trending fault. In 2017, the near-source station (distance Fox Creek region.

  6. Stress fractures in the lower extremity

    International Nuclear Information System (INIS)

    Berger, Ferco H.; Jonge, Milko C. de; Maas, Mario

    2007-01-01

    Stress fractures are fatigue injuries of bone usually caused by changes in training regimen in the population of military recruits and both professional and recreational athletes. Raised levels of sporting activity in today's population and refined imaging technologies have caused a rise in reported incidence of stress fractures in the past decades, now making up more than 10% of cases in a typical sports medicine practice. Background information (including etiology, epidemiology, clinical presentation and treatment and prevention) as well as state of the art imaging of stress fractures will be discussed to increase awareness amongst radiologists, providing the tools to play an important role in diagnosis and prognosis of stress fractures. Specific fracture sites in the lower extremity will be addressed, covering the far majority of stress fracture incidence. Proper communication between treating physician, physical therapist and radiologist is needed to obtain a high index of suspicion for this easily overlooked entity. Radiographs are not reliable for detection of stress fractures and radiologist should not falsely be comforted by them, which could result in delayed diagnosis and possibly permanent consequences for the patient. Although radiographs are mandatory to rule out differentials, they should be followed through when negative, preferably by magnetic resonance imaging (MRI), as this technique has proven to be superior to bone scintigraphy. CT can be beneficial in a limited number of patients, but should not be used routinely

  7. Hydraulic fracturing and the Crooked Lake Sequences: Insights gleaned from regional seismic networks

    Science.gov (United States)

    Schultz, Ryan; Stern, Virginia; Novakovic, Mark; Atkinson, Gail; Gu, Yu Jeffrey

    2015-04-01

    Within central Alberta, Canada, a new sequence of earthquakes has been recognized as of 1 December 2013 in a region of previous seismic quiescence near Crooked Lake, ~30 km west of the town of Fox Creek. We utilize a cross-correlation detection algorithm to detect more than 160 events to the end of 2014, which is temporally distinguished into five subsequences. This observation is corroborated by the uniqueness of waveforms clustered by subsequence. The Crooked Lake Sequences have come under scrutiny due to its strong temporal correlation (>99.99%) to the timing of hydraulic fracturing operations in the Duvernay Formation. We assert that individual subsequences are related to fracturing stimulation and, despite adverse initial station geometry, double-difference techniques allow us to spatially relate each cluster back to a unique horizontal well. Overall, we find that seismicity in the Crooked Lake Sequences is consistent with first-order observations of hydraulic fracturing induced seismicity.

  8. Evaluation of Hydraulic Fracturing (Fracking) Plays for Potential Impact on USACE-Managed Waterways

    Science.gov (United States)

    2015-01-01

    Approved for public release; distribution is unlimited. ERDC/TN DOTS-15-1 January 2015 Evaluation of Hydraulic Fracturing ( Fracking ) Plays...fracturing operations (hydrofracturing or “ fracking ”) to increase petrochemical (natural gas and petroleum) production resulted in elevated environmental...Shale, has raised concerns that fracking operations could impact waterways managed by the U.S. Army Corps of Engineers (USACE). The purpose of this

  9. An investigation of the mechanical and hydrologic behavior of tuff fractures under saturated conditions

    International Nuclear Information System (INIS)

    Voss, C.F.; Shotwell, L.R.

    1990-04-01

    The mechanical and hydrologic behavior of natural fractures in a partially welded tuff rock were investigated. Tuff cores, each containing part of the same natural fracture oriented subparallel to the core axis, were subjected a range of stress and hydraulic gradients while simultaneously monitoring changes in the fracture aperture and volumetric flow rate. The fractures were tested in three configurations: intact, mated, and offset. Fracture deformation was nonlinear over the stress range tested with permanent deformation and hysteresis occurring with each loading cycle. The offset samples had larger permanent deformation and significantly reduced normal stiffness at lower stress levels. The cubic flow law appears to be valid for the relatively undisturbed tuff fractures at the scale tested. The cubic law did not explain the observed hydraulic behavior of the offset fractures. 6 refs., 10 figs., 2 tabs

  10. Regional economic impacts of the unconventional promotion of natural gas (Hydraulic Fracturing). Preliminary study; Regionaloekonomische Auswirkungen der unkonventionellen Erdgasfoerderung (Hydraulic Fracturing). Vorstudie

    Energy Technology Data Exchange (ETDEWEB)

    Bizer, Kilian; Bossmeyer, Christoph

    2012-07-01

    Actually, there is a controversial public discussion on the exploitation of conventional natural gas by means of hydraulic fracturing (Fracking). The contribution under consideration examines the geologic, toxicological or technical as well as legal points of contact with respect to the different effects for the actor groups. Based on the existing scientific realizations, the regional economic effects of the fracking technology and the subsequent promotion of unconventional natural gas deposits have to be worked out.

  11. Information and dialogue process on safety and environmental effects of the hydraulic fracturing technology; Der Informations- und Dialogprozess zur Sicherheit und Umweltvertraeglichkeit der Fracking-Technologie

    Energy Technology Data Exchange (ETDEWEB)

    Borchardt, Dietrich; Richter, Sandra [Helmholtz-Zentrum fuer Umweltforschung - UFZ, Magdeburg (Germany); Ewen, Christoph [team ewen, Darmstadt (Germany); Hammerbacher, Ruth [hammerbacher gmbh - beratung und projekte, Osnabrueck (Germany)

    2012-10-15

    After the big success of hydraulic fracturing in the USA, natural gas utilities are now planning natural gas production from nonconventional deposits (shale gas, coal seam gas) by hydraulic fracturing also in Germany. In order to calm public fears, an 'information and dialogue process on safety and environmental effects of the hydraulic fracturing technology' was initiated. A risk study carried out by a team of neutral experts gives recommendations for a well-founded, careful and realistic discussion of the environmental compatibility of hydraulic fracturing.

  12. Information and dialogue process on safety and environmental effects of the hydraulic fracturing technology; Der Informations- und Dialogprozess zur Sicherheit und Umweltvertraeglichkeit der Fracking-Technologie

    Energy Technology Data Exchange (ETDEWEB)

    Borchardt, Dietrich; Richter, Sandra [Helmholtz-Zentrum fuer Umweltforschung - UFZ, Magdeburg (Germany); Ewen, Christoph [team ewen, Darmstadt (Germany); Hammerbacher, Ruth [hammerbacher gmbh - beratung und projekte, Osnabrueck (Germany)

    2012-10-15

    After the big success of hydraulic fracturing in the USA, natural gas utilities are now planning natural gas production from nonconventional deposits (shale gas, coal seam gas) by hydraulic fracturing also in Germany. In order to calm public fears, an 'information and dialogue process on safety and environmental effects of the hydraulic fracturing technology' was initiated. A risk study carried out by a team of neutral experts gives recommendations for a well-founded, careful and realistic discussion of the environmental compatibility of hydraulic fracturing.

  13. New parameters influencing hydraulic runner lifetime

    International Nuclear Information System (INIS)

    Sabourin, M; Bouffard, D A; Thibault, D; Levesque, M

    2010-01-01

    Traditionally, hydraulic runner mechanical design is based on calculation of static stresses. Today, validation of hydraulic runner design in terms of reliability requires taking into account the fatigue effect of dynamics loads. A damage tolerant approach based on fracture mechanics is the method chosen by Alstom and Hydro-Quebec to study fatigue damage in runners. This requires a careful examination of all factors influencing material fatigue behavior. Such material behavior depends mainly on the chemical composition, microstructure and thermal history of the component, and on the resulting residual stresses. Measurement of fracture mechanics properties of various steels have demonstrated that runner lifetime can be significantly altered by differences in the manufacturing process, although remaining in accordance with agreed practices and standards such as ASTM. Carbon content and heat treatment are suspected to influence fatigue lifetime. This will have to be investigated by continuing the current research.

  14. New parameters influencing hydraulic runner lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Sabourin, M; Bouffard, D A [Alstom Hydro Canada Inc, Hydraulic Engineering, 1350 chemin St-Roch, Sorel-Tracy (Quebec), J3P 5P9 (Canada); Thibault, D [Hydro-Quebec, Institut de Recherche d' Hydro-Quebec 1800 boul. Lionel-Boulet, Varennes (Quebec), J3X 1S1 (Canada); Levesque, M, E-mail: michel.sabourin@power.alstom.co [Ecole Polytechnique de Montreal, Departement de genie mecanique C.P.6079, succ. Centre-ville, Montreal (Quebec), H3C 3A7 (Canada)

    2010-08-15

    Traditionally, hydraulic runner mechanical design is based on calculation of static stresses. Today, validation of hydraulic runner design in terms of reliability requires taking into account the fatigue effect of dynamics loads. A damage tolerant approach based on fracture mechanics is the method chosen by Alstom and Hydro-Quebec to study fatigue damage in runners. This requires a careful examination of all factors influencing material fatigue behavior. Such material behavior depends mainly on the chemical composition, microstructure and thermal history of the component, and on the resulting residual stresses. Measurement of fracture mechanics properties of various steels have demonstrated that runner lifetime can be significantly altered by differences in the manufacturing process, although remaining in accordance with agreed practices and standards such as ASTM. Carbon content and heat treatment are suspected to influence fatigue lifetime. This will have to be investigated by continuing the current research.

  15. Numerical Modeling and Investigation of Fluid-Driven Fracture Propagation in Reservoirs Based on a Modified Fluid-Mechanically Coupled Model in Two-Dimensional Particle Flow Code

    Directory of Open Access Journals (Sweden)

    Jian Zhou

    2016-09-01

    Full Text Available Hydraulic fracturing is a useful tool for enhancing rock mass permeability for shale gas development, enhanced geothermal systems, and geological carbon sequestration by the high-pressure injection of a fracturing fluid into tight reservoir rocks. Although significant advances have been made in hydraulic fracturing theory, experiments, and numerical modeling, when it comes to the complexity of geological conditions knowledge is still limited. Mechanisms of fluid injection-induced fracture initiation and propagation should be better understood to take full advantage of hydraulic fracturing. This paper presents the development and application of discrete particle modeling based on two-dimensional particle flow code (PFC2D. Firstly, it is shown that the modeled value of the breakdown pressure for the hydraulic fracturing process is approximately equal to analytically calculated values under varied in situ stress conditions. Furthermore, a series of simulations for hydraulic fracturing in competent rock was performed to examine the influence of the in situ stress ratio, fluid injection rate, and fluid viscosity on the borehole pressure history, the geometry of hydraulic fractures, and the pore-pressure field, respectively. It was found that the hydraulic fractures in an isotropic medium always propagate parallel to the orientation of the maximum principal stress. When a high fluid injection rate is used, higher breakdown pressure is needed for fracture propagation and complex geometries of fractures can develop. When a low viscosity fluid is used, fluid can more easily penetrate from the borehole into the surrounding rock, which causes a reduction of the effective stress and leads to a lower breakdown pressure. Moreover, the geometry of the fractures is not particularly sensitive to the fluid viscosity in the approximate isotropic model.

  16. Economic Recovery of Oil Trapped at Fan Margins Using High Angle Wells and Multiple Hydraulic Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Mike L. Laue

    1997-05-30

    The distal fan margin in the northeast portion of the Yowlumne field contains significant reserves but is not economical to develop using vertical wells. Numerous interbedded shales and deteriorating rock properties limit producibility. In addition, extreme depths (13,000 ft) present a challenging environment for hydraulic fracturing and artificial lift. Lastly, a mature waterflood increases risk because of the uncertainty with size and location of flood fronts. This project attempts to demonstrate the effectiveness of exploiting the distal fan margin of this slope-basin clastic reservoir through the use of a high-angle well completed with multiple hydraulic-fracture treatments. The combination of a high-angle (or horizontal) well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. The equivalent production rate and reserves of three vertical wells are anticipated at one-half to two-thirds the cost.

  17. Pedicular stress fracture in the lumbar spine

    International Nuclear Information System (INIS)

    Chong, V.F.H.; Htoo, M.M.

    1997-01-01

    Spondylolisthesis with or without spondylolysis is common in the lumbar spine. Associated fracture in the pedicle ('pediculolysis') is unusual. The margins of pedicular stress fractures, like spondylolysis, usually appear sclerotic. A patient with a pedicular stress fracture with minimal marginal sclerosis suggesting an injury of recent onset is presented here. There was associated bilateral spondylolysis. The findings in this patient suggest that established pediculolysis probably represents a stress fracture that has failed to heal. (authors)

  18. Hydraulic Fracturing At Sedimentary Basin Scale Fracturation hydraulique à l'échelle des bassins sédimentaires

    Directory of Open Access Journals (Sweden)

    Schneider F.

    2006-12-01

    Full Text Available One key point for simulating the hydraulic fracturing at basin scale, is to be able to compute the stress tensor. This is generally not addressed in basin model because of the complexity of this problem. In order to get access to the stress tensor we have to assume that:- one of the principal stress is vertical and equals the overburden weight;- the horizontal stress is deduced from the vertical stress with the K0 coefficient that is a function of depth and of the tectonical setting. Consolidation is considered here as the combined effect of the mechanical compaction and the chemical compaction. The mechanical compaction is mainly caused by the rearrangement of grains during burial and could be represented at the macroscopical scale by an elastoplastic rheology. The chemical compaction is considered here as resulting from dissolution-precipitation mechanisms, generally induced by stress (pressure-solution. The chemical compaction could be represented at the macroscopical scale by a viscoplastic rheology. The complete elastoplastic yield is defined by the union of the consolidation elastoplastic yield and of the different failure criteria that could be seen as elastobrittle yields. Thus, the elastoplastic yield is composed of six elementary elastoplastic yields which define the onset of vertical compaction, horizontal compaction, vertical tensile fracturing, horizontal tensile fracturing, subvertical shear fracturing, and subhorizontal shear fracturing. Due to the consolidation, most of the parameters that describe the physical properties of the sediments evolve with the geological times. One difficulty is to quantify the degree of evolution of the porous medium during its geological history. Here, we have chosen to measure the evolution of the sediments by their porosity. The local simulations showed that fracturing may occur is numerous configurations. Some of these configurations indicate that the sediments can reach the limit of its elastic

  19. Boundary element simulation of petroleum reservoirs with hydraulically fractured wells

    Science.gov (United States)

    Pecher, Radek

    The boundary element method is applied to solve the linear pressure-diffusion equation of fluid-flow in porous media. The governing parabolic partial differential equation is transformed into the Laplace space to obtain the elliptic modified-Helmholtz equation including the homogeneous initial condition. The free- space Green's functions, satisfying this equation for anisotropic media in two and three dimensions, are combined with the generalized form of the Green's second identity. The resulting boundary integral equation is solved by following the collocation technique and applying the given time-dependent boundary conditions of the Dirichlet or Neumann type. The boundary integrals are approximated by the Gaussian quadrature along each element of the discretized domain boundary. Heterogeneous regions are represented by the sectionally-homogeneous zones of different rock and fluid properties. The final values of the interior pressure and velocity fields and of their time-derivatives are found by numerically inverting the solutions from the Laplace space by using the Stehfest's algorithm. The main extension of the mostly standard BEM-procedure is achieved in the modelling of the production and injection wells represented by internal sources and sinks. They are treated as part of the boundary by means of special single-node and both-sided elements, corresponding to the line and plane sources respectively. The wellbore skin and storage effects are considered for the line and cylindrical sources. Hydraulically fractured wells of infinite conductivity are handled directly according to the specified constraint type, out of the four alternatives. Fractures of finite conductivity are simulated by coupling the finite element model of their 1D-interior with the boundary element model of their 2D- exterior. Variable fracture width, fractures crossing zone boundaries, ``networking'' of fractures, fracture-tip singularity handling, or the 3D-description are additional advanced

  20. Impacts on water quality by hydraulic fracturing in Pennsylvania

    Science.gov (United States)

    Yan, B.; Stute, M.; Chillrud, S. N.; Ross, J. M.; Howarth, M.; Panettieri, R.; Saberi, P.

    2015-12-01

    Shale gas development, including drilling and hydraulic fracturing, is rapidly increasing throughout the United States and, indeed, the rest of the world. Systematic surveys of water quality both pre- and post drilling/production are sparse. To examine the impacts of shale gas production on water quality, pilot studies have been conducted in adjacent counties of western NY (Chemung, Tioga, Broome, and Delaware) and northern PA (Bradford, Susquehanna, and Wayne). These 7 counties along the border of NY and PA share similar geology and demographic compositions and have been identified as a key area to develop shale gas with the key difference that active fracking is occurring in PA but there is no fracking yet in NY. Measurements include a suite of major and trace elements, methane and its stable isotopes, noble gases and tritium for dating purposes, and the primary radioactive elements of potential concern, radon and radium. We found elevated methane levels on both sides of the border. Higher levels of major ions were observed in PA samples close to the gas wells in the valley, possibly from hydraulic fracturing activities. The lab analysis of samples collected in recently launched 100 Bottom Project is ongoing and the results will be presented in this conference.

  1. Fracture patterns and stresses in granite

    International Nuclear Information System (INIS)

    Price, N.J.

    1979-01-01

    If granite bodies are to be used as receptacles for toxic waste materials, the presence or absence of barren fractures and the virgin stresses in the granite are of fundamental importance. Unfortunately, very little is known regarding the incidence of fractures, or stresses, which exist at depths (of about 1 km) in granite bodies. A simple analysis is presented of a hypothetical intrusion which indicates the magnitudes of stresses and the possible fracture development which may be expected in such bodies. (auth)

  2. Influences of Hydraulic Fracturing on Fluid Flow and Mineralization at the Vein-Type Tungsten Deposits in Southern China

    Directory of Open Access Journals (Sweden)

    Xiangchong Liu

    2017-01-01

    Full Text Available Wolframite is the main ore mineral at the vein-type tungsten deposits in the Nanling Range, which is a world-class tungsten province. It is disputed how wolframite is precipitated at these deposits and no one has yet studied the links of the mechanical processes to fluid flow and mineralization. Finite element-based numerical experiments are used to investigate the influences of a hydraulic fracturing process on fluid flow and solubility of CO2 and quartz. The fluids are aqueous NaCl solutions and fluid pressure is the only variable controlling solubility of CO2 and quartz in the numerical experiments. Significant fluctuations of fluid pressure and high-velocity hydrothermal pulse are found once rock is fractured by high-pressure fluids. The fluid pressure drop induced by hydraulic fracturing could cause a 9% decrease of quartz solubility. This amount of quartz deposition may not cause a significant decrease in rock permeability. The fluid pressure decrease after hydraulic fracturing also reduces solubility of CO2 by 36% and increases pH. Because an increase in pH would cause a major decrease in solubility of tungsten, the fluid pressure drop accompanying a hydraulic fracturing process facilitates wolframite precipitation. Our numerical experiments provide insight into the mechanisms precipitating wolframite at the tungsten deposits in the Nanling Range as well as other metals whose solubility is strongly dependent on pH.

  3. Low polymer hydraulic fracturing applications in Reconcavo basin wells can reduce cost and improve conductivity

    International Nuclear Information System (INIS)

    Suzart, Joao Walter Pereira; Araujo, Paulo Fernando de

    2000-01-01

    Gels used for hydraulic-fracturing treatments generally contain high concentrations of polymer. The polymer helps the fracturing fluid achieve the level of viscosity necessary for transporting proppant through the rock matrix. However, high-polymer gels leave greater amounts of residue in the formation and can therefore cause formation damage. This paper describes how low polymer (L P) gels can be used for hydraulic-fracturing operations to reduce job costs and increase conductivity by reducing formation damage while maintaining the characteristics of a high-polymer gel. The L P fluid system has a low p H and contains an appropriate breaker concentration. Operators have achieved positive results with this system, which allows them to measure robust gel breaks and reduces the necessity for well cleaning. Consequently, formation damage can be significantly reduced. (author)

  4. Pedicular stress fracture in the lumbar spine

    Energy Technology Data Exchange (ETDEWEB)

    Chong, V.F.H.; Htoo, M.M. [Singapore General Hospital, Singapore, (Singapore). Department of Diagnostic Radiology

    1997-08-01

    Spondylolisthesis with or without spondylolysis is common in the lumbar spine. Associated fracture in the pedicle (`pediculolysis`) is unusual. The margins of pedicular stress fractures, like spondylolysis, usually appear sclerotic. A patient with a pedicular stress fracture with minimal marginal sclerosis suggesting an injury of recent onset is presented here. There was associated bilateral spondylolysis. The findings in this patient suggest that established pediculolysis probably represents a stress fracture that has failed to heal. (authors). 10 refs., 2 figs.

  5. Fracture Patterns within the Shale Hills Critical Zone Observatory

    Science.gov (United States)

    Singha, K.; White, T.; Perron, J.; Chattopadhyay, P. B.; Duffy, C.

    2012-12-01

    Rock fractures are known to exist within the deep Critical Zone and are expected to influence groundwater flow, but there are limited data on their orientation and spatial arrangement and no general framework for systematically predicting their effects. Here, we explore fracture patterns within the Susquehanna-Shale Hills Critical Zone Observatory, and consider how they may be influenced by weathering, rock structure, and stress via field observations of variable fracture orientation within the site, with implications for the spatial variability of structural control on hydrologic processes. Based on field observations from 16-m deep boreholes and surface outcrop, we suggest that the appropriate structural model for the watershed is steeply dipping strata with meter- to decimeter-scale folds superimposed, including a superimposed fold at the mouth of the watershed that creates a short fold limb with gently dipping strata. These settings would produce an anisotropy in the hydraulic conductivity and perhaps also flow, especially within the context of the imposed stress field. Recently conducted 2-D numerical stress modeling indicates that the proxy for shear fracture declines more rapidly with depth beneath valleys than beneath ridgelines, which may produce or enhance the spatial variability in permeability. Even if topographic stresses do not cause new fractures, they could activate and cause displacement on old fractures, making the rocks easier to erode and increasing the permeability, and potentially driving a positive feedback that enhances the growth of valley relief. Calculated stress fields are consistent with field observations, which show a rapid decline in fracture abundance with increasing depth below the valley floor, and predict a more gradual trend beneath ridgetops, leading to a more consistent (and lower) hydraulic conductivity with depth on the ridgetops when compared to the valley, where values are higher but more variable with depth. Hydraulic

  6. Jogger's fracture and other stress fractures of the lumbo-sacral spine

    International Nuclear Information System (INIS)

    Abel, M.S.

    1985-01-01

    The posterior rings of the lower lumbo-sacral vertebrae are subject to stress fractures at any part - pedicle, pars, or lamina. The site of fracture is apparently determined by the axis of weight bearing. The three illustrative clinical examples cited include a jogger with a laminar fracture, a ballet dancer with pedicle fractures, and a nine-year-old boy with fractures of pars and lamina. Chronic low back pain is the typical complaint with stress fractures of the lower lumbo-sacral spine. Special imaging techniques are usually needed to demonstrate these lesions, including vertebral arch views, multi-directional tomography, and computed tomography (CT). (orig.)

  7. Quantifying Water-Rock Interactions during Hydraulic Fracturing from the Analysis of Flowback Water

    Science.gov (United States)

    Osselin, F.; Nightingale, M.; Kloppmann, W.; Gaucher, E.; Clarkson, C.; Mayer, B.

    2017-12-01

    Hydraulic fracturing technologies have facilitated the rapid development of shale gas and other unconventional resources throughout the world. In order to get sufficient access to the trapped hydrocarbon, it is necessary to fracture the bedrock and increase its permeability. Fracturing fluids are usually composed of tens of thousand of cubic meters of low salinity water with numerous additives, such as viscosity agent or breakers. The objective of this study was to investigate and quantify the water-rock interactions during hydraulic fracturing. This study was based on repeated sampling of flowback water from a hydraulically fractured well in Alberta, Canada. The flowback water was sampled 24 times during the first week and one last time after one, and analyzed for major ions and trace elements, as well as stable isotopes of sulfate and water among others. Results showed that salinity rapidly increases up to 100 000 mg/L at the end of the first week. We demonstrate that conservative species such as Na and Cl follow a clear two end-members mixing line, while some species including sulfate had much higher concentrations (8 times higher than the expected value from the mixing line). This indicates that the rapid increase of salinity in flowback water is caused by both mixing with formation water initially present in the shale formation, and from water-rock interactions triggered by the fracturing fluid and in some cases by the additives. Stable isotope data suggest that additional sulfate is mobilized as a consequence of pyrite oxidation, releasing sulfate, iron and potentially other heavy metals into the flowback water. This release of excess sulfate can be detrimental because it has the potential to promote scaling of sulfate minerals. Moreover, pyrite oxidation is a highly acidifying reaction and this may decrease the effectiveness of other additives, and promote carbonate minerals dissolution enhancing further scaling. We propose that a better control of the

  8. Hydraulic fracturing in cells and tissues: fracking meets cell biology.

    Science.gov (United States)

    Arroyo, Marino; Trepat, Xavier

    2017-02-01

    The animal body is largely made of water. A small fraction of body water is freely flowing in blood and lymph, but most of it is trapped in hydrogels such as the extracellular matrix (ECM), the cytoskeleton, and chromatin. Besides providing a medium for biological molecules to diffuse, water trapped in hydrogels plays a fundamental mechanical role. This role is well captured by the theory of poroelasticity, which explains how any deformation applied to a hydrogel causes pressure gradients and water flows, much like compressing a sponge squeezes water out of it. Here we review recent evidence that poroelastic pressures and flows can fracture essential biological barriers such as the nuclear envelope, the cellular cortex, and epithelial layers. This type of fracture is known in engineering literature as hydraulic fracturing or 'fracking'. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Combined Permeability Improvement Technology of High-pressure Hydraulic Slotting with Hydraulic Fracturing and Its Application%高压水力割缝和压裂联合增透技术及应用

    Institute of Scientific and Technical Information of China (English)

    秦江涛; 陈玉涛

    2016-01-01

    针对白皎煤矿突出煤层构造应力高、透气性系数低、瓦斯抽采效果差等问题,在238底板瓦斯抽采巷对B4煤层采用了水力割缝和压裂联合增透技术,应用结果表明该技术相比水力压裂技术和普通抽采技术提高了煤层透气性,瓦斯抽采纯量较水力压裂钻孔提高了1.33倍,瓦斯体积分数是普通抽采钻孔的2.76倍,联合增透钻孔汇总瓦斯体积分数保持在30%以上且无衰减,具有良好的抽采效果.%To counter the problems of high structural stress, low air permeability coefficient and poor gas drainage effect of the outburst coal seam in Baijiao Mine, the gas drainage test in B4 seam by 238 floor drainage roadway was carried out with the combined permeability improvement technology of high-pressure hydraulic slotting with hydraulic fracturing. The application results showed that this technology improved the permeability of the coal seam as compared to the hydraulic fracturing technology and the conventional gas drainage technology. The pure gas drainage volume increased 1. 33 times to that by hydraulic fracturing, the volume fraction of gas was 2. 76 times higher than that by the conventional drainage boreholes, the summary volume fraction of gas with the combined permeability improvement technology maintained over 30% without any attenuation, so this technology has good drainage effect.

  10. Regulation of hydraulic fracturing in South Africa: a project life-cycle ...

    African Journals Online (AJOL)

    This note deals with the 2015 regulations pertaining to hydraulic fracturing in South Africa from a project life-cycle approach. A brief history of the fragmentation of the regulation of environmental and mining related matters is provided, followed by a discussion of the application of the 2015 regulations during the project life ...

  11. Diffusive Imaging of Hydraulically Induced and Natural Fracture Systems

    Science.gov (United States)

    Eftekhari, B.; Marder, M. P.; Patzek, T. W.

    2017-12-01

    Hydraulic fracturing of tight shales continues to provide the US with a major source of energy. Efficiency of gas recovery in shales depends upon the geometry of the resulting network of fractures, the details of which are not yet fully understood. The present research explores how much of the underlying geometry can be deduced from the time dependence of the flow of gas out of the reservoir. We consider both ideal and real gas. In the case of real gas, we calculate production rate for parallel planar hydrofractures embedded in an infinite reservoir. Transport is governed by a nonlinear diffusion equation, which we solve exactly with a scaling curve. The scaling curve production rate declines initially as 1 over square root time, then as an exponential, and finally as 1 over square root of time again at late time. We show that for a given hydraulically fractured well, the onsets of transition between different decline regimes provides a direct estimate of a characteristic spacing of the underlying fracture network. We show that the scaling solution accurately fits the production history of more than 15,000 wells in the Barnett Shale. Almost all of the wells either have not yet transitioned into the late time decline or have been refractured while in exponential decline. However, there are 36 wells which show the late time transition. These allow us to calculate the characteristic spacing, which turns out to have a mode at about 10 m, a minimum at 1.6 m and a maximum at 13.3 m. We estimate that over 30 years these wells will produce on average about 45% more gas because of diffusion from the infinite external reservoir than they would if this contribution is neglected. Finally, we compute the rate at which ideal gas diffuses within an infinite region of rock into a specific absorbing fractal fracture network, which we model using geological constraints and percolation theory. Our solution employs a Brownian walk and the first passage kinetic Monte Carlo algorithm

  12. High-Risk Stress Fractures: Diagnosis and Management.

    Science.gov (United States)

    McInnis, Kelly C; Ramey, Lindsay N

    2016-03-01

    Stress fractures are common overuse injuries in athletes. They occur during periods of increased training without adequate rest, disrupting normal bone reparative mechanisms. There are a host of intrinsic and extrinsic factors, including biochemical and biomechanical, that put athletes at risk. In most stress fractures, the diagnosis is primarily clinical, with imaging indicated at times, and management focused on symptom-free relative rest with advancement of activity as tolerated. Overall, stress fractures in athletes have an excellent prognosis for return to sport, with little risk of complication. There is a subset of injuries that have a greater risk of fracture progression, delayed healing, and nonunion and are generally more challenging to treat with nonoperative care. Specific locations of high-risk stress fracture include the femoral neck (tension side), patella, anterior tibia, medial malleolus, talus, tarsal navicular, proximal fifth metatarsal, and great toe sesamoids. These sites share a characteristic region of high tensile load and low blood flow. High-risk stress fractures require a more aggressive approach to evaluation, with imaging often necessary, to confirm early and accurate diagnosis and initiate immediate treatment. Treatment consists of nonweight-bearing immobilization, often with a prolonged period away from sport, and a more methodic and careful reintroduction to athletic activity. These stress fractures may require surgical intervention. A high index of suspicion is essential to avoid delayed diagnosis and optimize outcomes in this subset of stress fractures. Copyright © 2016 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

  13. Stress fractures in military training

    International Nuclear Information System (INIS)

    Jofre, M.J.; Sierralta, M.P.

    2002-01-01

    During military training, the incidence of overuse injuries like stress fractures increase. The aim of the study was to investigate the utility of bone scan in a military population with clinical suspected stress fractures or periostitis. Material and methods: A three-year retrospective analysis was made on patients who were clinically diagnosed with stress fractures at the Military Hospital Nuclear Medicine Department. Thirty-seven patients were studied (mean age 23. +/- 8 y.o; 31 males), 28 cases of which (76%) had tibial stress syndrome. Other localizations were lumbar spine, femoral, fibular, tarsal or metatarsal. Bone scintigraphy was performed injecting 1036 MBq of Tc99m-MDP i.v. Whole body images and lateral projections of lower extremities were done. Results: Bone scan in tibial syndrome was positive for 23 cases (82%), 65% of them were bilateral and 13% also had femoral injuries. X-rays were done in 10 cases and were all negative. In other localizations, the bone scans were negative, but demonstrated other degenerative lesions. All stress fractures were conservatively treated with non-steroidal anti-inflammatories and suspension of physical activity. Conclusions: Bone scan is a reliable confirmatory tool for tibial stress syndrome diagnosis. In addition, it helps to determine both the severity and extension of the injury as well as support the indication of rest in the military population

  14. Stress fractures in military training

    Energy Technology Data Exchange (ETDEWEB)

    Jofre, M J; Sierralta, M P [Military Hospital Nuclear Medicine Department, Santiago (Chile)

    2002-09-01

    During military training, the incidence of overuse injuries like stress fractures increase. The aim of the study was to investigate the utility of bone scan in a military population with clinical suspected stress fractures or periostitis. Material and methods: A three-year retrospective analysis was made on patients who were clinically diagnosed with stress fractures at the Military Hospital Nuclear Medicine Department. Thirty-seven patients were studied (mean age 23. +/- 8 y.o; 31 males), 28 cases of which (76%) had tibial stress syndrome. Other localizations were lumbar spine, femoral, fibular, tarsal or metatarsal. Bone scintigraphy was performed injecting 1036 MBq of Tc99m-MDP i.v. Whole body images and lateral projections of lower extremities were done. Results: Bone scan in tibial syndrome was positive for 23 cases (82%), 65% of them were bilateral and 13% also had femoral injuries. X-rays were done in 10 cases and were all negative. In other localizations, the bone scans were negative, but demonstrated other degenerative lesions. All stress fractures were conservatively treated with non-steroidal anti-inflammatories and suspension of physical activity. Conclusions: Bone scan is a reliable confirmatory tool for tibial stress syndrome diagnosis. In addition, it helps to determine both the severity and extension of the injury as well as support the indication of rest in the military population.

  15. Oil shale in situ research and development. Final report, August 1, 1977--December 22, 1978. [Hydraulic fractures; explosive rubblization

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, H.B.

    1978-01-01

    The selected Site Section 17 was prepared for hydraulic fracturing and explosive rubblization, and these operations accomplished. This report presents the field and laboratory preparations for the fracturing, rubblization, and evaluation operations. A series of four, parallel, hydraulically induced fractures was created during the first year. The evaluation tests showed the following about the four hydraulic fractures: (1) They were horizontal and narrow, that is, as large as 0.05 inches thick within a 50-foot radius and as small as 0.0011 inches thick for the average of all four fractures over the entire radius. (2) They extended at least 113 feet to the outer ring of production wells in a southeasterly direction. (3) They extended out beyond the outer ring of production wells in a northwesterly direction. (4) They had some degree of communication with the naturally fractured aquifer lying about them. And, (5), they had no significant communication with naturally fractured aquifer lying below them. The rubblization event took place on 21 August 1978, early in the second year of the contract. An evaluation of the areal extent, thickness, porosity, interconnectivity, and the influence of the explosion upon the adjacent aquifers was determined. The dynamic tests showed that the explosive slurry was loaded into the four hydraulic features and that detonation occurred simultaneously. The postrubblization evaluation demonstrated that: (1) There were four layers of damage of less than two-feet thick each, (2) massive permeability was apparent from all production wells, and (3) the permeability is in the form of block, open cracks rather than porous medium.

  16. Baseflow recession analysis in a large shale play: Climate variability and anthropogenic alterations mask effects of hydraulic fracturing

    Science.gov (United States)

    Arciniega-Esparza, Saúl; Breña-Naranjo, Jose Agustín; Hernández-Espriú, Antonio; Pedrozo-Acuña, Adrián; Scanlon, Bridget R.; Nicot, Jean Philippe; Young, Michael H.; Wolaver, Brad D.; Alcocer-Yamanaka, Victor Hugo

    2017-10-01

    Water resources development and landscape alteration exert marked impacts on water-cycle dynamics, including areas subjected to hydraulic fracturing (HF) for exploitation of unconventional oil and gas resources found in shale or tight sandstones. Here we apply a conceptual framework for linking baseflow analysis to changes in water demands from different sectors (e.g. oil/gas extraction, irrigation, and municipal consumption) and climatic variability in the semiarid Eagle Ford play in Texas, USA. We hypothesize that, in water-limited regions, baseflow (Qb) changes are partly due (along with climate variability) to groundwater abstraction. For a more realistic assessment, the analysis was conducted in two different sets of unregulated catchments, located outside and inside the Eagle Ford play. Three periods were considered in the analysis related to HF activities: pre-development (1980-2000), moderate (2001-2008) and intensive (2009-2015) periods. Results indicate that in the Eagle Ford play region, temporal changes in baseflow cannot be directly related to the increase in hydraulic fracturing. Instead, substantial baseflow declines during the intensive period of hydraulic fracturing represent the aggregated effects from the combination of: (1) a historical exceptional drought during 2011-2012; (2) increased groundwater-based irrigation; and (3) an intensive hydraulic fracturing activity.

  17. Microbial community changes in hydraulic fracturing fluids and produced water from shale gas extraction.

    Science.gov (United States)

    Murali Mohan, Arvind; Hartsock, Angela; Bibby, Kyle J; Hammack, Richard W; Vidic, Radisav D; Gregory, Kelvin B

    2013-11-19

    Microbial communities associated with produced water from hydraulic fracturing are not well understood, and their deleterious activity can lead to significant increases in production costs and adverse environmental impacts. In this study, we compared the microbial ecology in prefracturing fluids (fracturing source water and fracturing fluid) and produced water at multiple time points from a natural gas well in southwestern Pennsylvania using 16S rRNA gene-based clone libraries, pyrosequencing, and quantitative PCR. The majority of the bacterial community in prefracturing fluids constituted aerobic species affiliated with the class Alphaproteobacteria. However, their relative abundance decreased in produced water with an increase in halotolerant, anaerobic/facultative anaerobic species affiliated with the classes Clostridia, Bacilli, Gammaproteobacteria, Epsilonproteobacteria, Bacteroidia, and Fusobacteria. Produced water collected at the last time point (day 187) consisted almost entirely of sequences similar to Clostridia and showed a decrease in bacterial abundance by 3 orders of magnitude compared to the prefracturing fluids and produced water samplesfrom earlier time points. Geochemical analysis showed that produced water contained higher concentrations of salts and total radioactivity compared to prefracturing fluids. This study provides evidence of long-term subsurface selection of the microbial community introduced through hydraulic fracturing, which may include significant implications for disinfection as well as reuse of produced water in future fracturing operations.

  18. Seismicity Induced by Hydraulic Fracturing in Shales: A Bedding Plane Slip Model

    Czech Academy of Sciences Publication Activity Database

    Staněk, František; Eisner, Leo

    2017-01-01

    Roč. 122, č. 10 (2017), s. 7912-7926 ISSN 2169-9313 Institutional support: RVO:67985891 Keywords : microseismic * seismicity * hydraulic fracturing * bedding plane slip Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: 1.7 Other natural sciences Impact factor: 3.350, year: 2016

  19. Non–double-couple mechanisms of microearthquakes induced by hydraulic fracturing

    Czech Academy of Sciences Publication Activity Database

    Šílený, Jan; Hill, D. P.; Eisner, L.; Cornet, F. H.

    2009-01-01

    Roč. 114, B8 (2009), B08307/1-B08307/15 ISSN 0148-0227 R&D Projects: GA AV ČR IAA300120502; GA ČR GA205/09/0724 Grant - others:EC(XE) MTKI-CT-2004-517242 Institutional research plan: CEZ:AV0Z30120515 Keywords : microearthquakes * source mechanisms * hydraulic fracturing Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 3.082, year: 2009

  20. Numerical Simulation of Permeability Change in Wellbore Cement Fractures after Geomechanical Stress and Geochemical Reactions Using X-ray Computed Tomography Imaging.

    Science.gov (United States)

    Kabilan, Senthil; Jung, Hun Bok; Kuprat, Andrew P; Beck, Anthon N; Varga, Tamas; Fernandez, Carlos A; Um, Wooyong

    2016-06-21

    X-ray microtomography (XMT) imaging combined with three-dimensional (3D) computational fluid dynamics (CFD) modeling technique was used to study the effect of geochemical and geomechanical processes on fracture permeability in composite Portland cement-basalt caprock core samples. The effect of fluid density and viscosity and two different pressure gradient conditions on fracture permeability was numerically studied by using fluids with varying density and viscosity and simulating two different pressure gradient conditions. After the application of geomechanical stress but before CO2-reaction, CFD revealed fluid flow increase, which resulted in increased fracture permeability. After CO2-reaction, XMT images displayed preferential precipitation of calcium carbonate within the fractures in the cement matrix and less precipitation in fractures located at the cement-basalt interface. CFD estimated changes in flow profile and differences in absolute values of flow velocity due to different pressure gradients. CFD was able to highlight the profound effect of fluid viscosity on velocity profile and fracture permeability. This study demonstrates the applicability of XMT imaging and CFD as powerful tools for characterizing the hydraulic properties of fractures in a number of applications like geologic carbon sequestration and storage, hydraulic fracturing for shale gas production, and enhanced geothermal systems.

  1. Model of T-Type Fracture in Coal Fracturing and Analysis of Influence Factors of Fracture Morphology

    Directory of Open Access Journals (Sweden)

    Yuwei Li

    2018-05-01

    Full Text Available Special T-type fractures can be formed when coal is hydraulically fractured and there is currently no relevant theoretical model to calculate and describe them. This paper first establishes the height calculation model of vertical fractures in multi-layered formations and deduces the stress intensity factor (SIF at the upper and lower sides of the fracture in the process of vertical fracture extension. Combined with the fracture tip stress analysis method of fracture mechanics theory, the horizontal bedding is taken into account for tensile and shear failure, and the critical mechanical conditions for the formation of horizontal fracture in coal are obtained. Finally, the model of T-type fracture in coal fracturing is established, and it is verified by fracturing simulation experiments. The model calculation result shows that the increase of vertical fracture height facilitates the increase of horizontal fracture length. The fracture toughness of coal has a significant influence on the length of horizontal fracture and there is a threshold. When the fracture toughness is less than the threshold, the length of horizontal fracture remains unchanged, otherwise, the length of horizontal fracture increases rapidly with the increase of fracture toughness. When the shear strength of the interface between the coalbed and the interlayer increases, the length of the horizontal fracture of the T-type fracture rapidly decreases.

  2. Rare stress fracture: longitudinal fracture of the femur.

    Science.gov (United States)

    Pérez González, M; Velázquez Fragua, P; López Miralles, E; Abad Moretón, M M

    42-year-old man with pain in the posterolateral region of the right knee that began while he was running. Initially, it was diagnosed by magnetic resonance (MR) as a possible aggressive process (osteosarcoma or Ewing's sarcoma) but with computed tomography it was noted a cortical hypodense linear longitudinal image with a continuous, homogeneous and solid periosteal reaction without clear soft tissue mass that in this patient suggest a longitudinal distal femoral fatigue stress fracture. This type of fracture at this location is very rare. Stress fractures are entities that can be confused with an agressive process. MR iscurrently the most sensitive and specific imaging method for its diagnosis. Copyright © 2017 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

  3. Identification of MHF (massive hydraulic fracturing) fracture planes and flow paths: A correlation of well log data with patterns in locations of induced seismicity

    Energy Technology Data Exchange (ETDEWEB)

    Dreesen, D.; Malzahn, M.; Fehler, M.; Dash, Z.

    1987-01-01

    One of the critical steps in developing a hot dry rock geothermal system is the creation of flow paths through the rock between two wellbores. To date, circulation systems have only been created by drilling one wellbore, hydraulically fracturing the well (which induces microearthquakes), locating the microearthquakes and then drilling a second wellbore through the zone of seismicity. A technique for analyzing the pattern of seismicity to determine where fracture planes are located in the seismically active region has recently been developed. This allows us to distinguish portions of the seismically active volume which are most likely to contain significant flow paths. We applied this technique to seismic data collected during a massive hydraulic fracturing (MHF) treatment and found that the fracture planes determined by the seismic method are confirmed by borehole temperature and caliper logs which indicate where permeable fractures and/or zones of weakness intersect the wellbores. A geometric model based on these planes and well log data has enhanced our understanding of the reservoir flow paths created by fracturing and is consistent with results obtained during production testing of the reservoir.

  4. Analysis of fracture patterns and local stress field variations in fractured reservoirs

    Science.gov (United States)

    Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian

    2010-05-01

    A meaningful qualitative evaluation of permeabilities in fractured reservoirs in geothermal or hydrocarbon industry requires the spatial description of the existing discontinuity pattern within the area of interest and an analysis how these fractures might behave under given stress fields. This combined information can then be used for better estimating preferred fluid pathway directions within the reservoir, which is of particular interest for defining potential drilling sites. A description of the spatial fracture pattern mainly includes the orientation of rock discontinuities, spacing relationships between single fractures and their lateral extent. We have examined and quantified fracture patterns in several outcrops of granite at the Costa Brava, Spain, and in the Black Forest, Germany, for describing reservoir characteristics. For our analysis of fracture patterns we have used photogrammetric methods to create high-resolution georeferenced digital 3D images of outcrop walls. The advantage of this approach, compared to conventional methods for fracture analysis, is that it provides a better 3D description of the fracture geometry as the entity of position, extent and orientation of single fractures with respect to their surrounding neighbors is conserved. Hence for instance, the method allows generating fracture density maps, which can be used for a better description of the spatial distribution of discontinuities in a given outcrop. Using photogrammetric techniques also has the advantage to acquire very large data sets providing statistically sound results. To assess whether the recorded discontinuities might act as fluid pathways information on the stress field is needed. A 3D model of the regional tectonic structure was created and the geometry of the faults was put into a mechanical 3D Boundary Element (BE) Model. The model takes into account the elastic material properties of the geological units and the orientation of single fault segments. The

  5. Stress fractures of the foot and ankle.

    Science.gov (United States)

    Welck, M J; Hayes, T; Pastides, P; Khan, W; Rudge, B

    2017-08-01

    Stress fractures occur as a result of microscopic injuries sustained when bone is subjected to repeated submaximal stresses. Overtime, with repeated cycles of loading, accumulation of such injuries can lead to macro-structural failure and frank fracture. There are numerous stress fractures about the foot and ankle of which a trauma and orthopaedic surgeon should be aware. These include: metatarsal, tibia, calcaneus, navicular, fibula, talus, medial malleolus, sesamoid, cuneiform and cuboid. Awareness of these fractures is important as the diagnosis is frequently missed and appropriate treatment delayed. Late identification can be associated with protracted pain and disability, and may predispose to non-union and therefore necessitate operative intervention. This article outlines the epidemiology and risk factors, aetiology, presentation and management of the range of stress fractures in the foot and ankle. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Computed tomography of stress fracture

    International Nuclear Information System (INIS)

    Murcia, M.; Brennan, R.E.; Edeiken, J.

    1982-01-01

    An athletic young female developed gradual onset of pain in the right leg. Plain radiographs demonstrated solid periosteal reaction in the tibia compatible with stress fracture. She stopped sport activites but her pain continued. Follow-up radiographs of the tibia revealed changes suspicious for osteoid osteoma. Computed tomography (CT) scan demonstrated periosteal reaction, but in addition, lucent fracture lines in the tibial cortex were evident. CT obviated the need for more invasive diagnostic procedures in this patient. In selected cases CT may be useful to confirm the diagnosis of stress fracture when plain radiographic or routine tomographic studies are not diagnostic. (orig.)

  7. Computed tomography of stress fracture

    International Nuclear Information System (INIS)

    Murcia, M.; Brennan, R.E.; Edeiken, J.

    1982-01-01

    An athletic young female developed gradual onset of pain in the right leg. Plain radiographs demonstrated solid periosteal reaction in the tibia compatible with stress fracture. She stopped sport activites but her pain continued. Follow-up radiographs of the tibia revealed changes suspicious for osteoid osteoma. Computed tomography (CT) scan demonstrated periosteal reaction, but in addition, lucent fracture lines in the tibial cortex were evident. CT obviated the need for more invasive diagnostic procedures in this patient. In selected cases CT may be useful to confirm the diagnosis of stress fracture when plain radiographic or routine tomographic studies are not diagnostic

  8. Hydromechanical modeling of clay rock including fracture damage

    Science.gov (United States)

    Asahina, D.; Houseworth, J. E.; Birkholzer, J. T.

    2012-12-01

    Argillaceous rock typically acts as a flow barrier, but under certain conditions significant and potentially conductive fractures may be present. Fracture formation is well-known to occur in the vicinity of underground excavations in a region known as the excavation disturbed zone. Such problems are of particular importance for low-permeability, mechanically weak rock such as clays and shales because fractures can be relatively transient as a result of fracture self-sealing processes. Perhaps not as well appreciated is the fact that natural fractures can form in argillaceous rock as a result of hydraulic overpressure caused by phenomena such as disequlibrium compaction, changes in tectonic stress, and mineral dehydration. Overpressure conditions can cause hydraulic fracturing if the fluid pressure leads to tensile effective stresses that exceed the tensile strength of the material. Quantitative modeling of this type of process requires coupling between hydrogeologic processes and geomechanical processes including fracture initiation and propagation. Here we present a computational method for three-dimensional, hydromechanical coupled processes including fracture damage. Fractures are represented as discrete features in a fracture network that interact with a porous rock matrix. Fracture configurations are mapped onto an unstructured, three-dimensonal, Voronoi grid, which is based on a random set of spatial points. Discrete fracture networks (DFN) are represented by the connections of the edges of a Voronoi cells. This methodology has the advantage that fractures can be more easily introduced in response to coupled hydro-mechanical processes and generally eliminates several potential issues associated with the geometry of DFN and numerical gridding. A geomechanical and fracture-damage model is developed here using the Rigid-Body-Spring-Network (RBSN) numerical method. The hydrogelogic and geomechanical models share the same geometrical information from a 3D Voronoi

  9. Probabilistic Risk Assessment of Hydraulic Fracturing in Unconventional Reservoirs by Means of Fault Tree Analysis: An Initial Discussion

    Science.gov (United States)

    Rodak, C. M.; McHugh, R.; Wei, X.

    2016-12-01

    The development and combination of horizontal drilling and hydraulic fracturing has unlocked unconventional hydrocarbon reserves around the globe. These advances have triggered a number of concerns regarding aquifer contamination and over-exploitation, leading to scientific studies investigating potential risks posed by directional hydraulic fracturing activities. These studies, balanced with potential economic benefits of energy production, are a crucial source of information for communities considering the development of unconventional reservoirs. However, probabilistic quantification of the overall risk posed by hydraulic fracturing at the system level are rare. Here we present the concept of fault tree analysis to determine the overall probability of groundwater contamination or over-exploitation, broadly referred to as the probability of failure. The potential utility of fault tree analysis for the quantification and communication of risks is approached with a general application. However, the fault tree design is robust and can handle various combinations of regional-specific data pertaining to relevant spatial scales, geological conditions, and industry practices where available. All available data are grouped into quantity and quality-based impacts and sub-divided based on the stage of the hydraulic fracturing process in which the data is relevant as described by the USEPA. Each stage is broken down into the unique basic events required for failure; for example, to quantify the risk of an on-site spill we must consider the likelihood, magnitude, composition, and subsurface transport of the spill. The structure of the fault tree described above can be used to render a highly complex system of variables into a straightforward equation for risk calculation based on Boolean logic. This project shows the utility of fault tree analysis for the visual communication of the potential risks of hydraulic fracturing activities on groundwater resources.

  10. CANDIDATE GENE ANALYSIS IN ISRAELI SOLDIERS WITH STRESS FRACTURES

    Directory of Open Access Journals (Sweden)

    Ran Yanovich

    2012-03-01

    Full Text Available To investigate the association of polymorphisms within candidate genes which we hypothesized may contribute to stress fracture predisposition, a case-control, cross- sectional study design was employed. Genotyping 268 Single Nucleotide Polymorphisms- SNPs within 17 genes in 385 Israeli young male and female recruits (182 with and 203 without stress fractures. Twenty-five polymorphisms within 9 genes (NR3C1, ANKH, VDR, ROR2, CALCR, IL6, COL1A2, CBG, and LRP4 showed statistically significant differences (p < 0.05 in the distribution between stress fracture cases and non stress fracture controls. Seventeen genetic variants were associated with an increased stress fracture risk, and eight variants with a decreased stress fracture risk. None of the SNP associations remained significant after correcting for multiple comparisons (false discovery rate- FDR. Our findings suggest that genes may be involved in stress fracture pathogenesis. Specifically, the CALCR and the VDR genes are intriguing candidates. The putative involvement of these genes in stress fracture predisposition requires analysis of more cases and controls and sequencing the relevant genomic regions, in order to define the specific gene mutations

  11. Development of stress-modified fracture strain criterion for ductile fracture of API X65 steel

    International Nuclear Information System (INIS)

    Oh, Chang Kyun; Kim, Yun Jae; Park, Jin Moo; Kim, Woo Sik; Baek, Jong Hyun

    2005-01-01

    This paper presents a stress-modified fracture strain for API X65 steel used for gas pipeline, as a function of stress triaxiality. To determine the stress-modified fracture strain, tension test of bars with four different notch radii, made of API X65 steel, is firstly performed, from which true fracture strains are determined as a function of notch radius. Then detailed elastic-plastic, large strain Finite Element (FE) analyses are performed to estimate variations of stress triaxiality in the notched bars with load. Combining experimental with FE results provides the true fracture strain as a function of stress triaxiality, which is regarded as a criterion of ductile fracture. Application of the developed stress-modified fracture strain to failure prediction of gas pipes made of API X65 steel with various types of defects is discussed

  12. Multiscale pore networks and their effect on deformation and transport property alteration associated with hydraulic fracturing

    Science.gov (United States)

    Daigle, Hugh; Hayman, Nicholas; Jiang, Han; Tian, Xiao; Jiang, Chunbi

    2017-04-01

    clusters of organic-hosted pores prevents the overpressure from dissipating, resulting in localized overpressure at the micron scale. When the rock is subjected to a hydraulic fracture stimulation, the rock surrounding the main induced fracture experiences shear deformation. Those parts of the rock that contain overpressured fluids in the organic-hosted pores will be more likely to experience dilatancy in the form of brittle deformation; the portions of the rock lacking in organic-hosted pores will tend to experience compactive shear failure since the effective normal stresses are larger. The microcrack networks that propagate into the regions of organic-hosted porosity allow the hydrocarbons resident in those pores to migrate to the main induced tensile fractures. The disconnected nature of the microcrack networks causes only a slight increase in permeability, which is consistent with other observations. Our work illustrates how multiscale pore networks in shale interact with in situ stresses to affect the bulk shale rheology.

  13. STRESS FRACTURE PREVALENCE IN ELITE FIGURE SKATERS

    Directory of Open Access Journals (Sweden)

    Sanda Dubravcic-Simunjak

    2008-09-01

    Full Text Available Figure skating is a physically demanding sport that requires a unique combination of artistic ability, speed, agility, flexibility and power. During the last decades not only the competitive schedule has become tougher, but after introduction of the new judging system in 2003, also more emphasis is put on difficult technical elements, jumps, steps and spins (ISU Rules, 2006. More studies about possible increasing prevalence of stress fractures in figure skaters and contributing factors are lacking (Dubravcic-Simunjak et al., 2003; Moran, 2000; Pecina et al., 1990. Therefore the aim of this study was to obtain data about the current stress fracture cumulative risk among elite junior and senior figure skaters, as well as possible factors that may contribute to stress fracture incidence. An anonymous questionnaire, divided into 5 sections, inquired about the prevalence of stress fracture were mailed and distributed to all 62 International Skating Union (ISU members by the ISU headquarters in Lausanne, Switzerland. The guidelines of the Helsinki declaration 2004 were followed. From the 644 skaters who received the questionnaire, 412 completed ones were returned from 110 female juniors (78 single skaters, 12 pair skaters and 20 ice dancers and 135 female seniors (97 single skaters, 16 pair skaters and 22 ice dancers and from 79 male juniors (47 single skaters, 12 pair skaters and 20 ice dancers and 88 male seniors (50 single skaters, 16 pair skaters and 22 ice dancers, coming from different ISU members. The response rate was 62% in females and 67% in males. The median age for female skaters was 16 years and for males 18 years (range 12-25 years. All participants started to skate between 3 and 6 years of age and started to compete in national and international competitions when they were between 5 and 7 years old. At the time of this analysis, they had been skating between 9 and 20 years.In females 41 (16.7%, and in males 25 (13.8% figure skaters

  14. Impacts of transient heat transfer modeling on prediction of advanced cladding fracture during LWR LBLOCA

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youho, E-mail: euo@kaist.ac.kr; Lee, Jeong Ik, E-mail: jeongiklee@kaist.ac.kr; NO, Hee Cheon, E-mail: hcno@kaist.ac.kr

    2016-03-15

    Highlights: • Use of constant heat transfer coefficient for fracture analysis is not sound. • On-time heat transfer coefficient should be used for thermal fracture prediction. • ∼90% of the actual fracture stresses were predicted with the on-time transient h. • Thermal-hydraulic codes can be used to better predict brittle cladding fracture. • Effects of surface oxides on thermal shock fracture should be accounted by h. - Abstract: This study presents the importance of coherency in modeling thermal-hydraulics and mechanical behavior of a solid for an advanced prediction of cladding thermal shock fracture. In water quenching, a solid experiences dynamic heat transfer rate evolutions with phase changes of the fluid over a short quenching period. Yet, such a dynamic change of heat transfer rates has been overlooked in the analysis of thermal shock fracture. In this study, we are presenting quantitative evidence against the prevailing use of a constant heat transfer coefficient for thermal shock fracture analysis in water. We conclude that no single constant heat transfer could suffice to depict the actual stress evolution subject to dynamic fluid phase changes. Use of the surface temperature dependent heat transfer coefficient will remarkably increase predictability of thermal shock fracture of brittle materials. The presented results show a remarkable stress prediction improvement up to 80–90% of the actual stress with the use of the surface temperature dependent heat transfer coefficient. For thermal shock fracture analysis of brittle fuel cladding such as oxidized zirconium-based alloy or silicon carbide during LWR reflood, transient subchannel heat transfer coefficients obtained from a thermal-hydraulics code should be used as input for stress analysis. Such efforts will lead to a fundamental improvement in thermal shock fracture predictability over the current experimental empiricism for cladding fracture analysis during reflood.

  15. Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery.

    Science.gov (United States)

    Chen, Jun-Wen; Zhang, Qiang; Li, Xiao-Shuang; Cao, Kun-Fang

    2010-07-01

    The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (g(s-max)) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, g(s-max) was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of g(s-max) and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors.

  16. Analysis of BTEX groundwater concentrations from surface spills associated with hydraulic fracturing operations.

    Science.gov (United States)

    Gross, Sherilyn A; Avens, Heather J; Banducci, Amber M; Sahmel, Jennifer; Panko, Julie M; Tvermoes, Brooke E

    2013-04-01

    Concerns have arisen among the public regarding the potentialfor drinking-water contamination from the migration of methane gas and hazardous chemicals associated with hydraulic fracturing and horizontal drilling. However, little attention has been paid to the potentialfor groundwater contamination resulting from surface spills from storage and production facilities at active well sites. We performed a search for publically available data regarding groundwater contamination from spills at ULS. drilling sites. The Colorado Oil and Gas Conservation Commission (COGCC) database was selected for further analysis because it was the most detailed. The majority ofspills were in Weld County, Colorado, which has the highest density of wells that used hydraulic fracturing for completion, many producing both methane gas and crude oil. We analyzed publically available data reported by operators to the COGCC regarding surface spills that impacted groundwater From July 2010 to July 2011, we noted 77 reported surface spills impacting the groundwater in Weld County, which resulted in surface spills associated with less than 0.5% of the active wells. The reported data included groundwater samples that were analyzed for benzene, toluene, ethylbenzene, andxylene (BTEX) components of crude oil. For groundwater samples taken both within the spill excavation area and on the first reported date of sampling, the BTEX measurements exceeded National Drinking Water maximum contaminant levels (MCLs) in 90, 30, 12, and 8% of the samples, respectively. However, actions taken to remediate the spills were effective at reducing BJTEX levels, with at least 84% of the spills reportedly achieving remediation as of May 2012. Our analysis demonstrates that surface spills are an important route of potential groundwater contamination from hydraulic fracturing activities and should be a focus of programs to protect groundwater While benzene can occur naturally in groundwater sources, spills and migration

  17. Results of Scientific and Technical Supervision of Hydraulic Fracturing Operations

    Directory of Open Access Journals (Sweden)

    I.Kh. Makhmutov

    2017-11-01

    Full Text Available The paper presents actual results of the research conducted as part of a field pilot project which consisted in interpretation of minifrac test data and evaluation of the efficiency of the scientific and technical supervision of fracking operations. The research program involved 11 wells targeting Devonian terrigenous reservoirs. Minifrac tests in one perforation interval were performed only in seven wells, that is approximately in 64% of total well count. A reliable fracture closure estimate was obtained only in six wells (55%, beginning of pseudoradial flow was observed only in one well out of 11 wells (9%. Hence, conventional minifrac tests should be supplemented with other diagnostic injection tests. Analysis of the performance of hydraulic fracturing operations conducted according to this pilot project plan indicates that fracture modelling, and scientific and technical supervision of fracking operations performed by Hydrofrac Research Laboratory of Institute TatNIPIneft Tatneft PJSC have yielded beneficial effects, namely 1.44 times increase in oil production rates.

  18. Post-excavation analysis of a revised hydraulic model of the Room 209 fracture, URL, Manitoba, Canada

    International Nuclear Information System (INIS)

    Winberg, A.; Tin Chan; Griffiths, P.; Nakka, B.

    1989-10-01

    An excavation response test was conducted in the Room 209 on the 240 m level of the AECL Underground Research Laboratory. Model predictions prior to excavation were made of the geomechanical response of the rock mass and the hydraulic response of an intercepted fracture. The model results were compared with excavation response data collected in a comprehensive instrument array. The work performed has addressed discrepancies between calculated and in-situ measured hydraulic response as part of a post-test analysis. Already existing hydraulic conceptual models of the fracture were revised and any available information was included in the new model. The model reproduced the pre-excavation hydraulic head distribution and hydraulic test results in terms of normalized flow rate within 5% and 75%, respectively. It was also found that the model reproduced the results of cross-hole hydraulic interference tests at least from a qualitative standpoint. The next stage of the modelling addressed the response of the model to a simulation of the excavated pilot tunnel. The preliminary results suggested the presence of a skin of different permeability in a thin zone around the periphery of the tunnel. By altering the permeability in the floor and along the walls and roof of the periphery, a better correspondence between calculated and measured drawdown was obtained. The same also applied for measured groundwater inflow in quantity, though not for the actual distribution on inflow. As probable causes for the interpreted positive skin in the crown and wall, temporary partial unsaturation and propulsion of debris into the fracture were suggested. The negative skin in the floor was interpreted as an effect of the dense and high energy charges used in the excavation process. (authors)

  19. Study on interaction between induced and natural fractures by extended finite element method

    Science.gov (United States)

    Xu, DanDan; Liu, ZhanLi; Zhuang, Zhuo; Zeng, QingLei; Wang, Tao

    2017-02-01

    Fracking is one of the kernel technologies in the remarkable shale gas revolution. The extended finite element method is used in this paper to numerically investigate the interaction between hydraulic and natural fractures, which is an important issue of the enigmatic fracture network formation in fracking. The criteria which control the opening of natural fracture and crossing of hydraulic fracture are tentatively presented. Influence factors on the interaction process are systematically analyzed, which include the approach angle, anisotropy of in-situ stress and fluid pressure profile.

  20. An overview of hydraulic fracturing and other formation stimulation technologies for shale gas production

    OpenAIRE

    GANDOSSI Luca

    2013-01-01

    The technology of hydraulic fracturing for hydrocarbon well stimulation is not new, but only fairly recently has become a very common and widespread technique, especially in North America, due to technological advances that have allowed extracting natural gas from so-called unconventional reservoirs (tight sands, coal beds and shale formations). The conjunction of techniques such as directional drilling, high volume fracturing, micro-seismic monitoring, etc. with the development of multi-well...

  1. Anomalous Transport in Natural Fracture Networks Induced by Tectonic Stress

    Science.gov (United States)

    Kang, P. K.; Lei, Q.; Lee, S.; Dentz, M.; Juanes, R.

    2017-12-01

    Fluid flow and transport in fractured rock controls many natural and engineered processes in the subsurface. However, characterizing flow and transport through fractured media is challenging due to the high uncertainty and large heterogeneity associated with fractured rock properties. In addition to these "static" challenges, geologic fractures are always under significant overburden stress, and changes in the stress state can lead to changes in the fracture's ability to conduct fluids. While confining stress has been shown to impact fluid flow through fractures in a fundamental way, the impact of confining stress on transportthrough fractured rock remains poorly understood. The link between anomalous (non-Fickian) transport and confining stress has been shown, only recently, at the level of a single rough fracture [1]. Here, we investigate the impact of geologic (tectonic) stress on flow and tracer transport through natural fracture networks. We model geomechanical effects in 2D fractured rock by means of a finite-discrete element method (FEMDEM) [2], which can capture the deformation of matrix blocks, reactivation of pre-existing fractures, and propagation of new cracks, upon changes in the stress field. We apply the model to a fracture network extracted from the geological map of an actual rock outcrop to obtain the aperture field at different stress conditions. We then simulate fluid flow and particle transport through the stressed fracture networks. We observe that anomalous transport emerges in response to confining stress on the fracture network, and show that the stress state is a powerful determinant of transport behavior: (1) An anisotropic stress state induces preferential flow paths through shear dilation; (2) An increase in geologic stress increases aperture heterogeneity that induces late-time tailing of particle breakthrough curves. Finally, we develop an effective transport model that captures the anomalous transport through the stressed fracture

  2. Report on alternative techniques to hydraulic fracturing for the exploration and exploitation of non conventional hydrocarbons - National Assembly No. 1581 / Senate No. 174

    International Nuclear Information System (INIS)

    LENOIR, Jean-Claude; BATAILLE, Christian

    2013-01-01

    Based on several hearings, and on missions in the USA and in Poland, this report addresses the issue of alternative techniques to hydraulic fracturing which appeared to be more advanced than hearings performed for a preliminary report had suggested. A first part outlines the necessity of fracturing the rock, and presents several possible modalities, proposes a detailed overview of alternative techniques to hydraulic fracturing used in the USA and in Poland. The second part outlines that coal gas is already an exploitable resource without rock fracturing; it discusses the possible perspectives thus associated for the old French coal-mining sites, outlines that this resource can be exploited without requiring hydraulic fracturing, and comments the first assessments. The third part addresses the possible management of risks associated with hydraulic fracturing: risks vary from one region to the other and therefore require further studies; the non-conventional hydrocarbon issue is addressed in different ways in the USA; the use of this technique must be controlled by public authorities. The next part outlines the need of an assessment of national resources before any assessment of the economic impact. The last part formulates several proposals for the future

  3. The radiological diagnosis of stress fracture

    International Nuclear Information System (INIS)

    Li Yonggang; Wang Renfa; Zhang Jingfeng; Wang Min

    2005-01-01

    Objective: To study the radiological features and biomechanics of stress fracture. Methods: The X-ray, CT, MRI, and ECT signs in 20 cases of stress fracture and its correlation to biomechanics were analyzed. Results: Of the 20 cases, 14 cases occurred in the tibia, 2 cases in the metatarsal bone, 1 case in the rib, 1 case in the neck of femur and ribs, 1 case in the middle-inferior part of the femur, and 1 case in the fibula. Tow early cases of stress fracture demonstrated a characteristic sign of 'gray cortex'. The spherical or abnormal generation of bony callus and periosteum proliferation that demonstrated 'double cortex' sign in 2 cases were the sign of bone remodeling and the 'button sign' was the sign of bone healing. CT scan could clearly show the pathologic changes of bone and the soft tissue edema. Bone callus showed low signal on T 1 WI and slight high signal on T 2 WI. The area of bone edema on MRI that demonstrated low signal on T 1 WI and high signal on T 2 WI was larger than that on CT. MRI showed a linear band of low signal on both T 1 WI and T 2 WI in the area of bone fracture. ECT showed a focal area of increased uptake in the abnormal areas. The areas of bone stress fracture were characteristic and accorded with the biomechanical weak area in the bone. Conclusion: Stress fracture occurs in the special parts of the bone and has characteristic imaging features. X-ray should still be used to find the fracture of bones in the first inspection. CT and MRI are very helpful in the differentiation. Although sensitive, bone scan has lower specificity than either CT or MRI. (authors)

  4. Modeling Studies to Constrain Fluid and Gas Migration Associated with Hydraulic Fracturing Operations

    Science.gov (United States)

    Rajaram, H.; Birdsell, D.; Lackey, G.; Karra, S.; Viswanathan, H. S.; Dempsey, D.

    2015-12-01

    The dramatic increase in the extraction of unconventional oil and gas resources using horizontal wells and hydraulic fracturing (fracking) technologies has raised concerns about potential environmental impacts. Large volumes of hydraulic fracturing fluids are injected during fracking. Incidents of stray gas occurrence in shallow aquifers overlying shale gas reservoirs have been reported; whether these are in any way related to fracking continues to be debated. Computational models serve as useful tools for evaluating potential environmental impacts. We present modeling studies of hydraulic fracturing fluid and gas migration during the various stages of well operation, production, and subsequent plugging. The fluid migration models account for overpressure in the gas reservoir, density contrast between injected fluids and brine, imbibition into partially saturated shale, and well operations. Our results highlight the importance of representing the different stages of well operation consistently. Most importantly, well suction and imbibition both play a significant role in limiting upward migration of injected fluids, even in the presence of permeable connecting pathways. In an overall assessment, our fluid migration simulations suggest very low risk to groundwater aquifers when the vertical separation from a shale gas reservoir is of the order of 1000' or more. Multi-phase models of gas migration were developed to couple flow and transport in compromised wellbores and subsurface formations. These models are useful for evaluating both short-term and long-term scenarios of stray methane release. We present simulation results to evaluate mechanisms controlling stray gas migration, and explore relationships between bradenhead pressures and the likelihood of methane release and transport.

  5. Microseismic signatures of hydraulic fracture growth in sediment formations: Observations and modeling

    Czech Academy of Sciences Publication Activity Database

    Fischer, Tomáš; Hainzl, S.; Eisner, L.; Shapiro, S. A.; Le Calvez, J. H.

    2008-01-01

    Roč. 113, č. B2 (2008), B02307/1-B02307/12 ISSN 0148-0227 Grant - others:EC(XE) MTKI-CT-2004-517242 Institutional research plan: CEZ:AV0Z30120515 Keywords : microseismic data * hydraulic fracture simulation * Texas Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 3.147, year: 2008

  6. A critical review of the risks to water resources from unconventional shale gas development and hydraulic fracturing in the United States.

    Science.gov (United States)

    Vengosh, Avner; Jackson, Robert B; Warner, Nathaniel; Darrah, Thomas H; Kondash, Andrew

    2014-01-01

    The rapid rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources in the U.S. The rise of shale gas development has triggered an intense public debate regarding the potential environmental and human health effects from hydraulic fracturing. This paper provides a critical review of the potential risks that shale gas operations pose to water resources, with an emphasis on case studies mostly from the U.S. Four potential risks for water resources are identified: (1) the contamination of shallow aquifers with fugitive hydrocarbon gases (i.e., stray gas contamination), which can also potentially lead to the salinization of shallow groundwater through leaking natural gas wells and subsurface flow; (2) the contamination of surface water and shallow groundwater from spills, leaks, and/or the disposal of inadequately treated shale gas wastewater; (3) the accumulation of toxic and radioactive elements in soil or stream sediments near disposal or spill sites; and (4) the overextraction of water resources for high-volume hydraulic fracturing that could induce water shortages or conflicts with other water users, particularly in water-scarce areas. Analysis of published data (through January 2014) reveals evidence for stray gas contamination, surface water impacts in areas of intensive shale gas development, and the accumulation of radium isotopes in some disposal and spill sites. The direct contamination of shallow groundwater from hydraulic fracturing fluids and deep formation waters by hydraulic fracturing itself, however, remains controversial.

  7. Acoustic emission in a fluid saturated heterogeneous porous layer with application to hydraulic fracture

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, J.T. (California Univ., Berkeley, CA (USA). Dept. of Mechanical Engineering Lawrence Berkeley Lab., CA (USA))

    1988-11-01

    A theoretical model for acoustic emission in a vertically heterogeneous porous layer bounded by semi-infinite solid regions is developed using linearized equations of motion for a fluid/solid mixture and a reflectivity method. Green's functions are derived for both point loads and moments. Numerically integrated propagators represent solutions for intermediate heterogeneous layers in the porous region. These are substituted into a global matrix for solution by Gaussian elimination and back-substitution. Fluid partial stress and seismic responses to dislocations associated with fracturing of a layer of rock with a hydraulically conductive fracture network are computed with the model. A constitutive model is developed for representing the fractured rock layer as a porous material, using commonly accepted relationships for moduli. Derivations of density, tortuosity, and sinuosity are provided. The main results of the model application are the prediction of a substantial fluid partial stress response related to a second mode wave for the porous material. The response is observable for relatively large distances, on the order of several tens of meters. The visco-dynamic transition frequency associated with parabolic versus planar fluid velocity distributions across micro-crack apertures is in the low audio or seismic range, in contrast to materials with small pore size, such as porous rocks, for which the transition frequency is ultrasonic. Seismic responses are predicted for receiver locations both in the layer and in the outlying solid regions. In the porous region, the seismic response includes both shear and dilatational wave arrivals and a second-mode arrival. The second-mode arrival is not observable outside of the layer because of its low velocity relative to the dilatational and shear wave propagation velocities of the solid region.

  8. The concept of the average stress in the fracture process zone for the search of the crack path

    Directory of Open Access Journals (Sweden)

    Yu.G. Matvienko

    2015-10-01

    Full Text Available The concept of the average stress has been employed to propose the maximum average tangential stress (MATS criterion for predicting the direction of fracture angle. This criterion states that a crack grows when the maximum average tangential stress in the fracture process zone ahead of the crack tip reaches its critical value and the crack growth direction coincides with the direction of the maximum average tangential stress along a constant radius around the crack tip. The tangential stress is described by the singular and nonsingular (T-stress terms in the Williams series solution. To demonstrate the validity of the proposed MATS criterion, this criterion is directly applied to experiments reported in the literature for the mixed mode I/II crack growth behavior of Guiting limestone. The predicted directions of fracture angle are consistent with the experimental data. The concept of the average stress has been also employed to predict the surface crack path under rolling-sliding contact loading. The proposed model considers the size and orientation of the initial crack, normal and tangential loading due to rolling–sliding contact as well as the influence of fluid trapped inside the crack by a hydraulic pressure mechanism. The MATS criterion is directly applied to equivalent contact model for surface crack growth on a gear tooth flank.

  9. Finite element simulations of interactions between multiple hydraulic fractures in a poroelastic rock

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Usui, Tomoya; Paluszny, Adriana

    2017-01-01

    A fully coupled three-dimensional finite-element model for hydraulic fractures in permeable rocks is presented, and used to investigate the ranges of applicability of the classical analytical solutions that are known to be valid in limiting cases. This model simultaneously accounts for fluid flow...

  10. Maturity of nearby faults influences seismic hazard from hydraulic fracturing

    Science.gov (United States)

    Kozłowska, Maria; Brudzinski, Michael R.; Friberg, Paul; Skoumal, Robert J.; Baxter, Nicholas D.; Currie, Brian S.

    2018-02-01

    Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: (i) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values 1.5, and few post–shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ˜1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

  11. Maturity of nearby faults influences seismic hazard from hydraulic fracturing.

    Science.gov (United States)

    Kozłowska, Maria; Brudzinski, Michael R; Friberg, Paul; Skoumal, Robert J; Baxter, Nicholas D; Currie, Brian S

    2018-02-20

    Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: ( i ) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values 1.5, and few post-shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ∼1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

  12. “We need more data”! The politics of scientific information for water governance in the context of hydraulic fracturing

    OpenAIRE

    Michele-Lee Moore; Karena Shaw; Heather Castleden

    2018-01-01

    Proposed and actual developments of hydraulic fracturing, as a high-volume water user, have proven contentious in recent years. However, one point of agreement has emerged amongst all actors with regards to water use and hydraulic fracturing: we need more data. This consensus fits with a longstanding reification of the role of data in water governance, and yet we argue it hides a politically contested terrain. Based on a literature review, an empirical Delphi study and a workshop ...

  13. Importance of borehole deviation surveys for monitoring of hydraulic fracturing treatments

    Czech Academy of Sciences Publication Activity Database

    Bulant, P.; Eisner, L.; Pšenčík, Ivan; Le Calvez, J. H.

    2007-01-01

    Roč. 55, č. 6 (2007), s. 891-899 ISSN 0016-8025 Grant - others:GA ČR(CZ) GA205/07/0032; EC(XE) MTKI-CT-2004-517242 Institutional research plan: CEZ:AV0Z30120515 Source of funding: R - rámcový projekt EK Keywords : hydraulic fracture * borehole deviation * seismic rays Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.731, year: 2007

  14. Pioneer hydraulic fracturing intervention on Brazilian Amazon Forest; Operacao pioneira de fraturamento hidraulico na selva Amazonica brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Cledeilson; Silva, Luis A.; Duque, Luis H.; Steffan, Rodolfo H.P.; Guimaraes, Zacarias [Baker Hughes, Houston, TX (United States); Sabino, Afonso H. dos S.; Corregio, Fabio; Ferreira, Jose Carlos da Silva; Melo, Marcelo Moura; Ludovice, Roberto C. [Petroleo Brasileiro S.A (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2012-07-01

    Hydraulic fracturing is a stimulation technique where fluid is pumped with enough energy to create a fracture in the reservoir and to propagate it filling the broken zone with proppant agent. To the end of the treatment the proppant agent will support the fracture creating a production flow path, once it will have permeability higher than the original formation. Since a long time it was desired to use that technique to explore tight reservoirs in the Solimoes basin. However the lack of information on the interest zones, the great amount of equipment and fluids volumes involved hindered the application in an area that withholds a environmental certification. In November 10th of 2011 these challenges were surpassed. This article describes the technique, job details and results of the pioneering hydraulic fracturing intervention in the heart of the Amazon forest that became economically viable the gas production in tight reservoirs of the Solimoes basin with minimum environmental impact. (author)

  15. Characteristics and management of flowback/produced water from hydraulically fractured wells in California - findings from the California SB 4 assessment

    Science.gov (United States)

    Varadharajan, C.; Cooley, H.; Heberger, M. G.; Stringfellow, W. T.; Domen, J. K.; Sandelin, W.; Camarillo, M. K.; Jordan, P. D.; Reagan, M. T.; Donnelly, K.; Birkholzer, J. T.; Long, J. C. S.

    2015-12-01

    As part of a recent assessment of well stimulation in California, we analyzed the hazards and potential impacts of hydraulic fracturing (the primary form of well stimulation in California) on water resources, which included an analysis of the quantity and quality of flowback/produced water generated, current management and disposal practices, associated potential release mechanisms and transport pathways that can lead to contaminants being released into the environment, and practices to mitigate or avoid impacts from produced water on water resources. The wastewater returned after stimulation includes "recovered fluids" (flowback fluids collected into tanks following stimulation, but before the start of production) and "produced water" (water extracted with oil and gas during production). In contrast to hydraulic fracturing in regions with primarily gas production, the quantities of recovered fluids from hydraulically fractured wells in California are small in comparison to the fluids injected (typically analysis indicates some fraction of returning fracturing fluids is likely present in produced water from wells that have been hydraulically fractured. Chemical measurements of recovered fluids show that some samples can contain high levels of some contaminants, including total carbohydrates (indicating the presence of guar, a component of fracturing fluid), total dissolved solids (TDS), trace elements and naturally occurring radioactive material (NORM). Data on produced water chemistry are more limited. In California, produced water is typically managed via pipelines and disposed or reused in many ways. A majority of produced water from hydraulically fractured wells in California is disposed in percolation pits, many of which may lie in areas with good groundwater quality. Some of the remaining produced water is injected into Class II wells; although a few of the wells are under review or have been shut down since they were injecting into aquifers. Other methods of

  16. New tracers identify hydraulic fracturing fluids and accidental releases from oil and gas operations.

    Science.gov (United States)

    Warner, N R; Darrah, T H; Jackson, R B; Millot, R; Kloppmann, W; Vengosh, A

    2014-11-04

    Identifying the geochemical fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil and gas reservoirs has important applications for assessing hydrocarbon resource recovery, environmental impacts, and wastewater treatment and disposal. Here, we report for the first time, novel diagnostic elemental and isotopic signatures (B/Cl, Li/Cl, δ11B, and δ7Li) useful for characterizing hydraulic fracturing flowback fluids (HFFF) and distinguishing sources of HFFF in the environment. Data from 39 HFFFs and produced water samples show that B/Cl (>0.001), Li/Cl (>0.002), δ11B (25-31‰) and δ7Li (6-10‰) compositions of HFFF from the Marcellus and Fayetteville black shale formations were distinct in most cases from produced waters sampled from conventional oil and gas wells. We posit that boron isotope geochemistry can be used to quantify small fractions (∼0.1%) of HFFF in contaminated fresh water and likely be applied universally to trace HFFF in other basins. The novel environmental application of this diagnostic isotopic tool is validated by examining the composition of effluent discharge from an oil and gas brine treatment facility in Pennsylvania and an accidental spill site in West Virginia. We hypothesize that the boron and lithium are mobilized from exchangeable sites on clay minerals in the shale formations during the hydraulic fracturing process, resulting in the relative enrichment of boron and lithium in HFFF.

  17. HYFRAC3D, 3-D Hydraulic Rock Fracture Propagation by Finite Element Method

    International Nuclear Information System (INIS)

    Advani, S.H.; Lee, J.K.; Lee, T.S.

    2001-01-01

    1 - Description of program or function: HYFRAC3D is a finite element program for simulation of three-dimensional fracture geometries with a two-dimensional planar solution. The model predicts the height, width and wing length over time for a hydraulic fracture propagating in a multi-layered system of rock with variable fluid flow and rock mechanics properties. 2 - Method of solution: The program uses the finite element Method of solution. A backward difference scheme is used by taking the weight functions on the time axis. This implicit time matching scheme requires iteration since the fracture configuration at time t+dt is not known. 3 - Restrictions on the complexity of the problem: Graphics output is not available and program is limited to fracture propagation in a single plane without proppant transport

  18. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    Science.gov (United States)

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

  19. Spartan Release Engagement Mechanism (REM) stress and fracture analysis

    Science.gov (United States)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The revised stress and fracture analysis of the Spartan REM hardware for current load conditions and mass properties is presented. The stress analysis was performed using a NASTRAN math model of the Spartan REM adapter, base, and payload. Appendix A contains the material properties, loads, and stress analysis of the hardware. The computer output and model description are in Appendix B. Factors of safety used in the stress analysis were 1.4 on tested items and 2.0 on all other items. Fracture analysis of the items considered fracture critical was accomplished using the MSFC Crack Growth Analysis code. Loads and stresses were obtaind from the stress analysis. The fracture analysis notes are located in Appendix A and the computer output in Appendix B. All items analyzed met design and fracture criteria.

  20. Stress fractures: pathophysiology, clinical presentation, imaging features, and treatment options.

    Science.gov (United States)

    Matcuk, George R; Mahanty, Scott R; Skalski, Matthew R; Patel, Dakshesh B; White, Eric A; Gottsegen, Christopher J

    2016-08-01

    Stress fracture, in its most inclusive description, includes both fatigue and insufficiency fracture. Fatigue fractures, sometimes equated with the term "stress fractures," are most common in runners and other athletes and typically occur in the lower extremities. These fractures are the result of abnormal, cyclical loading on normal bone leading to local cortical resorption and fracture. Insufficiency fractures are common in elderly populations, secondary to osteoporosis, and are typically located in and around the pelvis. They are a result of normal or traumatic loading on abnormal bone. Subchondral insufficiency fractures of the hip or knee may cause acute pain that may present in the emergency setting. Medial tibial stress syndrome is a type of stress injury of the tibia related to activity and is a clinical syndrome encompassing a range of injuries from stress edema to frank-displaced fracture. Atypical subtrochanteric femoral fracture associated with long-term bisphosphonate therapy is also a recently discovered entity that needs early recognition to prevent progression to a complete fracture. Imaging recommendations for evaluation of stress fractures include initial plain radiographs followed, if necessary, by magnetic resonance imaging (MRI), which is preferred over computed tomography (CT) and bone scintigraphy. Radiographs are the first-line modality and may reveal linear sclerosis and periosteal reaction prior to the development of a frank fracture. MRI is highly sensitive with findings ranging from periosteal edema to bone marrow and intracortical signal abnormality. Additionally, a brief description of relevant clinical management of stress fractures is included.

  1. Transboundary Extraction of Groundwater in the Presence of Hydraulic Fracturing

    OpenAIRE

    Poudel, Biswo N.; Paudel, Krishna P.; Zilberman, David

    2013-01-01

    We studied transboundary ground water management problems in the presence of hydraulic fracturing (fracking). We found that the presence of risk suggests a need to exercise caution in fracking. We also found that a cooperative outcome implies the decrease in fracking and the increase in steady state survival rate of groundwater. However, water extraction rates remained the same in both cooperative and noncooperative solutions. We also argue that a Pigouvian type tax could be imposed on the na...

  2. Lower thoracic rib stress fractures in baseball pitchers.

    Science.gov (United States)

    Gerrie, Brayden J; Harris, Joshua D; Lintner, David M; McCulloch, Patrick C

    2016-01-01

    Stress fractures of the first rib on the dominant throwing side are well-described in baseball pitchers; however, lower thoracic rib fractures are not commonly recognized. While common in other sports such as rowing, there is scant literature on these injuries in baseball. Intercostal muscle strains are commonly diagnosed in baseball pitchers and have a nearly identical presentation but also a highly variable healing time. The diagnosis of a rib stress fracture can predict a more protracted recovery. This case series presents two collegiate baseball pitchers on one team during the same season who were originally diagnosed with intercostal muscle strains, which following magnetic resonance imaging (MRI) were found to have actually sustained lower thoracic rib stress fractures. The first sustained a stress fracture of the posterior aspect of the right 8th rib on the dominant arm side, while the second presented with a left-sided 10th rib stress fracture on the nondominant arm side. In both cases, MRI was used to visualize the fractures as plain radiographs are insensitive and commonly negative early in patient presentation. Patients were treated with activity modification, and symptomatic management for 4-6 weeks with a graduated return to throwing and competition by 8-10 weeks. The repetitive high stresses incurred by pitching may cause either dominant or nondominant rib stress fractures and this should be included in the differential diagnosis of thoracic injuries in throwers. It is especially important that athletic trainers and team physicians consider this diagnosis, as rib fractures may have a protracted course and delayed return to play. Additionally, using the appropriate imaging techniques to establish an accurate diagnosis can help inform return-to-play decisions, which have important practical applications in baseball, such as roster management and eligibility.

  3. Clinical evaluation of stress fractures using bone scintigraphy

    International Nuclear Information System (INIS)

    Furuta, Atsuhiko; Tanohata, Kazunori; Otake, Toru; Hashizume, Toshiyuki; Kobayashi, Yozi; Nakazima, Hiroyuki.

    1984-01-01

    Clinical evaluation of stress fractures were performed in 58 athletes using bone scintigraphy with sup(99m)Tc-MDP. Stress fractures of the tibia were most often seen in the males with running type sports. They occurred more often in the proximal tibia and on the right side. Stress fractures of the fibula were most often seen in females with jumping type sports, such as volley ball. They occurred more often in the distal fibula and on the right side. Tarsal bone fractures were seen most often rugby players. Metatarsal fractures occurred in the third fourth and fifth metatarsals. No lesion was seen in the first and second metatarsals. We feel that stress fractures of the femur can be differentiated from osteosarcoma by small loculated radionuclide accumulation as well as symptome, course and tomographic and CT finding. Bilateral involvement was seen in two cases in patellae and calcanei. Most of the other fractures were seen on the right side. Negative radiographs were seen in 36% of the patients and occurred most commonly in the tarsal bones excluding calcaneus. Bone scintigrams were positive in all cases and were most useful in fractures of the tarsal bones excluding calcaneus. (author)

  4. Clinical evaluation of stress fractures using bone scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Furuta, Atsuhiko; Tanohata, Kazunori; Otake, Toru; Hashizume, Toshiyuki (Kanto Rosai Hospital, Kawasaki, Kanagawa (Japan)); Kobayashi, Yozi; Nakazima, Hiroyuki

    1984-05-01

    Clinical evaluation of stress fractures were performed in 58 athletes using bone scintigraphy with sup(99m)Tc-MDP. Stress fractures of the tibia were most often seen in the males with running type sports. They occurred more often in the proximal tibia and on the right side. Stress fractures of the fibula were most often seen in females with jumping type sports, such as volley ball. They occurred more often in the distal fibula and on the right side. Tarsal bone fractures were seen most often rugby players. Metatarsal fractures occurred in the third fourth and fifth metatarsals. No lesion was seen in the first and second metatarsals. We feel that stress fractures of the femur can be differentiated from osteosarcoma by small loculated radionuclide accumulation as well as symptoms, course and tomographic and CT findings. Bilateral involvement was seen in two cases in patellae and calcanei. Most of the other fractures were seen on the right side. Negative radiographs were seen in 36% of the patients and occurred most commonly in the tarsal bones excluding calcaneus. Bone scintigrams were positive in all cases and were most useful in fractures of the tarsal bones excluding calcaneus.

  5. Stress fractures of the femora in soldiers

    International Nuclear Information System (INIS)

    Meurman, K.O.A.; Somer, K.; Lamminen, A.

    1981-01-01

    Amongst 936 stress fractures found in soldiers, there were 58 in the femora (6%); of these 31 were in the neck and 27 in the shaft. Two were bilateral, and two patients had other stress fractures. Three displacements were found in the necks. In the shaft, 20 fractures were proximal, four were in the middle third and three in the distal third. In the latter group, it is necessary to differentiate from a sarcoma. CT is a new aid in this respect. Sport in highly motivated individuals appears to contribute particularly to fractures of the shaft. The symptoms from these fractures are relatively mild. (orig.) [de

  6. Stress fractures of the femora in soldiers

    Energy Technology Data Exchange (ETDEWEB)

    Meurman, K O.A.; Somer, K; Lamminen, A

    1981-05-01

    Amongst 936 stress fractures found in soldiers, there were 58 in the femora (6%); of these 31 were in the neck and 27 in the shaft. Two were bilateral, and two patients had other stress fractures. Three displacements were found in the necks. In the shaft, 20 fractures were proximal, four were in the middle third and three in the distal third. In the latter group, it is necessary to differentiate from a sarcoma. CT is a new aid in this respect. Sport in highly motivated individuals appears to contribute particularly to fractures of the shaft. The symptoms from these fractures are relatively mild.

  7. Étude des distributions de contraintes autour d'un puits pétrolier. Application au calcul des pressions d'initiation de fracturation hydraulique Research on Stress Distribution Around an Oil Or Gas Well. Application to Calculating Pressures for Initiating Hydraulic Fracturing

    Directory of Open Access Journals (Sweden)

    Skoczylas F.

    2006-11-01

    Full Text Available Des méthodes de résolution analytiques et numériques ont été proposées, pour déterminer les distributions de contraintes autour de forages pétroliers dans le cas de matériaux peu résistants. Le calcul de ces distributions aboutit à la détermination des pressions de fracturation. Le critère de plasticité de Mohr-Coulomb a été choisi pour la résolution analytique. Cette étude permet d'établir trois schémas types de distribution de contraintes, au moment de la fracturation, pour un régime permanent d'écoulement. La géométrie axisymétrique du modèle a permis d'utiliser une méthode numérique par schéma aux différences finies. La loi de comportement du matériau est déduite du critère de plasticité de Drucker. Cette résolution permet le chargement incrémental en pression dans le forage et de simuler une injection rapide par un couplage simplifié fluide-squelette. Le modèle élastoplastique à deux surfaces de charge de Lade-Shao a finalement été retenu pour décrire l'écrouissage du matériau. La comparaison des résultats des différentes méthodes de calcul s'effectue sur la base de l'influence respective du coefficient de poussée au repos Ko, du coefficient de Poisson et de la résistance à la compression, Co, du matériau. Analytical and numerical methods are proposed, in order to determine stresses distribution around borehole for axisymetric problems in the case of low strengh materials. Calculation of these distributions leads to the determination of hydraulic fracture-pressure. Analytical solutions were found in the case of Mohr-Coulomb criterion and steady flow. These solutions leads to three typical stresses distributions when hydraulic fracture takes place. Because problem's axisymetry, the finite difference method was used. The constitutive law was deduced using Drücker plasticity criterion with an associated flow rule for elastic perfectly plastic behaviour. Such a numerical method can take into

  8. Correlation Between Fracture Network Properties and Stress Variability in Geological Media

    Science.gov (United States)

    Lei, Qinghua; Gao, Ke

    2018-05-01

    We quantitatively investigate the stress variability in fractured geological media under tectonic stresses. The fracture systems studied include synthetic fracture networks following power law length scaling and natural fracture patterns based on outcrop mapping. The stress field is derived from a finite-discrete element model, and its variability is analyzed using a set of mathematical formulations that honor the tensorial nature of stress data. We show that local stress perturbation, quantified by the Euclidean distance of a local stress tensor to the mean stress tensor, has a positive, linear correlation with local fracture intensity, defined as the total fracture length per unit area within a local sampling window. We also evaluate the stress dispersion of the entire stress field using the effective variance, that is, a scalar-valued measure of the overall stress variability. The results show that a well-connected fracture system under a critically stressed state exhibits strong local and global stress variabilities.

  9. 'Fracking' Controversy and Communication: Using National Survey Data to Understand Public Perceptions of Hydraulic Fracturing (Invited)

    Science.gov (United States)

    Boudet, H. S.

    2013-12-01

    The recent push to develop unconventional sources of oil and gas both in the U.S. and abroad via hydraulic fracturing ('fracking') has generated a great deal of controversy. Effectively engaging stakeholders and setting appropriate policies requires insights into current public perceptions of this issue. Using a nationally representative U.S. sample (N=1,061), we examine public perceptions of hydraulic fracturing including: 'top of mind' associations; familiarity with the issue; levels of support/opposition; and predictors of such judgments. Similar to findings on other emerging technologies, our results suggest limited familiarity with the process and its potential impacts and considerable uncertainty about whether to support it. Multiple regression analysis (r2 = 0.49) finds that women, those holding egalitarian worldviews, those who read newspapers more than once a week, those more familiar with hydraulic fracturing, and those who associate the process with environmental impacts are more likely to oppose fracking. In contrast, people more likely to support fracking tend to be older, hold a bachelor's degree or higher, politically conservative, watch TV news more than once a week, and associate the process with positive economic or energy supply outcomes. Based on these findings, we discuss recommendations for future research, risk communication, and energy policy.

  10. Simulation of a multistage fractured horizontal well in a water-bearing tight fractured gas reservoir under non-Darcy flow

    Science.gov (United States)

    Zhang, Rui-Han; Zhang, Lie-Hui; Wang, Rui-He; Zhao, Yu-Long; Huang, Rui

    2018-06-01

    Reservoir development for unconventional resources such as tight gas reservoirs is in increasing demand due to the rapid decline of production in conventional reserves. Compared with conventional reservoirs, fluid flow in water-bearing tight gas reservoirs is subject to more nonlinear multiphase flow and gas slippage in nano/micro matrix pores because of the strong collisions between rock and gas molecules. Economic gas production from tight gas reservoirs depends on extensive application of water-based hydraulic fracturing of horizontal wells, associated with non-Darcy flow at a high flow rate, geomechanical stress sensitivity of un-propped natural fractures, complex flow geometry and multiscale heterogeneity. How to efficiently and accurately predict the production performance of a multistage fractured horizontal well (MFHW) is challenging. In this paper, a novel multicontinuum, multimechanism, two-phase simulator is established based on unstructured meshes and the control volume finite element method to analyze the production performance of MFHWs. The multiple interacting continua model and discrete fracture model are coupled to integrate the unstimulated fractured reservoir, induced fracture networks (stimulated reservoir volumes, SRVs) and irregular discrete hydraulic fractures. Several simulations and sensitivity analyses are performed with the developed simulator for determining the key factors affecting the production performance of MFHWs. Two widely applied fracturing models, classic hydraulic fracturing which generates long double-wing fractures and the volumetric fracturing aimed at creating large SRVs, are compared to identify which of them can make better use of tight gas reserves.

  11. Rupture Dynamics and Scaling Behavior of Hydraulically Stimulated Micro-Earthquakes in a Shale Reservoir

    Science.gov (United States)

    Viegas, G. F.; Urbancic, T.; Baig, A. M.

    2014-12-01

    In hydraulic fracturing completion programs fluids are injected under pressure into fractured rock formations to open escape pathways for trapped hydrocarbons along pre-existing and newly generated fractures. To characterize the failure process, we estimate static and dynamic source and rupture parameters, such as dynamic and static stress drop, radiated energy, seismic efficiency, failure modes, failure plane orientations and dimensions, and rupture velocity to investigate the rupture dynamics and scaling relations of micro-earthquakes induced during a hydraulic fracturing shale completion program in NE British Columbia, Canada. The relationships between the different parameters combined with the in-situ stress field and rock properties provide valuable information on the rupture process giving insights into the generation and development of the fracture network. Approximately 30,000 micro-earthquakes were recorded using three multi-sensor arrays of high frequency geophones temporarily placed close to the treatment area at reservoir depth (~2km). On average the events have low radiated energy, low dynamic stress and low seismic efficiency, consistent with the obtained slow rupture velocities. Events fail in overshoot mode (slip weakening failure model), with fluids lubricating faults and decreasing friction resistance. Events occurring in deeper formations tend to have faster rupture velocities and are more efficient in radiating energy. Variations in rupture velocity tend to correlate with variation in depth, fault azimuth and elapsed time, reflecting a dominance of the local stress field over other factors. Several regions with different characteristic failure modes are identifiable based on coherent stress drop, seismic efficiency, rupture velocities and fracture orientations. Variations of source parameters with rock rheology and hydro-fracture fluids are also observed. Our results suggest that the spatial and temporal distribution of events with similar

  12. Comprehensive Assessment of New Proppants for Hydraulic Fracturing Utilization under the Consideration of Cost, Environmental & Health Impacts

    Science.gov (United States)

    Adebakin, Mariam Abiodun

    The advancement and increased practice of hydraulic fracturing, a process which involves the drilling of a well and the injection of fracture fluid (water, proppant and various chemicals) under high pressure to stimulate the production of oil and gas, has gradually gained public attention over the past years. This is because of its effectiveness in booming the nation's economy as well as the adverse effects in terms of risks this process poses to all forms of life. Several speculations have been raised about the choice of proppant used as a contributory factor to the risks hydraulic fracturing poses. Frac sand is the most widely used proppant in several wells in the United States but several health and environmental concerns has been raised on its short and long term use. It is therefore imperative to examine the impacts (health and environmental) as well as cost implication, if any, in selecting the most appropriate proppant in other to reduce and or completely eliminate its effect on humans and other forms of life. This study aims to compare other proppants (resin-coated sand and ceramic) with frac sand, focusing on cost, environmental and health implications when used. This study found that sand is the cheapest and most available proppant in terms of production cost compared to resin coated sand and ceramic proppant. However, sand cannot be used in deep wells as it is subjected to more stress leading to its disintegration and crushing in the well which eventually blocks the fissures created and the subsequent flow of oil and gas. In terms of health and environmental impacts, sand should be discouraged as it generates crystalline silica dust known to be injurious if inhaled.

  13. Etude théorique et expérimentale de la liaison de deux puits par fracturation hydraulique Theoretical and Experimental Analysis of the Linking of Two Wells by Hydraulic Fracturing

    Directory of Open Access Journals (Sweden)

    Bouteca M.

    2006-11-01

    Full Text Available La nécessité de réaliser, dans une couche mince et située à plus de 1000 m de profondeur, une communication hydraulique ou pneumatique entre deux sondages verticaux, a conduit à l'étude d'une méthode basée sur la fracturation hydraulique des puits à relier. Une telle approche suppose que l'on connaisse ou que l'on contrôle la direction des fractures développées. Les techniques actuelles ne permettant pas d'apprécier la direction de fracture avec une précision suffisante, la méthode proposée vise à influencer favorablement cette direction. Elle est basée sur une modification des contraintes effectives en place par une injection préalable de fluide dans les puits à relier. Les résultats obtenus au moyen de calculs analytiques et numériques à deux dimensions sont présentés, ainsi que les expériences réalisées sur un modèle physique en laboratoire. In a thin layer and at a depth of more than 1000 meters, the need to create a hydraulic or pneumatic communication between two vertical boreholes led to research on a method based on hydraulic fracturing in the wells to be linked. Such an approach supposes that the direction of the fractures thus created must be known or controlled. Current techniques cannot be used to assess fracture direction with sufficient accuracy. The method proposed here aims to have a favorable influence on this direction. It is based on making a change in the effective stresses in situ by the prior injection of fluid into the wells to be linked. The results obtained by two-dimensional analytical and digital computing are described together with the experiments performed on a physical model in the laboratory.

  14. Trochanteric Stress Fracture in a Female Window Cleaner

    OpenAIRE

    Lee, Bong-Jin; Song, Jyewon

    2016-01-01

    Stress fractures may occur at various sites in the femur including the head, neck, shaft, supracondylar and condylar regions. To the best of our knowledge, stress fracture occurring in the trochanteric region has not been previously reported. We report here a case of trochanteric stress fracture in a 53-year-old female window cleaner treated with hip nailing without adverse consequences. Careful consideration of this entity is needed when evaluating patients who have repetitive jumping up and...

  15. Interpretation of Microseismicity Observed From Surface and Borehole Seismic Arrays During Hydraulic Fracturing in Shale - Bedding Plane Slip Model

    Science.gov (United States)

    Stanek, F.; Jechumtalova, Z.; Eisner, L.

    2017-12-01

    We present a geomechanical model explaining microseismicity induced by hydraulic fracturing in shales developed from many datasets acquired with two most common types of seismic monitoring arrays, surface and dual-borehole arrays. The geomechanical model explains the observed source mechanisms and locations of induced events from two stimulated shale reservoirs. We observe shear dip-slip source mechanisms with nodal planes aligned with location trends. We show that such seismicity can be explained as a shearing along bedding planes caused by aseismic opening of vertical hydraulic fractures. The source mechanism inversion was applied only to selected high-quality events with sufficient signal-to-noise ratio. We inverted P- and P- and S-wave arrival amplitudes to full-moment tensor and decomposed it to shear, volumetric and compensated linear vector dipole components. We also tested an effect of noise presented in the data to evaluate reliability of non-shear components. The observed seismicity from both surface and downhole monitoring of shale stimulations is very similar. The locations of induced microseismic events are limited to narrow depth intervals and propagate along distinct trend(s) showing fracture propagation in direction of maximum horizontal stress from injection well(s). The source mechanisms have a small non-shear component which can be partly explained as an effect of noise in the data, i.e. events represent shearing on faults. We observe predominantly dip-slip events with a strike of the steeper (almost vertical) nodal plane parallel to the fracture propagation. Therefore the other possible nodal plane is almost horizontal. The rake angles of the observed mechanisms divide these dip-slips into two groups with opposite polarities. It means that we observe opposite movements on the nearly identically oriented faults. Realizing a typical structural weakness of shale in horizontal planes, we interpret observed microseismicity as a result of shearing

  16. Influence of heat treatment on the wear life of hydraulic fracturing tools

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Chao; Liu, Yonghong; Wang, Hanxiang; Qin, Jie; Shen, Yang; Zhang, Shihong [China University of Petroleum, Qingdao (China)

    2017-02-15

    Wear phenomenon has caused severe damage or failure of fracturing tools in oil and gas industry. In this paper, influence of heat treatment on the mechanical properties and wear resistance of fracturing tool made of lamellar graphite grey cast iron were investigated. The surface composition and microstructure were characterized by X-ray diffraction (XRD) and metallographic microscope. Sliding wear tests were performed to study the tribological behavior. Tests results showed that wear rates of treated specimens decreased by 33 %. Besides, worn morphology and wear debris were analyzed using Scanning electron microscope (SEM) and Energy dispersive Xray spectra (EDS). Wear failure mechanisms of specimens were identified. Furthermore, on-site experiment results indicated that wear loss of treated samples decreased by 37.5 %. The wear life of hydraulic fracturing tools can be improved obviously by the heat treatment.

  17. Influence of heat treatment on the wear life of hydraulic fracturing tools

    International Nuclear Information System (INIS)

    Zheng, Chao; Liu, Yonghong; Wang, Hanxiang; Qin, Jie; Shen, Yang; Zhang, Shihong

    2017-01-01

    Wear phenomenon has caused severe damage or failure of fracturing tools in oil and gas industry. In this paper, influence of heat treatment on the mechanical properties and wear resistance of fracturing tool made of lamellar graphite grey cast iron were investigated. The surface composition and microstructure were characterized by X-ray diffraction (XRD) and metallographic microscope. Sliding wear tests were performed to study the tribological behavior. Tests results showed that wear rates of treated specimens decreased by 33 %. Besides, worn morphology and wear debris were analyzed using Scanning electron microscope (SEM) and Energy dispersive Xray spectra (EDS). Wear failure mechanisms of specimens were identified. Furthermore, on-site experiment results indicated that wear loss of treated samples decreased by 37.5 %. The wear life of hydraulic fracturing tools can be improved obviously by the heat treatment

  18. 3-D description of fracture surfaces and stress-sensitivity analysis for naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.Q.; Jioa, D.; Meng, Y.F.; Fan, Y.

    1997-08-01

    Three kinds of reservoir cores (limestone, sandstone, and shale with natural fractures) were used to study the effect of morphology of fracture surfaces on stress sensitivity. The cores, obtained from the reservoirs with depths of 2170 to 2300 m, have fractures which are mated on a large scale, but unmated on a fine scale. A specially designed photoelectric scanner with a computer was used to describe the topography of the fracture surfaces. Then, theoretical analysis of the fracture closure was carried out based on the fracture topography generated. The scanning results show that the asperity has almost normal distributions for all three types of samples. For the tested samples, the fracture closure predicted by the elastic-contact theory is different from the laboratory measurements because plastic deformation of the aspirates plays an important role under the testing range of normal stresses. In this work, the traditionally used elastic-contact theory has been modified to better predict the stress sensitivity of reservoir fractures. Analysis shows that the standard deviation of the probability density function of asperity distribution has a great effect on the fracture closure rate.

  19. Lower limb stress fractures in sport: Optimising their management and outcome

    Science.gov (United States)

    Robertson, Greg A J; Wood, Alexander M

    2017-01-01

    Stress fractures in sport are becoming increasing more common, comprising up to 10% of all of sporting injuries. Around 90% of such injuries are located in the lower limb. This articles aims to define the optimal management of lower limb stress fractures in the athlete, with a view to maximise return rates and minimise return times to sport. Treatment planning of this condition is specific to the location of the injury. However, there remains a clear division of stress fractures by “high” and “low” risk. “Low risk” stress fractures are those with a low probability of fracture propagation, delayed union, or non-union, and so can be managed reliably with rest and exercise limitation. These include stress fractures of the Postero-Medial Tibial Diaphysis, Metatarsal Shafts, Distal Fibula, Medial Femoral Neck, Femoral Shaft and Calcaneus. “High risk” stress fractures, in contrast, have increased rates of fracture propagation, displacement, delayed and non-union, and so require immediate cessation of activity, with orthopaedic referral, to assess the need for surgical intervention. These include stress fractures of the Anterior Tibial Diaphysis, Fifth Metatarsal Base, Medial Malleolus, Lateral Femoral Neck, Tarsal Navicular and Great Toe Sesamoids. In order to establish the optimal methods for managing these injuries, we present and review the current evidence which guides the treatment of stress fractures in athletes. From this, we note an increased role for surgical management of certain high risk stress fractures to improve return times and rates to sport. Following this, key recommendations are provided for the management of the common stress fracture types seen in the athlete. Five case reports are also presented to illustrate the application of sport-focussed lower limb stress fracture treatment in the clinical setting. PMID:28361017

  20. Lower limb stress fractures in sport: Optimising their management and outcome.

    Science.gov (United States)

    Robertson, Greg A J; Wood, Alexander M

    2017-03-18

    Stress fractures in sport are becoming increasing more common, comprising up to 10% of all of sporting injuries. Around 90% of such injuries are located in the lower limb. This articles aims to define the optimal management of lower limb stress fractures in the athlete, with a view to maximise return rates and minimise return times to sport. Treatment planning of this condition is specific to the location of the injury. However, there remains a clear division of stress fractures by "high" and "low" risk. "Low risk" stress fractures are those with a low probability of fracture propagation, delayed union, or non-union, and so can be managed reliably with rest and exercise limitation. These include stress fractures of the Postero-Medial Tibial Diaphysis, Metatarsal Shafts, Distal Fibula, Medial Femoral Neck, Femoral Shaft and Calcaneus. "High risk" stress fractures, in contrast, have increased rates of fracture propagation, displacement, delayed and non-union, and so require immediate cessation of activity, with orthopaedic referral, to assess the need for surgical intervention. These include stress fractures of the Anterior Tibial Diaphysis, Fifth Metatarsal Base, Medial Malleolus, Lateral Femoral Neck, Tarsal Navicular and Great Toe Sesamoids. In order to establish the optimal methods for managing these injuries, we present and review the current evidence which guides the treatment of stress fractures in athletes. From this, we note an increased role for surgical management of certain high risk stress fractures to improve return times and rates to sport. Following this, key recommendations are provided for the management of the common stress fracture types seen in the athlete. Five case reports are also presented to illustrate the application of sport-focussed lower limb stress fracture treatment in the clinical setting.

  1. Radioisotopic and Radiological Evaluation in Patient with Stress Fracture

    International Nuclear Information System (INIS)

    Ko, Kwang Seop; Kim, Jai Young; Kang, Sung Koo; Kim, So Yon; Lee, Gwon Jun

    1987-01-01

    The stress fracture is a disease caused by and abnormal stress to the normal bone with constant, repeated pull. Early detection of stress fracture plays an important role in treatment and prevention of its complication. Bone scintigraphy was performed to evaluate 18 patients with stress fracture of the lower extremities from May, 1985 to April, 1987, in the Department of Internal Medicine of National Police Hospital. The results were as follows: 1) Seventeen of the 18 cases showed positive bone scans at the initial study performed from 1 week to 5 months after the onset of symptom. 2) Ten of the 18 patients had findings of stress fracture at the initial X-ray film. Two out of 8 negative case revealed positive findings in the follow-up studies. 3) The bone scans in the 2 cases taken 5 months after the onset of symptom; the one showed only slightly increased radio uptake, the other showed no abnormal findings. In conclusion, bone scanning is a more sensitive indicator of early stress fracture than radiologic study, The healing phase is characterized by a gradual decline in radioactivity at the fracture site in concordance with subsidence of symptom.

  2. Development of a new code to solve hydro-mechanical coupling, shear failure and tensile failure due to hydraulic fracturing operations.

    Science.gov (United States)

    María Gómez Castro, Berta; De Simone, Silvia; Carrera, Jesús

    2016-04-01

    Nowadays, there are still some unsolved relevant questions which must be faced if we want to proceed to the hydraulic fracturing in a safe way. How much will the fracture propagate? This is one of the most important questions that have to be solved in order to avoid the formation of pathways leading to aquifer targets and atmospheric release. Will the fracture failure provoke a microseismic event? Probably this is the biggest fear that people have in fracking. The aim of this work (developed as a part of the EU - FracRisk project) is to understand the hydro-mechanical coupling that controls the shear of existing fractures and their propagation during a hydraulic fracturing operation, in order to identify the key parameters that dominate these processes and answer the mentioned questions. This investigation focuses on the development of a new C++ code which simulates hydro-mechanical coupling, shear movement and propagation of a fracture. The framework employed, called Kratos, uses the Finite Element Method and the fractures are represented with an interface element which is zero thickness. This means that both sides of the element lie together in the initial configuration (it seems a 1D element in a 2D domain, and a 2D element in a 3D domain) and separate as the adjacent matrix elements deform. Since we are working in hard, fragile rocks, we can assume an elastic matrix and impose irreversible displacements in fractures when rock failure occurs. The formulation used to simulate shear and tensile failures is based on the analytical solution proposed by Okada, 1992 and it is part of an iterative process. In conclusion, the objective of this work is to employ the new code developed to analyze the main uncertainties related with the hydro-mechanical behavior of fractures derived from the hydraulic fracturing operations.

  3. Case report: bilateral ischial stress fractures in an elite tennis player

    International Nuclear Information System (INIS)

    Clarke, A.W.; Connell, D.A.

    2009-01-01

    A case report of bilateral ischial stress fractures in an elite tennis player initially mimicking hamstring pathology is described. This is an unusual site of stress fracture. Typical sites of stress fracture are well documented; however, awareness of less common sites of stress-related bone injury can aid early diagnosis and treatment before overt fracture occurs. (orig.)

  4. Case report: bilateral ischial stress fractures in an elite tennis player

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, A.W.; Connell, D.A. [Royal National Orthopaedic Hospital NHS Trust, Department of Radiology, London, Middlesex (United Kingdom)

    2009-07-15

    A case report of bilateral ischial stress fractures in an elite tennis player initially mimicking hamstring pathology is described. This is an unusual site of stress fracture. Typical sites of stress fracture are well documented; however, awareness of less common sites of stress-related bone injury can aid early diagnosis and treatment before overt fracture occurs. (orig.)

  5. Geological and petrological considerations relevant to the disposal of radioactive wastes by hydraulic fracturing: an example at the US Department of Energy's Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    Haase, C.S.

    1982-01-01

    At Oak Ridge National Laboratory the Pumpkin Valley Shale is used as a host formation for hydraulic-fracturing waste disposal. Determination of the relationships between the distribution of different lithologies and porosity-permeability trends within this host formation allows these properties, important to hydraulic-fracturing operations, to be related to measurable and mappable geological and petrological parameters. It also permits extrapolation of such patterns to little-studied portions of the Pumpkin Valley Shale. Such knowledge better allows for the satisfactory operation and assessment of the hydraulic fracturing at Oak Ridge National Laboratory

  6. Geological and petrological considerations relevant to the disposal of radioactive wastes by hydraulic fracturing: an example at the US Department of Energy's Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    Haase, C.S.

    1983-01-01

    At Oak Ridge National Laboratory the Pumpkin Valley Shale is used as a host formation for hydraulic fracturing waste disposal. Determination of the relationships between the distribution of different lithologies and porosity-permeability trends within this host formation allows these properties, important to hydraulic fracturing operations, to be related to measurable and mappable geological and petrological parameters. It also permits extrapolation of such patterns to little-studied portions of the Pumpkin Valley Shale. Such knowledge better allows for the satisfactory operation and assessment of the hydraulic fracturing at Oak Ridge National Laboratory

  7. Postpartum Sacral Stress Fracture: An Atypical Case Report

    Directory of Open Access Journals (Sweden)

    Andrea Speziali

    2015-01-01

    Full Text Available Sacral stress fractures are common in elderly people. However, sacral stress fracture should be always screened in the differential diagnoses of low back pain during the postpartum period. We present a case of sacral fracture in a thirty-six-year-old woman with low back pain and severe right buttock pain two days after cesarean section delivery of a 3.9 Kg baby. The diagnosis was confirmed by MRI and CT scan, while X-ray was unable to detect the fracture. Contribution of mechanical factors during the cesarean section is not a reasonable cause of sacral fracture. Pregnancy and lactation could be risk factors for sacral stress fracture even in atraumatic delivery such as cesarean section. Our patient had no risk factors for osteoporosis except for pregnancy and lactation. Transient or focal osteoporosis is challenging to assess and it cannot be ruled out even if serum test and mineral density are within the normal range.

  8. Tibial stress fractures in racing Standardbreds: 13 cases (1989-1993)

    International Nuclear Information System (INIS)

    Ruggles, A.J.; Moore, R.M.; Bertone, A.L.; Schneider, R.K.; Bailey, M.Q.

    1996-01-01

    To determine clinical signs, radiographic and scintigraphic findings, and performance outcome of racing Standardbreds with tibial stress fractures. Retrospective case series. 13 racing Standardbreds with tibial stress fractures. Information concerning clinical signs, diagnostic evaluation, and recommendations was obtained by review of the medical records. Performance information before and after diagnosis of the fracture was collected from racing records, and follow-up information was obtained from the owners or trainers by use of a telephone questionnaire. Horses with tibial stress fractures were moderately lame, and diagnosis was made by nuclear scintigraphy and radiography. Fractures were more likely to occur in 2-year-old horses than in older horses. The fracture location was unique for Standardbreds; 11 of 13 developed stress fractures in the mid-diaphysis of the tibia, whereas fractures in Thoroughbreds are usually in the proximal caudal or caudolateral cortex. Fractures occurred in young horses that had raced or were in advanced race training. All horses were treated with rest alone, and 10 of 13 horses raced after injury. The horses that raced after injury were able to return to a level of performance that was equal to or better than the level raced before injury. 8 of 10 horses established a lifetime-best winning time after injury. Tibial stress fractures are a cause of lameness in young racing Standardbreds. Diagnosis is aided by nuclear scintigraphy. The prognosis for return to previous level of performance after a tibial stress fracture is good

  9. Fatigue stress fractures of the sacrum: diagnosis with MR imaging

    International Nuclear Information System (INIS)

    Ahovuo, J.A.; Vusuri, T.

    2004-01-01

    The aim of this study was to describe the MRI findings and clinical observations in a fatigue stress fracture of the sacrum. In this retrospective study, 380 conscripts (53 women, 327 men; age range 18-29 years, mean age 20.7 years) who suffered from stress-related hip pain were studied with MRI of the pelvis. The findings of MRI were evaluated with regard to stress fracture of the sacrum. Thirty-one (8%) patients had MRI changes in signal intensity of the cranial part of the sacrum, extending to the first and second sacral foramina. The MRI changes in signal intensity were intermediate on T1-weighted images, and high on short tau inversion recovery or T2-weighted fat-suppressed images. A linear signal void fracture line was also seen. Multiple stress injuries to the pelvic bones were also seen in 7 of 31 (23%) patients. Five patients (16%) had bilateral sacral stress fracture. Fatigue sacral stress fractures appeared more commonly in women than in men (p<0.001). During recovery time 20 of the 31 patients underwent control MRI, and fatty marrow conversion was seen in 8 (40%) cases as high signal intensity on T1-weighted images, which disappeared 5-6 months after the onset of symptoms. Fatigue sacral stress fractures are associated with stress-related hip pain. These fractures were more common in women than in men. Other stress injuries of the pelvis may be seen simultaneously with sacral stress fractures. Signal intensity of the sacrum was normal after 5-6 months

  10. Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA

    Science.gov (United States)

    Day-Lewis, F. D.; Lane, J.W.; Gorelick, S.M.

    2006-01-01

    An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock. ?? Springer-Verlag 2004.

  11. Monitoring concentration and isotopic composition of methane in groundwater in the Utica Shale hydraulic fracturing region of Ohio.

    Science.gov (United States)

    Claire Botner, E; Townsend-Small, Amy; Nash, David B; Xu, Xiaomei; Schimmelmann, Arndt; Miller, Joshua H

    2018-05-03

    Degradation of groundwater quality is a primary public concern in rural hydraulic fracturing areas. Previous studies have shown that natural gas methane (CH 4 ) is present in groundwater near shale gas wells in the Marcellus Shale of Pennsylvania, but did not have pre-drilling baseline measurements. Here, we present the results of a free public water testing program in the Utica Shale of Ohio, where we measured CH 4 concentration, CH 4 stable isotopic composition, and pH and conductivity along temporal and spatial gradients of hydraulic fracturing activity. Dissolved CH 4 ranged from 0.2 μg/L to 25 mg/L, and stable isotopic measurements indicated a predominantly biogenic carbonate reduction CH 4 source. Radiocarbon dating of CH 4 in combination with stable isotopic analysis of CH 4 in three samples indicated that fossil C substrates are the source of CH 4 in groundwater, with one 14 C date indicative of modern biogenic carbonate reduction. We found no relationship between CH 4 concentration or source in groundwater and proximity to active gas well sites. No significant changes in CH 4 concentration, CH 4 isotopic composition, pH, or conductivity in water wells were observed during the study period. These data indicate that high levels of biogenic CH 4 can be present in groundwater wells independent of hydraulic fracturing activity and affirm the need for isotopic or other fingerprinting techniques for CH 4 source identification. Continued monitoring of private drinking water wells is critical to ensure that groundwater quality is not altered as hydraulic fracturing activity continues in the region. Graphical abstract A shale gas well in rural Appalachian Ohio. Photo credit: Claire Botner.

  12. Field instrumentation for hydrofracturing stress measurements

    International Nuclear Information System (INIS)

    Bjarnason, Bjarni; Torikka, Arne.

    1989-08-01

    A recently developed system for rock stress measurements by the hydraulic fracturing method is documented in detail. The new equipment is intended for measurement in vertical or nearvertical boreholes, down to a maximum depth of 1000 m. The minimum borehole, diameter required is 56 mm. Downhole instrumentation comprises a straddle packer assembly for borehole fracturing, equipment for determination of fracture orientations and a pressure transducer. The downhole tools are operated by means of a multihose system, containing high pressure hydraulic tubings, signal cable and carrying wire into one hose unit. The surface components of the equipment include a system for generation and control of water pressures up to approximately 75 MPa, an hydraulically operated drum for the multihose and a data acquisition system. All surface instrumentation is permanently mounted on a truck, which also serves as power source for the instrumentation. In addition to the description of instrumentation, the theoretical fundament and the testing procedures associated with the hydraulic fracturing method are briefly outlined

  13. Spontaneous stress fractures of the femoral neck

    International Nuclear Information System (INIS)

    Dorne, H.L.; Lander, P.H.

    1985-01-01

    The diagnosis of spontaneous stress fractures of the femoral neck, a form of insufficiency stress fracture, can be missed easily. Patients present with unremitting hip pain without a history of significant trauma or unusual increase in daily activity. The initial radiographic features include osteoporosis, minor alterations of trabecular alignment, minimal extracortical or endosteal reaction, and lucent fracture lines. Initial scintigraphic examinations performed in three of four patients showed focal increased radionuclide uptake in two and no focal abnormality in one. Emphasis is placed on the paucity of early findings. Evaluation of patients with persistent hip pain requires a high degree of clinical suspicion and close follow-up; the sequelae of undetected spontaneous fractures are subcapital fracture with displacement, angular deformity, and a vascular necrosis of the femoral head

  14. Investigating the Influence of Regional Stress on Fault and Fracture Permeability at Pahute Mesa, Nevada National Security Site

    Energy Technology Data Exchange (ETDEWEB)

    Reeves, Donald M. [Desert Research Inst. (DRI), Reno, NV (United States); Smith, Kenneth D. [Univ. of Nevada, Reno, NV (United States); Parashar, Rishi [Desert Research Inst. (DRI), Reno, NV (United States); Collins, Cheryl [Desert Research Inst. (DRI), Las Vegas, NV (United States); Heintz, Kevin M. [Desert Research Inst. (DRI), Las Vegas, NV (United States)

    2017-05-24

    Regional stress may exert considerable control on the permeability and hydraulic function (i.e., barrier to and/or conduit for fluid flow) of faults and fractures at Pahute Mesa, Nevada National Security Site (NNSS). In-situ measurements of the stress field are sparse in this area, and short period earthquake focal mechanisms are used to delineate principal horizontal stress orientations. Stress field inversion solutions to earthquake focal mechanisms indicate that Pahute Mesa is located within a transtensional faulting regime, represented by oblique slip on steeply dipping normal fault structures, with maximum horizontal stress ranging from N29°E to N63°E and average of N42°E. Average horizontal stress directions are in general agreement with large diameter borehole breakouts from Pahute Mesa analyzed in this study and with stress measurements from other locations on the NNSS.

  15. Upper extremity and rib stress fractures in a child

    International Nuclear Information System (INIS)

    Moon, B.S.; Price, C.T.; Campbell, J.B.

    1998-01-01

    Stress fractures in children are rare compared with the incidence in [ults. This report describes an 11-year-old girl with stress fractures of the acromion, clavicle, and first rib on the left and contralateral fractures of the first and second ribs. It was eventually discovered that these fractures were caused by a nervous tic consisting of repetitive, vigorous shrugging and translation of the shoulders. (orig.)

  16. Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

    Science.gov (United States)

    Lei, Qinghua; Wang, Xiaoguang; Xiang, Jiansheng; Latham, John-Paul

    2017-12-01

    A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a "through-going" joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.

  17. Comparison analysis on permeability improved effect of single and multi section hydraulic fracturing in deep depth seam%深部煤层单段/多段水力压裂增透效果对比

    Institute of Scientific and Technical Information of China (English)

    张春华; 张勇志; 李江涛; 李腾达

    2017-01-01

    为对比深部煤层钻孔内单段和多段水力压裂增透效果,基于谢桥煤矿待揭8煤层赋存条件,分别建立了单段和多段水力压裂增透模型,运用RFPA2D-Flow软件,模拟分析了水力压裂影响区内煤层水压场、应力场、裂隙场和渗透场特征和规律,并进行了效果验证.结果表明:单段压裂起裂时的煤体孔隙水压为7 MPa,多段压裂起裂时的煤体孔隙水压为16 MPa;煤层起裂后,单段压裂时钻孔中部煤体产生了明显的应力集中,而多段压裂时煤体应力分布虽有起伏但无明显应力集中;单段压裂时裂隙主要在钻孔中部位置向顶底板萌发延伸,有效压裂面积较小,多段压裂时各压裂段均可产生类似的裂隙场,有效压裂面积大;单段压裂时煤体渗透系数最大可达初值的249倍,多段水力压裂时最大可达初值的263倍.与钻孔单段水力压裂工艺相比,多段水力压裂可有效提高钻孔瓦斯抽采效果.%In order to compare the permeability effects of a single section and multi section hvdraulic fracturing in the deep seam boreholes,based on the deposition conditions of the proposed opened No.8 seam in Xieqiao Mine,a single section and multi section hydraulic fracturing and permeability improved models were individually established.A RFPA2D-Flow software was applied to simulate and analyze the features and law of the in-seam water pressure field,stress field,crack field and permeability field within the hydraulic fracturing influence zone and the effect verifications were conducted.The results showed that the pore pressure in the coal mass at the initial fracturing of the single section fracturing was 7 MPa and the pore pressure of the coal mass at the initial fracturing of the multi section fracturing was 16 MPa.When the fracturing operation started in the seam,during the single section fracturing,there was an obvious stress concentration occurred in the borehole middle part of the seam.And when a multi

  18. An overview of hydraulic fracturing and other formation stimulation technologies for shale gas production - Update 2015

    OpenAIRE

    GANDOSSI Luca; VON ESTORFF Ulrik

    2015-01-01

    The technology of hydraulic fracturing for hydrocarbon well stimulation is not new, but only fairly recently has become a very common and widespread technique, especially in North America, due to technological advances that have allowed extracting natural gas from so-called unconventional reservoirs (tight sands, coal beds and shale formations). The conjunction of techniques such as directional drilling, high volume fracturing, micro-seismic monitoring, etc. with the development of multi-well...

  19. Formulation of fracture gradient extension equations in the Sergipe Basin-Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Suzart, J. Walter P.; Moreto, Rodrigo [Halliburton, Rio de Janeiro, RJ (Brazil); Luduvice, Roberto; Gomes, Isaac Santana; Richard Junior, Emerson [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2008-07-01

    One of the challenges of drilling exploration wells is to accurately estimate fracture gradients. This may cause formation damage and lead to premature hydraulic fracturing and prevent an optimum hydraulic design during completion. To avoid this scenario, it is important to know the minimum pressure that causes fractures. This estimation may be based on density, overburden, Poisson's ratio, and minimum horizontal stress. It is now possible to monitor fracturing stimulation operations in real time, which allows real-time understanding of formation pressure response, including fracture extension behavior and screen out. It is possible to avoid risks related to unexpected high pressure applied on the formation while drilling and maintain well and equipment integrities. This may prevent non-productive time (NPT) caused by unplanned well-cleaning operations and material expenses. Real-time fracturing information is usually obtained from step-rate and/or mini-frac analyses. However, there are some scenarios where these tests and analyses may be uneconomical. This paper details an alternative solution. It uses modified Eaton's equations that are representative of the area of interest, which in the present case is the Sergipe Basin located in northeast Brazil. The modified Eaton's equations are used to estimate parameters of the minimum horizontal stress, fracture extension gradient, overburden, and Poisson's ratio. This is based on hydraulic fracturing jobs and density logs available from different locations within the Sergipe Basin. To validate the present method, the estimation results were compared with available step-rate test results for the area. (author)

  20. Trends in hydraulic fracturing distributions and treatment fluids, additives, proppants, and water volumes applied to wells drilled in the United States from 1947 through 2010: data analysis and comparison to the literature

    Science.gov (United States)

    Gallegos, Tanya J.; Varela, Brian A.

    2015-01-01

    Hydraulic fracturing is presently the primary stimulation technique for oil and gas production in low-permeability, unconventional reservoirs. Comprehensive, published, and publicly available information regarding the extent, location, and character of hydraulic fracturing in the United States is scarce. This national spatial and temporal analysis of data on nearly 1 million hydraulically fractured wells and 1.8 million fracturing treatment records from 1947 through 2010 (aggregated in Data Series 868) is used to identify hydraulic fracturing trends in drilling methods and use of proppants, treatment fluids, additives, and water in the United States. These trends are compared to the literature in an effort to establish a common understanding of the differences in drilling methods, treatment fluids, and chemical additives and of how the newer technology has affected the water use volumes and areal distribution of hydraulic fracturing. Historically, Texas has had the highest number of records of hydraulic fracturing treatments and associated wells in the United States documented in the datasets described herein. Water-intensive horizontal/directional drilling has also increased from 6 percent of new hydraulically fractured wells drilled in the United States in 2000 to 42 percent of new wells drilled in 2010. Increases in horizontal drilling also coincided with the emergence of water-based “slick water” fracturing fluids. As such, the most current hydraulic fracturing materials and methods are notably different from those used in previous decades and have contributed to the development of previously inaccessible unconventional oil and gas production target areas, namely in shale and tight-sand reservoirs. Publicly available derivative datasets and locations developed from these analyses are described.

  1. Hydraulic fracturing - an attempt of DEM simulation

    Science.gov (United States)

    Kosmala, Alicja; Foltyn, Natalia; Klejment, Piotr; Dębski, Wojciech

    2017-04-01

    Hydraulic fracturing is a technique widely used in oil, gas and unconventional reservoirs exploitation in order to enable the oil/gas to flow more easily and enhance the production. It relays on pumping into a rock a special fluid under a high pressure which creates a set of microcracks which enhance porosity of the reservoir rock. In this research, attempt of simulation of such hydrofracturing process using the Discrete Element Method approach is presented. The basic assumption of this approach is that the rock can be represented as an assembly of discrete particles cemented into a rigid sample (Potyondy 2004). An existence of voids among particles simulates then a pore system which can be filled out by fracturing fluid, numerically represented by much smaller particles. Following this microscopic point of view and its numerical representation by DEM method we present primary results of numerical analysis of hydrofracturing phenomena, using the ESyS-Particle Software. In particular, we consider what is happening in distinct vicinity of the border between rock sample and fracking particles, how cracks are creating and evolving by breaking bonds between particles, how acoustic/seismic energy is releasing and so on. D.O. Potyondy, P.A. Cundall. A bonded-particle model for rock. International Journal of Rock Mechanics and Mining Sciences, 41 (2004), pp. 1329-1364.

  2. Sacral Stress Fracture in an Amateur Badminton Player

    Directory of Open Access Journals (Sweden)

    Yusuke Yuasa

    2017-01-01

    Full Text Available Sacral stress fractures are rare among athletes but have been reported most frequently in long distance runners. We report herein the first case of a sacral stress fracture in an amateur badminton player. A 16-year-old, left-handed adolescent girl, who had just started to play badminton 3 months previously, complained of acute left buttock pain when she received a shuttlecock. Magnetic resonance imaging revealed a linear lesion of the left sacrum with low signal intensity on T1- and high signal intensity on T2-weighted images, which was consistent with a stress fracture. Conservative treatment with rest relieved her symptoms. Her fracture was considered to have occurred due to repetition of an exercise that caused excessive vertical power.

  3. Stress fractures of ankle and wrist in childhood: nature and frequency

    International Nuclear Information System (INIS)

    Oestreich, Alan E.; Bhojwani, Nicholas

    2010-01-01

    Stress fractures of many etiologies are found not infrequently in various tarsal bones but are less commonly recognized in carpal bones. To assess the distribution of tarsal and carpal stress fractures. During the last three decades, the senior author collected locations of tarsal and carpal bone stress fracture callus seen on plain radiographs. 527 children with tarsal and carpal stress fractures were identified (88 children had multiple bones involved). The totals were: calcaneus 244, cuboid 188, talus 121, navicular 24, cuneiforms 23, capitate 18, lunate 1, and scaphoid 1. Stress fractures were more frequently seen once we became aware each particular bone could be involved. Tarsal and carpal stress fractures in children are not rare. Careful perusal of these bones is urged in all susceptible children with limping or wrist pain. (orig.)

  4. Stress fractures of ankle and wrist in childhood: nature and frequency

    Energy Technology Data Exchange (ETDEWEB)

    Oestreich, Alan E. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States); Bhojwani, Nicholas [University of Cincinnati College of Medicine, Cincinnati, OH (United States)

    2010-08-15

    Stress fractures of many etiologies are found not infrequently in various tarsal bones but are less commonly recognized in carpal bones. To assess the distribution of tarsal and carpal stress fractures. During the last three decades, the senior author collected locations of tarsal and carpal bone stress fracture callus seen on plain radiographs. 527 children with tarsal and carpal stress fractures were identified (88 children had multiple bones involved). The totals were: calcaneus 244, cuboid 188, talus 121, navicular 24, cuneiforms 23, capitate 18, lunate 1, and scaphoid 1. Stress fractures were more frequently seen once we became aware each particular bone could be involved. Tarsal and carpal stress fractures in children are not rare. Careful perusal of these bones is urged in all susceptible children with limping or wrist pain. (orig.)

  5. Stress fractures: definition, diagnosis and treatment ?

    OpenAIRE

    Astur, Diego Costa; Zanatta, Fernando; Arliani, Gustavo Gon?alves; Moraes, Eduardo Ramalho; Pochini, Alberto de Castro; Ejnisman, Benno

    2015-01-01

    ABSTRACT Stress fractures were first described in Prussian soldiers by Breithaupt in 1855. They occur as the result of repeatedly making the same movement in a specific region, which can lead to fatigue and imbalance between osteoblast and osteoclast activity, thus favoring bone breakage. In addition, when a particular region of the body is used in the wrong way, a stress fracture can occur even without the occurrence of an excessive number of functional cycles. The objective of this study wa...

  6. Overcoming tortuosity in hydraulic fracture operations in the Pilar Field, Alagoas, Brazil; Operacoes de fraturamento hidraulico no Campo de Pilar, Alagoas

    Energy Technology Data Exchange (ETDEWEB)

    Payao, Edson da C. [PETROBRAS, Rio de Janeiro, RJ (Brazil); Gomes, Luiz A.Q.M.; Araujo, Josue de S. [Schlumberger, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    The growing demand of natural gas by the industries in the Northeast of Brazil is the main drive for the conversion campaign witnessed in the oil wells producing at marginal rates from the Coqueiro Seco formation in the Pilar field, State of Alagoas, to gas wells producing from the deep Penedo reservoir, with total depths in the vicinity of 3500 meters. One of the important steps for increasing natural gas production in the Pilar field is the hydraulic fracturing operations in the Penedo formation. The process of creating these fractures show a distinct behavior from the treatments performed in the shallow Coqueiro Seco formation, aiming at improved oil productivity. This paper describes the completion strategy for the wells converted from oil to gas producers, highlighting the problems faced and overcome during the hydraulic fracture treatments. In deviated wells crossing the deep Penedo reservoir, the risk of multiple fractures and influence of tortuosity have been diminished through corrective techniques, unique for each one of the existing wells. In the early hydraulic fracture treatments performed in the Pilar field, premature screen-outs were commonplace, disencouraging the use of the technique. The need to produce gas brought new ideas to the battlefield, and their implementation led to results beyond expectations. (author)

  7. 4D synchrotron X-ray imaging to understand porosity development in shales during exposure to hydraulic fracturing fluid

    Science.gov (United States)

    Kiss, A. M.; Bargar, J.; Kohli, A. H.; Harrison, A. L.; Jew, A. D.; Lim, J. H.; Liu, Y.; Maher, K.; Zoback, M. D.; Brown, G. E.

    2016-12-01

    Unconventional (shale) reservoirs have emerged as the most important source of petroleum resources in the United States and represent a two-fold decrease in greenhouse gas emissions compared to coal. Despite recent progress, hydraulic fracturing operations present substantial technical, economic, and environmental challenges, including inefficient recovery, wastewater production and disposal, contaminant and greenhouse gas pollution, and induced seismicity. A relatively unexplored facet of hydraulic fracturing operations is the fluid-rock interface, where hydraulic fracturing fluid (HFF) contacts shale along faults and fractures. Widely used, water-based fracturing fluids contain oxidants and acid, which react strongly with shale minerals. Consequently, fluid injection and soaking induces a host of fluid-rock interactions, most notably the dissolution of carbonates and sulfides, producing enhanced or "secondary" porosity networks, as well as mineral precipitation. The competition between these mechanisms determines how HFF affects reactive surface area and permeability of the shale matrix. The resultant microstructural and chemical changes may also create capillary barriers that can trap hydrocarbons and water. A mechanistic understanding of the microstructure and chemistry of the shale-HFF interface is needed to design new methodologies and fracturing fluids. Shales were imaged using synchrotron micro-X-ray computed tomography before, during, and after exposure to HFF to characterize changes to the initial 3D structure. CT reconstructions reveal how the secondary porosity networks advance into the shale matrix. Shale samples span a range of lithologies from siliceous to calcareous to organic-rich. By testing shales of different lithologies, we have obtained insights into the mineralogic controls on secondary pore network development and the morphologies at the shale-HFF interface and the ultimate composition of produced water from different facies. These results

  8. A geometrically based method for predicting stress-induced fracture aperture and flow in discrete fracture networks

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    networks, digitized from outcropping pavements. These networks cover a wide range of possible geometries and spatial distributions. The geometrically based method predicts the average hydraulic aperture and equivalent permeability of fractured porous media with error margins of less than 5%....

  9. Influence of microporosity on fracture stress of pyrocarbon coatings

    International Nuclear Information System (INIS)

    Krautwasser, P.; Nickel, H.; Taueber, K.

    1975-01-01

    In this paper recent investigations on fracture behaviour of integral PyC-coatings are presented. The fracture stresses of propene, acetylene, and methane-derived pyrocarbons are measured as a function of deposition temperature and deposition rate. The measured fracture stresses are interpreted in terms of microporosity values determined by X-ray small angle scattering (SAXS). It can be shown that the fracture stress is correlated unambigously with the concentration of micropores in the range of about 50 to 500A diameter. TEM inspection of the investigated materials revealed a component of disordered, tangled fibres with a high microporosity in agreement with SAXS results. This component increases with temperature in the range of 1250 to 1400 at the expense of of a high-density component. As a result, the coatings deposited in this temperature range show decreasing fracture stress with increasing amount of the porous glass wool like component. PyC coatings with a good irradiation behaviour had an initial pore size distribution typical for a relatively high content of tangled material. The assumption, that a relatively high amount of the disordered material is fafourable for a good behaviour i.e. integrity of coating up to high neutron doses, was confirmed besides other investigations by the relative low preirradiation fracture stresses of the well behaving coatings. This means, the integrity of pyrocarbon coatings after irradiation is favoured not so much by a high preirradiation fracture stress, but by the enhanced dimensional stability of the disordered porous material. In addition to this, the increase of the relatively low fractures stress due to the measured irradiation induced reduction of pores in the size range of 200 to 1000A diameter is in favour of coating integrity

  10. Bilateral femoral supracondylar stress fractures in a cross country runner.

    Science.gov (United States)

    Ross, Kate; Fahey, Mark

    2008-08-01

    Several high-risk factors lead to stress fractures. They include excessive training in athletes leading to overuse injuries, nutritional deficiencies, and endocrine disorders. While stress fractures are common, bilateral stress fractures are rarely seen. Few cases have been reported of bilateral femoral stress fractures in young athletes. This article presents a case of a 14-year-old cross country runner with a bilateral femoral supracondylar stress fracture. He presented with bilateral supracondylar stress fractures from running. The patient followed a strict vegan diet, but his parents stated that, to their knowledge, he was getting adequate protein and calcium. Treatment consisted of decreased activity to pain-free levels with acetaminophen for pain. Low-impact conditioning such as swimming and bicycling was allowed. Hamstring and quadricep stretching was suggested. Nutritional consultation was obtained to ensure appropriate nutrition on a vegan diet. At 1-month follow-up, he was pain free and allowed to proceed with a gradual return to running activities. In this case, the onset of a new workout routine was intolerable for this patient's low bone density, causing insufficiency fractures. Appropriate vegan diets were not associated with stress fracture in our literature review. He may have had an inadequate diet prior to this injury. As in this case, full recovery can be made after this rest period, and the patient may return to his or her original activity safely. In young athletes, diet and nutrition must be kept in mind.

  11. New developments of the Integrated Stress Determination Method and application to the Aespoe Hard Rock Laboratory, Sweden

    International Nuclear Information System (INIS)

    Ask, Daniel

    2004-04-01

    This thesis presents new developments of the Integrated Stress Determination Method (ISDM) with application to the Aespoe Hard Rock Laboratory (HRL), Oskarshamn, Sweden. The new developments involve a 12-parameter representation of the regional stress field in the rock mass. The method is applicable to data from hydraulic fracturing, hydraulic tests on pre-existing fractures (HTPF), and overcoring data from CSIR- and CSIRO-type of devices. When hydraulic fracturing/HTPF data are combined with overcoring data, the former may be used to constrain the elastic parameters, i.e. the problem involves 14 model parameters. The Swedish Nuclear Fuel and Waste Management Co. (SKB), have conducted a vast amount of rock stress measurements at the Aespoe HRL since the late 1980s. However, despite the large number of stress measurement data collected in this limited rock volume, variability in the stress field exists. Not only does the result vary depending on measuring technique, e.g. overcoring data indicated larger stress magnitudes compared to hydraulic fracturing data; the results are also affected by existing discontinuities, indicated by non-linear stress magnitudes and orientations versus depth. The objectives for this study are therefore threefold: (1) find explanations to the observed differences between existing hydraulic and overcoring stress data at the Aspo HRL; (2) explain the non-linear stress distribution indicated by existing stress data; and (3) apply the ISDM, including the new developments, based on the results obtained in step 1 and 2. To evaluate the observed differences between existing hydraulic and overcoring stress data, a detailed re-interpretation was conducted. Several measurement-related uncertainties were identified and corrected for when possible, which effectively reduced the discrepancies between the hydraulic and overcoring measuring results. Modeling studies managed by SKB have shown that the redistribution of the stresses at Aespoe HRL to a

  12. Modelling Subduction Zone Magmatism Due to Hydraulic Fracture

    Science.gov (United States)

    Lawton, R.; Davies, J. H.

    2014-12-01

    The aim of this project is to test the hypothesis that subduction zone magmatism involves hydraulic fractures propagating from the oceanic crust to the mantle wedge source region (Davies, 1999). We aim to test this hypothesis by developing a numerical model of the process, and then comparing model outputs with observations. The hypothesis proposes that the water interconnects in the slab following an earthquake. If sufficient pressure develops a hydrofracture occurs. The hydrofracture will expand in the direction of the least compressive stress and propagate in the direction of the most compressive stress, which is out into the wedge. Therefore we can calculate the hydrofracture path and end-point, given the start location on the slab and the propagation distance. We can therefore predict where water is added to the mantle wedge. To take this further we have developed a thermal model of a subduction zone. The model uses a finite difference, marker-in-cell method to solve the heat equation (Gerya, 2010). The velocity field was prescribed using the analytical expression of cornerflow (Batchelor, 1967). The markers contained within the fixed grid are used to track the different compositions and their properties. The subduction zone thermal model was benchmarked (Van Keken, 2008). We used the hydrous melting parameterization of Katz et.al., (2003) to calculate the degree of melting caused by the addition of water to the wedge. We investigate models where the hydrofractures, with properties constrained by estimated water fluxes, have random end points. The model predicts degree of melting, magma productivity, temperature of the melt and water content in the melt for different initial water fluxes. Future models will also include the buoyancy effect of the melt and residue. Batchelor, Cambridge UP, 1967. Davies, Nature, 398: 142-145, 1999. Gerya, Cambridge UP, 2010. Katz, Geochem. Geophys. Geosy, 4(9), 2003 Van Keken et.al. Phys. Earth. Planet. In., 171:187-197, 2008.

  13. Attitudes toward hydraulic fracturing: The opposing forces of political conservatism and basic knowledge about fracking

    OpenAIRE

    Choma, BL; Hanoch, Y; Currie, S

    2016-01-01

    publisher: Elsevier articletitle: Attitudes toward hydraulic fracturing: The opposing forces of political conservatism and basic knowledge about fracking journaltitle: Global Environmental Change articlelink: http://dx.doi.org/10.1016/j.gloenvcha.2016.03.004 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.

  14. Residual stresses associated with the hydraulic expansion of steam generator tubing into tubesheets

    International Nuclear Information System (INIS)

    Middlebrooks, W.B.; Harrod, D.L.; Gold, R.E.

    1991-01-01

    Westinghouse has used three different processes for the full depth expansion of tubes into the tube sheets of recirculating nuclear steam generators: mechanical rolling, explosive expansion and hydraulic expansion. Each process aims at expanding tubes tightly to tube sheets, leaving the smallest possible secondary side crevice depth, and minimizing the residual stress in the expanded tubes, all for the purpose of mitigating the effect of corrosion phenomena. The hydraulic expansion process was qualified and has been implemented since 1978, and more than 1.1 million tube ends have been hydraulically expanded into production units. In this paper, the results of the recent analytical studies related to the residual stress in the expanded tubes are summarized. The method of hydraulic expansion is explained, and some important parameters are given. Finite element method, theoretical incremental analysis, tube sheet yielding and residual stress, contact pressure, sensitivity analysis and temperature effect in the central region of tube sheets, and the residual stress in the transition zone are described. (K.I.)

  15. Disposal of radioactive grouts into hydraulically fractured shale

    International Nuclear Information System (INIS)

    1983-01-01

    A process for permanent waste disposal has been in operation for nearly 20 years at Oak Ridge National Laboratory (ORNL). In this method, intermediate-level radioactive waste effluents in the form of a slurry containing hydraulic binders (grouts) are injected by means of fracturing into a deep underground formation (a nearly impervious shale formation) considered to be isolated from the surface. The composition of the grout is carefully chosen so that the slurry thus injected solidifies in situ, ensuring fixation of the waste and rendering this type of disposal final in character. This process - ''hydrofracture'' or ''shale fracturing'' - immobilizes the wastes directly in situ, in such a condition that is well removed from the biosphere. It is an inexpensive process that is particularly suited for the permanent disposal of large batches of certain types of wastes under specific conditions. Some sections of this report are concerned with the general aspects of the hydrofracture process. Other sections are site specific and discuss the development of the process at ORNL and the operating experience with the ORNL facility. Sections 2 and 3 are concerned with the general aspects of site selection and are not site specific. Sections 4, 5, 6 and 8 are concerned with operating experience at ORNL and are site specific. Section 7 (safety assessment) is based on ORNL experience, but the considerations that are discussed in this section have general application. Details of the operating experience with the process at ORNL and West Valley are given in Appendix 1. Appendix 2 is a brief treatment of the theory of fracture mechanics

  16. Stress generation and hierarchical fracturing in reactive systems

    Science.gov (United States)

    Jamtveit, B.; Iyer, K.; Royne, A.; Malthe-Sorenssen, A.; Mathiesen, J.; Feder, J.

    2007-12-01

    Hierarchical fracture patterns are the result of a slowly driven fracturing process that successively divides the rocks into smaller domains. In quasi-2D systems, such fracture patterns are characterized by four sided domains, and T-junctions where new fractures stop at right angles to pre-existing fractures. We describe fracturing of mm to dm thick enstatite layers in a dunite matrix from the Leka ophiolite complex in Norway. The fracturing process is driven by expansion of the dunite matrix during serpentinization. The cumulative distributions of fracture lengths show a scaling behavior that lies between a log - normal and power law (fractal) distribution. This is consistent with a simple fragmentation model in which domains are divided according to a 'top hat' distribution of new fracture positions within unfractured domains. Reaction-assisted hierarchical fracturing is also likely to be responsible for other (3-D) structures commonly observed in serpentinized ultramafic rocks, including the mesh-textures observed in individual olivine grains, and the high abundance of rectangular domains at a wide range of scales. Spectacular examples of 3-D hierarchical fracture patterns also form during the weathering of basaltic intrusions (dolerites). Incipient chemical weathering of dolerites in the Karoo Basin in South Africa occurs around water- filled fractures, originally produced by thermal contraction or by externally imposed stresses. This chemical weathering causes local expansion of the rock matrix and generates elastic stresses. On a mm to cm scale, these stresses lead to mechanical layer-by-layer spalling, producing the characteristic spheroidal weathering patterns. However, our field observations and computer simulations demonstrate that in confined environments, the spalling process alone is unable to relieve the elastic stresses. In such cases, chemical weathering drives a much larger scale hierarchical fracturing process in which fresh dolerite undergoes a

  17. Conductivity Evolution of Fracture Proppant in Partial Monolayers and Multilayers

    Science.gov (United States)

    Fan, M.; Han, Y.; McClure, J. E.; Chen, C.

    2017-12-01

    Proppant is a granular material, typically sand, coated sand, or man-made ceramic materials, which is widely used in hydraulic fracturing to keep the induced fractures open. Optimization of proppant placement in a hydraulic fracture, as well as its role on the fracture's conductivity, is vital for effective and economical production of petroleum hydrocarbons. In this research, a numerical modeling approach, combining Discrete Element Method (DEM) with lattice Boltzmann (LB) method, was adopted to advance the understanding of fracture conductivity as function of proppant concentration under various effective stresses. DEM was used to simulate effective stress increase and the resultant proppant particle compaction and rearrangement during the process of reservoir depletion due to hydrocarbon extraction. DEM-simulated pore structure was extracted and imported into the LB simulator as boundary conditions to calculate the time-dependent permeability of the proppant pack. We first validated the DEM-LB coupling workflow; the simulated proppant pack permeabilities as functions of effective stress were in good agreement with laboratory measurements. Next, several proppant packs were generated with various proppant concentrations, ranging from partial-monolayer to multilayer structures. Proppant concentration is defined as proppant mass per unit fracture face area. Fracture conductivity as function of proppant concentration was measured in LB simulations. It was found that a partial-monolayer proppant pack with large-diameter particles was optimal in maintaining sufficient conductivity while lowering production costs. Three proppant packs with the same average diameter but different diameter distributions were generated. Specifically, we used the coefficient of variation (COV) of diameter, defined as the ratio of standard deviation of diameter to mean diameter, to characterize the heterogeneity in particle size. We obtained proppant pack porosity, permeability, and fracture

  18. Estimation of the controlling stress in creep fracture

    International Nuclear Information System (INIS)

    Henderson, J.; Ferguson, F.R.

    1975-01-01

    The implementation of correct criterion in creep design, has been shown to be of fundamental significance in the assessment of component life. The present report considers the problem of the means whereby the criterion may be derived for a particular metal without the availability of sophisticated complex-stress testing equipment and procedures such as the combined tension and torsion tests on thin walled tubular specimens employed in the earlier fundamental researches on the subject. By investigating a wide spectrum of engineering metals it was established that for homogeneous stress conditions two criteria appeared to be sufficient to cover all the metals studied for complex-stress creep fracture, either the maximum principal stress or the octahedral shear stress criterion. Further, it was found that those metals which developed random and continuous cracking during creep were controlled with respect to fracture time by the maximum principal stress, while metals which showed virtually no cracking were governed by the octahedral shear stress or second order invariant. The physical nature of the final fracture (transcrystalline or inter-crystalline), contrary to considerable current concepts, was found to be unrelated to which criterion was operative. Having reduced the possible fracture criteria to two, it only remained to develop a simple test method exploiting this finding to achieve the precise identification for a particular metal. Seven metals including aluminium, copper, titanium, cast iron and three steels have been investigated in the present report at temperatures where creep conditions are operative. The results have shown that the method leads to sufficiently accurate prediction of the complex stress creep fracture criterion for the metals studied

  19. A Holistic Assessment of Energy Production: Environmental, Economic, and Social Impacts of Hydraulic Fracturing in Williams County, North Dakota

    Science.gov (United States)

    Jagdeo, J.; Ravikumar, A. P.; Grubert, E.; Brandt, A. R.

    2016-12-01

    Unconventional oil and natural gas production in the U.S. has increased tenfold between 2005 and 2014 due to advances in hydraulic fracturing technology. Prior studies of hydraulic fracturing activity have mainly focused on two themes: the environmental impacts related to air and water pollution or the direct and spillover economic benefits resulting from oil booms at the state and local level. However, the impacts of hydraulic fracturing extend beyond these effects. Oil-boom counties have experienced environmental changes in land-use and water supply and witnessed social changes in demographics, crime, and health, factors that are not typically evaluated in regard to hydraulic fracturing. Hence, there is a need to consider the holistic effects of oil production on communities. This study examines the environmental, economic, and social impacts of oil and gas activity in Williams County, North Dakota by comparing its pre-boom ( 2005) and post-boom ( 2014) conditions. Annual oil production in Williams County increased from 3.4 million barrels in 2005 to 56 million barrels in 2014, providing an ideal test-case to study the impact of energy development on surrounding communities. We compared changes in multiple impact categories, attributed directly or indirectly to hydraulic fracturing activity, to trends at the national level. For example, between 2005 and 2014, CO2 and CH4 emissions primarily from oil and gas activity increased by 360 thousand metric tons CO2e, corresponding to a 20-fold increase. Concurrently, national emissions decreased by 10.5%. Over twenty indicators were analyzed across environmental, social and economic impact categories, including land-use change, median household income, and crime rates. The datasets were normalized using federal regulations for upper and lower bounds, or calibrated against national averages. Normalized indicators are then aggregated to provide a single-value `impact-factor'. Such `impact-factor' maps will provide a

  20. Atypical stress-avulsion fracture of the Lisfranc joint complex.

    LENUS (Irish Health Repository)

    O'Neill, Barry J

    2014-04-01

    Antiphospholipid syndrome and systemic erythematosus have been associated with metatarsal stress fractures. Stress fractures of the Lisfranc joint complex are uncommon injuries but have been reported to occur most frequently in ballet dancers. We present a case of an avulsion fracture of the Lisfranc joint complex that occurred spontaneously. We have reviewed the association between systemic conditions and metatarsal fractures and proposed a series of hypothetical pathological events that may have contributed to this unusual injury.

  1. Ultrasound-Diagnosed Tibia Stress Fracture: A Case Report.

    Science.gov (United States)

    Amoako, Adae; Abid, Ayesha; Shadiack, Anthony; Monaco, Robert

    2017-01-01

    Stress fractures are a frequent cause of lower extremity pain in athletes, and especially in runners. Plain imaging has a low sensitivity. Magnetic resonance imaging (MRI) or bone scan scintigraphy is the criterion standard, but expensive. We present the case of a young female distance runner with left shin pain. Plain radiography was unremarkable. Ultrasound showed focal hyperechoic elevation of the periosteum with irregularity over the distal tibia and increased flow on Doppler. These findings were consistent with a distal tibia stress fracture and confirmed by MRI. Examination of our case will highlight the utility of considering an ultrasound for diagnosis of tibial stress fracture.

  2. Ultrasound-Diagnosed Tibia Stress Fracture: A Case Report

    Directory of Open Access Journals (Sweden)

    Adae Amoako

    2017-04-01

    Full Text Available Stress fractures are a frequent cause of lower extremity pain in athletes, and especially in runners. Plain imaging has a low sensitivity. Magnetic resonance imaging (MRI or bone scan scintigraphy is the criterion standard, but expensive. We present the case of a young female distance runner with left shin pain. Plain radiography was unremarkable. Ultrasound showed focal hyperechoic elevation of the periosteum with irregularity over the distal tibia and increased flow on Doppler. These findings were consistent with a distal tibia stress fracture and confirmed by MRI. Examination of our case will highlight the utility of considering an ultrasound for diagnosis of tibial stress fracture.

  3. Exercise-induced rib stress fractures: influence of reduced bone mineral density

    DEFF Research Database (Denmark)

    Vinther, Anders; Kanstrup, Inge-Lis; Christiansen, Erik

    2005-01-01

    study investigated BMD in seven Danish national team rowers with previous rib stress fracture (RSF) and 7 controls (C) matched for gender, age, height, weight and training experience. Total body scan and specific scans of the lumbar spine (L2-L4), femoral neck and distal radius were performed using......Exercise-induced rib stress fractures have been reported frequently in elite rowers during the past decade. The etiology of rib stress fractures is unclear, but low bone mineral density (BMD) has been suggested to be a potential risk factor for stress fractures in weight-bearing bones. The present...... density may be a potential risk factor for the development of exercise-induced rib stress fractures in elite rowers....

  4. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1998-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  5. Investigations of some rock stress measuring techniques and the stress field in Norway

    Energy Technology Data Exchange (ETDEWEB)

    Hanssen, Tor Harald

    1997-12-31

    Rock stresses are important to the safe construction and operation of all man-made structures in rock, whether In mining, civil or petroleum engineering. The crucial issue is their relative magnitude and orientation. This thesis develops equipment and methods for further rock stress assessment and reevaluates existing overcoring rock stress measurements, and relates this information to the present geological setting. Both laboratory work and field work are involved. In the field, rock stresses are measured by the overcoring and the hydraulic fracturing technique. An observation technique for assessing likely high stresses is developed. The field data refer to several hydropower projects and to some offshore hydrocarbon fields. The principal sections are: (1) Tectonic setting in the western Fennoscandia, (2) Triaxial rock stress measurements by overcoring using the NTH cell (a strain gauge cell developed at the Norwegian technical university in Trondheim and based on the CSIR cell of the South African Council for Scientific and Industrial Research), (3) Laboratory testing of the NTH cell, (4) Quality ranking of stresses measured by the NTH cell, (4) Recalculated rock stresses and implications to the regional stress field, (5) Hydraulic fracturing stress measurements. 113 refs., 98 figs., 62 tabs.

  6. Stress Fracture and Nonunion of Coronoid Process in a Gymnast

    Directory of Open Access Journals (Sweden)

    T. Hetling

    2016-01-01

    Full Text Available Background. Gymnasts have high mechanical loading forces of up to 14 times body weight. Overuse lesions are typical in wrists and stress fractures in the olecranon, while isolated fractures of the coronoid process are uncommon. We present a case of retraumatized nonunion stress fracture of the ulnar coronoid process. Case Description. A 19-year-old gymnast presented with elbow pain after training. Imaging confirmed an old fracture of the coronoid process. We describe a 6-month multiphase return to competition rehabilitation program, which allowed him to compete pain-freely. Literature Review. Acute and overuse injuries in gymnasts are known but no nonunion of the coronoid process has been described before. Only one case of stress fracture of coronoid process in a gymnast was reported. Purpose and Clinical Relevance. We could successfully and conservatively return to sport a reactivated nonunion of a stress fracture of the coronoid process.

  7. Hydraulic failure defines the recovery and point of death in water-stressed conifers.

    Science.gov (United States)

    Brodribb, Tim J; Cochard, Hervé

    2009-01-01

    This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering to observe the recovery process. During both phases midday transpiration and leaf water potential (Psileaf) were monitored. Stomatal responses to Psileaf were established for each species and these relationships used to evaluate whether the recovery of gas exchange after drought was limited by postembolism hydraulic repair in leaves. Furthermore, the timing of gas-exchange recovery was used to determine the maximum survivable water stress for each species and this index compared with data for both leaf and stem vulnerability to water-stress-induced dysfunction measured for each species. Recovery of gas exchange after water stress took between 1 and >100 d and during this period all species showed strong 1:1 conformity to a combined hydraulic-stomatal limitation model (r2 = 0.70 across all plants). Gas-exchange recovery time showed two distinct phases, a rapid overnight recovery in plants stressed to 50% loss of Kleaf. Maximum recoverable water stress (Psimin) corresponded to a 95% loss of Kleaf. Thus, we conclude that xylem hydraulics represents a direct limit to the drought tolerance of these conifer species.

  8. Formation of Particulate Matter from the Oxidation of Evaporated Wastewater from Hydraulic Fracturing Activity

    Science.gov (United States)

    Hildebrandt Ruiz, L.; Bean, J. K.; Bilotto, A.

    2017-12-01

    The use of hydraulic fracturing for production of petroleum and natural gas has increased dramatically in the last decade, but the environmental impacts of this technology remain unclear. Experiments were conducted to quantify airborne emissions from twelve samples of hydraulic fracturing flowback wastewater collected in the Permian Basin, as well as the photochemical processing of these emissions leading to the formation of particulate matter. The concentration of total volatile carbon (TVC, hydrocarbons evaporating at room temperature) averaged 29 milligrams of carbon per liter (mgC/L) and the TVC evaporation rate averaged 1357 mgC/L-m2-min. After photochemical oxidation under high NOx conditions the amount of organic particulate matter formed per milliliter of wastewater evaporated averaged 24 micrograms (µg); the amount of ammonium nitrate formed averaged 262 µg. In the state of Texas, the potential formation of PM from evaporated flowback wastewater is similar to the estimated PM emissions from diesel engines used in oil rigs, emphasizing the need to quantify wastewater evaporation and atmospheric processing of these emissions.

  9. Case Study Analysis of the Impacts of Water Acquisition for Hydraulic Fracturing on Local Water Availability

    Science.gov (United States)

    Hydraulic fracturing (HF) is used to develop unconventional gas reserves, but the technology requires large volumes of water, placing demands on local water resources and potentially creating conflict with other users and ecosystems. This study examines the balance between water ...

  10. Proximal tibial stress fracture associated with mild osteoarthritis of the knee: case report.

    Science.gov (United States)

    Curković, Marko; Kovac, Kristina; Curković, Bozidar; Babić-Naglić, Durda; Potocki, Kristina

    2011-03-01

    Stress fractures are considered as multifactorial overuse injuries occurring in 0.3%-0.8% of patients suffering from rheumatic diseases, with rheumatoid arthritis being the most common underlying condition. Stress fractures can be classified according to the condition of the bone affected as: 1) fatigue stress fractures occurring when normal bone is exposed to repeated abnormal stresses; and 2) insufficiency stress fractures that occur when normal stress is applied to bone weakened by an underlying condition. Stress fractures are rarely associated with severe forms of knee osteoarthritis, accompanied with malalignment and obesity. We present a patient with a proximal tibial stress fracture associated with mild knee osteoarthritis without associated malalignment or obesity. Stress fracture should be considered when a patient with osteoarthritis presents with sudden deterioration, severe localized tenderness to palpation and localized swelling or periosteal thickening at the pain site and elevated local temperature. The diagnosis of stress fractures in patients with rheumatic diseases may often be delayed because plain film radiographs may not reveal a stress fracture soon after the symptom onset; moreover, evidence of a fracture may never appear on plain radiographs. Triple phase nuclear bone scans and magnetic resonance imaging are more sensitive in the early clinical course than plain films for initial diagnosis.

  11. Subsurface fracture mapping from geothermal wellbores. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hartenbaum, B.A.; Rawson, G.

    1983-08-01

    To advance the state-of-the-art in Hot Dry Rock technology, and evaluation is made of (1) the use of both electromagnetic and acoustic radar to map far-field fractures, (2) the use of more than twenty different conventional well logging tools to map borehole-fracture intercepts, (3) the use of magnetic dipole ranging to determine the relative positions of the injection well and the production well within the fractured zone, (4) the use of passive microseismic methods to determine the orientation and extent of hydraulic fractures, and (5) the application of signal processing techniques to fracture mapping including tomography, holography, synthetic aperture, image reconstruction, and the relative importance of phase and amplitude information. It is found that according to calculations, VHF backscatter radar has the potential for mapping fractures within a distance of 50 +- 20 meters from the wellbore. A new technique for improving fracture identification is presented. The range of acoustic radar is five to seven times greater than that of VHF radar when compared on the basis of equal resolution, i.e., equal wavelengths. Analyses of extant data indicate that when used synergistically the (1) caliper, (2) resistivity dipmeter, (3) televiewer, (4) television, (5) impression packer, and (6) acoustic transmission are useful for mapping borehole-fracture intercepts. A new model of hydraulic fracturing is presented which indicates that a hydraulic fracture is dynamically unstable; consequently, improvements in locating the crack tip may be possible. The importance of phase in signal processing is stressed and those techniques which employ phase data are emphasized for field use.

  12. Longitudinal stress fracture of the tibia

    International Nuclear Information System (INIS)

    Lopez, J.M.; Onatibia, A.; Galardi, A.; Laso, C.

    1997-01-01

    We present two cases of lengthwise stress fracture in tibia. This is an atypical and uncommon presentation. We describe the major clinical and radiological findings, stressing the enormous importance of CT in the correct diagnosis. (Author) 6 refs

  13. Analytical, numerical and experimental investigations of transverse fracture propagation from horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, M.M.; Hossain, M.M.; Crosby, D.G.; Rahman, M.K.; Rahman, S.S. [School of Petroleum Engineering, The University of New South Wales, 2052 Sydney (Australia)

    2002-08-01

    This paper presents results of a comprehensive study involving analytical, numerical and experimental investigations into transverse fracture propagation from horizontal wells. The propagation of transverse hydraulic fractures from horizontal wells is simulated and investigated in the laboratory using carefully designed experimental setups. Closed-form analytical theories for Mode I (opening) stress intensity factors for idealized fracture geometries are reviewed, and a boundary element-based model is used herein to investigate non-planar propagation of fractures. Using the mixed mode fracture propagation criterion of the model, a reasonable agreement is found with respect to fracture geometry, net fracture pressures and fracture propagation paths between the modeled fractures and the laboratory tested fractures. These results suggest that the propagation of multiple fractures requires higher net pressures than a single fracture, the underlying reason of which is theoretically justified on the basis of local stress distribution.

  14. Stress fractures about the tibia, foot, and ankle.

    Science.gov (United States)

    Shindle, Michael K; Endo, Yoshimi; Warren, Russell F; Lane, Joseph M; Helfet, David L; Schwartz, Elliott N; Ellis, Scott J

    2012-03-01

    In competitive athletes, stress fractures of the tibia, foot, and ankle are common and lead to considerable delay in return to play. Factors such as bone vascularity, training regimen, and equipment can increase the risk of stress fracture. Management is based on the fracture site. In some athletes, metabolic workup and medication are warranted. High-risk fractures, including those of the anterior tibial diaphysis, navicular, proximal fifth metatarsal, and medial malleolus, present management challenges and may require surgery, especially in high-level athletes who need to return to play quickly. Noninvasive treatment modalities such as pulsed ultrasound and extracorporeal shock wave therapy may have some benefit but require additional research.

  15. Estimation of the hydraulic conductivity of a two-dimensional fracture network using effective medium theory and power-law averaging

    Science.gov (United States)

    Zimmerman, R. W.; Leung, C. T.

    2009-12-01

    Most oil and gas reservoirs, as well as most potential sites for nuclear waste disposal, are naturally fractured. In these sites, the network of fractures will provide the main path for fluid to flow through the rock mass. In many cases, the fracture density is so high as to make it impractical to model it with a discrete fracture network (DFN) approach. For such rock masses, it would be useful to have recourse to analytical, or semi-analytical, methods to estimate the macroscopic hydraulic conductivity of the fracture network. We have investigated single-phase fluid flow through generated stochastically two-dimensional fracture networks. The centers and orientations of the fractures are uniformly distributed, whereas their lengths follow a lognormal distribution. The aperture of each fracture is correlated with its length, either through direct proportionality, or through a nonlinear relationship. The discrete fracture network flow and transport simulator NAPSAC, developed by Serco (Didcot, UK), is used to establish the “true” macroscopic hydraulic conductivity of the network. We then attempt to match this value by starting with the individual fracture conductances, and using various upscaling methods. Kirkpatrick’s effective medium approximation, which works well for pore networks on a core scale, generally underestimates the conductivity of the fracture networks. We attribute this to the fact that the conductances of individual fracture segments (between adjacent intersections with other fractures) are correlated with each other, whereas Kirkpatrick’s approximation assumes no correlation. The power-law averaging approach proposed by Desbarats for porous media is able to match the numerical value, using power-law exponents that generally lie between 0 (geometric mean) and 1 (harmonic mean). The appropriate exponent can be correlated with statistical parameters that characterize the fracture density.

  16. Sensitivity analysis of hydraulic fracturing Using an extended finite element method for the PKN model

    NARCIS (Netherlands)

    Garikapati, Hasini; Verhoosel, Clemens V.; van Brummelen, Harald; Diez, Pedro; Papadrakakis, M.; Papadopoulos, V.; Stefanou, G.; Plevris, V.

    2016-01-01

    Hydraulic fracturing is a process that is surrounded by uncertainty, as available data on e.g. rock formations is scant and available models are still rudimentary. In this contribution sensitivity analysis is carried out as first step in studying the uncertainties in the model. This is done to

  17. Thermo-hydro-mechanical behavior of fractured rock mass

    International Nuclear Information System (INIS)

    Coste, F.

    1997-12-01

    The purpose of this research is to model Thermo-Hydro-Mechanical behavior of fractured rock mass regarding a nuclear waste re-depository. For this, a methodology of modeling was proposed and was applied to a real underground site (EDF site at Nouvelle Romanche). This methodology consists, in a first step, to determine hydraulic and mechanical REV. Beyond the greatest of these REV, development of a finite element code allows to model all the fractures in an explicit manner. The homogenized mechanical properties are determined in drained and undrained boundary conditions by simulating triaxial tests that represent rock mass subject to loading. These simulations allow to study the evolution of hydraulic and mechanical properties as a function of stress state. Drained and undrained boundary conditions enable to discuss the validity of assimilation of a fractured rock mass to a porous medium. The simulations lead to a better understanding of the behavior of the fractured rock masses and allow to show the dominant role of the shear behavior of the fractures on the hydraulic and mechanical homogenized properties. From a thermal point of view, as long as conduction is dominant, thermal properties of the rock mass are almost the same as those the intact rock. (author)

  18. Incorporating Scale-Dependent Fracture Stiffness for Improved Reservoir Performance Prediction

    Science.gov (United States)

    Crawford, B. R.; Tsenn, M. C.; Homburg, J. M.; Stehle, R. C.; Freysteinson, J. A.; Reese, W. C.

    2017-12-01

    We present a novel technique for predicting dynamic fracture network response to production-driven changes in effective stress, with the potential for optimizing depletion planning and improving recovery prediction in stress-sensitive naturally fractured reservoirs. A key component of the method involves laboratory geomechanics testing of single fractures in order to develop a unique scaling relationship between fracture normal stiffness and initial mechanical aperture. Details of the workflow are as follows: tensile, opening mode fractures are created in a variety of low matrix permeability rocks with initial, unstressed apertures in the micrometer to millimeter range, as determined from image analyses of X-ray CT scans; subsequent hydrostatic compression of these fractured samples with synchronous radial strain and flow measurement indicates that both mechanical and hydraulic aperture reduction varies linearly with the natural logarithm of effective normal stress; these stress-sensitive single-fracture laboratory observations are then upscaled to networks with fracture populations displaying frequency-length and length-aperture scaling laws commonly exhibited by natural fracture arrays; functional relationships between reservoir pressure reduction and fracture network porosity, compressibility and directional permeabilities as generated by such discrete fracture network modeling are then exported to the reservoir simulator for improved naturally fractured reservoir performance prediction.

  19. Sulfide Generation by Dominant Halanaerobium Microorganisms in Hydraulically Fractured Shales

    Energy Technology Data Exchange (ETDEWEB)

    Booker, Anne E.; Borton, Mikayla A.; Daly, Rebecca A.; Welch, Susan A.; Nicora, Carrie D.; Hoyt, David W.; Wilson, Travis; Purvine, Samuel O.; Wolfe, Richard A.; Sharma, Shikha; Mouser, Paula J.; Cole, David R.; Lipton, Mary S.; Wrighton, Kelly C.; Wilkins, Michael J.; McMahon, Katherine

    2017-07-05

    ABSTRACT

    Hydraulic fracturing of black shale formations has greatly increased United States oil and natural gas recovery. However, the accumulation of biomass in subsurface reservoirs and pipelines is detrimental because of possible well souring, microbially induced corrosion, and pore clogging. Temporal sampling of produced fluids from a well in the Utica Shale revealed the dominance ofHalanaerobiumstrains within thein situmicrobial community and the potential for these microorganisms to catalyze thiosulfate-dependent sulfidogenesis. From these field data, we investigated biogenic sulfide production catalyzed by aHalanaerobiumstrain isolated from the produced fluids using proteogenomics and laboratory growth experiments. Analysis ofHalanaerobiumisolate genomes and reconstructed genomes from metagenomic data sets revealed the conserved presence of rhodanese-like proteins and anaerobic sulfite reductase complexes capable of converting thiosulfate to sulfide. Shotgun proteomics measurements using aHalanaerobiumisolate verified that these proteins were more abundant when thiosulfate was present in the growth medium, and culture-based assays identified thiosulfate-dependent sulfide production by the same isolate. Increased production of sulfide and organic acids during the stationary growth phase suggests that fermentativeHalanaerobiumuses thiosulfate to remove excess reductant. These findings emphasize the potential detrimental effects that could arise from thiosulfate-reducing microorganisms in hydraulically fractured shales, which are undetected by current industry-wide corrosion diagnostics.

    IMPORTANCEAlthough thousands of wells in deep shale formations across the United States have been hydraulically fractured for oil and gas recovery, the impact of microbial metabolism within these environments is poorly understood. Our

  20. The treatment of residual stress in fracture assessment of pressure vessels

    International Nuclear Information System (INIS)

    Green, D.; Knowles, J.

    1992-01-01

    The treatment of weld residual stress in the fracture assessment of cylindrical pressure vessels is considered through partitioning the stress into membrane, bending and self-balancing through wall components. The influence of each on fracture behavior is discussed. Stress intensity factor solutions appropriate to each type of stress are presented. Short range, medium range and long range stress categories are identified according to simple rules relating the effect of increasing crack length to stress intensity factor and ligament net stress. Proposals are made on how the stress intensity factor from these stress types may be incorporated into a Kr, Lr based fracture assessment

  1. Effects of fracture surface roughness and shear displacement on geometrical and hydraulic properties of three-dimensional crossed rock fracture models

    Science.gov (United States)

    Huang, Na; Liu, Richeng; Jiang, Yujing; Li, Bo; Yu, Liyuan

    2018-03-01

    While shear-flow behavior through fractured media has been so far studied at single fracture scale, a numerical analysis of the shear effect on the hydraulic response of 3D crossed fracture model is presented. The analysis was based on a series of crossed fracture models, in which the effects of fracture surface roughness and shear displacement were considered. The rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. The shear displacement was applied on one fracture, and at the same time another fracture shifted along with the upper and lower surfaces of the sheared fracture. The simulation results reveal the development and variation of preferential flow paths through the model during the shear, accompanied by the change of the flow rate ratios between two flow planes at the outlet boundary. The average contact area accounts for approximately 5-27% of the fracture planes during shear, but the actual calculated flow area is about 38-55% of the fracture planes, which is much smaller than the noncontact area. The equivalent permeability will either increase or decrease as shear displacement increases from 0 to 4 mm, depending on the aperture distribution of intersection part between two fractures. When the shear displacement continuously increases by up to 20 mm, the equivalent permeability increases sharply first, and then keeps increasing with a lower gradient. The equivalent permeability of rough fractured model is about 26-80% of that calculated from the parallel plate model, and the equivalent permeability in the direction perpendicular to shear direction is approximately 1.31-3.67 times larger than that in the direction parallel to shear direction. These results can provide a fundamental understanding of fluid flow through crossed fracture model under shear.

  2. The role of local stress perturbation on the simultaneous opening of orthogonal fractures

    Science.gov (United States)

    Boersma, Quinten; Hardebol, Nico; Barnhoorn, Auke; Bertotti, Giovanni; Drury, Martyn

    2016-04-01

    Orthogonal fracture networks (ladder-like networks) are arrangements that are commonly observed in outcrop studies. They form a particularly dense and well connected network which can play an important role in the effective permeability of tight hydrocarbon or geothermal reservoirs. One issue is the extent to which both the long systematic and smaller cross fractures can be simultaneously critically stressed under a given stress condition. Fractures in an orthogonal network form by opening mode-I displacements in which the main component is separation of the two fracture walls. This opening is driven by effective tensile stresses as the smallest principle stress acting perpendicular to the fracture wall, which accords with linear elastic fracture mechanics. What has been well recognized in previous field and modelling studies is how both the systematic fractures and perpendicular cross fractures require the minimum principle stress to act perpendicular to the fracture wall. Thus, these networks either require a rotation of the regional stress field or local perturbations in stress field. Using a mechanical finite element modelling software, a geological case of layer perpendicular systematic mode I opening fractures is generated. New in our study is that we not only address tensile stresses at the boundary, but also address models using pore fluid pressure. The local stress in between systematic fractures is then assessed in order to derive the probability and orientation of micro crack propagation using the theory of sub critical crack growth and Griffith's theory. Under effective tensile conditions, the results indicate that in between critically spaced systematic fractures, local effective tensile stresses flip. Therefore the orientation of the least principle stress will rotate 90°, hence an orthogonal fracture is more likely to form. Our new findings for models with pore fluid pressures instead of boundary tension show that the magnitude of effective tension

  3. Regulation Of Hydraulic Fracturing In South Africa: A Project Life-Cycle Approach?

    Directory of Open Access Journals (Sweden)

    Willemien du Plessis

    2015-12-01

    Full Text Available This note deals with the 2015 regulations pertaining to hydraulic fracturing in South Africa from a project life-cycle approach. A brief history of the fragmentation of the regulation of environmental and mining related matters is provided, followed by a discussion of the application of the 2015 regulations during the project life cycle, ie the pre-commencement phase, the design and authorisation phase, the testing phase, the operational phase and the decommissioning and closure phase.

  4. Strontium isotopes test long-term zonal isolation of injected and Marcellus formation water after hydraulic fracturing.

    Science.gov (United States)

    Kohl, Courtney A Kolesar; Capo, Rosemary C; Stewart, Brian W; Wall, Andrew J; Schroeder, Karl T; Hammack, Richard W; Guthrie, George D

    2014-08-19

    One concern regarding unconventional hydrocarbon production from organic-rich shale is that hydraulic fracture stimulation could create pathways that allow injected fluids and deep brines from the target formation or adjacent units to migrate upward into shallow drinking water aquifers. This study presents Sr isotope and geochemical data from a well-constrained site in Greene County, Pennsylvania, in which samples were collected before and after hydraulic fracturing of the Middle Devonian Marcellus Shale. Results spanning a 15-month period indicated no significant migration of Marcellus-derived fluids into Upper Devonian/Lower Mississippian units located 900-1200 m above the lateral Marcellus boreholes or into groundwater sampled at a spring near the site. Monitoring the Sr isotope ratio of water from legacy oil and gas wells or drinking water wells can provide a sensitive early warning of upward brine migration for many years after well stimulation.

  5. Status of the art: hydraulic conductivity of acid- fractures; Condutividade hidraulica de fratura acida: estado da arte

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Valdo Ferreira [Universidade Estadual do Norte Fluminense Darcy Ribeiro (LENEP/UENF), Macae, RJ (Brazil). Centro de Ciencia e Tecnologia. Lab. de Engenharia e Exploracao de Petroleo; Campos, Wellington [PETROBRAS, RJ (Brazil). E and P Engenharia de Producao. Gerencia de Completacao e Avaliacao], e-mail: wcampos@petrobras.com.br

    2010-06-15

    This paper presents a review of the hydraulic conductivity models developed for acid fractures in almost four decades of studies in petroleum engineering. These studies have often benefited from theories and experiments carried out in areas of knowledge such as physics, geology, hydrology, fluid mechanics, rock mechanics and tribology. The review showed that the pioneer study of Nierode and Kruk (1973) is still used in commercial software and influences the current studies. There was significant evolution on the quantitative surface topography characterization of the fractures and their impact on the hydraulic conductivity. The same occurred for the effects of acid dissolution on the rock resistance. Improvements on correlations similar to the Nierode and Kruk can be applied at once on the acid fracturing project and evaluation practice for the cases of rough dissolution pattern. A method to consider the overall conductivity from heterogeneous channels and roughness pattern was recently proposed. The complexity of the theoretical fundaments, specially the range of validity of the equations in face of the simplifications assumed, the difficulty of performing representative laboratory and field experiments, the difficulty of characterizing quantitatively the fractures surface topography and its effects on the conductivity, and the large variety of rocks and acid systems keep this subject open for research. (author)

  6. Modeling thermal stress propagation during hydraulic stimulation of geothermal wells

    Science.gov (United States)

    Jansen, Gunnar; Miller, Stephen A.

    2017-04-01

    A large fraction of the world's water and energy resources are located in naturally fractured reservoirs within the earth's crust. Depending on the lithology and tectonic history of a formation, fracture networks can range from dense and homogeneous highly fractured networks to single large scale fractures dominating the flow behavior. Understanding the dynamics of such reservoirs in terms of flow and transport is crucial to successful application of engineered geothermal systems (also known as enhanced geothermal systems or EGS) for geothermal energy production in the future. Fractured reservoirs are considered to consist of two distinct separate media, namely the fracture and matrix space respectively. Fractures are generally thin, highly conductive containing only small amounts of fluid, whereas the matrix rock provides high fluid storage but typically has much smaller permeability. Simulation of flow and transport through fractured porous media is challenging due to the high permeability contrast between the fractures and the surrounding rock matrix. However, accurate and efficient simulation of flow through a fracture network is crucial in order to understand, optimize and engineer reservoirs. It has been a research topic for several decades and is still under active research. Accurate fluid flow simulations through field-scale fractured reservoirs are still limited by the power of current computer processing units (CPU). We present an efficient implementation of the embedded discrete fracture model, which is a promising new technique in modeling the behavior of enhanced geothermal systems. An efficient coupling strategy is determined for numerical performance of the model. We provide new insight into the coupled modeling of fluid flow, heat transport of engineered geothermal reservoirs with focus on the thermal stress changes during the stimulation process. We further investigate the interplay of thermal and poro-elastic stress changes in the reservoir

  7. Length scale of secondary stresses in fracture and fatigue

    International Nuclear Information System (INIS)

    Dong, P.

    2008-01-01

    In an attempt to provide a consistent framework for the analysis and treatment of secondary stresses associated with welding and thermal loading in the context of fracture mechanics, this paper starts with an effective stress characterization procedure by introducing a length-scale concept. With it, a traction-based stress separation procedure is then presented to provide a consistent characterization of stresses from various sources based on their length scale. Their relative contributions to fracture driving force are then quantified in terms of their characteristic length scales. Special attention is given to the implications of the length-scale argument on both analysis and treatment of welding residual stresses in fracture assessment. A series of examples is provided to demonstrate how the present developments can be applied for treating not only secondary stresses but also externally applied stresses, as well as their combined effects on the structural integrity of engineering components

  8. The risk of hydraulic fracturing on public health in the UK and the UK's fracking legislation.

    Science.gov (United States)

    Reap, Elisabeth

    2015-01-01

    Hydraulic fracturing to extract natural gas from shale rock is a new, rapidly expanding industry in the United States (US). However, there is concern that these operations could be having large negative impacts such as groundwater contamination, increased air pollution and seismic events. The United Kingdom (UK) is looking at the potential for emulating the success of 'shale gas' in the US. Differences in population density and geological conditions mean that the public health impacts recorded in the US cannot be directly extrapolated to the UK. There is limited academic literature available but findings suggest that the UK government is not fully recognising the inherent risks of hydraulic fracturing exposed by this literature. Government reports suggest a reliance on engineering solutions and better practice to overcome problems found in the US when evidence suggests that there are inherent risks and impacts that cannot be eliminated. This study applies US results to approximate the impact of one exposure pathway, inhalation of hydrocarbons by the public from operational air emissions over the 30 year lifetime of a well and finds that 7.2 extra cancer cases from exposure to air contamination would be expected in the UK if all test sites, approved test sites and test sites awaiting approval as of January 2015 went on to extract gas. In conclusion, limited assessment of the public health implications of hydraulic fracturing operations is available but the UK government appears to not be applying the precautionary principle to potentially significant legislation.

  9. 'Cable-maker's clavicle': stress fracture of the medial clavicle

    International Nuclear Information System (INIS)

    Peebles, C.R.; Sulkin, T.; Sampson, M.A.

    2000-01-01

    A 50-year-old man presented with a non-traumatic painful swelling over the medial clavicle. Radiographs showed a poorly defined fracture and the possibility of an underlying pathology was raised. Computed tomography suggested a stress fracture. This prompted a further, more detailed occupational history to be obtained from the patient, which revealed a hitherto undescribed cause of clavicular stress fracture and obviated the need for further imaging or biopsy. (orig.)

  10. Stress Fractures of the Foot.

    Science.gov (United States)

    Hossain, Munier; Clutton, Juliet; Ridgewell, Mark; Lyons, Kathleen; Perera, Anthony

    2015-10-01

    Stress fractures of the foot and ankle may be more common among athletes than previously reported. A low threshold for investigation is warranted and further imaging may be appropriate if initial radiographs remain inconclusive. Most of these fractures can be treated conservatively with a period of non-weight-bearing mobilization followed by gradual return to activity. Early surgery augmented by bone graft may allow athletes to return to sports earlier. Risk of delayed union, nonunion, and recurrent fracture is high. Many of the patients may also have risk factors for injury that should be modified for a successful outcome. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Qian Li

    2017-09-01

    Full Text Available Hydraulic fracturing is used widely to stimulate coalbed methane production in coal mines. However, some factors associated with conventional hydraulic fracturing, such as the simple morphology of the fractures it generates and inhomogeneous stress relief, limit its scope of application in coal mines. These problems mean that gas extraction efficiency is low. Conventional fracturing may leave hidden pockets of gas, which will be safety hazards for subsequent coal mining operations. Based on a new drilling technique applicable to drilling boreholes in coal seams, this paper proposes a tree-type fracturing technique for stimulating reservoir volumes. Tree-type fracturing simulation experiments using a large-scale triaxial testing apparatus were conducted in the laboratory. In contrast to the single hole drilled for conventional hydraulic fracturing, the tree-type sub-boreholes induce radial and tangential fractures that form complex fracture networks. These fracture networks can eliminate the “blank area” that may host dangerous gas pockets. Gas seepage in tree-type fractures was analyzed, and gas seepage tests after tree-type fracturing showed that permeability was greatly enhanced. The equipment developed for tree-type fracturing was tested in the Fengchun underground coal mine in China. After implementing tree-type fracturing, the gas extraction rate was around 2.3 times greater than that for traditional fracturing, and the extraction rate remained high for a long time during a 30-day test. This shortened the gas drainage time and improved gas extraction efficiency.

  12. Taking a holistic approach to managing difficult stress fractures.

    Science.gov (United States)

    Miller, Timothy L; Best, Thomas M

    2016-09-09

    Stress fractures and other bony stress injuries occur along a spectrum of severity which can impact treatment and prognosis. When treating these injuries, it should be borne in mind that no two stress fractures behave exactly alike. Given that they are not a consistent injury, standardized treatment protocols can be challenging to develop. Treatment should be individualized to the patient or athlete, the causative activity, the anatomical site, and the severity of the injury. A holistic approach to the treatment of the most difficult stress fractures should be taken by orthopedists and sports medicine specialists. This approach is necessary to obtain optimal outcomes, minimize loss of fitness and time away from sports participation, and decrease the risk of recurrence.

  13. Longwall top coal caving (LTCC) mining technologies with roof softening by hydraulic fracturing method

    Science.gov (United States)

    Klishin, V.; Nikitenko, S.; Opruk, G.

    2018-05-01

    The paper discusses advanced top coal caving technologies for thick coal seams and addresses some issues of incomplete coal extraction, which can result in the environmental damage, landscape change, air and water pollution and endogenous fires. The authors put forward a fundamentally new, having no equivalent and ecology-friendly method to difficult-to-cave roof coal – directional hydraulic fracturing and nonexplosive disintegration.

  14. Stress analysis of implant-bone fixation at different fracture angle

    Science.gov (United States)

    Izzawati, B.; Daud, R.; Afendi, M.; Majid, MS Abdul; Zain, N. A. M.; Bajuri, Y.

    2017-10-01

    Internal fixation is a mechanism purposed to maintain and protect the reduction of a fracture. Understanding of the fixation stability is necessary to determine parameters influence the mechanical stability and the risk of implant failure. A static structural analysis on a bone fracture fixation was developed to simulate and analyse the biomechanics of a diaphysis shaft fracture with a compression plate and conventional screws. This study aims to determine a critical area of the implant to be fractured based on different implant material and angle of fracture (i.e. 0°, 30° and 45°). Several factors were shown to influence stability to implant after surgical. The stainless steel, (S. S) and Titanium, (Ti) screws experienced the highest stress at 30° fracture angle. The fracture angle had a most significant effect on the conventional screw as compared to the compression plate. The stress was significantly higher in S.S material as compared to Ti material, with concentrated on the 4th screw for all range of fracture angle. It was also noted that the screws closest to the intense concentration stress areas on the compression plate experienced increasing amounts of stress. The highest was observed at the screw thread-head junction.

  15. The ``gray cortex``: an early sign of stress fracture

    Energy Technology Data Exchange (ETDEWEB)

    Mulligan, M.E. [Dept. of Radiology, Univ. of Maryland Medical Center, Baltimore, MD (United States)

    1995-04-01

    The purpose of this report is to describe an early radiographic sign of stress fracture, the ``gray cortex.`` The imaging findings in three patients with tibial stress fractures were reviewed. The ``gray cortex`` sign was evident on the initial conventional radiographs in all three cases. It was prospectively reported as a sign of stress fracture in two patients and was evident on the initial radiographs (taken elsewhere) of the third patient, who was referred for additional workup of a possible neoplasm. Special imaging studies (technetium-99m bone scan, computed tomography, and magnetic resonance imaging) confirmed the diagnosis in all three cases. (orig.)

  16. The ''gray cortex'': an early sign of stress fracture

    International Nuclear Information System (INIS)

    Mulligan, M.E.

    1995-01-01

    The purpose of this report is to describe an early radiographic sign of stress fracture, the ''gray cortex.'' The imaging findings in three patients with tibial stress fractures were reviewed. The ''gray cortex'' sign was evident on the initial conventional radiographs in all three cases. It was prospectively reported as a sign of stress fracture in two patients and was evident on the initial radiographs (taken elsewhere) of the third patient, who was referred for additional workup of a possible neoplasm. Special imaging studies (technetium-99m bone scan, computed tomography, and magnetic resonance imaging) confirmed the diagnosis in all three cases. (orig.)

  17. Fracture Initiation of an Inhomogeneous Shale Rock under a Pressurized Supercritical CO2 Jet

    Directory of Open Access Journals (Sweden)

    Yi Hu

    2017-10-01

    Full Text Available Due to the advantages of good fracture performance and the application of carbon capture and storage (CCS, supercritical carbon dioxide (SC-CO2 is considered a promising alternative for hydraulic fracturing. However, the fracture initiation mechanism and its propagation under pressurized SC-CO2 jet are still unknown. To address these problems, a fluid–structure interaction (FSI-based numerical simulation model along with a user-defined code was used to investigate the fracture initiation in an inhomogeneous shale rock. The mechanism of fracturing under the effect of SC-CO2 jet was explored, and the effects of various influencing factors were analyzed and discussed. The results indicated that higher velocity jets of SC-CO2 not only caused hydraulic-fracturing ring, but also resulted in the increase of stress in the shale rock. It was found that, with the increase of perforation pressure, more cracks initiated at the tip. In contrast, the length of cracks at the root decreased. The length-to-diameter ratio and the aperture ratio distinctly affected the pressurization of SC-CO2 jet, and contributed to the non-linear distribution and various maximum values of the stress in shale rock. The results proved that Weibull probability distribution was appropriate for analysis of the fracture initiation. The studied parameters explain the distribution of weak elements, and they affect the stress field in shale rock.

  18. Fuel for Debate: Three Studies of the Political Mobilization for and against Hydraulic Fracturing in New York State

    Science.gov (United States)

    Dokshin, Fedor Aleksandrovich

    This dissertation uses the context of the unfolding boom in oil and gas production enabled by hydraulic fracturing ("fracking") technology to ask several interrelated questions: What motivates people to oppose or support industrial development? How do material interests interact with political identities to shape political mobilization? What consequences does this political contestation have for policymaking? Three stand-alone articles, each using unique data and methods, provide new evidence for answering these questions. The three studies place a common emphasis on the multiple meanings that fracking has for opponents and supporters of proposed development as well as the alternative structural conditions that give rise to the divergent beliefs and the social networks that facilitate mobilization. The first article, examines the passage of local zoning ordinances prohibiting fracking and identifies spatial and temporal processes that influenced the pattern of ordinance adoption. The second article, looks more closely at political mobilization for and against hydraulic fracturing by examining individual-level data collected from one town's debate over a proposed ban on oil and gas development. The third article uses a large set of public comments to directly examine the meanings that the public attached to hydraulic fracturing and whether residents who live in close proximity to proposed development understood the industry in systematically different terms than individuals who participated in the debate despite facing little or no direct impact from fracking.

  19. Thermal shale fracturing simulation using the Cohesive Zone Method (CZM)

    KAUST Repository

    Enayatpour, Saeid; van Oort, Eric; Patzek, Tadeusz

    2018-01-01

    Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

  20. Thermal shale fracturing simulation using the Cohesive Zone Method (CZM)

    KAUST Repository

    Enayatpour, Saeid

    2018-05-17

    Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

  1. Radium and barium removal through blending hydraulic fracturing fluids with acid mine drainage.

    Science.gov (United States)

    Kondash, Andrew J; Warner, Nathaniel R; Lahav, Ori; Vengosh, Avner

    2014-01-21

    Wastewaters generated during hydraulic fracturing of the Marcellus Shale typically contain high concentrations of salts, naturally occurring radioactive material (NORM), and metals, such as barium, that pose environmental and public health risks upon inadequate treatment and disposal. In addition, fresh water scarcity in dry regions or during periods of drought could limit shale gas development. This paper explores the possibility of using alternative water sources and their impact on NORM levels through blending acid mine drainage (AMD) effluent with recycled hydraulic fracturing flowback fluids (HFFFs). We conducted a series of laboratory experiments in which the chemistry and NORM of different mix proportions of AMD and HFFF were examined after reacting for 48 h. The experimental data combined with geochemical modeling and X-ray diffraction analysis suggest that several ions, including sulfate, iron, barium, strontium, and a large portion of radium (60-100%), precipitated into newly formed solids composed mainly of Sr barite within the first ∼ 10 h of mixing. The results imply that blending AMD and HFFF could be an effective management practice for both remediation of the high NORM in the Marcellus HFFF wastewater and beneficial utilization of AMD that is currently contaminating waterways in northeastern U.S.A.

  2. An Unusual Stress Fracture in an Archer with Hypophosphatasia

    Directory of Open Access Journals (Sweden)

    Umut Yavuz

    2013-01-01

    Full Text Available We report a 45-year-old male archer with stress fracture in his left ulna on the background of adult type of hypophosphatasia. The patient presented to several medical centers for pain around the left elbow and received medical treatment upon diagnosis of tenosynovitis. History of the patient revealed that he had had diagnosis of hypophosphatasia ten years ago and underwent percutaneous screwing for stress fracture on both of his femoral necks. Upon finding nondisplaced stress fracture on proximal metaphysis of the ulna on X-ray, the patient underwent magnetic resonance imaging (MRI in order to exclude pathological causes. No additional pathology was observed in MRI scanning. The patient’s sportive activities were restricted for 6 weeks and he received conservative management with arm slings. Adult type of hypophosphatasia is a disease manifesting with widespread osteoporosis and presenting with low serum level of alkali phosphatase (ALP. Stress fracture should definitely be considered in the patients with history of hypophosphatasia and refractory extremity pain.

  3. In-situ remediation of brine impacted soils and groundwater using hydraulic fracturing, desalinization and recharge wells

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, C. [Wiebe Environmental Services Inc., Calgary, AB (Canada); Ratiu, I. [GeoGrid Environmental Inc., Calgary, AB (Canada)

    2006-07-01

    This conference presentation focused on the in-stu remediation of brine impacted soils and groundwater using hydraulic fracturing, desalinization and recharge wells. A former oil battery was established in the 1940s, decommissioned in the late 1960s with a reclamation certificate issued in 1972. The land owner reported poor vegetative growth in the former battery area. The purpose of the study was to investigate the cause of poor growth and delineate contaminants of concern and to remediate impacted soil and groundwater associated with the former battery site. The investigation involved agrological, geophysical and hydrogeological investigation into the extent of anthropogenic impacts as well as the development of remediation options and plans to deal with issues of concern. The presentation provided the results of the investigation, options identified, and discussed limitation on salt remediation and treatment of saline soils. Other topics included hydraulic fracturing, injection wells that were installed to re-circulate treated groundwater though the salt plume, desalinization processes, and next steps. figs.

  4. Finite-element modelling of geomechanical and hydraulic responses to the room 209 heading extension excavation response experiment 2: post-excavation analysis of experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Chan, T; Griffith, P; Nakka, B W; Khair, K R

    1993-07-01

    An in situ excavation response test was conducted at the 240 Level of the Underground Research Laboratory (URL) in conjunction with the excavation of a tunnel (Room 209) through a narrow, near-vertical, water-bearing fracture oriented almost perpendicular to the tunnel axis. This report presents a post-excavation analysis of the predicted mechanical response of the granitic rock mass to the tunnel excavation and the near-field hydraulic response of the fracture zone, compares the numerical modelling predictions with the actual measured response, provides information on the rock mass and fracture from back-analysis of the responses, and makes recommendations for future experiments. Results indicate that displacements and stress changes were reasonably well predicted. Pressure drops at hydrology boreholes and inflow to the tunnel were overpredicted, and fracture permeability changes were underpredicted. The permeability change is considered too large to be solely stress-induced. The back-calculated deformation modulus indicated nonlinear softening of the rock within 3.5 m of the tunnel wall. This is likely due to both excavation damage and the confining stress dependence of the modulus. For future excavation experiments it is recommended that mechanical excavation should replace the drill-and-blast technique; excavation damage should be incorporated into mechanical models; an improved hydraulic fracture model should be developed; and a coupled geomechanical-hydraulic analysis of fracture flow should be developed. (author). 16 refs., 15 tabs., 156 figs.

  5. Finite-element modelling of geomechanical and hydraulic responses to the room 209 heading extension excavation response experiment 2: post-excavation analysis of experimental results

    International Nuclear Information System (INIS)

    Chan, T.; Griffith, P.; Nakka, B.W.; Khair, K.R.

    1993-07-01

    An in situ excavation response test was conducted at the 240 Level of the Underground Research Laboratory (URL) in conjunction with the excavation of a tunnel (Room 209) through a narrow, near-vertical, water-bearing fracture oriented almost perpendicular to the tunnel axis. This report presents a post-excavation analysis of the predicted mechanical response of the granitic rock mass to the tunnel excavation and the near-field hydraulic response of the fracture zone, compares the numerical modelling predictions with the actual measured response, provides information on the rock mass and fracture from back-analysis of the responses, and makes recommendations for future experiments. Results indicate that displacements and stress changes were reasonably well predicted. Pressure drops at hydrology boreholes and inflow to the tunnel were overpredicted, and fracture permeability changes were underpredicted. The permeability change is considered too large to be solely stress-induced. The back-calculated deformation modulus indicated nonlinear softening of the rock within 3.5 m of the tunnel wall. This is likely due to both excavation damage and the confining stress dependence of the modulus. For future excavation experiments it is recommended that mechanical excavation should replace the drill-and-blast technique; excavation damage should be incorporated into mechanical models; an improved hydraulic fracture model should be developed; and a coupled geomechanical-hydraulic analysis of fracture flow should be developed. (author). 16 refs., 15 tabs., 156 figs

  6. Diagnosis, treatment, and rehabilitation of stress fractures in the lower extremity in runners

    Directory of Open Access Journals (Sweden)

    Kahanov L

    2015-03-01

    Full Text Available Leamor Kahanov,1 Lindsey E Eberman,2 Kenneth E Games,2 Mitch Wasik2 1College of Health Science, Misericordia University, Dallas, PA, USA; 2Department of Applied Medicine and Rehabilitation, Indiana State University, Terre Haute, IN, USA Abstract: Stress fractures account for between 1% and 20% of athletic injuries, with 80% of stress fractures in the lower extremity. Stress fractures of the lower extremity are common injuries among individuals who participate in endurance, high load-bearing activities such as running, military and aerobic exercise and therefore require practitioner expertise in diagnosis and management. Accurate diagnosis for stress fractures is dependent on the anatomical area. Anatomical regions such as the pelvis, sacrum, and metatarsals offer challenges due to difficulty differentiating pathologies with common symptoms. Special tests and treatment regimes, however, are similar among most stress fractures with resolution between 4 weeks to a year. The most difficult aspect of stress fracture treatment entails mitigating internal and external risk factors. Practitioners should address ongoing risk factors to minimize recurrence. Keywords: medial tibial stress syndrome, stress injury, nonunion stress fracture

  7. Spills of Hydraulic Fracturing Chemicals on Agricultural Topsoil: Biodegradation, Sorption, and Co-contaminant Interactions.

    Science.gov (United States)

    McLaughlin, Molly C; Borch, Thomas; Blotevogel, Jens

    2016-06-07

    Hydraulic fracturing frequently occurs on agricultural land. Yet the extent of sorption, transformation, and interactions among the numerous organic frac fluid and oil and gas wastewater constituents upon environmental release is hardly known. Thus, this study aims to advance our current understanding of processes that control the environmental fate and toxicity of commonly used hydraulic fracturing chemicals. Poly(ethylene glycol) surfactants were completely biodegraded in agricultural topsoil within 42-71 days, but their transformation was impeded in the presence of the biocide glutaraldehyde and was completely inhibited by salt at concentrations typical for oil and gas wastewater. At the same time, aqueous glutaraldehyde concentrations decreased due to sorption to soil and were completely biodegraded within 33-57 days. While no aqueous removal of polyacrylamide friction reducer was observed over a period of 6 months, it cross-linked with glutaraldehyde, further lowering the biocide's aqueous concentration. These findings highlight the necessity to consider co-contaminant effects when we evaluate the risk of frac fluid additives and oil and gas wastewater constituents in agricultural soils in order to fully understand their human health impacts, likelihood for crop uptake, and potential for groundwater contamination.

  8. Stress Fractures of Tibia Treated with Ilizarov External Fixator.

    Science.gov (United States)

    Górski, Radosław; Żarek, Sławomir; Modzelewski, Piotr; Górski, Ryszard; Małdyk, Paweł

    2016-08-30

    Stress fractures are the result of cyclic loading of the bone, which gradually becomes damaged. Most often they are treated by rest or plaster cast and, in rare cases, by internal fixation. There is little published data on initial reposition followed by stabilization with the Ilizarov apparatus in such fractures. Six patients were treated with an external fixator according to the Ilizarov method for a stress fracture of the tibia between 2007 and 2015. Three patients were initially treated conservatively. Due to increasing tibial deformation, they were qualified for surgical treatment with external stabilization. In the other patients, surgery was the first-line treatment. All patients demonstrated risk factors for a stress fracture. After the surgery, they fully loaded the operated limb. No patient developed malunion, nonunion, infection or venous thrombosis. The average time from the first operation to the removal of the external fixator was 19 weeks. Radiographic and clinical outcomes were satisfactory in all patients. 1. The Ilizarov method allows for successful stabilization of stress fractures of the tibia. 2. It may be a good alternative to internal stabilization, especially in patients with multiple comorbidities which affect bone quality and may impair soft tissue healing.

  9. Stress fractures: definition, diagnosis and treatment.

    Science.gov (United States)

    Astur, Diego Costa; Zanatta, Fernando; Arliani, Gustavo Gonçalves; Moraes, Eduardo Ramalho; Pochini, Alberto de Castro; Ejnisman, Benno

    2016-01-01

    Stress fractures were first described in Prussian soldiers by Breithaupt in 1855. They occur as the result of repeatedly making the same movement in a specific region, which can lead to fatigue and imbalance between osteoblast and osteoclast activity, thus favoring bone breakage. In addition, when a particular region of the body is used in the wrong way, a stress fracture can occur even without the occurrence of an excessive number of functional cycles. The objective of this study was to review the most relevant literature of recent years in order to add key information regarding this pathological condition, as an updating article on this topic.

  10. Risk factors for stress fracture among young female cross-country runners.

    Science.gov (United States)

    Kelsey, Jennifer L; Bachrach, Laura K; Procter-Gray, Elizabeth; Nieves, Jeri; Greendale, Gail A; Sowers, Maryfran; Brown, Byron W; Matheson, Kim A; Crawford, Sybil L; Cobb, Kristin L

    2007-09-01

    To identify risk factors for stress fracture among young female distance runners. Participants were 127 competitive female distance runners, aged 18-26, who provided at least some follow-up data in a randomized trial among 150 runners of the effects of oral contraceptives on bone health. After completing a baseline questionnaire and undergoing bone densitometry, they were followed an average of 1.85 yr. Eighteen participants had at least one stress fracture during follow-up. Baseline characteristics associated (Pstress fracture occurrence were one or more previous stress fractures (rate ratio [RR] [95% confidence interval]=6.42 (1.80-22.87), lower whole-body bone mineral content (RR=2.70 [1.26-5.88] per 1-SD [293.2 g] decrease), younger chronologic age (RR=1.42 [1.05-1.92] per 1-yr decrease), lower dietary calcium intake (RR=1.11 [0.98-1.25] per 100-mg decrease), and younger age at menarche (RR=1.92 [1.15-3.23] per 1-yr decrease). Although not statistically significant, a history of irregular menstrual periods was also associated with increased risk (RR=3.41 [0.69-16.91]). Training-related factors did not affect risk. The results of this and other studies indicate that risk factors for stress fracture among young female runners include previous stress fractures, lower bone mass, and, although not statistically significant in this study, menstrual irregularity. More study is needed of the associations between stress fracture and age, calcium intake, and age at menarche. Given the importance of stress fractures to runners, identifying preventive measures is of high priority.

  11. Numerical modeling of shear stimulation in naturally fractured geothermal reservoirs

    OpenAIRE

    Ucar, Eren

    2018-01-01

    Shear-dilation-based hydraulic stimulations are conducted to create enhanced geothermal systems (EGS) from low permeable geothermal reservoirs, which are initially not amenable to energy production. Reservoir stimulations are done by injecting low-pressurized fluid into the naturally fractured formations. The injection aims to activate critically stressed fractures by decreasing frictional strength and ultimately cause a shear failure. The shear failure leads to a permanent ...

  12. NextGen Stress & Fracture for Lightweight Structures

    Data.gov (United States)

    National Aeronautics and Space Administration — The dream in stress and fracture analysis has always been to be able to simulate cracks initiating and then propagating in a stress field in a metal or composite...

  13. Stress- and Chemistry-Mediated Permeability Enhancement/Degradation in Stimulated Critically-Stressed Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Derek Elsworth; Abraham S. Grader; Chris Marone; Phillip Halleck; Peter Rose; Igor Faoro; Joshua Taron; André Niemeijer; Hideaki Yasuhara

    2009-03-30

    This work has investigated the interactions between stress and chemistry in controlling the evolution of permeability in stimulated fractured reservoirs through an integrated program of experimentation and modeling. Flow-through experiments on natural and artificial fractures in Coso diorite have examined the evolution of permeability under paths of mean and deviatoric stresses, including the role of dissolution and precipitation. Models accommodating these behaviors have examined the importance of incorporating the complex couplings between stress and chemistry in examining the evolution of permeability in EGS reservoirs. This document reports the findings of experiment [1,2] and analysis [3,4], in four sequential chapters.

  14. Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

    Directory of Open Access Journals (Sweden)

    Ferdinand Stoeckhert

    2015-06-01

    Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

  15. Diagnosis, treatment, and rehabilitation of stress fractures in the lower extremity in runners

    Science.gov (United States)

    Kahanov, Leamor; Eberman, Lindsey E; Games, Kenneth E; Wasik, Mitch

    2015-01-01

    Stress fractures account for between 1% and 20% of athletic injuries, with 80% of stress fractures in the lower extremity. Stress fractures of the lower extremity are common injuries among individuals who participate in endurance, high load-bearing activities such as running, military and aerobic exercise and therefore require practitioner expertise in diagnosis and management. Accurate diagnosis for stress fractures is dependent on the anatomical area. Anatomical regions such as the pelvis, sacrum, and metatarsals offer challenges due to difficulty differentiating pathologies with common symptoms. Special tests and treatment regimes, however, are similar among most stress fractures with resolution between 4 weeks to a year. The most difficult aspect of stress fracture treatment entails mitigating internal and external risk factors. Practitioners should address ongoing risk factors to minimize recurrence. PMID:25848327

  16. The risks of hydraulic fracturing and the responsibilities of engineers

    Directory of Open Access Journals (Sweden)

    Robert Kirkman

    2017-03-01

    Full Text Available One third of U.S. natural gas is extracted by injecting fluid at high pressure into shale formations, a process associated with a number of possible hazards and risks that have become the subject of intense public controversy. We develop a three-part schema to make sense of risks of hydraulic fracturing and the responsibilities of engineers: the lab, the field, and the forum. In the lab, researchers seek to answer basic questions about, for example, the behavior of shale under particular conditions; there uncertainty seems to arise at every turn. In the field, engineers and others work to implement technological processes, such as hydraulic fracturing and the subsequent extraction of oil and gas; hazards may arise as natural and social systems respond in sometimes surprising ways. In the forum, the public and their representatives deliberate about risk and acceptable risk, questions that are framed in ethical as well as technical terms. The difficulty of characterizing – and in living up to – the responsibilities of engineers lie in part in the apparent distance between the lab and the forum. We examine in turn uncertainties in the lab, hazards in the field, and deliberation in the forum, leading to the conclusion that scientists and engineers can and should help to inform public deliberation but that their research cannot, on its own, resolve all controversies. Scientists and engineers who seek to inform deliberation should be mindful of the scope and limits of their authority, clear and modest in communicating research findings to the public, and careful to avoid even apparent conflicts of interest wherever possible. We close by drawing from the lab-field-forum schema to suggest a direction for pedagogical innovations aimed at the formation of responsible engineers in the context of college-level degree programs.

  17. Integrated Modeling and Experiments to Characterize Coupled Thermo-hydro-geomechanical-chemical processes in Hydraulic Fracturing

    Science.gov (United States)

    Viswanathan, H. S.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Kang, Q.; Makedonska, N.; Hyman, J.; Jimenez Martinez, J.; Frash, L.; Chen, L.

    2015-12-01

    Hydraulic fracturing phenomena involve fluid-solid interactions embedded within coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Feedbacks between processes result in complex dynamics that must be unraveled if one is to predict and, in the case of unconventional resources, facilitate fracture propagation, fluid flow, and interfacial transport processes. The proposed work is part of a broader class of complex systems involving coupled fluid flow and fractures that are critical to subsurface energy issues, such as shale oil, geothermal, carbon sequestration, and nuclear waste disposal. We use unique LANL microfluidic and triaxial core flood experiments integrated with state-of-the-art numerical simulation to reveal the fundamental dynamics of fracture-fluid interactions to characterize the key coupled processes that impact hydrocarbon production. We are also comparing CO2-based fracturing and aqueous fluids to enhance production, greatly reduce waste water, while simultaneously sequestering CO2. We will show pore, core and reservoir scale simulations/experiments that investigate the contolling mechanisms that control hydrocarbon production.

  18. Reliability of Source Mechanisms for a Hydraulic Fracturing Dataset

    Science.gov (United States)

    Eyre, T.; Van der Baan, M.

    2016-12-01

    Non-double-couple components have been inferred for induced seismicity due to fluid injection, yet these components are often poorly constrained due to the acquisition geometry. Likewise non-double-couple components in microseismic recordings are not uncommon. Microseismic source mechanisms provide an insight into the fracturing behaviour of a hydraulically stimulated reservoir. However, source inversion in a hydraulic fracturing environment is complicated by the likelihood of volumetric contributions to the source due to the presence of high pressure fluids, which greatly increases the possible solution space and therefore the non-uniqueness of the solutions. Microseismic data is usually recorded on either 2D surface or borehole arrays of sensors. In many cases, surface arrays appear to constrain source mechanisms with high shear components, whereas borehole arrays tend to constrain more variable mechanisms including those with high tensile components. The abilities of each geometry to constrain the true source mechanisms are therefore called into question.The ability to distinguish between shear and tensile source mechanisms with different acquisition geometries is investigated using synthetic data. For both inversions, both P- and S- wave amplitudes recorded on three component sensors need to be included to obtain reliable solutions. Surface arrays appear to give more reliable solutions due to a greater sampling of the focal sphere, but in reality tend to record signals with a low signal to noise ratio. Borehole arrays can produce acceptable results, however the reliability is much more affected by relative source-receiver locations and source orientation, with biases produced in many of the solutions. Therefore more care must be taken when interpreting results.These findings are taken into account when interpreting a microseismic dataset of 470 events recorded by two vertical borehole arrays monitoring a horizontal treatment well. Source locations and

  19. A Discrete Fracture Network Model with Stress-Driven Nucleation and Growth

    Science.gov (United States)

    Lavoine, E.; Darcel, C.; Munier, R.; Davy, P.

    2017-12-01

    The realism of Discrete Fracture Network (DFN) models, beyond the bulk statistical properties, relies on the spatial organization of fractures, which is not issued by purely stochastic DFN models. The realism can be improved by injecting prior information in DFN from a better knowledge of the geological fracturing processes. We first develop a model using simple kinematic rules for mimicking the growth of fractures from nucleation to arrest, in order to evaluate the consequences of the DFN structure on the network connectivity and flow properties. The model generates fracture networks with power-law scaling distributions and a percentage of T-intersections that are consistent with field observations. Nevertheless, a larger complexity relying on the spatial variability of natural fractures positions cannot be explained by the random nucleation process. We propose to introduce a stress-driven nucleation in the timewise process of this kinematic model to study the correlations between nucleation, growth and existing fracture patterns. The method uses the stress field generated by existing fractures and remote stress as an input for a Monte-Carlo sampling of nuclei centers at each time step. Networks so generated are found to have correlations over a large range of scales, with a correlation dimension that varies with time and with the function that relates the nucleation probability to stress. A sensibility analysis of input parameters has been performed in 3D to quantify the influence of fractures and remote stress field orientations.

  20. Postpartum osteoporosis associated with proximal tibial stress fracture

    Energy Technology Data Exchange (ETDEWEB)

    Clemetson, I.A.; Anderson, S.E. [Department of Radiology, University Hospital of Bern, Inselspital, 3010, Bern (Switzerland); Popp, A.; Lippuner, K. [Department of Osteology, University Hospital of Bern, Inselspital, 3010, Bern (Switzerland); Ballmer, F. [Knee and Sports Medicine Unit, Lindenhofspital Bern, 3012, Bern (Switzerland)

    2004-02-01

    A 33-year-old woman presented with acute nonspecific knee pain, 6 months postpartum. MR imaging, computed tomography and radiography were performed and a proximal tibia plateau insufficiency fracture was detected. Bone densitometry demonstrated mild postpartum osteoporosis. To our knowledge these findings have not been described in this location and in this clinical setting. The etiology of the atraumatic fracture of the tibia is presumed to be due to a low bone mineral density. The bone loss was probably due to pregnancy, lactation and postpartum hormonal changes. There were no other inciting causes and the patient was normocalcemic. We discuss the presence of a postpartum stress fracture in a hitherto undescribed site in a patient who had lactated following an uncomplicated pregnancy and had no other identifiable cause for a stress fracture. (orig.)

  1. Postpartum osteoporosis associated with proximal tibial stress fracture

    International Nuclear Information System (INIS)

    Clemetson, I.A.; Anderson, S.E.; Popp, A.; Lippuner, K.; Ballmer, F.

    2004-01-01

    A 33-year-old woman presented with acute nonspecific knee pain, 6 months postpartum. MR imaging, computed tomography and radiography were performed and a proximal tibia plateau insufficiency fracture was detected. Bone densitometry demonstrated mild postpartum osteoporosis. To our knowledge these findings have not been described in this location and in this clinical setting. The etiology of the atraumatic fracture of the tibia is presumed to be due to a low bone mineral density. The bone loss was probably due to pregnancy, lactation and postpartum hormonal changes. There were no other inciting causes and the patient was normocalcemic. We discuss the presence of a postpartum stress fracture in a hitherto undescribed site in a patient who had lactated following an uncomplicated pregnancy and had no other identifiable cause for a stress fracture. (orig.)

  2. 77 FR 27451 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft...

    Science.gov (United States)

    2012-05-10

    ... (other than diesel fuels) pursuant to hydraulic fracturing operations related to oil, gas, or geothermal... during HF related to oil, gas, or geothermal operations must obtain a UIC permit before injection begins... diesel fuels are available through the UIC Class II Program, the well class for oil and gas activities.\\1...

  3. Magnitude and Peak Amplitude Relationship for Microseismicity Induced by a Hydraulic Fracture Experiment

    Science.gov (United States)

    Smith, T.; Arce, A. C.; Ji, C.

    2016-12-01

    Waveform cross-correlation technique is widely used to improve the detection of small magnitude events induced by hydraulic fracturing. However, when events are detected, assigning a reliable magnitude is a challenging task, especially considering their small signal amplitude and high background noise during injections. In this study, we adopt the Match & Locate algorithm (M&L, Zhang and Wen, 2015) to analyze seven hours of continuous seismic observations from a hydraulic fracturing experiment in Central California. The site of the stimulated region is only 300-400m away from a 16-receiver vertical-borehole array which spans 230 m. The sampling rate is 4000 Hz. Both the injection sites and borehole array are more than 1.7 km below the surface. This dataset has previously been studied by an industry group, producing a catalog of 1134 events with moment magnitudes (Mw) ranging from -3.1 to -0.9. In this study, we select 202 events from this catalog with high signal to noise ratios to use as templates. Our M&L analysis produces a new catalog that contains 2119 events, which is 10 times more detections than the number of templates and about two times the original catalog. Using these two catalogs, we investigate the relationship of moment magnitude difference (ΔMW) and local magnitude difference (ΔML) between the detected event and corresponding template event. ΔML is computed using the peak amplitude ratio between the detected and template event for each channel. Our analysis yields an empirical relationship of ΔMW=0.64-0.65ΔML with an R2 of 0.99. The coefficient of 2/3 suggests that the information of the event's corner frequency is entirely lost (Hanks and Boore, 1984). The cause might not be unique, which implies that Earth's attenuation at this depth range (>1.7 km) is significant; or the 4000 Hz sampling rate is not sufficient. This relationship is crucial to estimate the b-value of the microseismicity induced by hydraulic fracture experiments. The analysis

  4. Residual stresses associated with the hydraulic expansion of steam generator tubing into tubesheets

    International Nuclear Information System (INIS)

    Middlebrooks, W.B.; Harrod, D.L.; Gold, R.E.

    1993-01-01

    Various methods are being used to expand heat transfer tubes into the thick tubesheets of nuclear steam generators. The residual stresses in the as-expanded tubes and methods for reducing these stresses are important because of the role which residual stresses play in stress corrosion cracking and stress assisted corrosion of the tubing. Of the various expansion processes, the hydraulic expansion process is most amenable to analytical study. This paper presents results on the residual stresses and strains in hydraulically expanded tubes and the tubesheet as computed by two different finite element codes with three different finite element models and by a theoretical incremental analysis method. The calculations include a sensitivity analysis to assess the effects of the expansion variables and the effect of stress relief heat treatments. (orig.)

  5. Measurement of residual stresses using fracture mechanics weight functions

    International Nuclear Information System (INIS)

    Fan, Y.

    2000-01-01

    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed

  6. Measurement of residual stresses using fracture mechanics weight functions

    International Nuclear Information System (INIS)

    Fan, Y.

    2001-01-01

    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed. (author)

  7. The Contribution of SPECT/CT in the Diagnosis of Stress Fracture of the Proximal Tibia.

    Science.gov (United States)

    Okudan, Berna; Coşkun, Nazım; Arıcan, Pelin

    2018-02-01

    Stress fractures are injuries most commonly seen in the lower limbs and are usually caused by repetitive stress. While the distal and middle third of the tibia is the most frequent site for stress fractures (almost 50%), stress fractures of the proximal tibia is relatively rare and could be confused with other types of tibial fractures, thus altering management plans for the clinician. Early diagnosis of stress fractures is also important to avoid complications. Imaging plays an important role in the diagnosis of stress fractures, especially bone scan. Combined with single-photon emission computed tomography/computed tomography (SPECT/CT) it is an important imaging technique for stress fractures in both upper and lower extremities, and is widely preferred over other imaging techniques. In this case, we present the case of a 39-year-old male patient diagnosed with stress fracture of the proximal tibia and demonstrate the contribution of CT scan fused with SPECT imaging in the early diagnosis of stress fracture prior to other imaging modalities.

  8. “We need more data”! The politics of scientific information for water governance in the context of hydraulic fracturing

    Directory of Open Access Journals (Sweden)

    Michele-Lee Moore

    2018-02-01

    Full Text Available Proposed and actual developments of hydraulic fracturing, as a high-volume water user, have proven contentious in recent years. However, one point of agreement has emerged amongst all actors with regards to water use and hydraulic fracturing: we need more data. This consensus fits with a longstanding reification of the role of data in water governance, and yet we argue it hides a politically contested terrain. Based on a literature review, an empirical Delphi study and a workshop with a diverse array of participants from across Canada, we explore the data needs related to water governance and hydraulic fracturing. We then investigate three areas of deficiency that point to a lack of trust and oversight as well as the exclusion of community and Indigenous knowledge. We argue that in an era of neoliberal approaches to water governance, issues of trust, accountability and transparency all link back to a diminished role for data management within existing water governance arrangements. The challenge is that simply collecting more data will not help decision-makers navigate the complexity of water governance. Our findings suggest a growing call by participants for greater engagement by governments in data collection and knowledge management, new funding mechanisms for data collection and rethinking how and what to monitor if including multiple ways of knowing and values.

  9. Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

    Science.gov (United States)

    Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Guihéneuf, Nicolas; Becker, Matthew W.; Cole, Matthew; Burbey, Thomas J.; Lavenant, Nicolas; Boudin, Frédéric

    2017-08-01

    Fractured bedrock reservoirs are of socio-economical importance, as they may be used for storage or retrieval of fluids and energy. In particular, the hydromechanical behavior of fractures needs to be understood as it has implications on flow and governs stability issues (e.g., microseismicity). Laboratory, numerical, or field experiments have brought considerable insights to this topic. Nevertheless, in situ hydromechanical experiments are relatively uncommon, mainly because of technical and instrumental limitations. Here we present the early stage development and validation of a novel approach aiming at capturing the integrated hydromechanical behavior of natural fractures. It combines the use of surface tiltmeters to monitor the deformation associated with the periodic pressurization of fractures at depth in crystalline rocks. Periodic injection and withdrawal advantageously avoids mobilizing or extracting significant amounts of fluid, and it hinders any risk of reservoir failure. The oscillatory perturbation is intended to (1) facilitate the recognition of its signature in tilt measurements and (2) vary the hydraulic penetration depth in order to sample different volumes of the fractured bedrock around the inlet and thereby assess scale effects typical of fractured systems. By stacking tilt signals, we managed to recover small tilt amplitudes associated with pressure-derived fracture deformation. Therewith, we distinguish differences in mechanical properties between the three tested fractures, but we show that tilt amplitudes are weakly dependent on pressure penetration depth. Using an elastic model, we obtain fracture stiffness estimates that are consistent with published data. Our results should encourage further improvement of the method.

  10. Hydraulic fracturing to enhance geothermal energy recovery in deep and tight formations. Modell approach in petrothermy research project OPTIRISS

    Energy Technology Data Exchange (ETDEWEB)

    Rafiee, M.M.; Schmitz, S.; Barsch, M. [DBI - Gastechnologisches Institut gGmbH, Freiberg (Germany)

    2013-08-01

    In Germany numerous projects were successfully conducted in developments of geothermal energy which applied so far mostly for the hydrothermal deposit type. In Thuringia and Saxony there are currently project developments of geothermal resource taking into account for deep, tight formations in petrothermy and Enhanced geothermal system, (EGS). One of the potential tasks in generating these petrothermal producers and in the design of the underground power plant appears to be hydraulic fracturing with multi frac method. This is to create the heat exchanger surfaces in the rock and ensure maximum volumetric flow through it. Therefore it is very important for a sustainable heat production. However the promise of its adequate conductivity in the deep formation is one of the dominant contests in geothermal energy industry. In a multi frac method, two wells (normally horizontal wellbores at different depths) are drilled in direction of minimum horizontal stress of the formation rock. By multiple frac operation in separate sections, flow paths are generated between the wells through which it is possible to extract the heat from the rock. The numerical simulation of hydraulic fracture propagation processes in the rock is mainly from the research in the area of oil and gas industry. These techniques are mainly used for very low permeable formations in petroleum engineering (e.g. Shale gas). The development is at the beginning for EGS (e.g. granites). In this work single and multi fracking propagation processes in a synthetic example of deep hard formation are investigated. The numerical simulation is carried out to design and characterize frac processes and frac dimensions. Sensitivities to various rock parameters and different process designs are examined and optimum criteria are concluded. This shows that the minimum stress profile has the most effective role and should be modelled properly. The analysis indicates the optimum fracture length and height for adequate thermal

  11. Theoretical and laboratory investigations of flow through fractures in crystalline rock

    International Nuclear Information System (INIS)

    Witherspoon, P.A.; Watkins, D.J.; Tsang, Y.W.

    1981-01-01

    A theoretical model developed for flow through a deformable fracture subject to stresses was successfully tested against laboratory experiments. The model contains no arbitrary parameters and can be used to predict flow rates through a single fracture if the fractional fracture contact area can be estimated and if stress-deformation data are available. These data can be obtained from laboratory or in situ tests. The model has considerable potential for practical application. The permeability of ultralarge samples of fractured crystalline rock as a function of stresses was measured. Results from tests on a pervasively fractured 1-m-diameter specimen of granitic rock showed that drastically simplifying assumptions must be used to apply theoretical models to this type of rock mass. Simple models successfully reproduce the trend of reduced permeability as stress is applied in a direction normal to the fracture plane. The tests also demonstrated how fracture conductivity increases as a result of dilatancy associated with shear displacements. The effect of specimen size on the hydraulic properties of fractured rock was also investigated. Permeability tests were performed on specimens of charcoal black granite containing a single fracture subjected to normal stress. Results are presented for tests performed on a 0.914-m-diameter specimen and on the same specimen after it had been reduced to 0.764 m in diameter. The data show that fracture conductivity is sensitive to stress history and sample disturbance

  12. Expected Time to Return to Athletic Participation After Stress Fracture in Division I Collegiate Athletes.

    Science.gov (United States)

    Miller, Timothy L; Jamieson, Marissa; Everson, Sonsecharae; Siegel, Courtney

    2017-12-01

    Few studies have documented expected time to return to athletic participation after stress fractures in elite athletes. Time to return to athletic participation after stress fractures would vary by site and severity of stress fracture. Retrospective cohort study. Level 3. All stress fractures diagnosed in a single Division I collegiate men's and women's track and field/cross-country team were recorded over a 3-year period. Site and severity of injury were graded based on Kaeding-Miller classification system for stress fractures. Time to return to full unrestricted athletic participation was recorded for each athlete and correlated with patient sex and site and severity grade of injury. Fifty-seven stress fractures were diagnosed in 38 athletes (mean age, 20.48 years; range, 18-23 years). Ten athletes sustained recurrent or multiple stress fractures. Thirty-seven injuries occurred in women and 20 in men. Thirty-three stress fractures occurred in the tibia, 10 occurred in the second through fourth metatarsals, 3 occurred in the fifth metatarsal, 6 in the tarsal bones (2 navicular), 2 in the femur, and 5 in the pelvis. There were 31 grade II stress fractures, 11 grade III stress fractures, and 2 grade V stress fractures (in the same patient). Mean time to return to unrestricted sport participation was 12.9 ± 5.2 weeks (range, 6-27 weeks). No significant differences in time to return were noted based on injury location or whether stress fracture was grade II or III. The expected time to return to full unrestricted athletic participation after diagnosis of a stress fracture is 12 to 13 weeks for all injury sites. Athletes with grade V (nonunion) stress fractures may require more time to return to sport.

  13. Acetabular stress fractures in military endurance athletes and recruits: incidence and MRI and scintigraphic findings

    International Nuclear Information System (INIS)

    Williams, T.R.; Puckett, M.L.; Shin, A.Y.; Gorman, J.D.; Denison, G.

    2002-01-01

    Objective: To evaluate the incidence and the MRI and scintigraphic appearance of acetabular stress (fatigue) fractures in military endurance athletes and recruits. Design and patients: One hundred and seventy-eight active duty military endurance trainees with a history of activity-related hip pain were evaluated by both MRI and bone scan over a 2-year period. Patients in the study ranged in age from 17 to 45 years. They had hip pain related to activity and had plain radiographs of the hip and pelvis that were interpreted as normal or equivocal. The study was originally designed to evaluate the MRI and scintigraphic appearance of femoral neck stress fractures. Patients had scintigraphy and a limited MRI examination (coronal imaging only) within 48 h of the bone scan. Twelve patients demonstrated imaging findings compatible with acetabular stress fractures. Results: Stress fractures are common in endurance athletes and in military populations; however, stress fracture of the acetabulum is uncommon. Twelve of 178 patients (6.7%) in our study had imaging findings consistent with acetabular stress fractures. Two patterns were identified. Seven of the 12 (58%) patients had acetabular roof stress fractures. In this group, two cases of bilateral acetabular roof stress fractures were identified, one with a synchronous tensile sided femoral neck stress fracture. The remaining five of 12 (42%) patients had anterior column stress fractures, rarely occurring in isolation, and almost always occurring with inferior pubic ramus stress fracture (4 of 5, or 80%). One case of bilateral anterior column stress fractures was identified without additional sites of injury. Conclusions: Stress fractures are commonplace in military populations, especially endurance trainees. Acetabular stress fractures are rare and therefore unrecognized, but do occur and may be a cause for activity-related hip pain in a small percentage of military endurance athletes and recruits. (orig.)

  14. Hydraulic properties of fracture networks

    International Nuclear Information System (INIS)

    Dreuzy, J.R. de

    1999-12-01

    Fractured medium are studied in the general framework of oil and water supply and more recently for the underground storage of high level nuclear wastes. As fractures are generally far more permeable than the embedding medium, flow is highly channeled in a complex network of fractures. The complexity of the network comes from the broad distributions of fracture length and permeability at the fracture scale and appears through the increase of the equivalent permeability at the network scale. The goal of this thesis is to develop models of fracture networks consistent with both local-scale and global-scale observations. Bidimensional models of fracture networks display a wide variety of flow structures ranging from the sole permeable fracture to the equivalent homogeneous medium. The type of the relevant structure depends not only on the density and the length and aperture distributions but also on the observation scale. In several models, a crossover scale separates complex structures highly channeled from more distributed and homogeneous-like flow patterns at larger scales. These models, built on local characteristics and validated by global properties, have been settled in steady state. They have also been compared to natural well test data obtained in Ploemeur (Morbihan) in transient state. The good agreement between models and data reinforces the relevance of the models. Once validated and calibrated, the models are used to estimate the global tendencies of the main flow properties and the risk associated with the relative lack of data on natural fractures media. (author)

  15. Incidence and Time to Return to Training for Stress Fractures during Military Basic Training

    Directory of Open Access Journals (Sweden)

    Alexander M. Wood

    2014-01-01

    Full Text Available Currently, little is known about the length of time required to rehabilitate patients from stress fractures and their return to preinjury level of physical activity. Previous studies have looked at the return to sport in athletes, in a general population, where rehabilitation is not as controlled as within a captive military population. In this study, a longitudinal prospective epidemiological database was assessed to determine the incidence of stress fractures and the time taken to rehabilitate recruits to preinjury stage of training. Findings demonstrated a background prevalence of 5% stress fractures in Royal Marine training; femoral and tibial stress fractures take 21.1 weeks to return to training with metatarsal stress fractures being the most common injury taking 12.2 weeks. Rehabilitation from stress fractures accounts for 814 weeks of recruit rehabilitation time per annum. Stress fracture incidence is still common in military training; despite this stress fracture recovery times remain constant and represent a significant interruption in training. It takes on average 5 weeks after exercise specific training has restarted to reenter training at a preinjury level, regardless of which bone has a stress fracture. Further research into their prevention, treatment, and rehabilitation is required to help reduce these burdens.

  16. Fracture mechanical treatment of bridging stresses in ceramics

    International Nuclear Information System (INIS)

    Fett, T.; Munz, D.

    1993-12-01

    Failure of ceramic materials often starts from cracks which can originate at pores, inclusions or can be generated during surface treatment. Fracture occurs when the stress intensity factor of the most serious crack in a component reaches a critical value K lc , the fracture toughness of the material. In case of ideal brittle materials the fracture toughness is independent of the crack extension and, consequently, identical with the stress intensity factor K l0 necessary for the onset of stable crack growth. It is a well-known fact that failure of several ceramics is influenced by an increasing crack-growth resistance curve. Several effects are responsible for this behaviour. Crack-border interactions in the wake of the advancing crack, residual stress fields in the crack region of transformation-toughened ceramics, the generation of a micro-crack zone ahead the crack tip and crack branching. The effect of increasing crack resistance has consequences on many properties of ceramic materials. In this report the authors discuss the some aspects of R-curve behaviour as the representation by stress intensity factors or energies and the influence on the compliance using the bridging stress model. (orig.) [de

  17. Fatigue Analysis of the Piston Rod in a Kaplan Turbine Based on Crack Propagation under Unsteady Hydraulic Loads

    International Nuclear Information System (INIS)

    Liu, X; Luo, Y Y; Wang, Z W

    2014-01-01

    As an important component of the blade-control system in Kaplan turbines, piston rods are subjected to fluctuating forces transferred by the turbines blades from hydraulic pressure oscillations. Damage due to unsteady hydraulic loads might generate unexpected down time and high repair cost. In one running hydropower plant, the fracture failure of the piston rod was found twice at the same location. With the transient dynamic analysis, the retainer ring structure of the piston rod existed a relative high stress concentration. This predicted position of the stress concentration agreed well with the actual fracture position in the plant. However, the local strain approach was not able to explain why this position broke frequently. Since traditional structural fatigue analyses use a local stress strain approach to assess structural integrity, do not consider the effect of flaws which can significantly degrade structural life. Using linear elastic fracture mechanism (LEFM) approaches that include the effect of flaws is becoming common practice in many industries. In this research, a case involving a small semi-ellipse crack was taken into account at the stress concentration area, crack growth progress was calculated by FEM. The relationship between crack length and remaining life was obtained. The crack propagation path approximately agreed with the actual fracture section. The results showed that presence of the crack had significantly changed the local stress and strain distributions of the piston rod compared with non-flaw assumption

  18. Fatigue Analysis of the Piston Rod in a Kaplan Turbine Based on Crack Propagation under Unsteady Hydraulic Loads

    Science.gov (United States)

    Liu, X.; Y Luo, Y.; Wang, Z. W.

    2014-03-01

    As an important component of the blade-control system in Kaplan turbines, piston rods are subjected to fluctuating forces transferred by the turbines blades from hydraulic pressure oscillations. Damage due to unsteady hydraulic loads might generate unexpected down time and high repair cost. In one running hydropower plant, the fracture failure of the piston rod was found twice at the same location. With the transient dynamic analysis, the retainer ring structure of the piston rod existed a relative high stress concentration. This predicted position of the stress concentration agreed well with the actual fracture position in the plant. However, the local strain approach was not able to explain why this position broke frequently. Since traditional structural fatigue analyses use a local stress strain approach to assess structural integrity, do not consider the effect of flaws which can significantly degrade structural life. Using linear elastic fracture mechanism (LEFM) approaches that include the effect of flaws is becoming common practice in many industries. In this research, a case involving a small semi-ellipse crack was taken into account at the stress concentration area, crack growth progress was calculated by FEM. The relationship between crack length and remaining life was obtained. The crack propagation path approximately agreed with the actual fracture section. The results showed that presence of the crack had significantly changed the local stress and strain distributions of the piston rod compared with non-flaw assumption.

  19. Colloidal crystal templated molecular imprinted polymer for the detection of 2-butoxyethanol in water contaminated by hydraulic fracturing.

    Science.gov (United States)

    Dai, Jingjing; Vu, Danh; Nagel, Susan; Lin, Chung-Ho; Fidalgo de Cortalezzi, Maria

    2017-12-06

    The authors describe a molecularly imprinted polymer (MIP) that enables detection of 2-butoxyethanol (2BE), a pollutant associated with hydraulic fracturing contamination. Detection is based on a combination of a colloidal crystal templating and a molecular imprinting. The MIPs are shown to display higher binding capacity for 2BE compared to non-imprinted films (NIPs), with imprinting efficiencies of ∼ 2. The tests rely on the optical effects that are displayed by the uniformly ordered porous structure of the material. The reflectance spectra of the polymer films have characteristic Bragg peaks whose location varies with the concentration of 2BE. Peaks undergo longwave red shifts up to 50 nm on exposure of the MIP to 2BE in concentrations in the range from 1 ppb to 100 ppm. This allows for quantitative estimates of the 2BE concentrations present in aqueous solutions. The material is intended for use in the early detection of contamination at hydraulic fracturing sites. Graphical abstract Molecularly imprinted polymers (MIPs) sensor with the sensing ability on reflectance spectra responding to the presence of 2-butoxyethanol (2BE) for early detection of hydraulic fracking contamination.

  20. Multi-zone coupling productivity of horizontal well fracturing with complex fracture networks in shale gas reservoirs

    Directory of Open Access Journals (Sweden)

    Weiyao Zhu

    2018-02-01

    Full Text Available In this paper, a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro pores–complex fracture networks–wellbore during the development of shale reservoirs by means of horizontal well fracturing. First, hydraulic fractures were induced by means of Brazilian splitting tests. Second, the forms of the hydraulic fractures inside the rock samples were observed by means of X-ray CT scanning to measure the opening of hydraulic fractures. Third, based on the multi-scale unified flowing model, morphological description of fractures and gas flowing mechanism in the matrix–complex fracture network–wellbore, the productivity equation of single-stage horizontal well fracturing which includes diffusion, slipping and desorption was established. And fourthly, a productivity prediction model of horizontal well multi-stage fracturing in the shale reservoir was established considering the interference between the multi-stage fracturing zones and the pressure drop in the horizontal wellbore. The following results were obtained. First, hydraulic fractures are in the form of a complex network. Second, the measured opening of hydraulic fractures is in the range of 4.25–453 μm, averaging 112 μm. Third, shale gas flowing in different shapes of fracture networks follows different nonlinear flowing laws. Forth, as the fracture density in the strongly stimulated zones rises and the distribution range of the hydraulic fractures in strongly/weakly stimulated zones enlarges, gas production increases gradually. As the interference occurs in the flowing zones of fracture networks between fractured sections, the increasing amplitude of gas production rates decreases. Fifth, when the length of a simulated horizontal well is 1500 m and the half length of a fracture network in the strongly stimulated zone is 100 m, the productivity effect of stage 10 fracturing is the

  1. The effect of stress fracture interventions in a single elite infantry training unit (1983-2015).

    Science.gov (United States)

    Milgrom, Charles; Finestone, Aharon S

    2017-10-01

    Stress fractures can be seen as an undesired byproduct of demanding physical training. The threshold value of stress that places an individual bone at high risk for stress fracture has not been identified. In a prospective study of stress fractures in 1983, a 31% incidence was found during demanding Israeli infantry basic training by bone scan criteria. Within a subgroup of these recruits, an elite infantry unit was found to have a 40% incidence. Since then and until 2015, eight additional induction companies of the same elite infantry unit were prospectively monitored for stress fractures during their basic training. In all of the studies, stress fracture surveillance and the examining orthopedist were the same. A retrospective review of all nine studies and of eight training changes was performed to look for a temporal trend in stress fracture incidence and to see if these might be related to training changes. There was a statistically significant trend for lower radiological proven stress fractures (p=0.0001) and radiological proven stress fractures plus clinical stress fractures (p=0.0013), as well as lower stress fracture severity by radiological criteria (p=0.0001) between 1983 and 2015. The only training change that was associated, by multivariate logistic regression, with a decreased incidence of stress fracture was restricting training to the authorized training protocol (odds ratio, 3874; 95% CI, 1.526 to 9.931; p=0.004). Increased recruit weight was found by multivariate analysis to be associated with lower stress fracture incidence (odds ratio 1.034; 95% CI, 1.00 to 1.070; p=0.051). Moving the training to a base with flatter terrain and reducing the formal marching distance by 1/3 was associated with a decrease in high grade stress fractures (odds ratio, 10.03; 95% CI, 3.5 to 28.4; p=0.0001). Neither the combined changes of enforcing a seven hour a night sleep regimen, training in more comfortable boots and adding a physical therapist to the unit nor

  2. Report: Enhanced EPA Oversight and Action Can Further Protect Water Resources From the Potential Impacts of Hydraulic Fracturing

    Science.gov (United States)

    Report #15-P-0204, July 16, 2015. Enhanced EPA oversight of the permitting process for diesel fuel use during hydraulic fracturing can further EPA efforts to protect water resources, and establishment of a plan for determining whether to propose a chemical

  3. Multiple stress fractures in a young female runner.

    Science.gov (United States)

    Dusek, T; Pećina, M; Loncar-Dusek, M; Bojanic, I

    2004-01-01

    The effect of exercise on female's bone metabolism has received much attention in recent years. We report on unusual case of a female runner with low body mass and amenorrhea, who suffered 4 stress fractures. Three of the stress fractures occurred during her sports career, and the fourth occurred 7 years after the cessation of sports activities. It seems that exercise-induced amenorrhea together with food restriction in the young age may cause long-term consequences on bone metabolism.

  4. The Contribution of SPECT/CT in the Diagnosis of Stress Fracture of the Proximal Tibia

    Directory of Open Access Journals (Sweden)

    Berna Okudan

    2018-02-01

    Full Text Available Stress fractures are injuries most commonly seen in the lower limbs and are usually caused by repetitive stress. While the distal and middle third of the tibia is the most frequent site for stress fractures (almost 50%, stress fractures of the proximal tibia is relatively rare and could be confused with other types of tibial fractures, thus altering management plans for the clinician. Early diagnosis of stress fractures is also important to avoid complications. Imaging plays an important role in the diagnosis of stress fractures, especially bone scan. Combined with single-photon emission computed tomography/computed tomography (SPECT/CT it is an important imaging technique for stress fractures in both upper and lower extremities, and is widely preferred over other imaging techniques. In this case, we present the case of a 39-year-old male patient diagnosed with stress fracture of the proximal tibia and demonstrate the contribution of CT scan fused with SPECT imaging in the early diagnosis of stress fracture prior to other imaging modalities.

  5. Fracture predictions for cracks exposed to superimposed normal and shear stresses

    International Nuclear Information System (INIS)

    Richard, H.A.

    1985-01-01

    The author developed a special device and a fracture mechanics specimen and proposed a procedure for determining the fracture toughness when Mixed Mode and Mode II stresses are applied. This device makes it possible to generate pure normal stresses, superimposed normal and shearing stresses as well as pure shearing stresses in the cross section of the crack in the specimen, as desired. The so-called CTS fracture mechanics specimen has an edge crack. The load is transferred statically determind from the device to the specimen by means of six studs altogether. The experiments described, which were carried out with specimens made of the brittle materials PMMA (Plexiglas) and Araldit B, clearly show that it is possible to evaluate the validity of the individual fracture hypotheses by suitable experiments. It is also found that the fracture behaviour of different materials varies considerably both in quality and quantity. In conclusion, a practice-oriented fracture criterion is indicated which enables a practice-conforming evaluation of Mixed-Mode crack problems, as is shown by way of examples. (orig./HP) [de

  6. Estimates of hydraulic fracturing (Frac) sand production, consumption, and reserves in the United States

    Science.gov (United States)

    Bleiwas, Donald I.

    2015-01-01

    The practice of fracturing reservoir rock in the United States as a method to increase the flow of oil and gas from wells has a relatively long history and can be traced back to 1858 in Fredonia, New York, when a gas well situated in shale of the Marcellus Formation was successfully fractured using black powder as a blasting agent. Nearly all domestic hydraulic fracturing, often referred to as hydrofracking or fracking, is a process where fluids are injected under high pressure through perforations in the horizontal portion of a well casing in order to generate fractures in reservoir rock with low permeability (“tight”). Because the fractures are in contact with the well bore they can serve as pathways for the recovery of gas and oil. To prevent the fractures generated by the fracking process from closing or becoming obstructed with debris, material termed “proppant,” most commonly high-silica sand, is injected along with water-rich fluids to maintain or “prop” open the fractures. The first commercial application of fracking in the oil and gas industry took place in Oklahoma and Texas during the 1940s. In 1949, over 300 wells, mostly vertical, were fracked (ALL Consulting, LLC, 2012; McGee, 2012; Veil, 2012) and used silica sand as a proppant (Fracline, 2011). The resulting increase in well productivity demonstrated the significant potential that fracking might have for the oil and gas industry.

  7. Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, Arvind Murali; Hartsock, Angela; Hammack, Richard W; Vidic, Radisav D; Gregory, Kelvin B

    2013-12-01

    Hydraulic fracturing for natural gas extraction from shale produces waste brine known as flowback that is impounded at the surface prior to reuse and/or disposal. During impoundment, microbial activity can alter the fate of metals including radionuclides, give rise to odorous compounds, and result in biocorrosion that complicates water and waste management and increases production costs. Here, we describe the microbial ecology at multiple depths of three flowback impoundments from the Marcellus shale that were managed differently. 16S rRNA gene clone libraries revealed that bacterial communities in the untreated and biocide-amended impoundments were depth dependent, diverse, and most similar to species within the taxa [gamma]-proteobacteria, [alpha]-proteobacteria, δ-proteobacteria, Clostridia, Synergistetes, Thermotogae, Spirochetes, and Bacteroidetes. The bacterial community in the pretreated and aerated impoundment was uniform with depth, less diverse, and most similar to known iodide-oxidizing bacteria in the [alpha]-proteobacteria. Archaea were identified only in the untreated and biocide-amended impoundments and were affiliated to the Methanomicrobia class. This is the first study of microbial communities in flowback water impoundments from hydraulic fracturing. The findings expand our knowledge of microbial diversity of an emergent and unexplored environment and may guide the management of flowback impoundments.

  8. Experimental assessment of the sealing effectiveness of rock fracture grouting

    International Nuclear Information System (INIS)

    Schaffer, A.; Daemen, J.J.K.

    1987-03-01

    The objective of this investigation is to determine the effectiveness of cement grouts as sealants of fractures in rock. Laboratory experiments have been conducted on seven 15-cm granite cubes containing saw cuts, three 23-cm diameter andesite cores containing induced tension cracks, and one 15-cm diameter marble core containing a natural fracture. Prior to grouting, the hydraulic conductivity of the fractures is determined under a range of normal stresses, applied in loading and unloading cycles, from 0 to 14 MPa (2000 psi). Grout is injected through an axial borehole, at a pressure of 1.2 to 8.3 MPa (180 to 1200 psi), pressure selected to provide a likely groutable fracture aperture, while the fracture is stressed at a constant normal stress. The fracture permeability is measured after grouting. Flow tests on the ungrouted samples confirm the inverse relation between normal stress and fracture permeability. The equivalent aperture determined by these tests is a reliable indicator of groutability. Postgrouting permeability measurements as performed here, and frequently in practice, can be misleading, since incomplete grouting of fractures can result in major apparent reductions in permeability. The apparent permeability reduction is caused by grouting of a small area of a highly preferential flowpath directly adjacent to the hole used for grouting and for permeability testing. Experimental results confirm claims in the literature that ordinary portland cement inadequately penetrates fine fractures

  9. Stress fracture in posterior aspect of the tibia

    International Nuclear Information System (INIS)

    Moon, Tae Yong; Jung, Hyun Woo; Park, Chung Hun; Chun, Kyung Ah; Koo, Bong Sig; Lee, Sang Yong

    1999-01-01

    To determine correlation between stress fracture of the posterior tibia and flexor digitorum longus muscle injury caused by athletic or sporting activity during adolescence. Eleven cases diagnosed as stress fracture after X-ray and MR imaging of the lower leg were reviewed. With regard to each fracture, the following features were noted : age, sex, and athletic or sporting activity of the patient, and site. Using MR imaging techniques, axial and sagittal T1 and T2 weighted imaged were obtained in all cases and T1-Gd DTPA images in seven. The activities undertaken were running (n=3), football (n=2), ballet (n=2), taekwando (n=1), badminton (n=1), field hockey (n=1), and basketball (n=1). MR images revealed localized cortical thickness (n=11), linear intramedullary callus showing a low signal on T1 and T2 weighted images (n=9), marrow hyperemia (n=7), and flexor digitorum longus muscle injury showing a high signal on T1-Gd DTPA and T2 weighted image (n=7). Stress fracture of the posterior tibia might be induced by flexor digitorum longus muscle activity induced by athletic or sporting activities during adolescence

  10. Stress fracture in posterior aspect of the tibia

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Tae Yong; Jung, Hyun Woo; Park, Chung Hun [Pusan National Univ. College of Medicine, Pusan (Korea, Republic of); Chun, Kyung Ah [Catholic Univ Hospital, Pusan (Korea, Republic of); Koo, Bong Sig [Donga Univ. Hospital, Pusan (Korea, Republic of); Lee, Sang Yong [Chunbuk Natinoal Univ. Hospital, Chunju (Korea, Republic of)

    1999-01-01

    To determine correlation between stress fracture of the posterior tibia and flexor digitorum longus muscle injury caused by athletic or sporting activity during adolescence. Eleven cases diagnosed as stress fracture after X-ray and MR imaging of the lower leg were reviewed. With regard to each fracture, the following features were noted : age, sex, and athletic or sporting activity of the patient, and site. Using MR imaging techniques, axial and sagittal T1 and T2 weighted imaged were obtained in all cases and T1-Gd DTPA images in seven. The activities undertaken were running (n=3), football (n=2), ballet (n=2), taekwando (n=1), badminton (n=1), field hockey (n=1), and basketball (n=1). MR images revealed localized cortical thickness (n=11), linear intramedullary callus showing a low signal on T1 and T2 weighted images (n=9), marrow hyperemia (n=7), and flexor digitorum longus muscle injury showing a high signal on T1-Gd DTPA and T2 weighted image (n=7). Stress fracture of the posterior tibia might be induced by flexor digitorum longus muscle activity induced by athletic or sporting activities during adolescence.

  11. Stress fracture risk factors in female football players and their clinical implications.

    Science.gov (United States)

    Warden, Stuart J; Creaby, Mark W; Bryant, Adam L; Crossley, Kay M

    2007-08-01

    A stress fracture represents the inability of the skeleton to withstand repetitive bouts of mechanical loading, which results in structural fatigue, and resultant signs and symptoms of localised pain and tenderness. Reports of stress fractures in female football players are not prevalent; however, they are probably under-reported and their importance lies in the morbidity that they cause in terms of time lost from participation. By considering risk factors for stress fractures in female football players it may be possible to reduce the impact of these troublesome injuries. Risk factors for stress fractures in female football players include intrinsic risk factors such as gender, endocrine, nutritional, physical fitness and neuromusculoskeletal factors, as well as extrinsic risk factors such as training programme, equipment and environmental factors. This paper discusses these risk factors and their implications in terms of developing prevention and management strategies for stress fractures in female football players.

  12. First-rib stress fracture in two adolescent swimmers: a case report.

    Science.gov (United States)

    Low, Sara; Kern, Michael; Atanda, Alfred

    2016-01-01

    First-rib stress fractures have been described in adolescent athletes in various sports, with only one prior case report of first-rib stress fractures in an adolescent female swimmer. There is a need for research on the cause, management, and prevention of these injuries as they lead to significant morbidity and critical time away from sport for these aspiring athletes. We aimed to describe first-rib stress fractures as a potential cause for non-specific atraumatic chronic shoulder pain in adolescent swimmers and to discuss the different presentations, unique risk factors, treatment, and potential injury prevention strategies of such fractures. We discussed two such cases which were successfully treated with activity modification with restriction of all overhead activity, gradually progressive physical therapy and a return to swimming protocol. First-rib stress fractures can vary in presentation and should be in the differential diagnosis in adolescent swimmers with chronic shoulder pain. These injuries can be successfully managed with rest from overhead activities and physical therapy. Gradual return to competitive swimming can be achieved even with non-union of a first-rib stress fracture. Emphasis on balanced strength training in different muscle groups and proper swimming technique is essential to prevent these injuries.

  13. Rock mechanics issues and research needs in the disposal of wastes in hydraulic fractures

    International Nuclear Information System (INIS)

    Doe, T.W.; McClain, W.C.

    1984-07-01

    The proposed rock mechanics studies outlined in this document are designed to answer the basic questions concerning hydraulic fracturing for waste disposal. These questions are: (1) how can containment be assured for Oak Ridge or other sites; and (2) what is the capacity of a site. The suggested rock mechanics program consists of four major tasks: (1) numerical modeling, (2) laboratory testing, (3) field testing, and (4) monitoring. These tasks are described

  14. Managing flowback and produced water from hydraulic fracturing under stochastic environment

    Science.gov (United States)

    Zhang, X.; Sun, A. Y.; Duncan, I. J.; Vesselinov, V. V.

    2017-12-01

    A large volume of wastewater is being generated from hydraulic fracturing in shale gas plays, including flowback and produced water. The produced wastewater in terms of its quantity and quality has become one of the main environmental problems facing shale gas industries worldwide. Cost-effective planning and management of flowback and produced water is highly desirable. Careful choice of treatment, disposal, and reuse options can lower costs and reduce potential environmental impacts. To handle the recourse issue in decision-making, a two-stage stochastic management model is developed to provide optimal alternatives for fracturing wastewater management. The proposed model is capable of prompting corrective actions to allow decision makers to adjust the pre-defined management strategies. By using this two-stage model, potential penalties arising from decision infeasibility can be minimized. The applicability of the proposed model is demonstrated using a representative synthetic example, in which tradeoffs between economic and environmental goals are quantified. This approach can generate informed defensible decisions for shale gas wastewater management. In addition, probabilistic and non-probabilistic uncertainties are effectively addressed.

  15. Development of the T+M coupled flow–geomechanical simulator to describe fracture propagation and coupled flow–thermal–geomechanical processes in tight/shale gas systems

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Moridis, George J.

    2013-10-01

    We developed a hydraulic fracturing simulator by coupling a flow simulator to a geomechanics code, namely T+M simulator. Modeling of the vertical fracture development involves continuous updating of the boundary conditions and of the data connectivity, based on the finite element method for geomechanics. The T+M simulator can model the initial fracture development during the hydraulic fracturing operations, after which the domain description changes from single continuum to double or multiple continua in order to rigorously model both flow and geomechanics for fracture-rock matrix systems. The T+H simulator provides two-way coupling between fluid-heat flow and geomechanics, accounting for thermoporomechanics, treats nonlinear permeability and geomechanical moduli explicitly, and dynamically tracks changes in the fracture(s) and in the pore volume. We also fully accounts for leak-off in all directions during hydraulic fracturing. We first validate the T+M simulator, matching numerical solutions with the analytical solutions for poromechanical effects, static fractures, and fracture propagations. Then, from numerical simulation of various cases of the planar fracture propagation, shear failure can limit the vertical fracture propagation of tensile failure, because of leak-off into the reservoirs. Slow injection causes more leak-off, compared with fast injection, when the same amount of fluid is injected. Changes in initial total stress and contributions of shear effective stress to tensile failure can also affect formation of the fractured areas, and the geomechanical responses are still well-posed.

  16. Unusual longitudinal stress fractures of the femoral diaphysis: report of five cases

    International Nuclear Information System (INIS)

    Williams, M.; Timsit, M.A.; Karneff, A.; Pertuiset, E.

    1999-01-01

    We present five cases of a distinctive type of longitudinal stress fracture of the upper femoral shaft in which the fracture line is parallel to the outer surface of the bone, in contrast to the perpendicular orientation to the cortical surface in previously reported cases of diaphyseal stress fractures. In two cases the fracture recurred after 15 and 18 months, respectively. (orig.)

  17. Bilateral First Rib Stress Fractures in a Basketball Player

    Directory of Open Access Journals (Sweden)

    Abidin (Radyoloji Kilincer

    2016-04-01

    Full Text Available I read the article published by Aydogdu et al with a great interest. I congratulate them for this successfully written case report. Additionally, I want to focus an important point about the case they presented is that the diagnosis in that case is likely stress fracture. It is understood from the text and title that they avoided to make a diagnosis of stress fracture in the case, despite of history of lifting heavy weights for three days. And also I decided to mention through this article to an example of our case with bilateral first rib old fractures.

  18. Comparative Analysis of Hydraulic Fracturing Wastewater Practices in Unconventional Shale Development: Newspaper Coverage of Stakeholder Concerns and Social License to Operate

    Directory of Open Access Journals (Sweden)

    Joel Gehman

    2016-09-01

    Full Text Available In this article we review prior literature regarding the concept of social license to operate, and related concepts, including corporate social responsibility, sustainable development, stakeholder management and cumulative effects. Informed by these concepts, we search for newspaper articles published in North American provinces and states where the Barnett, Duvernay, Marcellus and Montney shale plays are located. Using these data, we tabulate coverage of stakeholder concerns related to hydraulic fracturing and wastewater practices, and compare the extent to which these concerns vary over place and time. Our vocabulary analyses identify differences in the types and quantities of newspaper coverage devoted to concerns regarding hydraulic fracturing activities in general and wastewater practices in particular. We interpret these differences as suggesting that obtaining a social license to operate is likely not a one size fits all proposition. By understanding which stakeholder concerns are most salient in particular places and times, oil and gas operators and regulators can better tailor their strategies and policies to address local concerns. In other words, the findings from this study indicate that conventional understandings of risk as a technical or economic problem may not be adequate for dealing with unconventional resource challenges such as hydraulic fracturing. Operators and regulators may also need to manage social and cultural risks.

  19. Reactivity of Dazomet, a Hydraulic Fracturing Additive: Hydrolysis and Interaction with Pyrite

    Science.gov (United States)

    Consolazio, N.; Lowry, G. V.; Karamalidis, A.; Hakala, A.

    2015-12-01

    The Marcellus Shale is currently the largest shale gas formation in play across the world. The low-permeability formation requires hydraulic fracturing to be produced. In this process, millions of gallons of water are blended with chemical additives and pumped into each well to fracture the reservoir rock. Although additives account for less than 2% of the fracking fluid mixture, they amount to hundreds of tons per frack job. The environmental properties of some of these additives have been studied, but their behavior under downhole conditions is not widely reported in the peer-reviewed literature. These compounds and their reaction products may return to the surface as produced or waste water. In the event of a spill or release, this water has the potential to contaminate surface soil and water. Of these additives, biocides may present a formidable challenge to water quality. Biocides are toxic compounds (by design), typically added to the Marcellus Shale to control bacteria in the well. An assessment of the most frequently used biocides indicated a need to study the chemical dazomet under reservoir conditions. The Marcellus Shale contains significant deposits of pyrite. This is a ubiquitous mineral within black shales that is known to react with organic compounds in both oxic and anoxic settings. Thus, the objective of our study was to determine the effect of pyrite on the hydrolysis of dazomet. Liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) was used to calculate the loss rate of aqueous dazomet. Gas chromatography-mass spectrometry (GC-MS) was used to identify the reaction products. Our experiments show that in water, dazomet rapidly hydrolyses in water to form organic and inorganic transformation products. This reaction rate was unaffected when performed under anoxic conditions. However, with pyrite we found an appreciable increase in the removal rate of dazomet. This was accompanied by a corresponding change in the distribution of observed

  20. Assessing the induced seismicity by hydraulic fracturing at the Wysin site (Poland)

    Science.gov (United States)

    Ángel López Comino, José; Cesca, Simone; Kriegerowski, Marius; Heimann, Sebastian; Dahm, Torsten; Mirek, Janusz; Lasocky, Stanislaw

    2017-04-01

    Induced seismicity related to industrial processes including shale gas and oil exploitation is a current issues that implies enough reasons to be concerned. Hydraulic fracturing usually induces weak events. However, scenarios with larger earthquakes are possible, e.g. if the injected fluids alter friction conditions and trigger the failure of neighbouring faults. This work is focused on a hydrofracking experiment monitored in the framework of the SHEER (SHale gas Exploration and Exploitation induced Risks) EU project at the Wysin site, located in the central-western part of the Peribaltic synclise of Pomerania, Poland. A specific network setup has been installed combining surface installation with three small-scale arrays and a shallow borehole installation. The fracking operations were carried out in June and July 2016 at a depth 4000 m. The monitoring has been operational before, during and after the termination of hydraulic fracturing operations. We apply a recently developed automated full waveform detection algorithm based on the stacking of smooth characteristic function and the identification of high coherence in the signals recorded at different stations. The method was tested with synthetic data and different detector levels yielding values of magnitude of completeness around 0.1. An unsupervised detection catalogue is generated with real data for a time period May-September 2016. We identify strong temporal changes (day/night) of the detection performance. A manual revision of the detected signals reveals that most detections are associated to local and regional seismic signals. Only two events could be assigned to the volume potentially affected by the fracking operations.

  1. A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

    Science.gov (United States)

    Mallants, Dirk; Simunek, Jirka; Gerke, Kirill

    2015-04-01

    Coal Seam Gas production generates large volumes of "produced" water that may contain compounds originating from the use of hydraulic fracturing fluids. Such produced water also contains elevated concentrations of naturally occurring inorganic and organic compounds, and usually has a high salinity. Leaching of produced water from storage ponds may occur as a result of flooding or containment failure. Some produced water is used for irrigation of specific crops tolerant to elevated salt levels. These chemicals may potentially contaminate soil, shallow groundwater, and groundwater, as well as receiving surface waters. This paper presents an application of scenario modelling using the reactive transport model for variably-saturated media HP1 (coupled HYDRUS-1D and PHREEQC). We evaluate the fate of hydraulic fracturing chemicals and naturally occurring chemicals in soil as a result of unintentional release from storage ponds or when produced water from Coal Seam Gas operations is used in irrigation practices. We present a review of exposure pathways and relevant hydro-bio-geo-chemical processes, a collation of physico-chemical properties of organic/inorganic contaminants as input to a set of generic simulations of transport and attenuation in variably saturated soil profiles. We demonstrate the ability to model the coupled processes of flow and transport in soil of contaminants associated with hydraulic fracturing fluids and naturally occurring contaminants.

  2. Hydromechanical and Thermomechanical Behaviour of Elastic Fractures during Thermal Stimulation of Naturally Fractured Reservoirs

    Science.gov (United States)

    Jalali, Mohammadreza; Valley, Benoît

    2015-04-01

    During the last two decades, incentives were put in place in order to feed our societies in energy with reduced CO2 emissions. Various policies have been considered to fulfill this strategy such as replacing coal by natural gas in power plants, producing electricity using CO2 free resources, and CO2 sequestration as a remediation for large point-source emitters (e.g. oil sands facilities, coal-fired power plants, and cement kilns). Naturally fractured reservoirs (NFRs) are among those geological structures which play a crucial role in the mentioned energy revolution. The behavior of fractured reservoirs during production processes is completely different than conventional reservoirs because of the dominant effects of fractures on fluid flux, with attendant issues of fracture fabric complexity and lithological heterogeneity. The level of complexity increases when thermal effects are taking place - as during the thermal stimulation of these stress-sensitive reservoirs in order to enhance the gas production in tight shales and/or increase the local conductivity of the fractures during the development of enhanced geothermal systems - where temperature is introduced as another degree of freedom in addition to pressure and displacement (or effective stress). Study of these stress-pressure-temperature effects requires a thermo-hydro-mechanical (THM) coupling approach, which considers the simultaneous variation of effective stress, pore pressure, and temperature and their interactions. In this study, thermal, hydraulic and mechanical behavior of partially open and elastic fractures in a homogeneous, isotropic and low permeable porous rock is studied. In order to compare the hydromechanical (HM) and thermomechanical (TM) characteristics of these fractures, three different injection scenarios, i.e. constant isothermal fluid injection rate, constant cooling without any fluid injection and constant cold fluid injection, are considered. Both thermomechanical and hydromechanical

  3. Acoustic Emission Based Surveillance System for Prediction of Stress Fractures

    Science.gov (United States)

    2007-09-01

    aging are susceptible to such fractures in contexts of osteoporosis, diabetes, cerebral palsy, fibrous dysplasia and osteogenesis imperfecta . This...disease, or, healthy people who have excessive exercise regimes (soldiers and athletes) experience these fractures [2]. Stress fractures interrupt

  4. Medial tibial plateau morphology and stress fracture location: A magnetic resonance imaging study.

    Science.gov (United States)

    Yukata, Kiminori; Yamanaka, Issei; Ueda, Yuzuru; Nakai, Sho; Ogasa, Hiroyoshi; Oishi, Yosuke; Hamawaki, Jun-Ichi

    2017-06-18

    To determine the location of medial tibial plateau stress fractures and its relationship with tibial plateau morphology using magnetic resonance imaging (MRI). A retrospective review of patients with a diagnosis of stress fracture of the medial tibial plateau was performed for a 5-year period. Fourteen patients [three female and 11 male, with an average age of 36.4 years (range, 15-50 years)], who underwent knee MRI, were included. The appearance of the tibial plateau stress fracture and the geometry of the tibial plateau were reviewed and measured on MRI. Thirteen of 14 stress fractures were linear, and one of them stellated on MRI images. The location of fractures was classified into three types. Three fractures were located anteromedially (AM type), six posteromedially (PM type), and five posteriorly (P type) at the medial tibial plateau. In addition, tibial posterior slope at the medial tibial plateau tended to be larger when the fracture was located more posteriorly on MRI. We found that MRI showed three different localizations of medial tibial plateau stress fractures, which were associated with tibial posterior slope at the medial tibial plateau.

  5. Estimating the Reactivation Potential of Pre-Existing Fractures in Subsurface Granitoids from Outcrop Analogues and in-Situ Stress Modeling: Implications for EGS Reservoir Stimulation with an Example from Thuringia (Central Germany)

    Science.gov (United States)

    Kasch, N.; Ustaszewski, K. M.; Siegburg, M.; Navabpour, P.; Hesse, G.

    2014-12-01

    The Mid-German Crystalline Rise (MGCR) in Thuringia (central Germany) is part of the European Variscan orogen and hosts large extents of Visean granites (c. 350 Ma), locally overlain by up to 3 km of Early Permian to Mid-Triassic volcanic and sedimentary rocks. A geothermal gradient of 36°C km-1 suggests that such subsurface granites form an economically viable hot dry rock reservoir at > 4 km depth. In order to assess the likelihood of reactivating any pre-existing fractures during hydraulic reservoir stimulation, slip and dilation tendency analyses (Morris et al. 1996) were carried out. For this purpose, we determined orientations of pre-existing fractures in 14 granite exposures along the southern border fault of an MGCR basement high. Additionally, the strike of 192 Permian magmatic dikes affecting the granite was considered. This analysis revealed a prevalence of NW-SE-striking fractures (mainly joints, extension veins, dikes and subordinately brittle faults) with a maximum at 030/70 (dip azimuth/dip). Borehole data and earthquake focal mechanisms reveal a maximum horizontal stress SHmax trending N150°E and a strike-slip regime. Effective in-situ stress magnitudes at 4.5 km depth, assuming hydrostatic conditions and frictional equilibrium along pre-existing fractures with a friction coefficient of 0.85 yielded 230 and 110 MPa for SHmax and Shmin, respectively. In this stress field, fractures with the prevailing orientations show a high tendency of becoming reactivated as dextral strike-slip faults if stimulated hydraulically. To ensure that a stimulation well creates fluid connectivity on a reservoir volume as large as possible rather than dissipating fluids along existing fractures, it should follow a trajectory at the highest possible angle to the orientation of prevailing fractures, i.e. subhorizontal and NE-SW-oriented. References: Morris, A., D. A. Ferrill, and D. B. Henderson (1996), Slip-tendency analysis and fault reactivation, Geology, 24, 275-278.

  6. Hydraulically Induced Seismicity in South-Eastern Brazil Linked to Water Wells

    Science.gov (United States)

    Convers, J.; Assumpcao, M.; Barbosa, J. R.

    2017-12-01

    While hydraulic stimulus on seismic activity is most commonly associated with hydraulic fracturing processes, we find in SE Brazil a rare case of seismicity influenced by hydraulic stimulation linked to seasonal rain and water wells in a farming area. These are thought to be the main factors influencing the seasonal seismicity activity in Jurupema, a farming town located in the interior of the state of Sao Paulo, southern Brazil. With temporary seismic station deployments during 2016 and 2017, we analyze the seismicity in this area, its temporal and spatial distribution, and its association with the drilling of ground water wells in this particular area. In a region where water wells are often drilled to provide irrigation for farming, these are often perforated down to about 100 m depth, penetrating below the uppermost sandstone rock layer ( 50 m) into a fractured basaltic rock layer, reaching the confined aquifer within it. While the wells are constantly pumped during the dry season, during the course of the rainy season (when these are not being used), a possible infiltration into the confined basaltic aquifer, from both the rainwater and the upper sandstone aquifer, adds changes to the pore pressure of the fractured rock, and modifies the tectonic pre-stress conditions, to facilitate stress release mechanisms in pre-existing faults and cracks. With our temporary seismic station deployments, we not only examine the seismicity in this region during both 2016 and 2017, but we additionally compare its characteristics to the nearby Bebedouro case in an apparent induced seismic case of analogous source, and seismic activity with magnitudes up to 2.9 occurring between 2005 and 2010.

  7. Rock stress investigations

    International Nuclear Information System (INIS)

    Pahl, A.; Heusermann, St.; Braeuer, V.; Gloeggler, W.

    1989-04-01

    On the research project 'Rock Stress Mesurements' the BGR has developed and tested several methods for use in boreholes at a depth of 200 m. Indirect stress measurements using overcoring methods with BGR-probes and CSIR-triaxial cells as well as direct stress measurements using the hydraulic-fracturing method were made. To determine in-situ rock deformation behavior borehole deformation tests, using a BGR-dilatometer, were performed. Two types of the BGR-probe were applied: a four-component-probe to determine horizontal stresses and a five-component-probe to determine a quasi three-dimensional stress field. The first time a computer for data processing was installed in the borehole together with the BGR-probe. Laboratory tests on low cylinders were made to study the stress-deformation behavior. To validate and to interprete the measurement results some test methods were modelled using the finite-element method. The dilatometer-tests yielded high values of Young's modulus, whereas laboratory tests showed lower values with a distinct deformation anisotropy. Stress measurements with the BGR-probe yielded horizontal stresses being higher than the theoretical overburden pressure. These results are comparable to the results of the hydraulic fracturing tests, whereas stresses obtained with CSIR-triaxial cells are lower. The detailed geological mapping of the borehole indicated relationships between stress and geology. With regard to borehole depth different zones of rock structure joint frequency, joint orientation, and orientation of microfissures as well as stress magnitude, stress direction, and degree of deformation anisotropy could be distinguished. (author) 4 tabs., 76 figs., 31 refs

  8. Influence of Bone Remodeling Inhibition on the Development of Experimental Stress Fractures

    National Research Council Canada - National Science Library

    Schaffler, Mitchell B

    2005-01-01

    .... Using a bisphosphonate (BIS) to suppress remodeling in the rabbit tibial stress fracture model, we found that antiresorptive therapy reduced the intensity of the stress fracture response in this model...

  9. The diagnosis of stress fractures of runners by an isotope scintigraphy

    International Nuclear Information System (INIS)

    Karvonen, J.; Nieminen, M.

    1988-01-01

    By means of isotope scintigraphy the suspected stress fractures in the lower limb bones of ten competitive runners were verified in nine cases (9/10). In all cases the X-rays were normal. By conservative treatment avoiding excessive stress, the intensive local isotope uptake in the bone and pain symptoms of the stress fracture disappeared after 2-4 months. (orig.)

  10. Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas.

    Science.gov (United States)

    Murali Mohan, Arvind; Hartsock, Angela; Hammack, Richard W; Vidic, Radisav D; Gregory, Kelvin B

    2013-12-01

    Hydraulic fracturing for natural gas extraction from shale produces waste brine known as flowback that is impounded at the surface prior to reuse and/or disposal. During impoundment, microbial activity can alter the fate of metals including radionuclides, give rise to odorous compounds, and result in biocorrosion that complicates water and waste management and increases production costs. Here, we describe the microbial ecology at multiple depths of three flowback impoundments from the Marcellus shale that were managed differently. 16S rRNA gene clone libraries revealed that bacterial communities in the untreated and biocide-amended impoundments were depth dependent, diverse, and most similar to species within the taxa γ-proteobacteria, α-proteobacteria, δ-proteobacteria, Clostridia, Synergistetes, Thermotogae, Spirochetes, and Bacteroidetes. The bacterial community in the pretreated and aerated impoundment was uniform with depth, less diverse, and most similar to known iodide-oxidizing bacteria in the α-proteobacteria. Archaea were identified only in the untreated and biocide-amended impoundments and were affiliated to the Methanomicrobia class. This is the first study of microbial communities in flowback water impoundments from hydraulic fracturing. The findings expand our knowledge of microbial diversity of an emergent and unexplored environment and may guide the management of flowback impoundments. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  11. Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity

    Science.gov (United States)

    2017-10-01

    AWARD NUMBER: W81XWH-16-1-0652 TITLE: Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity PRINCIPAL INVESTIGATOR...5a. CONTRACT NUMBER W81XWH-16-1-0652 Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity 5b. GRANT NUMBER W81XWH...to stress fracture risk. In particular, in Study 1, we will perform advanced skeletal imaging along with gait-assessments in subjects with history of

  12. Acetabular roof stress fracture: a rare cause of hip pain in children ...

    African Journals Online (AJOL)

    Stress fracture of acetabular roof is an unusual cause of hip pain. It is considered as an underdiagnosed entity. People who are more susceptible to experience this fracture are athletes, soldiers and dancers. We present the case of an 11 year old girl with a roof acetabular stress fracture for which the diagnosis and ...

  13. Numerical investigation and optimization of multiple fractures in tight gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Hou, M.Z. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE; Energie-Forschungszentrum Niedersachsen, Goslar (Germany); Zhou, L. [Energie-Forschungszentrum Niedersachsen, Goslar (Germany)

    2013-08-01

    The main objective of the project DGMK-680 in phase 2 was to investigate the influence of fractures on each other in a multi-fracture system including their space optimization by using the numerical program FLAC3D with our own developments, which treats all fractures in one 3D geometric model under 3D stress state with fully hydro-mechanical coupling effect. The case study was conducted on a horizontal wellbore at location A, which was stimulated hydraulically with a total of eight transverse fractures in summer 2009. Transverse multiple fractures were simulated using the modified continuum method. In the simulation all fractures were generated in one single model, comprising 22 different rock layers. Each layer was assumed to be homogeneous with regard to its rock and hydromechanical parameters. Thus the influence of the individual fractures on each other can be investigated. The simulation procedure applied, which is a consecutive execution ofa hydraulic and a mechanical computation, is the same for all fractures. The only differences are the primary in-situ stresses, the initial pore pressure, the injection parameters (location, rate, volume, duration), which lead to different patterns of fracture propagations. But there are still some common points, such as irregular patterns of the fracture front, which represents the heterogeneity of the model. All fractures (1 to 8) have their fracture average half-length between 70 m to 115 m, height between 93 m to 114 m and average width between 18 mm to 31 mm. The percentage difference of fracture height for individual fractures is obviously smaller than that of the fracture half-lengths, because the fracture barriers at bottom and top limit the fracture propagation in z-direction. Incomparison with the analytical simulator (FracPro) most results match well. Simulation of multiple fractures at location A, with the newly developed algorithms, shows that individual transverse multiple fractures at distances between 100

  14. Regulation of Water Pollution from Hydraulic Fracturing in Horizontally-Drilled Wells in the Marcellus Shale Region, USA

    Directory of Open Access Journals (Sweden)

    Heather Hatzenbuhler

    2012-12-01

    Full Text Available Hydraulic fracturing is an industrial process used to extract fossil fuel reserves that lie deep underground. With the introduction of horizontal drilling, new commercial sources of energy have become available. Wells are drilled and injected with large quantities of water mixed with specially selected chemicals at high pressures that allow petroleum reserves to flow to the surface. While the increased economic activities and the outputs of domestic energy are welcomed, there is growing concern over negative environmental impacts from horizontal drilling in shale formations. The potential for water contamination, land destruction, air pollution, and geologic disruption has raised concerns about the merits of production activities used during extraction. This paper looks at the impacts of horizontal drilling using hydraulic fracturing on water supplies and takes a comprehensive look at legislative and regulatory approaches to mitigate environmental risks in the Marcellus shale region. The overview identifies shortcomings associated with regulatory controls by local and state governments and offers two policy suggestions to better protect waters of the region.

  15. Laboratory testing of cement grouting of fractures in welded tuff

    International Nuclear Information System (INIS)

    Sharpe, C.J.; Daemen, J.J.

    1991-03-01

    Fractures in the rock mass surrounding a repository and its shafts, access drifts, emplacement rooms and holes, and exploratory or in-situ testing holes, may provide preferential flowpaths for the flow of groundwater or air, potentially containing radionuclides. Such cracks may have to be sealed. The likelihood that extensive or at least local grouting will be required as part of repository sealing has been noted in numerous publications addressing high level waste repository closing. The objective of this work is to determine the effectiveness of fracture sealing (grouting) in welded tuff. Experimental work includes measurement of intact and fracture permeability under various normal stresses and injection pressures. Grout is injected into the fractures. The effectiveness of grouting is evaluated in terms of grout penetration and permeability reduction, compared prior to and after grouting. Analysis of the results include the effect of normal stress, injection pressure, fracture roughness, grout rheology, grout bonding, and the radial extent of grout penetration. Laboratory experiments have been performed on seventeen tuff cylinders with three types of fractures: (1) tension induced cracks, (2) natural fractures, and (3) sawcuts. Prior to grouting, the hydraulic conductivity of the intact rock and of the fractures is measured under a range of normal stresses. The surface topography of the fracture is mapped, and the results are used to determine aperture distributions across the fractures. 72 refs., 76 figs., 25 tabs

  16. Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, volumes, and physical-chemical properties of chemicals

    Science.gov (United States)

    Hydraulic fracturing (HF) fluid chemicals spilled on-site may impact drinking water resources. While chemicals generally make up <2% of the total injected fluid composition by mass, spills may have undiluted concentrations. HF fluids typically consist of a mixture of base flui...

  17. Hydraulic gradients in rock aquifers

    International Nuclear Information System (INIS)

    Dahlblom, P.

    1992-05-01

    This report deals with fractured rock as a host for deposits of hazardous waste. In this context the rock, with its fractures containing moving groundwater, is called the geological barrier. The desired properties of the geological barrier are low permeability to water, low hydraulic gradients and ability to retain matter dissolved in the water. The hydraulic gradient together with the permeability and the porosity determines the migration velocity. Mathematical modelling of the migration involves calculation of the water flow and the hydrodynamic dispersion of the contaminant. The porous medium approach can be used to calculate mean flow velocities and hydrodynamic dispersion of a large number of fractures are connected, which means that a large volume have to be considered. It is assumed that the porous medium approach can be applied, and a number of idealized examples are shown. It is assumed that the groundwater table is replenished by percolation at a constant rate. One-dimensional analytical calculations show that zero hydraulic gradients may exist at relatively large distance from the coast. Two-dimensional numerical calculations show that it may be possible to find areas with low hydraulic gradients and flow velocities within blocks surrounded by areas with high hydraulic conductivity. (au)

  18. Investigations on the influence of the stress state on fracture-mechanical values

    International Nuclear Information System (INIS)

    Schmidt, P.

    1979-01-01

    Fracture toughness obtained from specimen can be applied to construction elements only when the same stress state exists. In standardised fracture-mechanical tests plain strain is realised. Using the stress intensity factor, a critical crack length or a critical load can be obtained. Above these values a crack propagates in an unstable way. The specimen are tested under uni-axial load. In this paper investigations have been made whether a biaxial load increases the stress state over the plain strain and whether consequently a decrease of the critical fracture toughness and a shift of the temperatures Tsub(g)sub(y) and Tsub(s) results which characterise the fracture behaviour of steel. In order to answer these questions the tests were made which induced due to their geometry an additional nominal stress parallel to the crack front in spite of uni-axial loading. The results were compared with those from specimen without an additional nominal stress and having in their cross section under same test conditions nearly the same plain strain. The fracture toughness of both specimen types were compared at temperatures between 142 K and 252 K and correlated to other material-characterising values. The tests were completed by stress analysis and by comparing the crack opening displacement. Due to the additional stress, Tsub(g)sub(y) was found to be 20 K higher than for the reference specimen. The fracture toughness decreases significantly in certain temperature ranges. The plastic stress concentration factor was comperatively higher and the remaining plastic crack opening decreases up to 25%. (orig.) [de

  19. Hydrology and Hydraulic Properties of a Bedded Evaporite Formation

    International Nuclear Information System (INIS)

    BEAUHEIM, RICHARD L.; ROBERTS, RANDALL M.

    2000-01-01

    The Permian Salado Formation in the Delaware Basin of New Mexico is an extensively studied evaporite deposit because it is the host formation for the Waste Isolation Pilot Plant, a repository for transuranic wastes. Geologic and hydrologic studies of the Salado conducted since the mid-1970's have led to the development of a conceptual model of the hydrogeology of the formation that involves far-field permeability in anhydrite layers and at least some impure halite layers. Pure halite layers and some impure halite layers may not possess an interconnected pore network adequate to provide permeability. Pore pressures are probably very close to lithostatic pressure. In the near field around an excavation, dilation, creep, and shear have created and/or enhanced permeability and decreased pore pressure. Whether flow occurs in the far field under natural gradients or only after some threshold gradient is reached is unknown. If far-field flow does occur, mean pore velocities are probably on the order of a meter per hundreds of thousands to tens of millions of years. Flow dimensions inferred from most hydraulic-test responses are subradial, which is believed to reflect channeling of flow through fracture networks, or portions of fractures, that occupy a diminishing proportion of the radially available space, or through percolation networks that are not ''saturated'' (fully interconnected). This is probably related to the directional nature of the permeability created or enhanced by excavation effects. Inferred values of permeability cannot be separated from their associated flow dimensions. Therefore, numerical models of flow and transport should include heterogeneity that is structured to provide the same flow dimensions as are observed in hydraulic tests. Modeling of the Salado Formation around the WIPP repository should also include coupling between hydraulic properties and the evolving stress field because hydraulic properties change as the stress field changes

  20. Value of lateral blood pool imaging in patients with suspected stress fractures of the tibia.

    Science.gov (United States)

    Mohan, Hosahalli K; Clarke, Susan E M; Centenara, Martin; Lucarelli, Amanda; Baron, Daniel; Fogelman, Ignac

    2011-03-01

    To critically evaluate the use of lateral blood pool imaging in athletes with lower limb pain and with a clinical suspicion of stress fracture. Two experienced nuclear medicine physicians evaluated 3-phase bone scans using 99mTc-methylene diphosphonate performed in 50 consecutive patients referred from a specialist sports injury clinic for suspected tibial stress fracture. The vascularity to the tibia as seen on the blood pool (second phase) images in the anterior/posterior views was compared with the lateral/medial view assessments. Stress fractures were presumed to be present when on the delayed images (third phase) there was a focal or fusiform area of increased tracer uptake involving the tibial cortex. Shin splints which are a recognized cause of lower limb pain in athletes mimicking stress fracture were diagnosed if increased tracer uptake was seen extending along the posterior tibial surface with no significant focal or fusiform area of uptake within this. Inter-reviewer agreement for the assessment of vascularity was also assessed using Cohen's Kappa scores. Twenty-four stress fractures in 24 patients and 66 shin splints in 40 patients were diagnosed. In 18 patients stress fracture and shin splints coexisted. In 10 patients no tibial pathology was identified. Of the 24 patients diagnosed with stress fractures, lateral/medial blood pool imaging was superior in the assessment of blood pool activity (P tibial stress fractures, lateral views of the tibia provide the optimal method for evaluation of vascularity. Prospective studies with quantitative or semi-quantitative assessment of skeletal vascularity could provide supplementary information relating to the pathophysiology of stress fractures, for example, the time scale of vascular changes after a tibial stress fracture, and potentially could have clinical relevance as to the assessment of the severity of stress fractures and their prognosis.