Sample records for advanced hydraulic fracturing

  1. Advanced Hydraulic Fracturing Technology for Unconventional Tight Gas Reservoirs

    Stephen Holditch; A. Daniel Hill; D. Zhu


    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

  2. Development of an Advanced Hydraulic Fracture Mapping System

    Norm Warpinski; Steve Wolhart; Larry Griffin; Eric Davis


    The project to develop an advanced hydraulic fracture mapping system consisted of both hardware and analysis components in an effort to build, field, and analyze combined data from tiltmeter and microseismic arrays. The hardware sections of the project included: (1) the building of new tiltmeter housings with feedthroughs for use in conjunction with a microseismic array, (2) the development of a means to use separate telemetry systems for the tilt and microseismic arrays, and (3) the selection and fabrication of an accelerometer sensor system to improve signal-to-noise ratios. The analysis sections of the project included a joint inversion for analysis and interpretation of combined tiltmeter and microseismic data and improved methods for extracting slippage planes and other reservoir information from the microseisms. In addition, testing was performed at various steps in the process to assess the data quality and problems/issues that arose during various parts of the project. A prototype array was successfully tested and a full array is now being fabricated for industrial use.

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

    Murdoch, L. [FRx Inc., Cincinnati, OH (United States)]|[Clemson Univ., SC (United States); Siegrist, B. [Oak Ridge National Lab., TN (United States); Vesper, S. [Univ. of Cincinnati, OH (United States)] [and others


    Many contaminated areas consist of a source area and a plume. In the source area, the contaminant moves vertically downward from a release point through the vadose zone to an underlying saturated region. Where contaminants are organic liquids, NAPL may accumulate on the water table, or it may continue to migrate downward through the saturated region. Early developments of permeable barrier technology have focused on intercepting horizontally moving plumes with vertical structures, such as trenches, filled with reactive material capable of immobilizing or degrading dissolved contaminants. This focus resulted in part from a need to economically treat the potentially large volumes of contaminated water in a plume, and in part from the availability of construction technology to create the vertical structures that could house reactive compounds. Contaminant source areas, however, have thus far remained largely excluded from the application of permeable barrier technology. One reason for this is the lack of conventional construction methods for creating suitable horizontal structures that would place reactive materials in the path of downward-moving contaminants. Methods of hydraulic fracturing have been widely used to create flat-lying to gently dipping layers of granular material in unconsolidated sediments. Most applications thus far have involved filling fractures with coarse-grained sand to create permeable layers that will increase the discharge of wells recovering contaminated water or vapor. However, it is possible to fill fractures with other compounds that alter the chemical composition of the subsurface. One early application involved development and field testing micro-encapsulated sodium percarbonate, a solid compound that releases oxygen and can create aerobic conditions suitable for biodegradation in the subsurface for several months.

  4. Hydraulic Fracture Containment in Sand

    Dong, Y.


    The mechanism of hydraulic fracturing in soft, high permeability material is considered fundamentally different from that in hard, low permeability rock, where a tensile fracture is created and conventional linear elastic fracture mechanics (LEFM) applies. The fracturing and associated modeling work

  5. Effect of Natural Fractures on Hydraulic Fracturing

    Ben, Y.; Wang, Y.; Shi, G.


    Hydraulic Fracturing has been used successfully in the oil and gas industry to enhance oil and gas production in the past few decades. Recent years have seen the great development of tight gas, coal bed methane and shale gas. Natural fractures are believed to play an important role in the hydraulic fracturing of such formations. Whether natural fractures can benefit the fracture propagation and enhance final production needs to be studied. Various methods have been used to study the effect of natural fractures on hydraulic fracturing. Discontinuous Deformation Analysis (DDA) is a numerical method which belongs to the family of discrete element methods. In this paper, DDA is coupled with a fluid pipe network model to simulate the pressure response in the formation during hydraulic fracturing. The focus is to study the effect of natural fractures on hydraulic fracturing. In particular, the effect of rock joint properties, joint orientations and rock properties on fracture initiation and propagation will be analyzed. The result shows that DDA is a promising tool to study such complex behavior of rocks. Finally, the advantages of disadvantages of our current model and future research directions will be discussed.

  6. Complex Fluids and Hydraulic Fracturing.

    Barbati, Alexander C; Desroches, Jean; Robisson, Agathe; McKinley, Gareth H


    Nearly 70 years old, hydraulic fracturing is a core technique for stimulating hydrocarbon production in a majority of oil and gas reservoirs. Complex fluids are implemented in nearly every step of the fracturing process, most significantly to generate and sustain fractures and transport and distribute proppant particles during and following fluid injection. An extremely wide range of complex fluids are used: naturally occurring polysaccharide and synthetic polymer solutions, aqueous physical and chemical gels, organic gels, micellar surfactant solutions, emulsions, and foams. These fluids are loaded over a wide range of concentrations with particles of varying sizes and aspect ratios and are subjected to extreme mechanical and environmental conditions. We describe the settings of hydraulic fracturing (framed by geology), fracturing mechanics and physics, and the critical role that non-Newtonian fluid dynamics and complex fluids play in the hydraulic fracturing process.

  7. Gravity-Driven Hydraulic Fractures

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.


    This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness

  8. Hydraulic fracturing system and method

    Ciezobka, Jordan; Salehi, Iraj


    A hydraulic fracturing system and method for enhancing effective permeability of earth formations to increase hydrocarbon production, enhance operation efficiency by reducing fluid entry friction due to tortuosity and perforation, and to open perforations that are either unopened or not effective using traditional techniques, by varying a pump rate and/or a flow rate to a wellbore.

  9. Hydraulic fracturing with distinct element method

    Pruiksma, J.P.; Bezuijen, A.


    In this report, hydraulic fracturing is investigated using the distinct element code PFC2D from Itasca. Special routines were written to be able to model hydraulic fracturing. These include adding fluid flow to PFC2D and updating the fluid flow domains when fractures appear. A brief description of t

  10. Hydraulic fracture during epithelial stretching

    Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier


    The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here, we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression manoeuvres. After pressure equilibration, cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics.

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

    Jiangang Chen


    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.

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

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


    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.

  13. Hydraulic fracturing chemicals and fluids technology

    Fink, Johannes


    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...

  14. Characterization of a hydraulically induced bedrock fracture


    Hydraulic fracturing is a controversial practice because of concerns about environmental impacts due to its widespread use in recovering unconventional petroleum and natural gas deposits. However, water-only hydraulic fracturing has been used safely and successfully for many years to increase the permeability of aquifers used for drinking and irrigation water supply. This process extends and widens existing bedrock fractures, allowing groundwater storage to increase. Researchers have studied ...

  15. Hydraulic Fracturing and the Environment

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


    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

  16. Data Analytics of Hydraulic Fracturing Data

    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)


    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.

  17. Self-potential observations during hydraulic fracturing

    Moore, Jeffrey R.; Glaser, Steven D.


    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.

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

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


    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

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

    Zang, A.; Stephansson, O.; Stenberg, L.; Plenkers, K.; Specht, S.; Milkereit, C.; Schill, E.; Kwiatek, G.; Dresen, G.; Zimmermann, G.; Dahm, T.; Weber, M.


    In this article, 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 multi-stage hydraulic fracturing with minimal impact on the environment, i.e. 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, 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 hypocenters 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 multi-stage hydraulic fracturing with several phases of opening and closing of fracture walls is evaluated using data from acoustic emissions, seismic broadband 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 is found to be smaller in the progressive treatment with frequent

  20. Partially decoupled modeling of hydraulic fracturing processes

    Settari, A.; Puchyr, P.J.; Bachman, R.C. (Simtech Consulting Services, Calgary (CA))


    A new method of partial decoupling of the problem of modeling a hydraulic fracture in a reservoir is described. According to the authors this approach has significant advantages over previous methods with fully coupled or completely uncoupled models. Better accuracy can be achieved in modeling the fracture propagation, and the new system is very efficient and versatile. Virtually any reservoir model can be used for predicting postfracture productivity. Examples of single- and multiphase applications for modeling fractured wells are discussed.

  1. Universal asymptotic umbrella for hydraulic fracture modeling

    Linkov, Aleksandr M


    The paper presents universal asymptotic solution needed for efficient modeling of hydraulic fractures. We show that when neglecting the lag, there is universal asymptotic equation for the near-front opening. It appears that apart from the mechanical properties of fluid and rock, the asymptotic opening depends merely on the local speed of fracture propagation. This implies that, on one hand, the global problem is ill-posed, when trying to solve it as a boundary value problem under a fixed position of the front. On the other hand, when properly used, the universal asymptotics drastically facilitates solving hydraulic fracture problems (both analytically and numerically). We derive simple universal asymptotics and comment on their employment for efficient numerical simulation of hydraulic fractures, in particular, by well-established Level Set and Fast Marching Methods.

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

    Ahmad Ghassemi


    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

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

    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

  4. Advanced Performance Hydraulic Wind Energy

    Jones, Jack A.; Bruce, Allan; Lam, Adrienne S.


    The Jet Propulsion Laboratory, California Institute of Technology, has developed a novel advanced hydraulic wind energy design, which has up to 23% performance improvement over conventional wind turbine and conventional hydraulic wind energy systems with 5 m/sec winds. It also has significant cost advantages with levelized costs equal to coal (after carbon tax rebate). The design is equally applicable to tidal energy systems and has passed preliminary laboratory proof-of-performance tests, as funded by the Department of Energy.

  5. The hydraulic fracturing of geothermal formations

    Naceur, K. Ben; Economides, M.J.; Schlumberger, Dowell


    Hydraulic fracturing has been attempted in geothermal formations as a means to stimulate both production and injection wells. Since most geothermal formations contain fissures and on occasion massive natural fissures, the production behavior of the man-made fractures results in certain characteristic trends. A model is offered that allows the presence of a finite or infinite conductivity fracture intercepting a fissured medium. The method is based on a numerical discretization of the formation allowing transient interporosity flow. Type curves for pressure drawdown and cumulative production are given for infinite acting and closed reservoirs. Since most of the fissured formations exhibit a degree of anisotropy, the effects of the orientation of the hydraulic fracture with respect to the fissure planes, and of the ratio between the directional permeabilities are then discussed. Guidelines are offered as to the size of appropriate stimulation treatments based on the observed fissured behavior of the reservoir.

  6. Monitoring hydraulic fracturing with seismic emission volume

    Niu, F.; Tang, Y.; Chen, H.; TAO, K.; Levander, A.


    Recent developments in horizontal drilling and hydraulic fracturing have made it possible to access the reservoirs that are not available for massive production in the past. Hydraulic fracturing is designed to enhance rock permeability and reservoir drainage through the creation of fracture networks. Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. Based on data acquisition, seismic monitoring techniques have been divided into two categories: downhole and surface monitoring. Surface monitoring is challenging because of the extremely low signal-to-noise ratio of the raw data. We applied the techniques used in earthquake seismology and developed an integrated monitoring system for mapping hydraulic fractures. The system consists of 20 to 30 state-of-the-art broadband seismographs, which are generally about hundreds times more sensible than regular geophones. We have conducted two experiments in two basins with very different geology and formation mechanism in China. In each case, we observed clear microseismic events, which may correspond to the induced seismicity directly associated with fracturing and the triggered ones at pre-existing faults. However, the magnitude of these events is generally larger than magnitude -1, approximately one to two magnitudes larger than those detected by downhole instruments. Spectrum-frequency analysis of the continuous surface recordings indicated high seismic energy associated with injection stages. The seismic energy can be back-projected to a volume that surrounds each injection stage. Imaging seismic emission volume (SEV) appears to be an effective way to map the stimulated reservior volume, as well as natural fractures.

  7. Etat de l'art en fracturation hydraulique State-Of-The-Art in Hydraulic Fracturing

    Bouteca M.


    Full Text Available Cet article est un abrégé des connaissances de base sur la mécanique de la fracturation hydraulique (éléments de mécanique de la rupture, pression de fracturation et pression de fermeture, sur l'avancement actuel des travaux de modélisation de la propagation de fracture classés par type d'approche mécanique (bidimensionnelle, pseudotridimensionnelle, tridimensionnelle et par méthode de résolution (analytique, numérique, sur les propriétés des fluides de fracturation et des agents de soutènement. Deux chapitres à caractère plus pratique sont consacrés à la préparation et à la mise en oeuvre de la fracturation hydraulique ainsi qu'à l'évaluation des résultats de la fracturation hydraulique en termes de perméabilité, dimensions et direction de fracture. This article is an abridged review of basic knowledge about the mechanics of hydraulic fracturing (fracture mechanics, fracturing pressure and closure pressure, about recent advances in the modeling of fracture propagation classified by type of mechanical approach (two-dimensional, pseudo-three-dimensional, three-dimensional and by method of solution (analytic, numeric, and about the properties of fracturing fluids and propping agents. Two chapters having a more practical nature are devoted to the preparation and implementation of hydraulic fracturing as well as to the evaluation of hydraulic-fracturing results in terms of permeability and fracture sizes and direction.

  8. Smart magnetic markers use in hydraulic fracturing.

    Zawadzki, Jarosław; Bogacki, Jan


    One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite.

  9. Hydraulic fracture model comparison study: Complete results

    Warpinski, N.R. [Sandia National Labs., Albuquerque, NM (United States); Abou-Sayed, I.S. [Mobil Exploration and Production Services (United States); Moschovidis, Z. [Amoco Production Co. (US); Parker, C. [CONOCO (US)


    Large quantities of natural gas exist in low permeability reservoirs throughout the US. Characteristics of these reservoirs, however, make production difficult and often economic and stimulation is required. Because of the diversity of application, hydraulic fracture design models must be able to account for widely varying rock properties, reservoir properties, in situ stresses, fracturing fluids, and proppant loads. As a result, fracture simulation has emerged as a highly complex endeavor that must be able to describe many different physical processes. The objective of this study was to develop a comparative study of hydraulic-fracture simulators in order to provide stimulation engineers with the necessary information to make rational decisions on the type of models most suited for their needs. This report compares the fracture modeling results of twelve different simulators, some of them run in different modes for eight separate design cases. Comparisons of length, width, height, net pressure, maximum width at the wellbore, average width at the wellbore, and average width in the fracture have been made, both for the final geometry and as a function of time. For the models in this study, differences in fracture length, height and width are often greater than a factor of two. In addition, several comparisons of the same model with different options show a large variability in model output depending upon the options chosen. Two comparisons were made of the same model run by different companies; in both cases the agreement was good. 41 refs., 54 figs., 83 tabs.

  10. Review of Hydraulic Fracturing for Preconditioning in Cave Mining

    He, Q.; Suorineni, F. T.; Oh, J.


    Hydraulic fracturing has been used in cave mining for preconditioning the orebody following its successful application in the oil and gas industries. In this paper, the state of the art of hydraulic fracturing as a preconditioning method in cave mining is presented. Procedures are provided on how to implement prescribed hydraulic fracturing by which effective preconditioning can be realized in any in situ stress condition. Preconditioning is effective in cave mining when an additional fracture set is introduced into the rock mass. Previous studies on cave mining hydraulic fracturing focused on field applications, hydraulic fracture growth measurement and the interaction between hydraulic fractures and natural fractures. The review in this paper reveals that the orientation of the current cave mining hydraulic fractures is dictated by and is perpendicular to the minimum in situ stress orientation. In some geotechnical conditions, these orientation-uncontrollable hydraulic fractures have limited preconditioning efficiency because they do not necessarily result in reduced fragmentation sizes and a blocky orebody through the introduction of an additional fracture set. This implies that if the minimum in situ stress orientation is vertical and favors the creation of horizontal hydraulic fractures, in a rock mass that is already dominated by horizontal joints, no additional fracture set is added to that rock mass to increase its blockiness to enable it cave. Therefore, two approaches that have the potential to create orientation-controllable hydraulic fractures in cave mining with the potential to introduce additional fracture set as desired are proposed to fill this gap. These approaches take advantage of directional hydraulic fracturing and the stress shadow effect, which can re-orientate the hydraulic fracture propagation trajectory against its theoretical predicted direction. Proppants are suggested to be introduced into the cave mining industry to enhance the

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


    Jan 7, 2015 ... maximum depth of the tunnel is 90–100 m from the peak of a mountain located above the .... g is the gravity acceleration l is the length of the test ..... process and is a hydraulically-active fracture conducting ground- water flow.

  12. Micromechanical Aspects of Hydraulic Fracturing Processes

    Galindo-torres, S. A.; Behraftar, S.; Scheuermann, A.; Li, L.; Williams, D.


    A micromechanical model is developed to simulate the hydraulic fracturing process. The model comprises two key components. Firstly, the solid matrix, assumed as a rock mass with pre-fabricated cracks, is represented by an array of bonded particles simulated by the Discrete Element Model (DEM)[1]. The interaction is ruled by the spheropolyhedra method, which was introduced by the authors previously and has been shown to realistically represent many of the features found in fracturing and communition processes. The second component is the fluid, which is modelled by the Lattice Boltzmann Method (LBM). It was recently coupled with the spheropolyhedra by the authors and validated. An advantage of this coupled LBM-DEM model is the control of many of the parameters of the fracturing fluid, such as its viscosity and the injection rate. To the best of the authors' knowledge this is the first application of such a coupled scheme for studying hydraulic fracturing[2]. In this first implementation, results are presented for a two-dimensional situation. Fig. 1 shows one snapshot of the LBM-DEM coupled simulation for the hydraulic fracturing where the elements with broken bonds can be identified and the fracture geometry quantified. The simulation involves a variation of the underground stress, particularly the difference between the two principal components of the stress tensor, to explore the effect on the fracture path. A second study focuses on the fluid viscosity to examine the effect of the time scales of different injection plans on the fracture geometry. The developed tool and the presented results have important implications for future studies of the hydraulic fracturing process and technology. references 1. Galindo-Torres, S.A., et al., Breaking processes in three-dimensional bonded granular materials with general shapes. Computer Physics Communications, 2012. 183(2): p. 266-277. 2. Galindo-Torres, S.A., A coupled Discrete Element Lattice Boltzmann Method for the

  13. Phenomenon of methane driven caused by hydraulic fracturing in methane-bearing coal seams

    Huang Bingxiang; Cheng Qingying; Chen Shuliang


    The methane concentration of the return current will always be enhanced to a certain degree when hydraulic fracturing with bedding drilling is implemented to a gassy coal seam in an underground coal mine. The methane in coal seam is driven out by hydraulic fracturing. Thus, the phenomenon is named as methane driven effect of hydraulic fracturing. After deep-hole hydraulic fracturing at the tunneling face of the gassy coal seam, the coal methane content exhibits a‘low-high-low”distribution along exca-vation direction in the following advancing process, verifying the existence of methane driven caused by hydraulic fracturing in methane-bearing coal seam. Hydraulic fracturing causes the change of pore-water and methane pressure in surrounding coal. The uneven distribution of the pore pressure forms a pore pressure gradient. The free methane migrates from the position of high pore (methane) pressure to the position of low pore (methane) pressure. The methane pressure gradient is the fundamental driving force for methane-driven coal seam hydraulic fracturing. The uneven hydraulic crack propagation and the effect of time (as some processes need time to complete and are not completed instantaneously) will result in uneven methane driven. Therefore, an even hydraulic fracturing technique should be used to avoid the negative effects of methane driven; on the other hand, by taking fully advantage of methane driven, two technologies are presented.

  14. Hydraulic fracturing in granite under geothermal conditions

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


    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.


    Zuorong Chen; A.P. Bunger; Xi Zhang; Robert G. Jeffrey


    Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient application of this technology, but is also a great challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on the existing pore pressure cohesive finite elements has been established to investigate the propagation of a penny-shaped hydraulic fracture in an infinite elastic medium. The effect of cohesive material parameters and fluid viscosity on the hydraulic fracture behaviour has been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by rock fracture toughness demonstrates the ability of the cohesive zone finite element model in simulating the hydraulic fracture growth for this case.

  16. The EPA's Study on the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources

    Burden, Susan


    Natural gas plays a key role in our nation's clean energy future. The United States has vast reserves of natural gas that are commercially viable as a result of advances in horizontal drilling and hydraulic fracturing technologies, which enable greater access to gas in rock formations deep underground. These advances have spurred a significant increase in the production of both natural gas and oil across the country. However, as the use of hydraulic fracturing has increased, so have concerns about its potential human health and environmental impacts, especially for drinking water. In response to public concern, the US Congress requested that the US Environmental Protection Agency (EPA) conduct scientific research to examine the relationship between hydraulic fracturing and drinking water resources. In 2011, the EPA began research to assess the potential impacts of hydraulic fracturing on drinking water resources, if any, and to identify the driving factors that may affect the severity and frequency of such impacts. The study is organized around the five stages of the hydraulic fracturing water cycle, from water acquisition through the mixing of chemicals and the injection of fracturing fluid to post-fracturing treatment and/or disposal of wastewater. EPA scientists are using a transdisciplinary research approach involving laboratory studies, computer modeling, toxicity assessments, and case studies to answer research questions associated with each stage of the water cycle. This talk will provide an overview of the EPA's study, including a description of the hydraulic fracturing water cycle and a summary of the ongoing research projects.

  17. Strategies for Creating Prescribed Hydraulic Fractures in Cave Mining

    He, Q.; Suorineni, F. T.; Oh, J.


    The cave mining method was traditionally applied to massive low-grade, weak orebodies at shallow depths (less than 500 m) that favour cave propagation under gravity. Currently, this method is being applied to stronger orebodies and is taking place at depths of up to 2000 m below the surface. To ensure continuous cave propagation, preconditioning of the orebody is essential in this latter caving environment to improve rock mass caveability and to decrease fragmentation sizes. Hydraulic fracturing was initiated in the oil industry and is now being used in the cave mining industry as a preconditioning method and for stalled caves reactivation. A limitation of conventional hydraulic fracturing in the cave mining industry is that the hydraulic fracture orientation is uncontrollable and is dictated by the minimum in situ stress orientation. The preconditioning effectiveness of orientation-uncontrollable hydraulic fractures is limited in some geotechnical conditions, and the concept of creating orientation-controllable hydraulic fractures, here termed prescribed hydraulic fractures, is proposed to fill this gap. In this paper, the feasibility of the proposed approaches to creating prescribed hydraulic fractures is presented based on previous studies and numerical modelling. The numerical modelling code reliability in simulating the hydraulic fracture propagation and reorientation process was validated by comparing with laboratory results in the reported literature. In addition, the sensitivity of the prescribed hydraulic fracturing to the in situ stress condition and rock mass properties is examined.

  18. Coupled Fracture and Flow in Shale in Hydraulic Fracturing

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


    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 (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.

  19. Investigation of possible wellbore cement failures during hydraulic fracturing operations

    Researchers used the peer-reviewed TOUGH+ geomechanics computational software and simulation system to investigate the possibility of fractures and shear failure along vertical wells during hydraulic fracturing operations.

  20. Hydraulic Fracturing and Drinking Water Resources: Update on EPA Hydraulic Fracturing Study

    Natural gas plays a key role in our nation's energy future and the process known as hydraulic fracturing (HF) is one way of accessing that resource. Over the past few years, several key technical, economic, and energy developments have spurred increased use of HF for gas extracti...

  1. A review on hydraulic fracturing of unconventional reservoir

    Quanshu Li


    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.

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

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


    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.

  3. Veining Failure and Hydraulic Fracturing in Shales

    Mighani, S.; Sondergeld, C. H.; Rai, C. S.


    During the hydraulic fracturing, the pressurized fluid creates new fractures and reactivates existing natural fractures forming a highly conductive Stimulated Reservoir Volume (SRV) around the borehole. We extend the previous work on Lyons sandstone and pyrophyllite to anisotropic shale from the Wolfcamp formation. We divide the rock anisotropy into two groups: a) conventional and b) unconventional (shaly) anisotropy. X-ray Computed Tomography (CT), compressional velocity anisotropy, and SEM analysis are used to identify three causes of anisotropy: bedding planes, clay lamination, and calcite veins. Calcite vein is a subsequently filled with calcite bonded weakly to the matrix. Velocity anisotropy and visual observations demonstrate the calcite filled veins to be mostly subparallel to the fabric direction. Brazilian tests are carried out to observe the fracture initiation and propagation under tension. High speed photography (frame rate 300,000 frame/sec) was used to capture the failure. Strain gauges and Acoustic Emission (AE) sensors recorded the deformation leading up to and during failure. SEM imaging and surface profilometry were employed to study the post-failure fracture system and failed surface topology. Fracture permeability was measured as a function of effective stress. Brazilian tests on small disks containing a centered single vein revealed the shear strength of the veins. We interpret the strain data and number, frequency, and amplitude of AE events which are correlated well with the observed fracture process zone, surface roughness, and permeability. The unpropped fracture has enhanced permeability by two orders of magnitude. The observed anisotropic tensile failure seems to have a universal trend with a minimum strength occurring at 15o orientation with respect to the loading axis. The veins at 15o orientation with respect to the loading axis were easily activated at 30% of the original failure load. The measured strength of the vein is as low as 6

  4. [Hydraulic fracturing - a hazard for drinking water?].

    Ewers, U; Gordalla, B; Frimmel, F


    Hydraulic fracturing (fracking) is a technique used to release and promote the extraction of natural gas (including shale gas, tight gas, and coal bed methane) from deep natural gas deposits. Among the German public there is great concern with regard to the potential environmental impacts of fracking including the contamination of ground water, the most important source of drinking water in Germany. In the present article the risks of ground water contamination through fracking are discussed. Due to the present safety requirements and the obligatory geological and hydrogeological scrutiny of the underground, which has to be performed prior to fracking, the risk of ground water contamination by fracking can be regarded as very low. The toxicity of chemical additives of fracking fluids is discussed. It is recommended that in the future environmental impact assessment and approval of fracs should be performed by the mining authorities in close cooperation with the water authorities. Furthermore, it is recommended that hydraulic fracturing in the future should be accompanied by obligatory ground water monitoring.


    Hydraulic fracturing, a technique commonly used to increase the yields of oil wells, could improve the effectiveness of several methods of in situ remediation. This project consisted of laboratory and field tests in which hydraulic fractures were created in soil. Laboratory te...

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

    Salimzadeh Saeed


    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.

  7. Sensors for hydraulic-induced fracturing characterization

    Mireles, Jose, Jr.; Estrada, Horacio; Ambrosio, Roberto C.


    Hydraulic induced fracturing (HIF) in oil wells is used to increase oil productivity by making the subterranean terrain more deep and permeable. In some cases HIF connects multiple oil pockets to the main well. Currently there is a need to understand and control with a high degree of precision the geometry, direction, and the physical properties of fractures. By knowing these characteristics (the specifications of fractures), other drill well locations and set-ups of wells can be designed to increase the probability of connection of the oil pockets to main well(s), thus, increasing productivity. The current state of the art of HIF characterization does not meet the requirements of the oil industry. In Mexico, the SENER-CONACyT funding program recently supported a three party collaborative effort between the Mexican Petroleum Institute, Schlumberger Dowell Mexico, and the Autonomous University of Juarez to develop a sensing scheme to measure physical parameters of a HIF like, but not limited to pressure, temperature, density and viscosity. We present in this paper a review of HIF process, its challenges and the progress of sensing development for down hole measurement parameters of wells for the Chicontepec region of Mexico.

  8. Subcritical growth of natural hydraulic fractures

    Garagash, D.


    Joints are the most common example of brittle tensile failure in the crust. Their genesis at depth is linked to the natural hydraulic fracturing, which requires pore fluid pressure in excess of the minimum in situ stress [Pollard and Aidyn, JSG1988]. Depending on the geological setting, high pore pressure can result form burial compaction of interbedded strata, diagenesis, or tectonics. Common to these loading scenarios is slow build-up of pore pressure over a geological timescale, until conditions for initiation of crack growth are met on favorably oriented/sized flaws. The flaws can vary in size from grain-size cracks in igneous rocks to a fossil-size flaws in clastic rock, and once activated, are inferred to propagate mostly subcritically [Segall JGR 1984; Olson JGR 1993]. Despite many observational studies of natural hydraulic fractures, the modeling attempts appear to be few [Renshaw and Harvey JGR 1994]. Here, we use boundary integral formulation for the pore fluid inflow from the permeable rock into a propagating joint [Berchenko et al. IJRMMS 1997] coupled with the criteria for subcritical propagation assisted by the environmental effects of pore fluid at the crack tip to solve for the evolution of a penny-shape joint, which, in interbedded rock, may eventually evolve to short-blade geometry (propagation confined to a bed). Initial growth is exceedingly slow, paced by the stress corrosion reaction kinetics at the crack tip. During this stage the crack is fully-drained (i.e. the fluid pressure in the crack is equilibrated with the ambient pore pressure). This "slow" stage is followed by a rapid acceleration, driven by the increase of the mechanical stress intensity factor with the crack length, towards the terminal joint velocity. We provide an analytical expression for the latter as a function of the rock diffusivity, net pressure loading at the initiation (or flaw lengthscale), and parameters describing resistance to fracture growth. Due to a much slower

  9. Dry and hydraulic extensile fracturing of porous impermeable materials

    Visser, J.H.M.; Van Mier, J.C.M.


    Extensile hydraulic fracturing of mortar is investigated and compared to extensile dry fracturing of sandstone. The extensile fracture experiments have been performed in a Hookean cell in deformation control. The cell allows for axial loading and radial fluid pressure loading of cylindrical specimen

  10. Laboratory tests of hydraulic fracturing and swell healing

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


    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...

  11. Hydraulic fracturing - an attempt of DEM simulation

    Kosmala, Alicja; Foltyn, Natalia; Klejment, Piotr; Dębski, Wojciech


    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.

  12. Studies investigate effects of hydraulic fracturing

    Balcerak, Ernie


    The use of hydraulic fracturing, also known as fracking, to enhance the retrieval of natural gas from shale has been increasing dramatically—the number of natural gas wells rose about 50% since 2000. Shale gas has been hailed as a relatively low-cost, abundant energy source that is cleaner than coal. However, fracking involves injecting large volumes of water, sand, and chemicals into deep shale gas reservoirs under high pressure to open fractures through which the gas can travel, and the process has generated much controversy. The popular press, advocacy organizations, and the documentary film Gasland by Josh Fox have helped bring this issue to a broad audience. Many have suggested that fracking has resulted in contaminated drinking water supplies, enhanced seismic activity, demands for large quantities of water that compete with other uses, and challenges in managing large volumes of resulting wastewater. As demand for expanded domestic energy production intensifies, there is potential for substantially increased use of fracking together with other recovery techniques for "unconventional gas resources," like extended horizontal drilling.

  13. Pulsating hydraulic fracturing technology in low permeability coal seams

    Wang Wenchao; Li Xianzhong; Lin Baiquan; Zhai Cheng


    Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme-ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing;the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 L/min at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.

  14. Transport efficiency and dynamics of hydraulic fracture networks

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique


    Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/fα behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

  15. Transport efficiency and dynamics of hydraulic fracture networks

    Till eSachau


    Full Text Available Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/fα behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

  16. Electrical and Magnetic Imaging of Proppants in Shallow Hydraulic Fractures

    Denison, J. L. S.; Murdoch, L. C.; LaBrecque, D. J.; Slack, W. W.


    Hydraulic fracturing is an important tool to increase the productivity of wells used for oil and gas production, water resources, and environmental remediation. Currently there are relatively few tools available to monitor the distribution of proppants within a hydraulic fracture, or the propagation of the fracture itself. We have been developing techniques for monitoring hydraulic fractures by injecting electrically conductive, dielectric, or magnetically permeable proppants. We then use the resulting contrast with the enveloping rock to image the proppants using geophysical methods. Based on coupled laboratory and numerical modeling studies, three types of proppants were selected for field evaluation. Eight hydraulic fractures were created near Clemson, SC in May of 2015 by injecting specialized proppants at a depth of 1.5 m. The injections created shallow sub-horizontal fractures extending several meters from the injection point.Each cell had a dense array of electrodes and magnetic sensors on the surface and four shallow vertical electrode arrays that were used to obtain data before and after hydraulic fracturing. Net vertical displacement and transient tilts were also measured. Cores from 130 boreholes were used to characterize the general geometries, and trenching was used to characterize the forms of two of the fractures in detail. Hydraulic fracture geometries were estimated by inverting pre- and post-injection geophysical data. Data from cores and trenching show that the hydraulic fractures were saucer-shaped with a preferred propagation direction. The geophysical inversions generated images that were remarkably similar in form, size, and location to the ground truth from direct observation. Displacement and tilt data appear promising as a constraint on fracture geometry.

  17. Numerical analysis of fracture propagation during hydraulic fracturing operations in shale gas systems

    Researchers used the TOUGH+ geomechanics computational software and simulation system to examine the likelihood of hydraulic fracture propagation (the spread of fractures) traveling long distances to connect with drinking water aquifers.

  18. A review of numerical simulation strategies for hydraulic fracturing, natural fracture reactivation and induced microseismicity prediction

    Shahid, A.S.A.; Fokker, P.A.; Rocca, V.


    Hydraulic fracturing, natural fracture reactivation and resulting induced microseismicity are interconnected phenomena involved in shale gas exploitation. Due to their multi-physics and their complexity, deep understanding of these phenomena as well as their mutual interaction require the adoption

  19. Discrete modeling of hydraulic fracturing processes in a complex pre-existing fracture network

    Kim, K.; Rutqvist, J.; Nakagawa, S.; Houseworth, J. E.; Birkholzer, J. T.


    Hydraulic fracturing and stimulation of fracture networks are widely used by the energy industry (e.g., shale gas extraction, enhanced geothermal systems) to increase permeability of geological formations. Numerous analytical and numerical models have been developed to help understand and predict the behavior of hydraulically induced fractures. However, many existing models assume simple fracturing scenarios with highly idealized fracture geometries (e.g., propagation of a single fracture with assumed shapes in a homogeneous medium). Modeling hydraulic fracture propagation in the presence of natural fractures and homogeneities can be very challenging because of the complex interactions between fluid, rock matrix, and rock interfaces, as well as the interactions between propagating fractures and pre-existing natural fractures. In this study, the TOUGH-RBSN code for coupled hydro-mechanical modeling is utilized to simulate hydraulic fracture propagation and its interaction with pre-existing fracture networks. The simulation tool combines TOUGH2, a simulator of subsurface multiphase flow and mass transport based on the finite volume approach, with the implementation of a lattice modeling approach for geomechanical and fracture-damage behavior, named Rigid-Body-Spring Network (RBSN). The discrete fracture network (DFN) approach is facilitated in the Voronoi discretization via a fully automated modeling procedure. The numerical program is verified through a simple simulation for single fracture propagation, in which the resulting fracture geometry is compared to an analytical solution for given fracture length and aperture. Subsequently, predictive simulations are conducted for planned laboratory experiments using rock-analogue (soda-lime glass) samples containing a designed, pre-existing fracture network. The results of a preliminary simulation demonstrate selective fracturing and fluid infiltration along the pre-existing fractures, with additional fracturing in part

  20. Controlled Source Electromagnetic Monitoring of Hydraulic Fracturing

    Couchman, M. J.; Everett, M. E.


    Controlled Source Electromagnetics (CSEM) have been used as a direct hydrocarbon indicator since the 1960s, with a resurgence in marine conventional settings in the new millennium, with many studies revolving around detecting a thin resistive layer such as a reservoir at 1m-3km depth. The presence of the resistive layer is characterized by a jump in electric field amplitude recorded at the boundary between the layer and the host sediments. Here the lessons learned from these studies are applied to terrestrial unconventional settings. However, unlike in marine settings where resistive hydrocarbon-charged fluids comprise a conventional reservoir, on land we are interested in electrically conductive injected fluids. The work shown here is a means to develop further methods to enable more reliable terrestrial CSEM monitoring of the flow of injected fluids associated with hydraulic fracturing of unconventional reservoirs and to detect subsurface fluids based on their CSEM signature and in turn, to infer the subsurface flow of electrically conductive injected fluids. Overall this project attempts to create more efficient fracturing, by determining fluid pathways, hence making projects more cost effective by reducing the cost of extraction. The predictive model developed focuses on the mapping of fluid flow in from a horizontal pipe in a uniform halfspace using a long in-line Horizontal Electric Dipole (HED) with electric field amplitude recorded by an array of electric field sensors. The code provided has been edited to include a long-dipole source in addition to the half dipole source originally in place in order to align with current CSEM field practices. The well casing has also been included due to its large effect on CSEM response.

  1. The Potential Impacts of Hydraulic Fracturing on Agriculture

    Beng Ong


    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...

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

    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

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

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


    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 indu...

  4. Periodic Hydraulic Testing for Discerning Fracture Network Connections

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


    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.

  5. Hydraulic fracturing with chlorine dioxide cleanup

    Williams, D.A.; Newlove, J.C.; Horton, R.L.


    This patent describes a method for fracturing a subterranean formation penetrated by a wellbore. It comprises: injecting a fracturing fluid into the formation to form a vertical fracture therein, the fracturing fluid being gelled with a polymer selected from guar, guar derivatives, acrylamide, acrylamide derivatives, cellulose, cellulose derivatives, and mixtures thereof and crosslinked with an organometallic crosslinking compound and having temperature stability above about 175{degrees} F.; packing the fracture with particulate propping agent; backflowing fluids from the formation through the propped fracture to remove a portion of the polymer; injecting at matrix rates sufficient aqueous solution of chlorine dioxide down the wellbore and into the propped fracture to penetrate at least 60 feet of the propped fracture length and contact polymer in the fracturing fluid and polymer residue in the propped fracture and on the fracture walls, the amount of the chlorine dioxide in the aqueous medium being sufficient to degrade polymer in the fracturing fluid and polymer residue; permitting the chlorine dioxide to remain in contact with the polymer in the fracturing fluid and with the polymer residue on the fracture walls and in the fracture for sufficient time to degrade the polymer thereby reducing the fracturing fluid viscosity and dissolving portions of the polymer residue; and flowing formation fluid from the formation through the propped fracture and into the wellbore to remove substantial portions of the polymer and degraded polymer from the fracture.

  6. Numerical Analysis on the Formation of Fracture Network during the Hydraulic Fracturing of Shale with Pre-Existing Fractures

    Jianming He


    Full Text Available In this paper, configurations of pre-existing fractures in cubic rock blocks were investigated and reconstructed for the modeling of experimental hydraulic fracturing. The fluid-rock coupling process of hydraulic fracturing was simulated based on the displacement discontinuities method. The numerical model was validated against the related laboratory experiments. The stimulated fracture configurations under different conditions can be clearly shown using the validated numerical model. First, a dominated fracture along the maximum principle stress direction is always formed when the stress difference is large enough. Second, there are less reopened pre-existing fractures, more newly formed fractures and less shear fractures with the increase of the cohesion value of pre-existing fractures. Third, the length of the stimulated shear fracture decreases rapidly with the increase of the friction coefficient, while the length of the tensile fracture has no correlation to the fiction coefficient. Finally, the increase of the fluid injection rate is favorable to the formation of a fracture network. The unfavorable effects of the large stress difference and the large cohesion of pre-existing fractures can be partly suppressed by an increase of the injection rate in the hydraulic fracturing treatment. The results of this paper are useful for understanding fracture propagation behaviors during the hydraulic fracturing of shale reservoirs with pre-existing fractures.

  7. Calculation Method and Distribution Characteristics of Fracture Hydraulic Aperture from Field Experiments in Fractured Granite Area

    Cao, Yang-Bing; Feng, Xia-Ting; Yan, E.-Chuan; Chen, Gang; Lü, Fei-fei; Ji, Hui-bin; Song, Kuang-Yin


    Knowledge of the fracture hydraulic aperture and its relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the qualitative relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.

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

    Timotej Verbovšek


    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.

  9. Imaging hydraulic fractures by microseismic migration for downhole monitoring system

    Lin, Ye; Zhang, Haijiang


    It has been a challenge to accurately characterize fracture zones created by hydraulic fracturing from microseismic event locations. This is because generally detected events are not complete due to the associated low signal to noise ratio and some fracturing stages may not produce microseismic events even if fractures are well developed. As a result, spatial distribution of microseismic events may not well represent fractured zones by hydraulic fracturing. Here, we propose a new way to characterize the fractured zones by reverse time migration (RTM) of microseismic waveforms from some events. This is based on the fact that fractures filled with proppants and other fluids can act as strong scatterers for seismic waves. Therefore, for multi-stage hydraulic fracturing, recorded waveforms from microseismic events induced in a more recent stage may be scattered by fractured zones from previous stages. Through RTM of microseismic waveforms in the current stage, we can determine fractured zones created in previous stages by imaging area of strong scattering. We test the feasibility of this method using synthetic models with different configurations of microseismic event locations and borehole sensor positions for a 2D downhole microseismic monitoring system. Synthetic tests show that with a few events fractured zones can be directly imaged and thus the stimulated reservoir volume (SRV) can be estimated. Compared to the conventional location-based SRV estimation method, the proposed new method does not depend on the completeness of detected events and only a limited number of detected and located events are necessary for characterizing fracture distribution. For simplicity, the 2D model is used for illustrating the concept of microseismic RTM for imaging the fracture zone but the method can be adapted to real cases in the future.

  10. Hydraulic fracturing model based on the discrete fracture model and the generalized J integral

    Liu, Z. Q.; Liu, Z. F.; Wang, X. H.; Zeng, B.


    The hydraulic fracturing technique is an effective stimulation for low permeability reservoirs. In fracturing models, one key point is to accurately calculate the flux across the fracture surface and the stress intensity factor. To achieve high precision, the discrete fracture model is recommended to calculate the flux. Using the generalized J integral, the present work obtains an accurate simulation of the stress intensity factor. Based on the above factors, an alternative hydraulic fracturing model is presented. Examples are included to demonstrate the reliability of the proposed model and its ability to model the fracture propagation. Subsequently, the model is used to describe the relationship between the geometry of the fracture and the fracturing equipment parameters. The numerical results indicate that the working pressure and the pump power will significantly influence the fracturing process.

  11. Earthquakes Induced by Hydraulic Fracturing in Poland Township, Ohio

    Skoumal, R.; Brudzinski, M. R.; Currie, B. S.


    Felt seismicity induced by hydraulic fracturing is very rare with only a handful of reported cases worldwide. Using an optimized multi-station cross-correlation template matching routine, 77 earthquakes were identified in Poland Township, Mahoning County, Ohio that were closely related spatially and temporally to active hydraulic fracturing operations. We identified earthquakes as small as M ~1 up to M 3, one of the largest earthquakes induced by hydraulic fracturing in the United States. These events all occurred 4-12 March 2014 and the rate decayed once the Ohio Department of Natural Resources issued a shutdown of hydraulic fracturing at a nearby well on 10 March. Using a locally derived velocity model and double difference relocation, the earthquake epicenters occurred during six stimulation stages along two horizontal well legs that were located ~0.8 km away. Nearly 100 stages in nearby wells at greater distances from the earthquake source region did not coincide with detected seismicity. During the sequence, hypocenters migrated ~600 m along an azimuth of 083 degrees defining a vertically oriented plane of seismicity close to the top of the Precambrian basement. The focal mechanism determined for the M 3 event had a vertically oriented left-lateral fault plane consistent with the earthquake distribution and the regional stress field. The focal mechanism, orientation, and depth of hypocenters were similar to that of the 2011 Youngstown earthquake sequence that occurred ~20 km away, but was correlated with wastewater injection instead of hydraulic fracturing. Considering the relatively large magnitude of these events and the b-value of 0.85, it appears the hydraulic fracturing induced slip along a pre-existing fault/fracture zone optimally oriented in the regional stress field.

  12. Impact of ductility on hydraulic fracturing in shales

    MacMinn, Chris; Auton, Lucy


    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. Treatment Process Requirements for Waters Containing Hydraulic Fracturing Chemicals

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


    A wide variety of chemical additives are used as part of the hydraulic fracturing (HyF) process. There is concern that HyF chemicals will be released into the environment and contaminate drinking water, agricultural water, or other water used for beneficial purposes. There is also interest in using produced water (water extracted from the subsurface during oil and gas production) for irrigation and other beneficial purposes, especially in the arid Southwest US. Reuse of produced water is not speculative: produced water can be low in salts and is being used in California for irrigation after minimal treatment. In this study, we identified chemicals that are used for hydraulic fracturing in California and conducted an analysis to determine if those chemicals would be removed by a variety of technically available treatment processes, including oil/water separation, air stripping, a variety of sorption media, advanced oxidation, biological treatment, and a variety of membrane treatment systems. The approach taken was to establish major physiochemical properties for individual chemicals (log Koc, Henry's constant, biodegradability, etc.), group chemicals by function (e.g corrosion inhibition, biocides), and use those properties to predict the fate of chemical additives in a treatment process. Results from this analysis is interpreted in the context of what is known about existing systems for the treatment of produced water before beneficial reuse, which includes a range of treatment systems from oil/water separators (the most common treatment) to sophisticated treatment trains used for purifying produced water for groundwater recharge. The results show that most HyF chemical additives will not be removed in existing treatment systems, but that more sophisticated treatment trains can be designed to remove additives before beneficial reuse.

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

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


    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

  15. Fault activation by hydraulic fracturing in western Canada

    Bao, Xuewei; Eaton, David W.


    Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.

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

    Zawadzki, Jaroslaw; Bogacki, Jan


    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

  17. Guiding-controlling technology of coal seam hydraulic fracturing fractures extension

    Zhai; Cheng; Li; Min; Sun; Chen; Zhang; Jianguo; Yang; Wei; Li; Quangui


    Aiming at the uncontrollable problem of extension direction of coal seam hydraulic fracturing,this study analyzed the course of fractures variation around the boreholes in process of hydraulic fracturing,and carried out the numerical simulations to investigate the effect of artificial predetermined fractures on stress distribution around fractured holes.The simulation results show that partial coal mass occurs relatively strong shear failure and forms weak surfaces,and then fractures extended along the desired direction while predetermined fractures changed stress distribution.Directional fracturing makes the fractures link up and the pressure on coal mass is relieved within fractured regions.Combining deep hole controlling blasting with hydraulic fracturing was proposed to realize the extension guiding-controlling technology of coal seam fractures.Industrial experiments prove that this technology can avoid local stress concentration and dramatically widen the pressure relief scope of deep hole controlling blasting.The permeability of fractured coal seam increased significantly,and gas extraction was greatly improved.Besides,regional pressure relief and permeability increase was achieved in this study.

  18. Hydraulic fracture design and optimization of gas storage wells

    Mohaghegh, S.; Ameri, S. [Petroleum and Natural Gas and Engineering Department, West Virginia University, P.O. Box 6070, Morgantown, WV (United States); Balanb, B. [Schlumberger Austin Product Center, 8311 North FM 620 Road, Austin, TX (United States); Platon, V. [Baker Atlas, 10201 Westheimer Rd., Houston, TX (United States)


    Conventional hydraulic fracture design and optimization involves the use of two- or three-dimensional hydraulic fracture simulators. These simulators need a wealth of reservoir data as input to provide users with usable results. In many cases, such data are not available or very expensive to acquire. This paper provides a new methodology that can be used in cases where detail reservoir data are not available or prohibitively expensive to acquire. Through the use of two virtual intelligence techniques, namely neural networks and genetic algorithms, hydraulic fracture treatments are designed using only the available data. The unique design optimization method presented here is a logical continuation of the study that was presented in two previous papers [McVey et al., 1996, Identification of parameters influencing the response of gas storage wells to hydraulic fracturing with the aid of a neural network, SPE Computer Applications Journal, Apr., 54-57; Mohaghegh et al., 1996b, Predicting well stimulation results in a gas storage field in the absence of reservoir data, using neural networks, SPE Reservoir Engineering Journal, Nov., 54-57]. A quick review of these papers is included here. This method will use the available data on each well, which includes basic well information, production history and results of previous frac job treatments, and provides engineer with a detail optimum hydraulic fracture design unique to each well. The expected post-hydraulic fracture deliverability for the designed treatment is also provided to assist engineers in estimating incremental increase in recovery to be used in economic calculations. There are no simulated data throughout this study and all data used for development and verification of all methods are actual field data.

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

    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

  20. Interaction of hydraulic and buckling mechanisms in blowout fractures.

    Nagasao, Tomohisa; Miyamoto, Junpei; Jiang, Hua; Tamaki, Tamotsu; Kaneko, Tsuyoshi


    The etiology of blowout fractures is generally attributed to 2 mechanisms--increase in the pressure of the orbital contents (the hydraulic mechanism) and direct transmission of impacts on the orbital walls (the buckling mechanism). The present study aims to elucidate whether or not an interaction exists between these 2 mechanisms. We performed a simulation experiment using 10 Computer-Aided-Design skull models. We applied destructive energy to the orbits of the 10 models in 3 different ways. First, to simulate pure hydraulic mechanism, energy was applied solely on the internal walls of the orbit. Second, to simulate pure buckling mechanism, energy was applied solely on the inferior rim of the orbit. Third, to simulate the combined effect of the hydraulic and buckling mechanisms, energy was applied both on the internal wall of the orbit and inferior rim of the orbit. After applying the energy, we calculated the areas of the regions where fracture occurred in the models. Thereafter, we compared the areas among the 3 energy application patterns. When the hydraulic and buckling mechanisms work simultaneously, fracture occurs on wider areas of the orbital walls than when each of these mechanisms works separately. The hydraulic and buckling mechanisms interact, enhancing each other's effect. This information should be taken into consideration when we examine patients in whom blowout fracture is suspected.

  1. Triaxial coreflood study of the hydraulic fracturing of Utica Shale

    Carey, J. W.; Frash, L.; Viswanathan, H. S.


    One of the central questions in unconventional oil and gas production research is the cause of limited recovery of hydrocarbon. There are many hypotheses including: 1) inadequate penetration of fractures within the stimulated volume; 2) limited proppant delivery; 3) multiphase flow phenomena that blocks hydrocarbon migration; etc. Underlying any solution to this problem must be an understanding of the hydrologic properties of hydraulically fractured shale. In this study, we conduct triaxial coreflood experiments using a gasket sealing mechanism to characterize hydraulic fracture development and permeability of Utica Shale samples. Our approach also includes fracture propagation with proppants. The triaxial coreflood experiments were conducted with an integrated x-ray tomography system that allows direct observation of fracture development using x-ray video radiography and x-ray computed tomography at elevated pressure. A semi-circular, fracture initiation notch was cut into an end-face of the cylindrical samples (1"-diameter with lengths from 0.375 to 1"). The notch was aligned parallel with the x-ray beam to allow video radiography of fracture growth as a function of injection pressure. The proppants included tungsten powder that provided good x-ray contrast for tracing proppant delivery and distribution within the fracture system. Fractures were propagated at injection pressures in excess of the confining pressure and permeability measurements were made in samples where the fractures propagated through the length of the sample, ideally without penetrating the sample sides. Following fracture development, permeability was characterized as a function of hydrostatic pressure and injection pressure. X-ray video radioadiography was used to study changes in fracture aperture in relation to permeability and proppant embedment. X-ray tomography was collected at steady-state conditions to fully characterize fracture geometry and proppant distribution.

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

    Roubinet, D; Jougnot, D; Irving, J


    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 interaction...

  3. Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity

    Chae, B.; Ichikawa, Y.; Kim, Y.


    Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of

  4. Field experiments in a fractured clay till. 1. Hydraulic conductivity and fracture aperture

    McKay, Larry D.; Cherry, John A.; Gillham, Robert W.


    Field values of horizontal hydraulic conductivity measured in the upper 1.5-5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1-2 orders of magnitude lower than those measured in piezometers designed to reduce smearing. Measurements of hydraulic conductivity in small-scale seepage collectors or piezometers, which typically intersect fewer than 10 fractures, vary over a much greater range, 10-10 to 10-6 m/s, than large-scale values based on infiltration into 5.5-m-deep trenches which intersect thousands of fractures (range 10-7 to 3×10-7 m/s). Values of hydraulic fracture aperture, 1-43 μm, and fracture porosity, 3×10-5 to 2×10-3, were calculated using the cubic law with fracture orientation/distribution measurements and the small-scale hydraulic conductivity measurements. This paper provides the first reliable determination of the magnitude and spatial distribution of hydraulically derived fracture parameters in a clay deposit. The absence of such data has, until now, severely limited the application of quantitative groundwater flow and contaminant transport models in this type of deposit.

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

    Rasch, Elisabet Dueholm; Köhne, Michiel


    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 i

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

    Rasch, Elisabet Dueholm; Köhne, Michiel


    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 i

  7. 78 FR 25267 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources


    ... AGENCY Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water... research on the potential impacts of hydraulic fracturing on drinking water resources from April 30, 2013... research to examine the relationship between hydraulic fracturing and drinking water resources. The...

  8. Analytic crack solutions for tilt fields around hydraulic fractures

    Warpinski, N.R.


    The recent development of downhole tiltmeter arrays for monitoring hydraulic fractures has provided new information on fracture growth and geometry. These downhole arrays offer the significant advantages of being close to the fracture (large signal) and being unaffected by the free surface. As with surface tiltmeter data, analysis of these measurements requires the inversion of a crack or dislocation model. To supplement the dislocation models of Davis [1983], Okada [1992] and others, this work has extended several elastic crack solutions to provide tilt calculations. The solutions include constant-pressure 2D, penny-shaped, and 3D-elliptic cracks and a 2D-variable-pressure crack. Equations are developed for an arbitrary inclined fracture in an infinite elastic space. Effects of fracture height, fracture length, fracture dip, fracture azimuth, fracture width and monitoring distance on the tilt distribution are given, as well as comparisons with the dislocation model. The results show that the tilt measurements are very sensitive to the fracture dimensions, but also that it is difficult to separate the competing effects of the various parameters.

  9. Understanding hydraulic fracturing: a multi-scale problem.

    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


    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'.

  10. Effect of ground stress on hydraulic fracturing of methane well

    DU Chun-zhi; MAO Xian-biao; MIAO Xie-xing; WANG Peng


    Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the permeability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) otherwise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with increasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.

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

    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...

  12. A review of numerical simulation strategies for hydraulic fracturing, natural fracture reactivation and induced microseismicity prediction

    Shahid, A.S.A.; Fokker, P.A.; Rocca, V.


    Hydraulic fracturing, natural fracture reactivation and resulting induced microseismicity are interconnected phenomena involved in shale gas exploitation. Due to their multi-physics and their complexity, deep understanding of these phenomena as well as their mutual interaction require the adoption o

  13. Scale and Time Effects in Hydraulic Fracturing.


    Results on Teton Dam Silt Test Groove Dry Water Fracturing No. Size Density Content Pressure b d t/m 3 %kg/cm 2 in. in. - IG2 3. 1.51.5920.43.2 G3 2.0...a loose zone through which water pressures were applied. • 111 Table 5.2 Summary of Type IV Test Results on Teton Dam Silt Series Test Slot Dry Water Fracturing...Series Test Slot Dry Water Fracturing No. No. Width Density Content Pressure in. t/m 3 % kg/cm 2 S12 0.125 1.60 19.1 3.6 S13 0.25 1.60 19.5 3.9 I S14

  14. Numerical Study on the Permeability of the Hydraulic-Stimulated Fracture Network in Naturally-Fractured Shale Gas Reservoirs

    Zhaobin Zhang


    Full Text Available As hydraulic fracturing is a fluid-rock coupling process, the permeability of the hydraulic-stimulated fracture network in the initial stage has great effects on the propagation of the hydraulic fracture network in the following stages. In this work, the permeability of the hydraulic-stimulated fracture network in shale gas reservoirs is investigated by a newly-proposed model based on the displacement discontinuity method. The permeability of the fracture network relies heavily on fracture apertures, which can be calculated with high precision by the displacement discontinuity method. The hydraulic fracturing processes are simulated based on the natural fracture networks reconstructed from the shale samples in the Longmaxi formation of China. The flow fields are simulated and the permeability is calculated based on the fracture configurations and fracture apertures after hydraulic fracturing treatment. It is found that the anisotropy of the permeability is very strong, and the permeability curves have similar shapes. Therefore, a fitting equation of the permeability curve is given for convenient use in the future. The permeability curves under different fluid pressures and crustal stress directions are obtained. The results show that the permeability anisotropy is stronger when the fluid pressure is higher. Moreover, the permeability anisotropy reaches the minimum value when the maximum principle stress direction is perpendicular to the main natural fracture direction. The investigation on the permeability is useful for answering how the reservoirs are hydraulically stimulated and is useful for predicting the propagation behaviors of the hydraulic fracture network in shale gas reservoirs.

  15. Fluid Compressibility Effects during Hydraulic Fracture: an Opportunity for Gas Fracture Revival

    Mighani, S.; Boulenouar, A.; Moradian, Z.; Evans, J. B.; Bernabe, Y.


    Hydraulic fracturing results when internal pore pressure is increased above a critical value. As the fracture extends, the fluid flows to the crack tip. The fracturing process depends strongly on the physical properties of both the porous solid and the fluid (e.g. porosity and elastic moduli for the solid, viscosity and compressibility for the fluid). It is also affected by the in-situ stress and pore pressure conditions. Here, we focus on the effect of fluid properties on hydraulic fracturing under conventional triaxial loading. Cylinders of Solnhofen limestone (a fine-grained, low permeability rock) were prepared with a central borehole through which different pressurized fluids such as oil, water or argon, were introduced. Preliminary experiments were performed using a confining pressure of 5 MPa and axial stress of 7 MPa. Our goal was to monitor fracture extension using strain gauges, acoustic emissions (AE) recording and ultrasonic velocity measurements. We also tried to compare the data with analytical models of fracture propagation. Initial tests showed that simple bi-wing fractures form when the fracturing fluid is relatively incompressible. With argon as pore fluid, a complex fracture network was formed. We also observed that the breakdown pressure was higher with argon than with less compressible fluids. After fracturing occurred, we cycled fluid pressure for several times. During the first cycles, re-opening of the fracture was associated with additional propagation. In general, it took 4 cycles to inhibit further propagation. Analytical models suggest that initial fractures occurring with compressible fluids tend to stabilize. Hence, formation and extension of additional fractures may occur, leading to a more complex morphology. Conversely, fractures formed by incompressible fluids remain critically stressed as they extend, thus producing a simple bi-wing fracture. Using compressible fracturing fluids could be a suitable candidate for an efficient

  16. Optimisation of the Near-Wellbore Geometry of Hydraulic Fractures Propagating from Cased Perforated Completions

    van de Ketterij, R.G.


    Hydraulic fracturing is a technique frequently used to stimulate the production of an oil or gas well by creating a fracture in the porous rock around the wellbore. The success of a hydraulic fracture treatment depends heavily on the created fracture geometry. The optimum situation arises when a sin

  17. Aerobic biodegradation of organic compounds in hydraulic fracturing fluids.

    Kekacs, Daniel; Drollette, Brian D; Brooker, Michael; Plata, Desiree L; Mouser, Paula J


    Little is known of the attenuation of chemical mixtures created for hydraulic fracturing within the natural environment. A synthetic hydraulic fracturing fluid was developed from disclosed industry formulas and produced for laboratory experiments using commercial additives in use by Marcellus shale field crews. The experiments employed an internationally accepted standard method (OECD 301A) to evaluate aerobic biodegradation potential of the fluid mixture by monitoring the removal of dissolved organic carbon (DOC) from an aqueous solution by activated sludge and lake water microbial consortia for two substrate concentrations and four salinities. Microbial degradation removed from 57 % to more than 90 % of added DOC within 6.5 days, with higher removal efficiency at more dilute concentrations and little difference in overall removal extent between sludge and lake microbe treatments. The alcohols isopropanol and octanol were degraded to levels below detection limits while the solvent acetone accumulated in biological treatments through time. Salinity concentrations of 40 g/L or more completely inhibited degradation during the first 6.5 days of incubation with the synthetic hydraulic fracturing fluid even though communities were pre-acclimated to salt. Initially diverse microbial communities became dominated by 16S rRNA sequences affiliated with Pseudomonas and other Pseudomonadaceae after incubation with the synthetic fracturing fluid, taxa which may be involved in acetone production. These data expand our understanding of constraints on the biodegradation potential of organic compounds in hydraulic fracturing fluids under aerobic conditions in the event that they are accidentally released to surface waters and shallow soils.

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

    Lianchong Li


    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.

  19. Analytical and numerical simulations of a hydraulic fracturing experiment

    Zhou, M.Z.; Namiq, M.A.; Zhou, L.; Gou, Y. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. of Petroleum Engineering


    Based on simulations of a previously published hydraulic fracturing experiment performed by Casas et al. (2006), this paper presents the performance assessment of the famous analytical fracture 2D-models (PKN and KGD) and a 3D numerical model (FDM program FLAC3D of the ITASCA Inc.). Strain-softening models are used in the FLAC3D to describe the fracture creation and propagation as well as to present the material softening properties (permeability, tensile strength, cohesion, friction and dilation angel) as functions of the plastic strain. The results show that the numerical simulator has a much better performance and produces more reliable results than the analytical fracture models. However, numerical models have limitations and thus potential for further development. (orig.)

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

    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.

  1. Field investigation into directional hydraulic fracturing for hard roof in Tashan Coal Mine

    Bing-Xiang HUANG; Bin YU; Feng FENG; Zhao LI; You-Zhuang WANG; Jin-Rong LIU


    Research and development of safe and effective control technology of hard roof is an inevitable trend at present.Directional hydraulic fracturing technology is expected to become a safe and effective way to control and manage hard roof.In order to make hard roof fracture in a directional way,a hydraulic fracture field test has been conducted in the third panel district of Tashan Coal Mine in Datong.First,two hydraulic fracturing drilling holes and four observing drilling holes were arranged in the roof,followed by a wedge-shaped ring slot in each hydraulic fracturing drilling hole.The hydraulic fracturing holes were then sealed and,hydraulic fracturing was conducted.The results show that the hard roof is fractured directionally by the hydraulic fracturing function of the two fracturing drilling holes; the sudden drop,or the overall downward trend of hydraulic pressure from hydraulic monitoring is the proof that the rock in the hard roof has been fractured.The required hydraulic pressure to fracture the hard roof in Tashan coal mine,consisting of carboniferous sandstone layer,is 50.09 MPa,and the fracturing radius of a single drilling hole is not less than 10.5 m.The wedge-shaped ring slot made in the bottom of the hydraulic fracturing drilling hole plays a guiding role for crack propagation.After the hydraulic fracturing drill hole is cracked,the propagation of the resulting hydraulic crack,affected mainly by the regional stress field,will turn to other directions.

  2. Phase-field modeling of hydraulic fracture

    Wilson, Zachary A.; Landis, Chad M.


    In this work a theoretical framework implementing the phase-field approach to fracture is used to couple the physics of flow through porous media and cracks with the mechanics of fracture. The main modeling challenge addressed in this work, which is a challenge for all diffuse crack representations, is on how to allow for the flow of fluid and the action of fluid pressure on the aggregate within the diffuse damage zone of the cracks. The theory is constructed by presenting the general physical balance laws and conducting a consistent thermodynamic analysis to constrain the constitutive relationships. Constitutive equations that reproduce the desired responses at the various limits of the phase-field parameter are proposed in order to capture Darcy-type flow in the intact porous medium and Stokes-type flow within open cracks. A finite element formulation for the solution of the governing model equations is presented and discussed. Finally, the theoretical and numerical model is shown to compare favorably to several important analytical solutions. More complex and interesting calculations are also presented to illustrate some of the advantageous features of the approach.

  3. Treatment of hydraulic fracturing wastewater by wet air oxidation.

    Wang, Wei; Yan, Xiuyi; Zhou, Jinghui; Ma, Jiuli


    Wastewater produced by hydraulic fracturing for oil and gas production is characterized by high salinity and high chemical oxygen demand (COD). We applied a combination of flocculation and wet air oxidation technology to optimize the reduction of COD in the treatment of hydraulic fracturing wastewater. The experiments used different values of flocculant, coagulant, and oxidizing agent added to the wastewater, as well as different reaction times and treatment temperatures. The use of flocculants for the pretreatment of fracturing wastewater was shown to improve treatment efficiency. The addition of 500 mg/L of polyaluminum chloride (PAC) and 20 mg/L of anionic polyacrylamide (APAM) during pretreatment resulted in a COD removal ratio of 8.2% and reduced the suspended solid concentration of fracturing wastewater to 150 mg/L. For a solution of pretreated fracturing wastewater with 12 mL of added H2O2, the COD was reduced to 104 mg/L when reacted at 300 °C for 75 min, and reduced to 127 mg/L when reacted at the same temperature for 45 min while using a 1 L autoclave. An optimal combination of these parameters produced treated wastewater that met the GB 8978-1996 'Integrated Wastewater Discharge Standard' level I emission standard.

  4. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    Kim, Jihoon; Moridis, George


    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  5. Numerical modeling of concrete hydraulic fracturing with extended finite element method

    REN QingWen; DONG YuWen; YU TianTang


    The extended finite element method (XFEM) is a new numerical method for modeling discontinuity.Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan-tages of the XFEM for hydraulic fracturing analysis are displayed.

  6. Numerical modeling of concrete hydraulic fracturing with extended finite element method


    The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan- tages of the XFEM for hydraulic fracturing analysis are displayed.

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

    Yanfang Wu


    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.

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

    Arroyo, Marino; Trepat, Xavier


    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'.

  9. Experiment on Hydraulic Fracturing in Rock and Induced Earthquake

    Yan Yuding; Li Yalin; Zhang Zhuan; Ouyang Lisheng; Xie Mingfu


    Experiment on rock hydraulic fracturing strength under different confining pressures was conducted on a series of test specimens with various pre-cracks prepared from 7 types of rock.Combining the data of an actual reservoir-induced earthquake with the experimental results of the contemporary tectonic stress field according to the theory of rock strength and the principle and method of rock fracture mechanics, the authors tentatively investigated the earthquakes induced by pore-water pressure in rock and obtained the initial results as follows: ( 1 ) One type of induced earthquake may occur in the case of larger tectonic stress on such weak planes that strike in similar orientation of principle tectonic compressional stress in the shallows of the rock mass; the pore-water pressure σp may generate tensile fracture on them and induce small earthquakes; (2) Two types of induced earthquake may occur in the case of larger tectonic stress, i.e., ① on such weakness planes that strike in similar orientation of principle tectonic compressioual stress, σ1, in the shallows of the rockmass, the pore-water pressure, σp, may generate tensile fracture on them and induce small earthquakes; ② When the tectonic stress approximates the shear strength of the fracture, the pore-water pressure σp may reduce the normal stress, σn, on the fracture face causing failure of the originally stable fracture,producing gliding fracture and thus inducing an earthquake. σp may also increase the fracture depth, leading to an induced earthquake with the magnitude larger than the previous potential magnitude; (3) There is a depth limit for each type of rock mass, and no induced earthquake will occur beyond this limit.

  10. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.


    ... 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...

  11. Anaerobic Biodegradation of Ethylene Glycol within Hydraulic Fracturing Fluid

    Heyob, K. M.; Mouser, P. J.


    Ethylene glycol (EG) is a commonly used organic additive in hydraulic fracturing fluids used for shale gas recovery. Under aerobic conditions, this compound readily biodegrades to acetate and CO2 or is oxidized through the glycerate pathway. In the absence of oxygen, organisms within genera Desulfovibrio, Acetobacterium, and others can transform EG to acetaldehyde, a flammable and suspected carcinogenic compound. Acetaldehyde can then be enzymatically degraded to ethanol or acetate and CO2. However, little is known on how EG degrades in the presence of other organic additives, particularly under anaerobic conditions representative of deep groundwater aquifers. To better understand the fate and attenuation of glycols within hydraulic fracturing fluids we are assessing their biodegradation potential and pathways in batch anaerobic microcosm treatments. Crushed Berea sandstone was inoculated with groundwater and incubated with either EG or a synthetic fracturing fluid (SFF) containing EG formulations. We tracked changes in dissolved organic carbon (DOC), EG, and its transformation products over several months. Approximately 41% of bulk DOC in SFF is degraded within 21 days, with 58% DOC still remaining after 63 days. By comparison, this same SFF degrades by 70% within 25 days when inoculated with sediment-groundwater microbial communities, suggesting that bulk DOC degradation occurs at a slower rate and to a lesser extent with bedrock. Aerobic biodegradation of EG occurs rapidly (3-7 days); however anaerobic degradation of EG is much slower, requiring several weeks for substantial DOC loss to be observed. Ongoing experiments are tracking the degradation pathways of EG alone and in the presence of SFF, with preliminary data showing incomplete glycol transformation within the complex hydraulic fracturing fluid mixture. This research will help to elucidate rates, processes, and pathways for EG biodegradation and identify key microbial taxa involved in its degradation.

  12. Method development for determining the hydraulic conductivity of fractured porous media

    Dixon, Kenneth L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)


    Plausible, but unvalidated, theoretical model constructs for unsaturated hydraulic conductivity of fractured porous media are currently used in Performance Assessment (PA) modeling for cracked saltstone and concrete (Flach 2011). The Nuclear Regulatory Commission (NRC) has expressed concern about the lack of model support for these assumed Moisture Characteristic Curves (MCC) data, as noted in Requests for Additional Information (RAIs) PA-8 and SP-4 (Savannah River Remediation, LLC, 2011). The objective of this task was to advance PA model support by developing an experimental method for determining the hydraulic conductivity of fractured cementitious materials under unsaturated conditions, and to demonstrate the technique on fractured saltstone samples. The task was requested through Task Technical Request (TTR) HLW-SSF-TTR-2012-0016 and conducted in accordance with Task Technical & Quality Assurance Plan (TTQAP) SRNL-TR-2012-00090. Preliminary method development previously conducted by Kohn et al. (2012) identified transient outflow extraction as the most promising method for characterizing the unsaturated properties of fractured porous media. While the research conducted by Kohn et al. (2012) focused on fractured media analogs such as stacked glass slides, the current task focused directly on fractured saltstone. For this task, four sample types with differing fracture geometries were considered: 1) intact saltstone, 2) intact saltstone with a single saw cut, smooth surface fracture, 3) micro-fractured saltstone (induced by oven drying), and 4) micro-fractured saltstone with a single, fully-penetrating, rough-surface fracture. Each sample type was tested initially for saturated hydraulic conductivity following method ASTM D 5084 using a flexible wall permeameter. Samples were subsequently tested using the transient outflow extraction method to determine cumulative outflow as a function of time and applied pressure. Of the four sample types tested, two yielded

  13. The Potential Impacts of Hydraulic Fracturing on Agriculture

    Beng Ong


    Full Text Available 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 locally. Opponents to fracking, however, alleged that the process pollutes the air, contaminates the soil and water, particularly in farming/rural communities. Due to page limitson this paper, we discussed only the potential impacts of hydraulic fracturing on water, and consequently, agriculture. Any impact on agriculture extends beyond the perimeter of a farm or plot of rural land where fracking operations occur. Fruits, vegetables, dairy, and meats from an impacted farming region may be shipped to other parts of the country, or even internationally. Fracking challenges stakeholders to confront the trade-offs between economic development and public health/safety; thus multiple viewpoints and issues were raised.Keywords: Hydraulic Fracking; Environmental Sustainability; Water Contamination; Agriculture vs. Energy; Shale Gas.

  14. Simulation of Hydraulic and Natural Fracture Interaction Using a Coupled DFN-DEM Model

    J. Zhou; H. Huang; M. Deo


    The presence of natural fractures will usually result in a complex fracture network due to the interactions between hydraulic and natural fracture. The reactivation of natural fractures can generally provide additional flow paths from formation to wellbore which play a crucial role in improving the hydrocarbon recovery in these ultra-low permeability reservoir. Thus, accurate description of the geometry of discrete fractures and bedding is highly desired for accurate flow and production predictions. Compared to conventional continuum models that implicitly represent the discrete feature, Discrete Fracture Network (DFN) models could realistically model the connectivity of discontinuities at both reservoir scale and well scale. In this work, a new hybrid numerical model that couples Discrete Fracture Network (DFN) and Dual-Lattice Discrete Element Method (DL-DEM) is proposed to investigate the interaction between hydraulic fracture and natural fractures. Based on the proposed model, the effects of natural fracture orientation, density and injection properties on hydraulic-natural fractures interaction are investigated.

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

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


    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

  16. Analysis of Proppant Hydraulic Fracturing in a Sand Oil Reservoir in Southwest of Iran

    Reza Masoomi; Iniko Bassey; Dolgow Sergie Viktorovich; Hosein Dehghani


    Hydraulic fracturing is one way to increase the productivity of oil and gas wells. One of the most fundamental successes of hydraulic fracturing operation is selecting the proper size and type of proppants which are used during the process. The aim of this study is optimizing the type and size of used propant in hydraulic fracturing operation in a sand oil reservoir in southwest of Iran. In this study sand and ceramic (sintered bauxite) have been considered as proppant type. Also the various ...

  17. Multi-hazard risk assessment applied to hydraulic fracturing operations

    Garcia-Aristizabal, Alexander; Gasparini, Paolo; Russo, Raffaella; Capuano, Paolo


    Without exception, the exploitation of any energy resource produces impacts and intrinsically bears risks. Therefore, to make sound decisions about future energy resource exploitation, it is important to clearly understand the potential environmental impacts in the full life-cycle of an energy development project, distinguishing between the specific impacts intrinsically related to exploiting a given energy resource and those shared with the exploitation of other energy resources. Technological advances as directional drilling and hydraulic fracturing have led to a rapid expansion of unconventional resources (UR) exploration and exploitation; as a consequence, both public health and environmental concerns have risen. The main objective of a multi-hazard risk assessment applied to the development of UR is to assess the rate (or the likelihood) of occurrence of incidents and the relative potential impacts on surrounding environment, considering different hazards and their interactions. Such analyses have to be performed considering the different stages of development of a project; however, the discussion in this paper is mainly focused on the analysis applied to the hydraulic fracturing stage of a UR development project. The multi-hazard risk assessment applied to the development of UR poses a number of challenges, making of this one a particularly complex problem. First, a number of external hazards might be considered as potential triggering mechanisms. Such hazards can be either of natural origin or anthropogenic events caused by the same industrial activities. Second, failures might propagate through the industrial elements, leading to complex scenarios according to the layout of the industrial site. Third, there is a number of potential risk receptors, ranging from environmental elements (as the air, soil, surface water, or groundwater) to local communities and ecosystems. The multi-hazard risk approach for this problem is set by considering multiple hazards

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

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


    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. Determining the spatial altitude of the hydraulic fractures.

    Khamiev, Marsel; Kosarev, Victor; Goncharova, Galina


    Mathematical modeling and numerical simulation are the most widely used approaches for the solving geological problems. They imply software tools which are based on Monte Carlo method. The results of this project presents shows the possibility of using PNL tool to determine fracturing location. The modeled media is a homogeneous rock (limestone) cut by a vertical borehole (d=216 mm) with metal casing 9 mm thick. The cement sheath is 35 mm thick. The borehole is filled with fresh water. The rock mass is cut by crack, filled with a mixture of doped (gadolinium oxide Gd2O3) proppant (75%) and water (25%). A pulse neutron logging (PNL) tool is used for quality control in hydraulic fracturing operations. It includes a fast neutron source (so-called "neutron generator") and a set of thermal (or epithermal) neutron-sensing devices, forming the so-called near (ND) and far (FD) detectors. To evaluate neutron properties various segments (sectors) of the rock mass, the detector must register only neutrons that come from this very formation. It's possible if detecting block includes some (6 for example) thermal neutron detectors arranged circumferentially inside the tool. As a result we get few independent well logs, each accords with define rock sector. Afterwards synthetic logs processing we can determine spatial position of the hydraulic fracture.

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

    Dong, Xin; Lu, Hao; Huang, Houxu; Hao, Yiqing; Xia, Yuanpu


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

    Dong Xin


    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.

  2. Experimental Investigation on the Basic Law of Hydraulic Fracturing After Water Pressure Control Blasting

    Huang, Bingxiang; Li, Pengfeng; Ma, Jian; Chen, Shuliang


    Because of the advantages of integrating water pressure blasting and hydraulic fracturing, the use of hydraulic fracturing after water pressure control blasting is a method that is used to fully transform the structure of a coal-rock mass by increasing the number and range of hydraulic cracks. An experiment to study hydraulic fracturing after water pressure blasting on cement mortar samples (300 × 300 × 300 mm3) was conducted using a large-sized true triaxial hydraulic fracturing experimental system. A traditional hydraulic fracturing experiment was also performed for comparison. The experimental results show that water pressure blasting produces many blasting cracks, and follow-up hydraulic fracturing forces blasting cracks to propagate further and to form numerous multidirectional hydraulic cracks. Four macroscopic main hydraulic cracks in total were noted along the borehole axial and radial directions on the sample surfaces. Axial and radial main failure planes induced by macroscopic main hydraulic cracks split the sample into three big parts. Meanwhile, numerous local hydraulic cracks were formed on the main failure planes, in different directions and of different types. Local hydraulic cracks are mainly of three types: local hydraulic crack bands, local branched hydraulic cracks, and axial layered cracks. Because local hydraulic cracks produce multiple local layered failure planes and lamellar ruptures inside the sample, the integrity of the sample decreases greatly. The formation and propagation process of many multidirectional hydraulic cracks is affected by a combination of water pressure blasting, water pressure of fracturing, and the stress field of the surrounding rock. To a certain degree, the stress field of surrounding rock guides the formation and propagation process of the blasting crack and the follow-up hydraulic crack. Following hydraulic fracturing that has been conducted after water pressure blasting, the integrity of the sample is found to

  3. Hydraulic fracturing water use variability in the United States and potential environmental implications

    Gallegos, Tanya J.; Varela, Brian A.; Haines, Seth S.; Engle, Mark A.


    Abstract Until now, up‐to‐date, comprehensive, spatial, national‐scale data on hydraulic fracturing water volumes have been lacking. Water volumes used (injected) to hydraulically fracture over 263,859 oil and gas wells drilled between 2000 and 2014 were compiled and used to create the first U.S. map of hydraulic fracturing water use. Although median annual volumes of 15,275 m3 and 19,425 m3 of water per well was used to hydraulically fracture individual horizontal oil and gas wells, respecti...

  4. A maximum likelihood estimator for bedrock fracture transmissivities and its application to the analysis and design of borehole hydraulic tests

    West, Anthony C. F.; Novakowski, Kent S.; Gazor, Saeed


    We propose a new method to estimate the transmissivities of bedrock fractures from transmissivities measured in intervals of fixed length along a borehole. We define the scale of a fracture set by the inverse of the density of the Poisson point process assumed to represent their locations along the borehole wall, and we assume a lognormal distribution for their transmissivities. The parameters of the latter distribution are estimated by maximizing the likelihood of a left-censored subset of the data where the degree of censorship depends on the scale of the considered fracture set. We applied the method to sets of interval transmissivities simulated by summing random fracture transmissivities drawn from a specified population. We found the estimated distributions compared well to the transmissivity distributions of similarly scaled subsets of the most transmissive fractures from among the specified population. Estimation accuracy was most sensitive to the variance in the transmissivities of the fracture population. Using the proposed method, we estimated the transmissivities of fractures at increasing scale from hydraulic test data collected at a fixed scale in Smithville, Ontario, Canada. This is an important advancement since the resultant curves of transmissivity parameters versus fracture set scale would only previously have been obtainable from hydraulic tests conducted with increasing test interval length and with degrading equipment precision. Finally, on the basis of the properties of the proposed method, we propose guidelines for the design of fixed interval length hydraulic testing programs that require minimal prior knowledge of the rock.

  5. Physical-chemical evaluation of hydraulic fracturing chemicals in the context of produced water treatment.

    Camarillo, Mary Kay; Domen, Jeremy K; Stringfellow, William T


    Produced water is a significant waste stream that can be treated and reused; however, the removal of production chemicals-such as those added in hydraulic fracturing-must be addressed. One motivation for treating and reusing produced water is that current disposal methods-typically consisting of deep well injection and percolation in infiltration pits-are being limited. Furthermore, oil and gas production often occurs in arid regions where there is demand for new water sources. In this paper, hydraulic fracturing chemical additive data from California are used as a case study where physical-chemical and biodegradation data are summarized and used to screen for appropriate produced water treatment technologies. The data indicate that hydraulic fracturing chemicals are largely treatable; however, data are missing for 24 of the 193 chemical additives identified. More than one-third of organic chemicals have data indicating biodegradability, suggesting biological treatment would be effective. Adsorption-based methods and partitioning of chemicals into oil for subsequent separation is expected to be effective for approximately one-third of chemicals. Volatilization-based treatment methods (e.g. air stripping) will only be effective for approximately 10% of chemicals. Reverse osmosis is a good catch-all with over 70% of organic chemicals expected to be removed efficiently. Other technologies such as electrocoagulation and advanced oxidation are promising but lack demonstration. Chemicals of most concern due to prevalence, toxicity, and lack of data include propargyl alcohol, 2-mercaptoethyl alcohol, tetrakis hydroxymethyl-phosphonium sulfate, thioglycolic acid, 2-bromo-3-nitrilopropionamide, formaldehyde polymers, polymers of acrylic acid, quaternary ammonium compounds, and surfactants (e.g. ethoxylated alcohols). Future studies should examine the fate of hydraulic fracturing chemicals in produced water treatment trains to demonstrate removal and clarify interactions

  6. Hydraulic Fracturing, Wastewater Injection and Unintended Earthquakes (Invited)

    Ellsworth, W. L.


    It has long been known that increasing the pore pressure within a pre-stressed fault can induce an earthquake by reducing the effective normal stress and thereby the frictional strength of the fault. Underground fluid pressures are routinely modified by a wide range of industrial activities including impoundment of reservoirs, mining, and petroleum production, all of which are known to have potential for inducing earthquakes. Recently, attention has been drawn to the earthquake hazard associated with the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. In this talk, I review recent investigations of both activities with a focus on the emerging understanding of the development of predictive models for both seismicity and risk. By design, hydraulic fracturing induces numerous high-frequency microseismic events as part of the process of creating a connected fracture network to enhance formation permeability. During the brief time (hours) that high fluid pressure is applied to the well bore, seismic events occur as a combination tensile (hydrofracture) and shear (hydroshear) failures. The fluid volume injected in a single hydrofrac stage is commonly of the order of several thousand cubic meters. Growth of the fracture network typically follows square-root scaling with time, suggesting a diffusive growth mechanism. Magnitudes are normally below zero for events in the target formation. Larger, unintended events sometimes occur and available evidence points to shear failure of pre-existing faults as their source. Earthquakes with magnitudes as large as Mw 3.6 occurred during hydraulic fracturing operations in the Horn River Basin, B. C., Canada. Some of these occurred before the diffusive pressure front would have reached the hypocenter, suggesting rapid transmission of pore

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

    Zhaohui Chong


    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

  8. Simulations of hydraulic fracturing and leakage in sedimentary basins

    Lothe, Ane Elisabeth


    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

  9. Simulations of hydraulic fracturing and leakage in sedimentary basins

    Lothe, Ane Elisabeth


    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

  10. Implicit level set algorithms for modelling hydraulic fracture propagation.

    Peirce, A


    Hydraulic fractures are tensile cracks that propagate in pre-stressed solid media due to the injection of a viscous fluid. Developing numerical schemes to model the propagation of these fractures is particularly challenging due to the degenerate, hypersingular nature of the coupled integro-partial differential equations. These equations typically involve a singular free boundary whose velocity can only be determined by evaluating a distinguished limit. This review paper describes a class of numerical schemes that have been developed to use the multiscale asymptotic behaviour typically encountered near the fracture boundary as multiple physical processes compete to determine the evolution of the fracture. The fundamental concepts of locating the free boundary using the tip asymptotics and imposing the tip asymptotic behaviour in a weak form are illustrated in two quite different formulations of the governing equations. These formulations are the displacement discontinuity boundary integral method and the extended finite-element method. Practical issues are also discussed, including new models for proppant transport able to capture 'tip screen-out'; efficient numerical schemes to solve the coupled nonlinear equations; and fast methods to solve resulting linear systems. Numerical examples are provided to illustrate the performance of the numerical schemes. We conclude the paper with open questions for further research. This article is part of the themed issue 'Energy and the subsurface'.

  11. Sulfide Generation by Dominant Halanaerobium Microorganisms in Hydraulically Fractured Shales

    Booker, Anne E.; Borton, Mikalya; Daly, Rebecca; Welch, Susan; Nicora, Carrie D.; Hoyt, David W.; Wilson, Travis; Purvine, Samuel O.; Wolfe, Richard; Sharma, Shihka; Mouser, Paula J.; Cole, David R.; Lipton, Mary S.; Wrighton, Kelly C.; Wilkins, Michael J.


    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 of Halanaerobium strains within the in situ microbial community and the potential for these microor- ganisms to catalyze thiosulfate-dependent sulfidogenesis. From these field data, we investigated biogenic sulfide production catalyzed by a Halanaerobium strain iso- lated from the produced fluids using proteogenomics and laboratory growth experi- ments. Analysis of Halanaerobium isolate 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 sul- fide. Shotgun proteomics measurements using a Halanaerobium isolate verified that these proteins were more abundant when thiosulfate was present in the growth medium, and culture-based assays identified thiosulfate-dependent sulfide produc- tion by the same isolate. Increased production of sulfide and organic acids during the stationary growth phase suggests that fermentative Halanaerobium uses thiosul- fate 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 diagnos- tics.

  12. Technology and means of a coal seam interval hydraulic fracturing for the seam degassing intensification

    Klishin, VI; Opruk, GY; Tatsienko, AL


    Interval hydraulic fracturing use for the seam degassing intensification actuality is explained. The known methods of degassing are reviewed. Technological scheme of the interval coal seam hydraulic fracturing implementation is worked out. The equipment to fulfill degassing intensification measures is suggested.

  13. Characterization of Hydraulic Fracture with Inflated Dislocation Moving Within a Semi-infinite Medium

    OUYANG Zhi-hua; ELSWORTH Derek; LI Qiang


    Hydraulic fracturing is accompanied by a change in pore fluid pressure. As a result, this may be conveniently represented as inflated dislocation moving within a semi-infinite medium. Theory is developed to describe the pore pressures that build up around an inflated volumetric dislocation migrating within a saturated porous-elastic semi-infinite medium as analog to hydraulic fracturing emplacement. The solution is capable of evaluating the system behavior of both constant fluid pressure and zero flux surface conditions through application of a superposition. Characterization of horizontal moving dislocation processes is conducted as an application of these techniques. Where the mechanical and hydraulic parameters are defined, a priori, type curve matching of responses may be used to evaluate emplacement location uniquely. Pore pressure response elicited at a dilation, subject to pressure control is of interest in representing hydraulic fracturing where leak-off is an important component. The effect of hydraulic fracturing on fracture fluid pressure is evaluated in a poroelastic hydraulic fracture model utilizing dislocation theory. A minimum set of dimensionless parameters are defined that describe the system. Pore fluid pressures recorded during hydraulic fracturing of a well in the San Joaquin Valley of Central California is examined using the proposed model. The estimated geometry of the hydraulic fracture is matched with reasonable fidelity with the measured data.

  14. Hydraulic fracturing water use variability in the United States and potential environmental implications

    Gallegos, Tanya J.; Varela, Brian A.; Haines, Seth S.; Engle, Mark A.


    Until now, up-to-date, comprehensive, spatial, national-scale data on hydraulic fracturing water volumes have been lacking. Water volumes used (injected) to hydraulically fracture over 263,859 oil and gas wells drilled between 2000 and 2014 were compiled and used to create the first U.S. map of hydraulic fracturing water use. Although median annual volumes of 15,275 m3 and 19,425 m3 of water per well was used to hydraulically fracture individual horizontal oil and gas wells, respectively, in 2014, about 42% of wells were actually either vertical or directional, which required less than 2600 m3 water per well. The highest average hydraulic fracturing water usage (10,000−36,620 m3 per well) in watersheds across the United States generally correlated with shale-gas areas (versus coalbed methane, tight oil, or tight gas) where the greatest proportion of hydraulically fractured wells were horizontally drilled, reflecting that the natural reservoir properties influence water use. This analysis also demonstrates that many oil and gas resources within a given basin are developed using a mix of horizontal, vertical, and some directional wells, explaining why large volume hydraulic fracturing water usage is not widespread. This spatial variability in hydraulic fracturing water use relates to the potential for environmental impacts such as water availability, water quality, wastewater disposal, and possible wastewater injection-induced earthquakes.

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

    Yong Sheng


    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.

  16. Hydraulic fracturing water use variability in the United States and potential environmental implications

    Gallegos, Tanya J.; Varela, Brian A.; Haines, Seth S.; Engle, Mark A.


    Until now, up-to-date, comprehensive, spatial, national-scale data on hydraulic fracturing water volumes have been lacking. Water volumes used (injected) to hydraulically fracture over 263,859 oil and gas wells drilled between 2000 and 2014 were compiled and used to create the first U.S. map of hydraulic fracturing water use. Although median annual volumes of 15,275 m3 and 19,425 m3 of water per well was used to hydraulically fracture individual horizontal oil and gas wells, respectively, in 2014, about 42% of wells were actually either vertical or directional, which required less than 2600 m3 water per well. The highest average hydraulic fracturing water usage (10,000-36,620 m3 per well) in watersheds across the United States generally correlated with shale-gas areas (versus coalbed methane, tight oil, or tight gas) where the greatest proportion of hydraulically fractured wells were horizontally drilled, reflecting that the natural reservoir properties influence water use. This analysis also demonstrates that many oil and gas resources within a given basin are developed using a mix of horizontal, vertical, and some directional wells, explaining why large volume hydraulic fracturing water usage is not widespread. This spatial variability in hydraulic fracturing water use relates to the potential for environmental impacts such as water availability, water quality, wastewater disposal, and possible wastewater injection-induced earthquakes.

  17. Simulation of Hydraulic Fracture in Unsaturated Soils with High Degree of Saturation

    Tielin Chen


    Full Text Available A numerical simulation approach of hydraulic fracture process, considering the couplings of the stress distribution, the fluid flow of the water-air mixture, the compression and dissolution of air, and the element damage evolution, has been developed to investigate the mechanisms of crack initiation and propagation in porous media during hydraulic fracturing. The concept of homogenized pore fluid has been adopted to represent the water air mixture. A large number of numerical analysis on hydraulic fracturing in clay with incipient injection slot have been carried out to study the mechanism of hydraulic fracturing in unsaturated soil with the characteristic of critical model I type of crack loading using stress intensity factor KIc. The results provide a numerical picture depicting the mechanisms of crack initiation and propagation during hydraulic fracturing. The numerical results are in good agreement with the experimental results, which confirms the adequacy and the power of the numerical approach.

  18. Solution of hydraulic fracture problem accounting for lag

    Linkov, Alexander M


    The paper presents a method for solving hydraulic fracture problems accounting for the lag. The method consists in matching the outer (basic) solution neglecting the lag, with the inner (auxiliary) solution of the derived 1D integral equation with conditions, accounting for the lag and asymptotic behavior of the opening and the net-pressure. The method refers to practically important cases, when the influence of the local perturbation, caused by the lag, becomes insignificant at a distance, where the leading plane-state asymptotics near the fracture front is still applicable. The universal asymptotics are used for finding the matching constants of the basic (outer) solution and for formulation of matching condition for the solution of inner (auxiliary) problem. The method is illustrated by the solution of the Spence and Sharp plane-strain problem for a fracture propagating symmetrically from the inlet, where a Newtonian fluid is pumped at a constant rate. It is stated that the method developed for deep fractu...

  19. In-situ stress from hydraulic fracture measurements in G Tunnel, Nevada Test Site

    Smith, C.; Vollendorf, W. C.; Warren, W. E.


    Hydraulic fracture work in G Tunnel, Nevada Test Site, performed to obtain the in-situ stress state is discussed. Field equipment and procedures are described; analysis is developed to relate the hydraulic fracture pressures to the in-situ stress state. Pressure data are analyzed to provide estimates of the stress state at a number of locations in the tunnel complex. A unique feature of the work is the mineback - a mining process in which the rock is cut away to reveal the actual plane of the fracture. Advantages, limitations, and problem areas associated with extracting in-situ stress fields from hydraulic fracture pressure records are discussed in detail.

  20. Analysis of Proppant Hydraulic Fracturing in a Sand Oil Reservoir in Southwest of Iran

    Reza Masoomi


    Full Text Available Hydraulic fracturing is one way to increase the productivity of oil and gas wells. One of the most fundamental successes of hydraulic fracturing operation is selecting the proper size and type of proppants which are used during the process. The aim of this study is optimizing the type and size of used propant in hydraulic fracturing operation in a sand oil reservoir in southwest of Iran. In this study sand and ceramic (sintered bauxite have been considered as proppant type. Also the various types of resin-coated sand and resin-coated ceramic have been considered. Then the various scenarios have been designed to optimize the size and type of proppant used in hydraulic fracturing in a sand oil reservoir in southwest of Iran. Also in this study increasing the cumulative oil recovery in fractured and Non-fractured wells in a sand oil reservoir in southwest of Iran have been investigated.

  1. 77 FR 36273 - Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using...


    ... AGENCY Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using... agency has developed on the use of diesel fuels in oil and gas hydraulic fracturing and to solicit input... discuss ``Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel...

  2. Hydraulic Fracture Propagation Through an Orthogonal Discontinuity: A Laboratory, Analytical and Numerical Study

    Llanos, Ella María; Jeffrey, Robert G.; Hillis, Richard; Zhang, Xi


    Rocks are naturally fractured, and lack of knowledge of hydraulic fracture growth through the pre-existing discontinuities in rocks has impeded enhancing hydrocarbon extraction. This paper presents experimental results from uniaxial and biaxial tests, combined with numerical and analytical modelling results to develop a criterion for predicting whether a hydraulic fracture will cross a discontinuity, represented at the laboratory by unbonded machined frictional interfaces. The experimental results provide the first evidence for the impact of viscous fluid flow on the orthogonal fracture crossing. The fracture elliptical footprint also reflects the importance of both the applied loading stress and the viscosity in fracture propagation. The hydraulic fractures extend both in the direction of maximum compressive stress and in the direction with discontinuities that are arranged to be normal to the maximum compressive stress. The modelling results of fracture growth across discontinuities are obtained for the locations of slip starting points in initiating fracture crossing. Our analysis, in contrast to previous work on the prediction of frictional crossing, includes the non-singular stresses generated by the finite pressurised hydraulic fracture. Experimental and theoretical outcomes herein suggest that hydraulic fracture growth through an orthogonal discontinuity does not depend primarily on the interface friction coefficient.

  3. Organic compounds in hydraulic fracturing fluids and wastewaters: A review.

    Luek, Jenna L; Gonsior, Michael


    High volume hydraulic fracturing (HVHF) of shale to stimulate the release of natural gas produces a large quantity of wastewater in the form of flowback fluids and produced water. These wastewaters are highly variable in their composition and contain a mixture of fracturing fluid additives, geogenic inorganic and organic substances, and transformation products. The qualitative and quantitative analyses of organic compounds identified in HVHF fluids, flowback fluids, and produced waters are reviewed here to communicate knowledge gaps that exist in the composition of HVHF wastewaters. In general, analyses of organic compounds have focused on those amenable to gas chromatography, focusing on volatile and semi-volatile oil and gas compounds. Studies of more polar and non-volatile organic compounds have been limited by a lack of knowledge of what compounds may be present as well as quantitative methods and standards available for analyzing these complex mixtures. Liquid chromatography paired with high-resolution mass spectrometry has been used to investigate a number of additives and will be a key tool to further research on transformation products that are increasingly solubilized through physical, chemical, and biological processes in situ and during environmental contamination events. Diverse treatments have been tested and applied to HVHF wastewaters but limited information has been published on the quantitative removal of individual organic compounds. This review focuses on recently published information on organic compounds identified in flowback fluids and produced waters from HVHF. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    Kim, Jihoon; Um, Evan; Moridis, George


    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

  5. A National Assessment of the Potential Impacts of Hydraulic Fracturing Activities on Drinking Water Resources

    Ridley, C.; Burden, S.; Fleming, M. M.; Knightes, C. D.; Koplos, J.; LeDuc, S. D.; Ring, S.; Stanek, J.; Tuccillo, M. E.; Weaver, J.; Frithsen, J.


    The U.S. Environmental Protection Agency recently released a draft assessment of the potential impacts of hydraulic fracturing on drinking water resources. As part of the draft assessment, we reviewed, analyzed, and synthesized information from over 950 sources and concluded that there are above and below ground mechanisms by which hydraulic fracturing activities have the potential to impact drinking water resources. These mechanisms include: Water withdrawals in times of, or in areas with, low water availability; Spills of hydraulic fracturing fluids and produced water; Fracturing directly into underground drinking water resources; Below ground migration of liquids and gases; and Inadequate treatment and discharge of wastewater. Of the potential mechanisms identified in this report, we found specific instances where one or more mechanisms led to impacts on drinking water resources, including contamination of drinking water wells. The number of identified cases, however, was small compared to the number of hydraulically fractured wells. This finding could reflect a rarity of effects on drinking water resources, but may also be due to other limiting factors. These factors include: insufficient pre- and post-fracturing data on the quality of drinking water resources; the paucity of long-term systematic studies; the presence of other sources of contamination precluding a definitive link between hydraulic fracturing activities and an impact; and the inaccessibility of some information on hydraulic fracturing activities and potential impacts. Disclaimer: The views expressed are those of the authors and do not necessarily reflect the views or polices of the EPA.

  6. The Shear Mechanisms of Natural Fractures during the Hydraulic Stimulation of Shale Gas Reservoirs

    Zhaobin Zhang


    Full Text Available The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of fractures. Both a single fracture and a complex fracture network are used to investigate the shear mechanisms. The investigation based on a single fracture shows that the non-ignorable shearing length of a natural fracture could be formed before the natural fracture is filled by pressurized fluid. Therefore, for the hydraulic fracturing treatment of the naturally fractured shale gas reservoirs, the shear strength of shale is generally more important than the tensile strength. The fluid-rock coupling propagation processes of a complex fracture network are simulated under different crustal stress conditions and the results agree well with those of the single fracture. The propagation processes of complex fracture network show that a smaller crustal stress difference is unfavorable to the shearing of natural fractures, but is favorable to the formation of complex fracture network.

  7. Influence of pore pressure to the development of a hydraulic fracture in poroelastic medium

    Golovin, Sergey V


    In this paper we demonstrate the influence of the pore pressure to the development of a hydraulically-driven fracture in a poroelastic medium. We present a novel numerical model for propagation of a planar hydraulic fracture and prove its correctness by demonstration of the numerical convergence and by comparison with known solutions. The advantage of the algorithm is that it does not require the distinguishing of the fracture's tips and reconstruction of the numerical mesh according to the fracture propagation. Next, we perform a thorough analysis of the interplay of fluid filtration and redistribution of stresses near the fracture. We demonstrate that the fracture length decreases with the increase of the Biot's number (the parameter that determines the contribution of the pore pressure to the stress) and explain this effect by analysing the near-fracture pore pressure, rock deformation and stresses. We conclude, that the correct account for the fluid exchange between the fracture and the rock should be bas...

  8. Fracturing Fluid Characterization Facility (FFCF): Recent advances

    Shah, S.N.; Fagan, J.E.


    The objectives of this project are: (1)Investigate fluid rheological behavior, dynamic fluid leak-off behavior, and proppant transport characteristics of various fracturing fluids used for stimulating oil and gas bearing formations. (2) Develop new information for characterizing the behavior of fracturing fluids under conditions more representative of the behavior in actual fractures. (3) Continue utilizing the advanced capabilities of the high pressure simulator (HPS) to perform near-term research and development activities and not to construct a large-scale simulator that was proposed originally. This paper describes equipment enhancements, data acquisition and instrumentation upgrades, R&D test results, and future research planned for the Fracturing Fluid Characterization Facility.

  9. Optimization of Multiple Hydraulically Fractured Horizontal Wells in Unconventional Gas Reservoirs

    Wei Yu


    Full Text Available Accurate placement of multiple horizontal wells drilled from the same well pad plays a critical role in the successful economical production from unconventional gas reservoirs. However, there are high cost and uncertainty due to many inestimable and uncertain parameters such as reservoir permeability, porosity, fracture spacing, fracture half-length, fracture conductivity, gas desorption, and well spacing. In this paper, we employ response surface methodology to optimize multiple horizontal well placement to maximize Net Present Value (NPV with numerically modeling multistage hydraulic fractures in combination with economic analysis. This paper demonstrates the accuracy of numerical modeling of multistage hydraulic fractures for actual Barnett Shale production data by considering the gas desorption effect. Six uncertain parameters, such as permeability, porosity, fracture spacing, fracture half-length, fracture conductivity, and distance between two neighboring wells with a reasonable range based on Barnett Shale information, are used to fit a response surface of NPV as the objective function and to finally identify the optimum design under conditions of different gas prices based on NPV maximization. This integrated approach can contribute to obtaining the optimal drainage area around the wells by optimizing well placement and hydraulic fracturing treatment design and provide insight into hydraulic fracture interference between single well and neighboring wells.

  10. Optimization of Hydraulic Fracturing Fluid System in a Sand Oil Reservoir in Southwest of Iran

    Reza Masoomi


    Full Text Available Fracturing fluid is one of the most important components of a hydraulic fracturing operation. Currently a lot of fluids are available for hydraulic fracturing. In order to selecting the most appropriate fracturing fluid for oil and gas wells with special characteristics, should be well understood fluid properties and should be informed about how changes in fluid properties to achieve the desired results. The aim of this study is optimization of viscosity and gel concentration in water base and foam base fluids which are used in hydraulic fracturing process in a sand oil reservoir in southwest of Iran. For this purpose various scenarios have been designed for various kinds of water base fluids and foam base fluids. Then the cumulative oil production has been estimated versus time and fracture half length. In addition the final required fracturing fluid and proppant have been determined for hydraulic fracturing in studied reservoir. Also in this study increasing the cumulative oil recovery in fractured and Non-fractured wells in a sand oil reservoir in southwest of Iran have been investigated.

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

    Zhiheng Zhao


    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.

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

    Cong Wang


    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.

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

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


    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.

  14. EPA Releases Draft Assessment on the Potential Impacts to Drinking Water Resources from Hydraulic Fracturing Activities

    WASHINGTON-The Environmental Protection Agency (EPA) is releasing a draft assessment today on the potential impacts of hydraulic fracturing activities on drinking water resources in the United States. The assessment, done at the request of Congress, shows

  15. Advanced Hydraulic Studies on Enhancing Particle Removal

    He, Cheng

    The removal of suspended solids and attached pollutants is one of the main treatment processes in wastewater treatment. This thesis presents studies on the hydraulic conditions of various particle removal facilities for possible ways to increase their treatment capacity and performance by utilizing...... and improving hydraulic conditions. Unlike most traditional theses which usually focus only on one particular subject of study, this thesis contains four relatively independent studies which cover the following topics: a newly proposed particle settling enhancement plate, the redesign of the inlet zone......, introduction and conclusions as well as the study results. All studies were carried out with a combination of numerical model and measurements. In the first part of the thesis a new concept of using a vortex to increase particle removal from liquid was proposed and the new particle settling enhancement plates...

  16. Characterisation of hydraulic fractures in limestones using X-ray microtomography

    Renard, Francois; Desrues, Jacques; Plougonven, Erwan; Ougier-Simonin, Audrey


    Hydraulic tension fractures were produced in porous limestones using a specially designed hydraulic cell. The 3D geometry of the samples was imaged using X-ray computed microtomography before and after fracturation. Using these data, it was possible to estimate the permeability tensor of the core samples, extract the path of the rupture and compare it to the heterogeneities initially present in the rock.

  17. Selective oxidation of bromide in wastewater brines from hydraulic fracturing.

    Sun, Mei; Lowry, Gregory V; Gregory, Kelvin B


    Brines generated from oil and natural gas production, including flowback water and produced water from hydraulic fracturing of shale gas, may contain elevated concentrations of bromide (~1 g/L). Bromide is a broad concern due to the potential for forming brominated disinfection byproducts (DBPs) during drinking water treatment. Conventional treatment processes for bromide removal is costly and not specific. Selective bromide removal is technically challenging due to the presence of other ions in the brine, especially chloride as high as 30-200 g/L. This study evaluates the ability of solid graphite electrodes to selectively oxidize bromide to bromine in flowback water and produced water from a shale gas operation in Southwestern PA. The bromine can then be outgassed from the solution and recovered, as a process well understood in the bromine industry. This study revealed that bromide may be selectively and rapidly removed from oil and gas brines (~10 h(-1) m(-2) for produced water and ~60 h(-1) m(-2) for flowback water). The electrolysis occurs with a current efficiency between 60 and 90%, and the estimated energy cost is ~6 kJ/g Br. These data are similar to those for the chlor-alkali process that is commonly used for chlorine gas and sodium hydroxide production. The results demonstrate that bromide may be selectively removed from oil and gas brines to create an opportunity for environmental protection and resource recovery.

  18. Primary factors governing hydraulic fractures in heterogeneous stratified porous formations

    Cleary, M.P.


    Some primary material, macrostructural and tectonic features of typical geological formations are identified, insofar as they affect the hydraulic fracturing operation whereby suitably treated fluid is pumped into massive crack(s) underground: the retardation or channeling due to strata interfaces, discontinuities and other heterogeneities is roughly characterized, in the context of fully three-dimensional crack shape evolution, and the initiation from oriented boreholes is discussed in detail. A general-purpose numerical scheme is described, efficiently based on a physically transparent distribution of discontinuity multipoles (or dislocations) and the solution of resulting singular integral equations, which permits precise quantification of these effects: in particular, the barriers provided by adjacent stiffer and tougher strata are properly rationalized and the roles of inelastic slippage, blunting, branching, arrest, and re-initiation are placed in more transparent perspective. Stabilization effects due to alterations of pore-fluid pressure (and hence effective decohering stress), or the flux of formation fluid into the open region near to the crack tip, are described as potentially unfavorable for hydrofrac containment. However, the dominant time-dependent mechanism of frac fluid penetration into the narrow crack aperture attracts most attention: this process is very naturally and tractably incorporated in our comprehensive numerical formulation so that realistic simulation of actual field operations should be feasible in the near future.


    Wojciech Cel


    Full Text Available Poland, due to the estimated shale gas deposits amounting to 346-768 billion m3 has become one of the most attractive regions for shale gas exploration in Europe. Throughout the period 2010-2015, 72 exploratory drillings have been made (as of 4.01.2016 while hydraulic fracturing was carried out 25 times. Employing new drilling and shale gas prospecting technologies raises a question pertaining to their impact on the environment. The number of chemical compounds used (approximately 2000 for the production of new technological fluids may potentially pollute the environment. The fact that the composition of these fluids remains undisclosed hinders the assessment of their impact on the environment and devising optimal methods for managing this type of waste. The presented work indicates the chemical compounds which may infiltrate to groundwater, identified on the basis of technological fluids characteristics, as well as the review of studies pertaining to their impact on potable water carried out in the United States. The study focused on marking heavy metals, calcium, sodium, magnesium, potassium, chlorides and sulphates in the surface waters collected in proximity of Lewino well.

  20. Texas review of hydraulic fracturing water use and consumption

    Nicot, J.; Reedy, R. C.; Costley, R.


    Hydraulic fracturing (HF) has a long history in the state of Texas where are located (1) several established plays, such as the Barnett Shale, (2) plays of recent interest, such as the Eagle Ford or the Wolfcamp, and (3) older plays being revisited such as the Wolfberry or the Granite Wash. We compiled current water use for year 2011 (about 82,000 acre-feet) and compared it to an older analysis done for year 2008 (about 36,000 acre-feet). A private database compiling state information and providing water use is complemented by a survey of the industry. Industry survey is the only way to access fresh water consumption estimated to be only a fraction of the total water use because of reuse of flowback water, use of recycled water from treatment plants and produced water, and use of brackish water. We analyzed these different components of the HF budget as well as their source, surface water vs. groundwater, with a focus on impacts on aquifers and groundwater resources.


    David S. Schechter


    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.

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

    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)


    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.

  3. A fully-coupled geomechanics and flow model for hydraulic fracturing and reservoir engineering applications

    Charoenwongsa, S.; Kazemi, H.; Miskimins, J.; Fakcharoenphol [Colorado School of Mines, Golden, CO (United States)


    A fully coupled geomechanics flow model was used to assess how the changes in pore pressure and temperature influence rock stresses in tight gas reservoirs. The finite difference method was used to develop simulations for phases, components, and thermal stresses. A wave component was used to model the propagation of the strain displacement front as well as changes in stress with time. Fluid and heat flow volumes were modelled separately from rock formation properties. The influence of hydraulic fracturing on stress distributions surrounding the fracture was investigated as well as the effect of filter cake and filtrate. Results of the study showed that significant changes in shear stresses near hydraulic fractures occur as a result of hydraulic fracture face displacement perpendicular to the fracture face. While temperature effects also caused changes in stress distributions, changes in pore pressure did not significantly impact shear stresses as the filtrate did not travel very far into the reservoir. 17 refs., 17 figs.

  4. Energy Release Rate in hydraulic fracture: can we neglect an impact of the hydraulically induced shear stress?

    Wrobel, Michal; Piccolroaz, Andrea


    A novel hydraulic fracture (HF) formulation is introduced which accounts for the hydraulically induced shear stress at the crack faces. It utilizes a general form of the elasticity operator alongside a revised fracture propagation condition based on the critical value of the energy release rate. It is shown that the revised formulation describes the underlying physics of HF in a more accurate way and is in agreement with the asymptotic behaviour of the linear elastic fracture mechanics. A number of numerical simulations by means of the universal HF algorithm previously developed in Wrobel & Mishuris (2015) are performed in order to: i) compare the modified HF formulation with its classic counterpart and ii) investigate the peculiarities of the former. Computational advantages of the revised HF model are demonstrated. Asymptotic estimations of the main solution elements are provided for the cases of small and large toughness. The modified formulation opens new ways to analyse the physical phenomenon of HF ...

  5. Comparison of Measured and Modelled Hydraulic Conductivities of Fractured Sandstone Cores

    Baraka-Lokmane, S.; Liedl, R.; Teutsch, G.

    - A new method for characterising the detailed fracture geometry in sandstone cores is presented. This method is based on the impregnation of samples with coloured resin, without significant disturbance of the fractures. The fractures are made clearly visible by the resin, thus allowing the fracture geometry to be examined digitally. In order to model the bulk hydraulic conductivity, the samples are sectioned serially perpendicular to the flow direction. The hydraulic conductivity of individual sections is estimated by summing the contribution of the matrix and each fracture from the digital data. Finally, the hydraulic conductivity of the bulk sample is estimated by a harmonic average in series along the flow path. Results of this geometrical method are compared with actual physical conductivity values measured from fluid experiments carried out prior to sectioning. The predicted conductivity from the fracture geometry parameters (e.g., fracture aperture, fracture width, fracture length and fracture relative roughness all measured using an optical method) is in good agreement with the independent physical measurements, thereby validating the approach.

  6. An Experimental Investigation of Hydraulic Jet Fracturing Technology with Coiled Tubing


    To solve the increasingly serious problem of "many wells, but low productivity" in China, the hydraulic jetting fracturing technology with coiled tubing, as a new measure for effectively improving the production rate of individual well and enhancing oil and gas recovery, merits much attention nowa- days. On the basis of study of the hydraulic jetting fracturing mechanism with coiled tubing and numerical simulation of pressure distribution inside the pores, the mechanism of pressure rise inside the pores caused by the pressure boost action within the jetting pore and the hydraulic isolation action is examined, and the influence of main parameters on the pressure distribution inside the pores is analyzed. 3 kinds of operating methods of hydraulic jetting fracturing with coiled tubing are raised with the tubular diameter of coiled tub- ing as an important feature parameter. According to the experimental study, the fracturing mechanism and computational resuks of numerical simulation are both examined. It is considered that under the same pres- sure drop of jet nozzle, the pressure inside the pores increases with the confining pressure nearly at a line- ar state. When the vertical depth of the borehole is rather big and the rupture pressure of the formation is higher, it is recommended to use higher pressure drop of jet nozzle for achieving better pressure boost and hydraulic isolation effect. For the hydraulic jetting fracturing with coiled tubing, the coiled tubing with tu- bular diameter not less than 50. 8 mm (2 in. ) is usually used.

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

    Salimzadeh, Saeed; Usui, Tomoya; Paluszny, Adriana


    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...... within the fracture and rock matrix, poroelastic deformation, propagation of the fractures, and fluid leakage into the rock formation. The model is validated against available asymptotic analytical solutions for penny-shaped fractures, in the viscosity-dominated, toughness-dominated, storage......-dominated, and leakoff-dominated regimes. However, for intermediate regimes, these analytical solutions cannot be used to predict the key hydraulic fracturing variables, i.e. injection pressure, fracture aperture, and length. For leakoff-dominated cases in permeable rocks, the asymptotic solutions fail to accurately...

  8. Permeability Enhancement in Enhanced Geothermal System as a result of Hydraulic Fracturing and Jacking

    Jalali, Mohammadreza; Klepikova, Maria; Fisch, Hansruedi; Amann, Florian; Loew, Simon


    A decameter-scale in-situ hydraulic stimulation and circulation (ISC) experiment has been initiated by the newly-founded Swiss Competence Centre for Energy Research - Supply of Electricity (SCCER-SoE) at Nagra's Grimsel Test Site (GTS) as a part of the work-package WP1 of the Deep Underground Laboratory (DUG-Lab) initiative. The experiment area is situated in the southern part of the GTS in a low fracture density volume of the Grimsel granodiorite. The hydraulic properties of the granitic rock mass are supposed to be similar to those expected in the crystalline basement of the alpine foreland where deep enhanced geothermal systems might be developed in future. The main objectives of the multi-disciplinary experiment are to provide a high resolution pre- and post-stimulation characterization of fracture permeability and connectivity, to investigate patterns of preferential flow paths, to describe the pressure propagation during the stimulation phases and to evaluate the efficiency of the fracture-matrix heat exchanger. A comprehensive test & monitoring layout including a fair number of boreholes instrumented with a variety of sensors (e.g. pressure, strain, displacement, temperature, and seismic sensors) is designed to collect detailed data during multiple hydraulic stimulation runs. The diffusion of fluid pressure is expected to be governed mainly by the properties and geometry of the existent fracture network. The hydraulic transmissivity of fractures are in the range of 10-7 to 10-9 m2/s whereas the matrix rock has a very low hydraulic conductivity (K ˜ 10-12 m/s). As part of the stress measurement campaign during the pre-stimulation phase of the ISC experiment, a series of hydraulic fracturing (HF) and hydraulic tests in pre-existing fractures (HTPF) were conducted. The tests were accompanied by micro-seismic monitoring within several observation boreholes to investigate the initiation and propagation of the induced fractures. Together with results from over

  9. Hydraulic fracturing for natural gas: impact on health and environment.

    Carpenter, David O


    Shale deposits exist in many parts of the world and contain relatively large amounts of natural gas and oil. Recent technological developments in the process of horizontal hydraulic fracturing (hydrofracturing or fracking) have suddenly made it economically feasible to extract natural gas from shale. While natural gas is a much cleaner burning fuel than coal, there are a number of significant threats to human health from the extraction process as currently practiced. There are immediate threats to health resulting from air pollution from volatile organic compounds, which contain carcinogens such as benzene and ethyl-benzene, and which have adverse neurologic and respiratory effects. Hydrogen sulfide, a component of natural gas, is a potent neuro- and respiratory toxin. In addition, levels of formaldehyde are elevated around fracking sites due to truck traffic and conversion of methane to formaldehyde by sunlight. There are major concerns about water contamination because the chemicals used can get into both ground and surface water. Much of the produced water (up to 40% of what is injected) comes back out of the gas well with significant radioactivity because radium in subsurface rock is relatively water soluble. There are significant long-term threats beyond cancer, including exacerbation of climate change due to the release of methane into the atmosphere, and increased earthquake activity due to disruption of subsurface tectonic plates. While fracking for natural gas has significant economic benefits, and while natural gas is theoretically a better fossil fuel as compared to coal and oil, current fracking practices pose significant adverse health effects to workers and near-by residents. The health of the public should not be compromized simply for the economic benefits to the industry.

  10. Discrete fracture network modeling of hydraulic stimulation coupling flow and geomechanics

    McClure, Mark


    Discrete Fracture Network Modeling of Hydraulic Stimulation describes the development and testing of a model that couples fluid-flow, deformation, friction weakening, and permeability evolution in large, complex two-dimensional discrete fracture networks.  The model can be used to explore the behavior of hydraulic stimulation in settings where matrix permeability is low and preexisting fractures play an important role, such as Enhanced Geothermal Systems and gas shale.  Used also to describe pure shear stimulation, mixed-mechanism stimulation, or pure opening-mode stimulation. A variety of nov

  11. Numerical simulation of surface and downhole deformation induced by hydraulic fracturing

    He Yi-Yuan; Zhang Bao-Ping; Duan Yu-Ting; Xue Cheng-Jin; Yan Xin; He Chuan; Hu Tian-Yue


    Tiltmeter mapping technology infers hydraulic fracture geometry by measuring fracture-induced rock deformation, which recorded by highly sensitive tiltmeters placed at the surface and in nearby observation wells. By referencing Okada’s linear elastic theory and Green’s function method, we simulate and analyze the surface and downhole deformation caused by hydraulic fracturing using the homogeneous elastic half-space model and layered elastic model. Simulation results suggest that there is not much difference in the surface deformation patterns between the two models, but there is a significant difference in the downhole deformation patterns when hydraulic fracturing penetrates a stratum. In such cases, it is not suitable to assume uniform elastic half-space when calculating the downhole deformation. This work may improve the accuracy and reliability of the inversion results of tiltmeter monitoring data.

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

    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)


    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)

  13. High Resolution Hydraulic Profiling and Groundwater Sampling using FLUTe™ System in a Fractured Limestone Setting

    Janniche, Gry Sander; Christensen, Anders G.; Grosen, Bernt;

    innovative investi-gation methods for characterization of the source zone hydrogeology and contamination, including FLUTe system hydraulic profiling and Water-FLUTe multilevel groundwater sampling, in fractured bryo-zoan limestone bedrock. High resolution hydraulic profiling was conducted in three cored......Characterization of the contaminant source zone architecture and the hydraulics is essential to develop accurate site specific conceptual models, delineate and quantify contaminant mass, perform risk as-sessment, and select and design remediation alternatives. This characterization is particularly...... challeng-ing in deposit types as fractured limestone. The activities of a bulk distribution facility for perchloroe-thene (PCE) and trichloroethene (TCE) at the Naverland site near Copenhagen, Denmark, has resulted in PCE and TCE DNAPL impacts to a fractured clay till and an underlying fractured limestone...

  14. 水溶性减阻剂在页岩气滑溜水压裂中的应用进展%Recent Advances in Water-Soluble Friction Reducers for Slickwater Hydraulic Fracturing Used in Completion of Shale Gas

    张文龙; 伊卓; 杜凯; 祝纶宇; 刘希; 林蔚然


    Slickwater hydraulic fracturing is widely used to improve the efficiency of shale gas exploitation in North America and it also has a broad application prospect in China. The friction reducers are water-soluble polymeric additives which are added to slickwater to reduce friction loss during pumping. In this paper,the mechanism of water-soluble polymeric drag reduction was summed up,and recent progresses in the research of friction reducers,including polysaccharides friction reducers,poly(ethylene oxide) friction reducers and polyacrylamide friction reducer,used in the completion of shale gas were reviewed. The environmentally friendly friction reducers with high drag reduce ability,low damage to shale reservoir and low cost would be the development direction in future.%滑溜水压裂是致密页岩气开采主要采用的增产手段,水溶性减阻剂是滑溜水压裂液中用于降低流体在管道输送过程中所受阻力的化学试剂。介绍了减阻剂的减阻机理,综述了水溶性减阻剂在页岩气滑溜水压裂领域应用的研究进展,包括生物基多糖减阻剂、聚氧化乙烯减阻剂和聚丙烯酰胺类减阻剂在页岩气压裂领域应用的研究现状。对水溶性减阻剂的应用前景进行了展望,减阻性能好、对储层伤害低、环境友好和成本较低廉的减阻剂是未来研究的重点。

  15. 4D synchrotron X-ray imaging to understand porosity development in shales during exposure to hydraulic fracturing fluid

    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.


    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

  16. Directional hydraulic fracturing to control hard-roof rockburst in coal mines

    Fan Jun; Dou Linming; He Hu; Du Taotao; Zhang Shibin; Gui Bing; Sun Xinglin


    Hard roof is the main factor that induces rock-burst.In view of the present obvious weakness of control measures for hard roof rockburst in domestic collieries,the mechanism and field application of directional hydraulic fracturing technology for rock-burst prevention have been investigated in this paper using theoretical analysis and numerical simulation.The results show that the weighting span of the main roof and the released kinetic energy as well as the total elastic energy decreased greatly after the directional fracturing of hard roof with the mining progression,thereby reducing the rockburst hazard degree to coal body.The directional hydraulic fracturing technology was carried out in 6305 working face of Jisan Coal Mine to prevent rockburst.Field practices have proved that this technology is much simpler and safer to operate with better prevention effect compared with blasting.By optimizing the operation procedures and developing a new technology of automated high-pressure delivery pipe,the maximum fracturing radius now reaches more than 9 m and the borehole depth exceeds 20 m.Additionally,drilling cutting method was applied to monitor the stress of the coal mass before and after the fracturing,and the drill cuttings dropped significantly which indicates that the burst prevention effect of directional hydraulic fracturing technology is very remarkable.The research results of this paper have laid a theoretical and practical foundation for the widespread application of the directional hydraulic fracturing technology in China.

  17. IPIRG programs - advances in pipe fracture technology

    Wilkowski, G.; Olson, R.; Scott, P. [Batelle, Columbus, OH (United States)


    This paper presents an overview of the advances made in fracture control technology as a result of the research performed in the International Piping Integrity Research Group (IPIRG) program. The findings from numerous experiments and supporting analyses conducted to investigate the behavior of circumferentially flawed piping and pipe systems subjected to high-rate loading typical of seismic events are summarized. Topics to be discussed include; (1) Seismic loading effects on material properties, (2) Piping system behavior under seismic loads, (3) Advances in elbow fracture evaluations, and (4) {open_quotes}Real{close_quotes} piping system response. The presentation for each topic will be illustrated with data and analytical results. In each case, the state-of-the-art in fracture mechanics prior to the first IPIRG program will be contrasted with the state-of-the-art at the completion of the IPIRG-2 program.

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

    Lee, Youho, E-mail:; Lee, Jeong Ik, E-mail:; NO, Hee Cheon, E-mail:


    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.

  19. Advances in treating exposed fractures.

    Nogueira Giglio, Pedro; Fogaça Cristante, Alexandre; Ricardo Pécora, José; Partezani Helito, Camilo; Lei Munhoz Lima, Ana Lucia; Dos Santos Silva, Jorge


    The management of exposed fractures has been discussed since ancient times and remains of great interest to present-day orthopedics and traumatology. These injuries are still a challenge. Infection and nonunion are feared complications. Aspects of the diagnosis, classification and initial management are discussed here. Early administration of antibiotics, surgical cleaning and meticulous debridement are essential. The systemic conditions of patients with multiple trauma and the local conditions of the limb affected need to be taken into consideration. Early skeletal stabilization is necessary. Definitive fixation should be considered when possible and provisional fixation methods should be used when necessary. Early closure should be the aim, and flaps can be used for this purpose.

  20. Variable frequency of pulse hydraulic fracturing for improving permeability in coal seam

    Li Quangui; Lin Baiquan; Zhai Cheng; Ni Guanhua; Peng Shen; Sun Chen; Cheng Yanying


    Variable frequency, a new pattern of pulse hydraulic fracturing, is presented for improving permeability in coal seam. A variable frequency pulse hydraulic fracturing testing system was built, the mould with triaxial loading was developed. Based on the monitor methods of pressure sensor and acoustic emission, the trials of two patterns of pulse hydraulic fracturing of single frequency and variable frequency were carried out, and at last fracturing mechanism was analyzed. The results show that the effect of variable frequency on fracture extension is better than that of single frequency based on the analysis of macro-scopic figures and AE. And the shortage of single frequency is somewhat remedied when the frequency is variable. Under variable frequency, the pressure process can be divided into three stages: low fre-quency band, pressure stability band and high frequency band, and rupture pressure of the sample is smaller than that of the condition of single frequency. Based on the Miner fatigue theory, the effect of different loading sequences on sample rupture is discussed and the results show that it is better to select the sequence of low frequency at first and then high frequency. Our achievements can give a basis for the improvement and optimization of the pulse hydraulic fracturing technology.

  1. Numerical Investigation into the Influence of Bedding Plane on Hydraulic Fracture Network Propagation in Shale Formations

    Yushi, Zou; Xinfang, Ma; Shicheng, Zhang; Tong, Zhou; Han, Li


    Shale formations are often characterized by low matrix permeability and contain numerous bedding planes (BPs) and natural fractures (NFs). Massive hydraulic fracturing is an important technology for the economic development of shale formations in which a large-scale hydraulic fracture network (HFN) is generated for hydrocarbon flow. In this study, HFN propagation is numerically investigated in a horizontally layered and naturally fractured shale formation by using a newly developed complex fracturing model based on the 3D discrete element method. In this model, a succession of continuous horizontal BP interfaces and vertical NFs is explicitly represented and a shale matrix block is considered impermeable, transversely isotropic, and linearly elastic. A series of simulations is performed to illustrate the influence of anisotropy, associated with the presence of BPs, on the HFN propagation geometry in shale formations. Modeling results reveal that the presence of BP interfaces increases the injection pressure during fracturing. HF deflection into a BP interface tends to occur under high strength and elastic anisotropy as well as in low vertical stress anisotropy conditions, which generate a T-shaped or horizontal fracture. Opened BP interfaces may limit the growth of the fracture upward and downward, resulting in a very low stimulated thickness. However, the opened BP interfaces favor fracture complexity because of the improved connection between HFs and NFs horizontally under moderate vertical stress anisotropy. This study may help predict the HF growth geometry and optimize the fracturing treatment designs in shale formations with complex depositional heterogeneity.

  2. Characterization of hydraulic fractures and reservoir properties of shale using natural tracers

    Heath, J. E.; Gardner, P.; Kuhlman, K. L.; Malama, B.


    Hydraulic fracturing plays a major role in the economic production of hydrocarbon from shale. Current fracture characterization techniques are limited in diagnosing the transport properties of the fractures on the near wellbore scale to that of the entire stimulated reservoir volume. Microseismic reveals information on fracture geometries, but not transport properties. Production analysis (e.g., rate transient analysis using produced fluids) estimates fracture and reservoir flow characteristics, but often relies on simplified models in terms of fracture geometries and fluid storage and transport. We present the approach and potential benefits of incorporating natural tracers with production data analysis for fracture and reservoir characterization. Hydraulic fracturing releases omnipresent natural tracers that accumulate in low permeability rocks over geologic time (e.g., radiogenic 4He and 40Ar). Key reservoir characteristics govern the tracer release, which include: the number, connectivity, and geometry of fractures; the distribution of fracture-surface-area to matrix-block-volume; and the nature of hydrocarbon phases within the reservoir (e.g., methane dissolved in groundwater or present as a separate gas phase). We explore natural tracer systematics using numerical techniques under relevant shale-reservoir conditions. We evaluate the impact on natural tracer transport due to a variety of conceptual models of reservoir-transport properties and boundary conditions. Favorable attributes for analysis of natural tracers include the following: tracer concentrations start with a well-defined initial condition (i.e., equilibrium between matrix and any natural fractures); there is a large suite of tracers that cover a range of at least 7x in diffusion coefficients; and diffusive mass-transfer out of the matrix into hydraulic fractures will cause elemental and isotopic fractionation. Sandia National Laboratories is a multi-program laboratory managed and operated by

  3. Induced seismicity caused by hydraulic fracturing in deep geothermal wells in Germany and adjacent areas

    Plenefisch, Thomas; Brückner, Lisa; Ceranna, Lars; Gestermann, Nicolai; Houben, Georg; Tischner, Torsten; Wegler, Ulrich; Wellbrink, Matthias; Bönnemann, Christian; Bertram, Andreas; Kirschbaum, Bernd


    Recently, the BGR has worked out a study on the potential environmental impact caused by hydraulic fracturing or chemical stimulations in deep geothermal reservoirs in Germany and adjacent areas. The investigations and analyses are based on existing studies and information provided by operators. The two environmental impacts being essentially considered in the report are induced seismicity and possible contamination of the groundwater reservoirs which serve for drinking water supply. Altogether, in this study, information on 30 hydraulic frac operations and 26 chemical stimulations including information from neighboring countries were compiled and analyzed. Out of the hydraulic stimulations two thirds were carried out as waterfracs and one third as fracturing with proppants. Parameters used in the study to characterize the induced seismicity are maximum magnitude, number of seismic events, size of the seismically active volume, and the relation of this volume to fault zones and the cap rock, as well as, finally, the impacts at the Earth's surface. The response of the subsurface to hydraulic fracturing is variable: There are some activities, which cause perceptible seismic events, others, where no perceptible but instrumentally detected events occurred, and moreover activities without even any instrumentally detected events. A classification of seismic hazard with respect to tectonic region, geology, or depth of the layer is still difficult, since the number of hydraulic fracturing measures in deep geothermal wells is small making a statistically sound analysis impossible. However, there are some indications, that hydraulic fracturing in granite in tectonically active regions like the Upper Rhine Graben results in comparatively stronger, perceptible seismicity compared to hydraulic fracturing in the sedimentary rocks of the North German basin. The maximum magnitudes of induced earthquakes caused by hydraulic fracturing of deep geothermal wells in Germany are

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

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


    -dominated, and leakoff-dominated regimes. However, for intermediate regimes, these analytical solutions cannot be used to predict the key hydraulic fracturing variables, i.e. injection pressure, fracture aperture, and length. For leakoff-dominated cases in permeable rocks, the asymptotic solutions fail to accurately...... predict the lower-bound for fracture radius and apertures, and the upper-bound for fracture pressure. This is due to the poroelastic effects in the dilated rock matrix, as well as due to the multi-dimensional flow within matrix, which in many simulation codes is idealised as being one-dimensional, normal...

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

    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

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

    Mike L. Laue


    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.

  7. Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion

    Xu, Y.; Song, H. W.; Zhang, S. H.; Cheng, M.


    The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on damage theory for fracture prediction considering the deformation history was introduced. And the modified ductile fracture criterion was applied to predict the failure for hydraulic bulging of AISI 304 austenitic steel sheets. The material parameters in terms of the function of strain rate in the failure criterion were determined from the equivalent fracture strains corresponding tensile tests under different stress conditions. Then, in the finite element simulation the effect of strain rates and their distribution as well during practical sheet metal forming process was considered. The hydraulic bulging tests were carried out to identify the fracture behavior predicted from FE analysis. A comparison between the prediction and experimental results showed that the proposed approach with a modified ductile fracture criteria can give better fracture predictions than traditional ways.

  8. Particle-based simulation of hydraulic fracture and fluid/heat flow in geothermal reservoirs

    Mora, Peter; Wang, Yucang; Alonso-Marroquin, Fernando


    Realizing the potential of geothermal energy as a cheap, green, sustainable resource to provide for the planet's future energy demands that a key geophysical problem be solved first: how to develop and maintain a network of multiple fluid flow pathways for the time required to deplete the heat within a given region. We present the key components for micro-scale particle-based numerical modeling of hydraulic fracture, and fluid and heat flow in geothermal reservoirs. They are based on the latest developments of ESyS-Particle - the coupling of the Lattice Solid Model (LSM) to simulate the nonlinear dynamics of complex solids with the Lattice Boltzmann Method (LBM) applied to the nonlinear dynamics of coupled fluid and heat flow in the complex solid-fluid system. The coupled LSM/LBM can be used to simulate development of fracture systems in discontinuous media, elastic stress release, fluid injection and the consequent slip at joint surfaces, and hydraulic fracturing; heat exchange between hot rocks and water within flow pathways created through hydraulic fracturing; and fluid flow through complex, narrow, compact and gouge-or powder-filled fracture and joint systems. We demonstrate the coupled LSM/LBM to simulate the fundamental processes listed above, which are all components for the generation and sustainability of the hot-fractured rock geothermal energy fracture systems required to exploit this new green-energy resource.

  9. Modeling the Interaction Between Hydraulic and Natural Fractures Using Dual-Lattice Discrete Element Method

    Zhou, Jing [Universiyt of Utah; Huang, Hai [Idaho National Lab. (INL), Idaho Falls, ID (United States); Deo, Milind


    The interaction between hydraulic fractures (HF) and natural fractures (NF) will lead to complex fracture networks due to the branching and merging of natural and hydraulic fractures in unconventional reservoirs. In this paper, a newly developed hydraulic fracturing simulator based on discrete element method is used to predict the generation of complex fracture network in the presence of pre-existing natural fractures. By coupling geomechanics and reservoir flow within a dual lattice system, this simulator can effectively capture the poro-elastic effects and fluid leakoff into the formation. When HFs are intercepting single or multiple NFs, complex mechanisms such as direct crossing, arresting, dilating and branching can be simulated. Based on the model, the effects of injected fluid rate and viscosity, the orientation and permeability of NFs and stress anisotropy on the HF-NF interaction process are investigated. Combined impacts from multiple parameters are also examined in the paper. The numerical results show that large values of stress anisotropy, intercepting angle, injection rate and viscosity will impede the opening of NFs.

  10. Mixed integer simulation optimization for optimal hydraulic fracturing and production of shale gas fields

    Li, J. C.; Gong, B.; Wang, H. G.


    Optimal development of shale gas fields involves designing a most productive fracturing network for hydraulic stimulation processes and operating wells appropriately throughout the production time. A hydraulic fracturing network design-determining well placement, number of fracturing stages, and fracture lengths-is defined by specifying a set of integer ordered blocks to drill wells and create fractures in a discrete shale gas reservoir model. The well control variables such as bottom hole pressures or production rates for well operations are real valued. Shale gas development problems, therefore, can be mathematically formulated with mixed-integer optimization models. A shale gas reservoir simulator is used to evaluate the production performance for a hydraulic fracturing and well control plan. To find the optimal fracturing design and well operation is challenging because the problem is a mixed integer optimization problem and entails computationally expensive reservoir simulation. A dynamic simplex interpolation-based alternate subspace (DSIAS) search method is applied for mixed integer optimization problems associated with shale gas development projects. The optimization performance is demonstrated with the example case of the development of the Barnett Shale field. The optimization results of DSIAS are compared with those of a pattern search algorithm.

  11. Overview of microseismic monitoring of hydraulic fracturing for unconventional oil and gas plays

    Shemeta, J. E.


    The exponential growth of unconventional resources for oil and gas production has been driven by the use of horizontal drilling and hydraulic fracturing. These drilling and completion methods increase the contact area of the low permeability and porosity hydrocarbon bearing formations and allow for economic production in what was previously considered uncommercial rock. These new resource plays have sparked an enormous interest in microseismic monitoring of hydraulic fracture treatments. As a hydraulic fracture is pumped, microseismic events are emitted in a volume of rock surrounding the stimulated fracture. The goal of the monitoring is to identify and locate the microseismic events to a high degree of precision and to map the position of the induced hydraulic fracture in time and space. The microseismic events are very small, typically having a moment-magnitude range of -4 to 0. The microseismic data are collected using a variety of seismic array designs and instrumentation, including borehole, shallow borehole, near-surface and surface arrays, using either of three-component clamped 15 Hz borehole sondes to simple vertical 10 Hz geophones for surface monitoring. The collection and processing of these data is currently under rapid technical development. Each monitoring method has technical challenges which include accurate velocity modeling, correct seismic phase identification and signal to noise issues. The microseismic locations are used to guide hydrocarbon exploration and production companies in crucial reservoir development decisions such as the direction to drill the horizontal well bores and the appropriate inter-well spacing between horizontal wells to optimally drain the resource. The fracture mapping is also used to guide fracture and reservoir engineers in designing and calibrating the fluid volumes and types, injection rates and pressures for the hydraulic fracture treatments. The microseismic data can be located and mapped in near real-time during

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

    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


    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)

  13. Hydraulic fracturing to enhance the remediation of DNAPL in low permeability soils

    Murdoch, L. [Univ. of Cincinnati, OH (United States); Slack, B. [FRX Inc., Cincinnati, OH (United States)


    Meager rates of fluid flow are a major obstacle to in situ remediation of low permeability soils. This paper describes methods designed to avoid that obstacle by creating fractures and filling them with sand to increase well discharge and change paths of fluid flow in soil. Gently dipping fractures 10 m in maximum dimension and 1 to 2 cm thick can be created in some contaminated soils at depths of a few in or greater. Hydraulic fractures can also be used to create electrically conductive layers or to deliver granules of chemically or biologically active compounds that will degrade contaminants in place. Benefits of applying hydraulic fractures to DNAPL recovery include rates of fluid recovery, enhancing upward gradients to improve hydrodynamic stabilization, forming flat-lying reactive curtains to intersect compounds moving downward, or improving the performance of electrokinetics intended to recover compounds dissolved in water. 30 refs., 7 figs., 1 tab.

  14. Draft Genome Sequence of Methanohalophilus mahii Strain DAL1 Reconstructed from a Hydraulic Fracturing-Produced Water Metagenome

    Lipus, Daniel; Vikram, Amit


    We report here the 1,882,100-bp draft genome sequence of Methanohalophilus mahii strain DAL1, recovered from Marcellus Shale hydraulic fracturing-produced water using metagenomic contig binning. Genome annotation revealed several key methanogenesis genes and provides valuable information on archaeal activity associated with hydraulic fracturing-produced water environments. PMID:27587817

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

    Dodge, Jennifer; Metze, Tamara


    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:

  16. Advanced geothermal hydraulics model -- Phase 1 final report, Part 2

    W. Zheng; J. Fu; W. C. Maurer


    An advanced geothermal well hydraulics model (GEODRIL) is being developed to accurately calculate bottom-hole conditions in these hot wells. In Phase 1, real-time monitoring and other improvements were added to GEODRIL. In Phase 2, GEODRIL will be integrated into Marconi's Intelligent Drilling Monitor (IDM) that will use artificial intelligence to detect lost circulation, fluid influxes and other circulation problems in geothermal wells. This software platform has potential for significantly reducing geothermal drilling costs.

  17. A Holistic Assessment of Energy Production: Environmental, Economic, and Social Impacts of Hydraulic Fracturing in Williams County, North Dakota

    Jagdeo, J.; Ravikumar, A. P.; Grubert, E.; Brandt, A. R.


    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

  18. A method to evaluate hydraulic fracture using proppant detection.

    Liu, Juntao; Zhang, Feng; Gardner, Robin P; Hou, Guojing; Zhang, Quanying; Li, Hu


    Accurate determination of the proppant placement and propped fracture height are important for evaluating and optimizing stimulation strategies. A technology using non-radioactive proppant and a pulsed neutron gamma energy spectra logging tool to determine the placement and height of propped fractures is proposed. Gd2O3 was incorporated into ceramic proppant and a Monte Carlo method was utilized to build the logging tools and formation models. Characteristic responses of the recorded information of different logging tools to fracture widths, proppant concentrations and influencing factors were studied. The results show that Gd capture gamma rays can be used to evaluate propped fractures and it has higher sensitivity to the change of fracture width and traceable proppant content compared with the exiting non-radioactive proppant evaluation techniques and only an after-fracture measurement is needed for the new method; The changes in gas saturation and borehole size have a great impact on determining propped fractures when compensated neutron and pulsed neutron capture tool are used. A field example is presented to validate the application of the new technique.




    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.

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

    J. Zhou; H. Huang; M. Deo


    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.

  1. Impact of hydraulic perforation on fracture initiation and propagation in shale rocks

    ZHAO Xi; JU Yang; YANG Yong; SU Sun; GONG WenBo


    To enhance the oil and gas recovery rate,hydraulic fracturing techniques have been widely adopted for stimulation of low-permeability reservoirs.Pioneering work indicates that hydraulic perforation and layout could significantly affect fracture initiation and propagation in low-permeability reservoir rocks subjected to complex in-situ stresses.This paper reports on a novel numerical method that incorporates fracture mechanics principles and the numerical tools FRANC3D and ANSYS to investigate the three-dimensional initiation and propagation behavior of hydro-fracturing cracks in shale rock.Considering the transverse isotropic property of shale rocks,the mechanical parameters of reservoir rocks attained from laboratory tests were adopted in the simulation.The influence of perforation layouts on the 3D initiation of hydro-fracturing fractures in reservoir rocks under geo-stresses was quantitatively illuminated.The propagation and growth of fractures in three dimensions in different perforating azimuth values were illustrated.The results indicate that:1) the optimal perforation direction should be parallel to the maximum horizontal principal stress,2) the crack plane gradually turns toward the direction of the maximum horizontal principal stress when they are not in parallel,3) compared with the linear and symmetric pattern,the staggered perforation is the optimal one,4) the proper perforation density is four to six holes per meter,5) the optimal perforation diameter in this model is 30 mm,and 6) the influence of the perforation depth on the fracture initiation pressure is low.

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

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


    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

  3. Hydraulic fracturing model featuring initiation beyond the wellbore wall for directional well in coal bed

    Li, Yuwei; Jia, Dan; Wang, Meng; Liu, Jia; Fu, Chunkai; Yang, Xinliang; Ai, Chi


    In developing internal fracture systems in coal beds, the initiation mechanism differs greatly from that of conventional ones and initiations may be produced beyond the wellbore wall. This paper describes the features of the internal structure of coal beds and RFPA2D simulation is used to attest the possible occurrence of initiation beyond the wellbore wall in coal bed hydraulic fracturing. Using the theory of elasticity and fracture mechanics, we analyse the stress distribution in the vicinal coal rock. Then by taking into consideration the effects of the spatial relationship between coal bed cleats and the wellbore, we establish a model for calculating both tensile and shear initiation pressure that occur along cleats beyond the wellbore wall. The simulation in this paper indicates that for shear initiations that happen along coal cleats, the pressure required to initiate fracture for cleats beyond the wellbore wall is evidently lower than that on the wellbore wall, thus it is easier to initiate shear fractures for cleats beyond the wellbore wall. For tensile failure, the pressure required to initiate tensile fracture for cleats beyond the wellbore wall is obviously higher than that for cleats at the wellbore wall, thus it is easier to initiate tensile fractures for cleats at the wellbore wall. On the one hand, this paper has proved the possible occurrence of initiations beyond the wellbore wall and has changed the current assumption that hydraulic fractures can only occur at the wellbore wall. On the other hand, the established theoretical model provides a new approach to calculating the initiation pressure in hydraulic fracturing.

  4. A Geochemical Framework for Evaluating Shale-Hydraulic Fracture Fluid Interactions

    Harrison, A. L.; Jew, A. D.; Dustin, M. K.; Joe-Wong, C. M.; Thomas, D.; Maher, K.; Brown, G. E.; Bargar, J.; Bill, M.; Conrad, M. E.


    The development of shale oil and gas reservoirs has increased dramatically due to the application of hydraulic fracturing techniques. Fracture fluids contain dissolved oxygen and numerous chemical additives [1] that are out of equilibrium with the reducing conditions in shale reservoirs and could react extensively with shale minerals and alter porosity. Yet, the complex dissolution-precipitation reactions in shales along with the poorly constrained characteristics of many fracture fluid additives hinder predictive modeling based on established reaction kinetics and thermodynamic constants [2]. Here, we are developing a reaction framework to better predict reaction progress and porosity evolution upon exposure of shales to hydraulic fracturing fluids. To this end, the reactive transport model CrunchFlow [3] was applied to the results of batch reactor experiments containing shales of different mineralogical and organic compositions exposed to simulated fracturing fluid. Despite relatively good agreement between modeled and experimental data for pH and aqueous Ca concentrations, which are strongly governed by carbonate dissolution, the model is presently unable to reproduce observed trends in aqueous Fe concentration. This is largely attributable to the dearth of thermodynamic data for certain fracture fluid components and the complex interactions between multiple Fe-bearing mineral phases. Experimental results revealed that the presence of organic fracture fluid components strongly influenced the precipitation of Fe-bearing phases, which are speculated to coat fracture fluid polymers that formed in the reactors. The incorporation of these effects in our reactive transport model will permit improved prediction of reservoir permeability evolution and metal release during hydraulic fracturing operations. [1] Stringfellow et al. (2014) J. Hazard. Mater. [2] Carroll et al. (2013) Environ. Sci. Technol. [3] Steefel and Maher (2009) Rev. Mineral. Geochem.

  5. On the fracture toughness of advanced materials

    Launey, Maximilien E.; Ritchie, Robert O.


    Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. In the first instance, such resistance to fracture is a function of bonding and crystal structure (or lack thereof), but can be developed through the design of appropriate nano/microstructures. However, the creation of tough microstructures in structural materials, i.e., metals, polymers, ceramics and their composites, is invariably a compromise between resistance to intrinsic damage mechanisms ahead of the tip of a crack (intrinsic toughening) and the formation of crack-tip shielding mechanisms which principally act behind the tip to reduce the effective 'crack-driving force' (extrinsic toughening). Intrinsic toughening is essentially an inherent property of a specific microstructure; it is the dominant form of toughening in ductile (e.g., metallic) materials. However, for most brittle (e.g., ceramic) solids, and this includes many biological materials, it is largely ineffective and toughening conversely must be developed extrinsically, by such shielding mechanisms as crack bridging. From a fracture mechanics perspective, this results in toughening in the form of rising resistance-curve behavior where the fracture resistance actually increases with crack extension. The implication of this is that in many biological and high-strength advanced materials, toughness is developed primarily during crack growth and not for crack initiation. This is an important realization yet is still rarely reflected in the way that toughness is measured, which is invariably involves the use of single-value (crack-initiation) parameters such as

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

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


    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.

  7. Theory and application of rock burst prevention using deep hole high pressure hydraulic fracturing

    Shan-Kun ZHAO; Jun LIU; Xiang-Zhi WEI; Chuan-Hong DING; Yu-Lei LV; Gang-Feng LI


    In order to analyze the mechanism of deep hole high pressure hydraulic fracturing,nonlinear dynamic theory,damage mechanics,elastic-plastic mechanics are used,and the law of crack propagation and stress transfer under two deep hole hydraulic fracturing in tectonic stress areas is studied using seepage-stress coupling models with RFPA simulation software.In addition,the effects of rock burst control are tested using multiple methods,either in the stress field or in the energy field.The research findings show that with two deep holes hydraulic fracturing in tectonic stress areas,the direction of the main crack propagation under shear-tensile stress is parallel to the greatest principal stress direction.High-pressure hydraulic fracturing water seepage can result in the destruction of the coal structure,while also weakening the physical and mechanical properties of coal and rock.Therefore the impact of high stress concentration in hazardous areas will level off,which has an effect on rock burst prevention and control in the region.

  8. The Role of Toxicological Science in Meeting the Challenges and Opportunities of Hydraulic Fracturing

    We briefly describe how toxicology can inform the discussion and debate of the merits of hydraulic fracturing by providing information on the potential toxicity of the chemical and physical agents associated with this process, individually and in combination. We consider upstream...

  9. 78 FR 34611 - Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands


    ... initial comment period. DATES: The comment period for the proposed rule published May 24, 2013 (78 FR... The revised proposed rule was published on May 24, 2013 (78 FR 31636), with a 30-day comment period... Bureau of Land Management 43 CFR Part 3160 RIN 1004-AE26 Oil and Gas; Hydraulic Fracturing on Federal...

  10. Chloride concentration gradients in tank-stored hydraulic fracturing fluids following flowback

    Pamela J. Edwards; Linda L. Tracy; William K. Wilson


    A natural gas well in West Virginia was hydraulically fractured and the flowback was recovered and stored in an 18-foot-deep tank. Both in situ field test kit and laboratory measurements of electrical conductivity and chloride concentrations increased substantially with depth, although the laboratory measurements showed a greater increase. The field test kit also...

  11. Natural hydraulic fractures and the mechanical stratigraphy of shale-dominated strata

    Imber, Jonathan; Armstrong, Howard; Atar, Elizabeth; Clancy, Sarah; Daniels, Susan; Grattage, Joshua; Herringshaw, Liam; Trabucho-Alexandre, João; Warren, Cassandra; Wille, Jascha; Yahaya, Liyana


    The aim of this study is to investigate stratigraphic variations in the spatial distribution and density of natural hydraulic and other fractures within oil mature, shale-dominated strata from the Cleveland Basin, northeast England. The studied interval includes the Pliensbachian Cleveland Ironstone and Toarcian Whitby Mudstone Formations. The Cleveland Ironstone Formation (ca. 25m thick) consists of silt- and mudstone units with discrete ironstone layers (seams). Ironstones account for 20% of the thickness of the formation. The Whitby Mudstone Formation is up to ca. 100 m thick; up to 2% of its total thickness consists of discrete calcium carbonate horizons, such as the Top Jet Dogger. Natural hydraulic fractures, characterised by plumose marks and concentric arrest lines on fracture surfaces are ubiquitous throughout both formations; shear fractures with mm- to cm-scale displacements occur locally, particularly within silt- and mudstones. Natural hydraulic fractures locally contain thin, sometimes fibrous, calcite fills and are commonly observed to terminate at bedding plane interfaces between silt- or mudstone and carbonate beds. We have recorded fracture locations and apertures along 139 transects in both shale (i.e. silt- and mudstone intervals) and carbonate strata. Natural hydraulic and shear fractures, measured along transects up to 50m long within all lithologies in both formations, typically display uniform distributions. There is no correlation between spacing distribution and bulk extension in any lithology. Median fracture densities recorded within the Cleveland Ironstone Formation are higher in intervening ironstone beds (<2.1 fractures per m in ironstone layers) compared with dominant shales (<0.9 fractures per m in silt- and mudstones). A qualitatively similar pattern occurs within the Whitby Mudstone Formation. However, the absolute values of median fracture density within different members of the Whitby Mudstone Formation range from 2

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

    Burton, Taylour G., E-mail: [Civil and Environmental Engineering, University of Houston, W455 Engineering Bldg. 2, Houston, TX 77204-4003 (United States); Rifai, Hanadi S., E-mail: [Civil and Environmental Engineering, University of Houston, N138 Engineering Bldg. 1, Houston, TX 77204-4003 (United States); Hildenbrand, Zacariah L., E-mail: [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: [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: [Collaborative Laboratories for Environmental Analysis and Remediation, University of Texas at Arlington, Arlington, TX 76019 (United States); Schug, Kevin A., E-mail: [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)


    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

  13. Scale dependence of the hydraulic properties of a fractured aquifer estimated using transfer functions

    Pedretti, D.; Russian, A.; Sanchez-Vila, X.; Dentz, M.


    We present an investigation of the scale dependence of hydraulic parameters in fractured media based on the concept of transfer functions (TF). TF methods provide an inexpensive way to perform aquifer parameter estimation, as they relate the fluctuations of an observation time series (hydraulic head fluctuations) to an input function (aquifer recharge) in frequency domain. Fractured media are specially sensitive to this approach as hydraulic parameters are strongly scale-dependent, involving nonstationary statistical distributions. Our study is based on an extensive data set, involving up to 130 measurement points with periodic head measurements that in some cases extend for more than 30 years. For each point, we use a single-porosity and dual-continuum TF formulation to obtain a distribution of transmissivities and storativities in both mobile and immobile domains. Single-porosity TF estimates are compared with data obtained from the interpretation of over 60 hydraulic tests (slug and pumping tests). Results show that the TF is able to estimate the scale dependence of the hydraulic parameters, and it is consistent with the behavior of estimates from traditional hydraulic tests. In addition, the TF approach seems to provide an estimation of the system variance and the extension of the ergodic behavior of the aquifer (estimated in approximately 500 m in the analyzed aquifer). The scale dependence of transmissivity seems to be independent from the adopted formulation (single or dual-continuum), while storativity is more sensitive to the presence of multiple continua.

  14. A New Physics-Based Modeling of Multiple Non-Planar Hydraulic Fractures Propagation

    Zhou, Jing [University of Utah; Huang, Hai [Idaho National Lab. (INL), Idaho Falls, ID (United States); Deo, Milind [University of Utah; Jiang, Shu [Energy & Geoscience Institute


    Because of the low permeability in shale plays, closely spaced hydraulic fractures and multilateral horizontal wells are generally required to improve production. Therefore, understanding the potential fracture interaction and stress evolution is critical in optimizing fracture/well design and completion strategy in multi-stage horizontal wells. In this paper, a novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple non-planar fractures propagation. The numerical model from Discrete Element Method (DEM) is used to simulate the mechanics of fracture propagations and interactions, while a conjugate irregular lattice network is generated to represent fluid flow in both fractures and formation. The fluid flow in the formation is controlled by Darcy’s law, but within fractures it is simulated by using cubic law for laminar flow through parallel plates. 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. We investigate the fracture propagation path in both homogeneous and heterogeneous reservoirs using the simulator developed. Stress shadow caused by the transverse fracture will change the orientation of principal stress in the fracture neighborhood, which may inhibit or alter the growth direction of nearby fracture clusters. However, the initial in-situ stress anisotropy often helps overcome this phenomenon. Under large in-situ stress anisotropy, the hydraulic fractures are more likely to propagate in a direction that is perpendicular to the minimum horizontal stress. Under small in-situ stress anisotropy, there is a greater chance for fractures from nearby clusters to merge with each other. Then, we examine the differences in fracture geometry caused by fracturing in cemented or uncemented wellbore. Moreover, the impact of

  15. Determination of hydraulic fracture parameters using a non-stationary fluid injection

    Valov, A. V.; Golovin, S. V.


    In this paper, one provides a theoretical justification of the possibility of hydraulic fracture parameters determination by using a non-stationary fluid injection. It is assumed that the fluid is pumped into the fractured well with the time-periodic flow rate. It is shown that there is a phase shift between waves of fluid pressure and velocity. For the modelling purposes, the length and width of the fracture are assumed to be fixed. In the case of infinite fracture, one constructs an exact solution that ensures analytical determination of the phase shift in terms of the physical parameters of the problem. In the numerical calculation, the phase shift between pressure and velocity waves is found for a finite fracture. It is shown that the value of the phase shift depends on the physical parameters and on the fracture geometry. This makes it possible to determine parameters of hydraulic fracture, in particular its length, by the experimental measurement of the time shift and comparison with the numerical solution.

  16. Correlating laboratory observations of fracture mechanical properties to hydraulically-induced microseismicity in geothermal reservoirs.

    Stephen L. Karner, Ph.D


    To date, microseismicity has provided an invaluable tool for delineating the fracture network produced by hydraulic stimulation of geothermal reservoirs. While the locations of microseismic events are of fundamental importance, there is a wealth of information that can be gleaned from the induced seismicity (e.g. fault plane solutions, seismic moment tensors, source characteristics). Closer scrutiny of the spatial and temporal evolution of seismic moment tensors can shed light on systematic characteristics of fractures in the geothermal reservoir. When related to observations from laboratory experiments, these systematic trends can be interpreted in terms of mechanical processes that most likely operate in the fracture network. This paper reports on mechanical properties that can be inferred from observations of microseismicity in geothermal systems. These properties lead to interpretations about fracture initiation, seismicity induced after hydraulic shut-in, spatial evolution of linked fractures, and temporal evolution of fracture strength. The correlations highlight the fact that a combination of temperature, stressing rate, time, and fluid-rock interactions can alter the mechanical and fluid transport properties of fractures in geothermal systems.

  17. Non-symmetry of a hydraulic fracture due to the inhomogeneity of the reservoir

    Baykin, Alexey N


    It is usually assumed that hydraulic fracture has two symmetrical wings with respect to the fluid injection point. Hence, authors limit themselves to modelling of one half of the fracture. In our work we demonstrate that the case of a symmetrical fracture occurs only in a homogeneous reservoir with constant physical parameters and confining {\\it in situ} stress. Otherwise, inhomogeneity in the stress or the rock permeability can significantly change the dynamics of the fracture propagation. The mathematical model of the hydraulic fracturing used in the paper is adopted from our earlier work \\cite{Golovin_Baykin_2016_Pore}. In present paper we perform numerical experiments demonstrating that in case of non-constant confining stress or reservoir permeability the fracture is developing non-symmetrically. An important role is played by the action of the backstress that is formed near the fracture due to the pore pressure. To support this observation we give a formal definition of the backstress and compare the va...

  18. Correlating laboratory observations of fracture mechanical properties to hydraulically-induced microseismicity in geothermal reservoirs.

    Stephen L. Karner, Ph.D


    To date, microseismicity has provided an invaluable tool for delineating the fracture network produced by hydraulic stimulation of geothermal reservoirs. While the locations of microseismic events are of fundamental importance, there is a wealth of information that can be gleaned from the induced seismicity (e.g. fault plane solutions, seismic moment tensors, source characteristics). Closer scrutiny of the spatial and temporal evolution of seismic moment tensors can shed light on systematic characteristics of fractures in the geothermal reservoir. When related to observations from laboratory experiments, these systematic trends can be interpreted in terms of mechanical processes that most likely operate in the fracture network. This paper reports on mechanical properties that can be inferred from observations of microseismicity in geothermal systems. These properties lead to interpretations about fracture initiation, seismicity induced after hydraulic shut-in, spatial evolution of linked fractures, and temporal evolution of fracture strength. The correlations highlight the fact that a combination of temperature, stressing rate, time, and fluid-rock interactions can alter the mechanical and fluid transport properties of fractures in geothermal systems.

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

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


    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)

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

    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)


    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

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

    Mouser, P. J.; Kekacs, D.


    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.

  2. Statistical Analysis of Seismicity Associated with Hydraulic Fracturing in Western Canada

    Shcherbakov, R.; Ghofrani, H.; Kothari, S.; Atkinson, G. M.; Cheadle, B.; Eaton, D. W. S.; Tiampo, K. F.


    The unconventional extraction of shale oil or gas is typically carried out by the subsurface injection of large volumes of fluids. The fluids are used in the process of hydraulic fracturing and subsequent wastewater injection into high volume disposal wells. These operations are usually accompanied by various levels of seismic activity and sometimes result in the occurrence of moderate to large earthquakes. It is suggested that the increase in seismic activity within the central U.S. in the last decade or so is primely associated with large-scale disposal of wastewater. The Western Canada Sedimentary Basin (WCSB) is an active exploration area for the extraction of oil and gas. The average rate of seismicity is lower than in the central U.S., however, there are several active clusters, where in the last 8-10 years, there has been an increase in the occurrence of moderate earthquakes. In this study, we analyze the statistical properties of seismicity associated with the WCSB. We find that the increase in seismicity rate is mostly associated with the hydraulic fracturing operations in several well defined spatial zones. Hydraulic fracturing involves high-pressure injections of fluids and is performed in multiple stages. This is done along horizontal wells which are drilled at average depths of 2 to 3 km. The triggering of large earthquakes is mostly due to injection of fluids into nearby tectonic faults which are close to failure. To model the rate of the occurrence of earthquakes we introduce a modified version of the Epidemic Type Aftershock Sequence model. The earthquake occurrence rate associated with several prominent clusters is characterized by bursts of activity associated with specifics of hydraulic fracturing operations. The proposed model can be used in the probabilistic assessment and mitigation of the risks associated with hydraulic fracturing.

  3. Computational and physical consequences of interaction of closely located simultaneous hydraulic fractures

    Rejwer, Ewa


    Strong interaction of closely located, nearly parallel hydraulic fractures and its influence on their propagation are studied. Both computational and physical aspects of the problem are considered. It is shown that from the computational point of view, when a distance between cracks is small as compared with their sizes, the system becomes ill-conditioned and numerical results deteriorate. The physical consequence of the interaction consists in decreasing of the crack opening and even greater decrease of conductivity. Then the resistance to fluid flow grows what results in the propagation of only those fractures, the distance between which is large enough. The research aims to suggests a means to overcome the computational difficulty and to improve numerical simulation of hydraulic fractures in shales. Numerical experiments are carried out for a 2D problem by using the complex variable hypersingular boundary element method of higher order accuracy. The condition number of the main matrix of a system, the open...


    David S. Schechter


    This report describes the work performed during the second 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 artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling the fluid flow in fracture surface, examining the fluid transfer mechanisms and describing the fracture aperture distribution under different overburden pressure using X-ray CT scanner.


    David S. Schechter


    This report describes the work performed during the second 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 artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on investigating the effect of CO{sub 2} injection rates in homogeneous and fractured cores on oil recovery and a strategy to mitigate CO{sub 2} bypassing in a fractured core.

  6. Hydraulic-fracture stimulation treatments at East Mesa, Well 58-30. Geothermal-reservoir well-stimulation program


    East Mesa Well 58-30 was selected for two stimulation treatments: a conventional hydraulic fracture in a deep, low permeability interval, and a dendritic fracture in a shallow, high permeability interval of completion. The well selection, pre-stimulation evaluation, fracture treatment design, and post-stimulation evaluation are presented.

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

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


    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.

  8. Some effects of stress, friction and fluid flow on hydraulic fracturing

    Hanson, M.E.; Anderson, G.D.; Shaffer, R.J.; Thorson, L.D.


    We are conducting a DOE funded research program which is aimed at understanding the hydraulic fracturing process, especially those phenomena and parameters which strongly affect or control the fracture geometry. Our theoretical and experimental studies consistently confirm the well known fact that in-situ stress has a primary effect on fracture geometry and that fractures propagate perpendicular to the least principal stress. In addition, we find that frictional interfaces in reservoirs can affect fracturing. We have also quantified some of the effects on fracture geometry due to frictional slippage along interfaces. We found that variation of friction along an interface can result in abrupt steps in the fracture path. These effects have been seen in the mine back of emplaced fractures and are demonstrated both theoretically and in the laboratory. Further experiments and calculations are starting to indicate the possible control of the fracture height by the vertical change in the cables to X-608A wells should be replaced, and develop v across categories of persons affected. Respondents were selected according to a purposive sampling strategy, wn are also included. The management plan for the operation of the plant is discussed. (DMC)

  9. Genome-Centric Analysis of Microbial Populations Enriched by Hydraulic Fracture Fluid Additives in a Coal Bed Methane Production Well.

    Robbins, Steven J; Evans, Paul N; Parks, Donovan H; Golding, Suzanne D; Tyson, Gene W


    Coal bed methane (CBM) is generated primarily through the microbial degradation of coal. Despite a limited understanding of the microorganisms responsible for this process, there is significant interest in developing methods to stimulate additional methane production from CBM wells. Physical techniques including hydraulic fracture stimulation are commonly applied to CBM wells, however the effects of specific additives contained in hydraulic fracture fluids on native CBM microbial communities are poorly understood. Here, metagenomic sequencing was applied to the formation waters of a hydraulically fractured and several non-fractured CBM production wells to determine the effect of this stimulation technique on the in-situ microbial community. The hydraulically fractured well was dominated by two microbial populations belonging to the class Phycisphaerae (within phylum Planctomycetes) and candidate phylum Aminicenantes. Populations from these phyla were absent or present at extremely low abundance in non-fractured CBM wells. Detailed metabolic reconstruction of near-complete genomes from these populations showed that their high relative abundance in the hydraulically fractured CBM well could be explained by the introduction of additional carbon sources, electron acceptors, and biocides contained in the hydraulic fracture fluid.

  10. Hydraulics.

    Decker, Robert L.; Kirby, Klane

    This curriculum guide contains a course in hydraulics to train entry-level workers for automotive mechanics and other fields that utilize hydraulics. The module contains 14 instructional units that cover the following topics: (1) introduction to hydraulics; (2) fundamentals of hydraulics; (3) reservoirs; (4) lines, fittings, and couplers; (5)…

  11. Cooperative federalism and hydraulic fracturing: a human right to a clean environment.

    Burleson, Elizabeth


    This Article argues that filling the energy governance gaps regarding unconventional natural gas can best be accomplished through collaborative governance that is genuinely adaptive and cooperative. Through cooperative federalism, combined with procedural rights for inclusive, innovative decision-making, state and non-state actors should design and implement the requisite safeguards before further natural gas development advances. Hydraulic fracturing provisions are strikingly fragmented and have sparked a fierce debate about chemical disclosure, radioactive wastewater disposal, and greenhouse gas emissions. United States natural gas production may stunt the direction and intensity of renewable energy by up to two decades and will not provide a bridge to a sound energy policy if it "erode[s] efforts to prepare a landing at the other end of the bridge." Unconventional natural gas extraction need not become a transition to a new addiction. This Article analyzes how cooperative federalism and inclusive decision-making can provide legitimacy and transparency when balancing property rights against police powers to regulate natural gas production.

  12. Regulatory and Non-regulatory Responses to Hydraulic Fracturing in Local Communities

    Phartiyal, P.


    The practice of extracting oil and gas from tight rock formations using advances in technology, such as hydraulic fracturing and directional drilling, has expanded exponentially in states and localities across the country. As the scientific data collection and analysis catches up on the many potential impacts of this unconventional oil and gas development, communities are turning to their local officials to make decisions on whether and how fracking should proceed. While most regulatory authority on the issue rests with the state agencies, local officials have experimented with a wide range of regulatory, non-regulatory, and fiscal tools to manage the impacts of fracking. These impacts can occur on the local air, water, seismicity, soil, roads, schools, and affect residents, on-site workers, emergency and social services. Local officials' approaches are often influenced by their prior experience with minerals extraction in their localities. The speaker will present examples of the kinds of information sources, tools and approaches communities across the country are using, from noise barriers to setback requirements to information sharing in order to be able to balance the promise and perils of oil and gas development in their jurisdictions.

  13. Blade-shaped (PKN) Hydraulic Fracture Driven By A Turbulent Fluid In An Impermeable Rock

    Zolfaghari, Navid; Bunger, Andrew P


    High flow rate, water-driven hydraulic fractures are more common now than ever in the oil and gas industry. Although the fractures are small, the high injection rate and low viscosity of the water, lead to high Reynolds numbers and potentially turbulence in the fracture. Here we present a semi-analytical solution for a blade-shaped (PKN) geometry hydraulic fracture driven by a turbulent fluid in the limit of zero fluid leak-off to the formation. We model the turbulence in the PKN fracture using the Gaukler-Manning-Strickler parametrization, which relates the the flow rate of the water to the pressure gradient along the fracture. The key parameter in this relation is the Darcy-Weisbach friction factor for the roughness of the crack wall. Coupling this turbulence parametrization with conservation of mass allows us to write a nonlinear pde for the crack width as a function of space and time. By way of a similarity ansatz, we obtain a semi-analytical solution using an orthogonal polynomial series. Embedding the a...

  14. Numerical Investigation of Influence of In-Situ Stress Ratio, Injection Rate and Fluid Viscosity on Hydraulic Fracture Propagation Using a Distinct Element Approach

    Bo Zhang


    Full Text Available Numerical simulation is very useful for understanding the hydraulic fracturing mechanism. In this paper, we simulate the hydraulic fracturing using the distinct element approach, to investigate the effect of some critical parameters on hydraulic fracturing characteristics. The breakdown pressure obtained by the distinct element approach is consistent with the analytical solution. This indicates that the distinct element approach is feasible on modeling the hydraulic fracturing. We independently examine the influence of in-situ stress ratio, injection rate and fluid viscosity on hydraulic fracturing. We further emphasize the relationship between these three factors and their contributions to the hydraulic fracturing. With the increase of stress ratio, the fracture aperture increases almost linearly; with the increase of injection rate and fluid viscosity, the fracture aperture and breakdown pressure increase obviously. A low value of product of injection rate and fluid viscosity (i.e., Qμ will lead to narrow fracture aperture, low breakdown pressure, and complex or dispersional hydraulic fractures. A high value of Qμ would lead wide fracture aperture, high breakdown pressure, and simple hydraulic fractures (e.g., straight or wing shape. With low viscosity fluid, the hydraulic fracture geometry is not sensitive to stress ratio, and thus becomes a complex fracture network.

  15. Numerical evaluation of effective unsaturated hydraulic properties for fractured rocks

    Lu, Zhiming [Los Alamos National Laboratory; Kwicklis, Edward M [Los Alamos National Laboratory


    To represent a heterogeneous unsaturated fractured rock by its homogeneous equivalent, Monte Carlo simulations are used to obtain upscaled (effective) flow properties. In this study, we present a numerical procedure for upscaling the van Genuchten parameters of unsaturated fractured rocks by conducting Monte Carlo simulations of the unsaturated flow in a domain under gravity-dominated regime. The simulation domain can be chosen as the scale of block size in the field-scale modeling. The effective conductivity is computed from the steady-state flux at the lower boundary and plotted as a function of the averaging pressure head or saturation over the domain. The scatter plot is then fitted using van Genuchten model and three parameters, i.e., the saturated conductivity K{sub s}, the air-entry parameter {alpha}, the pore-size distribution parameter n, corresponding to this model are considered as the effective K{sub s}, effective {alpha}, and effective n, respectively.

  16. The Impact of Mineralogy on the Geochemical Alteration of Shales During Hydraulic Fracturing Operations

    Maher, K.; Harrison, A. L.; Jew, A. D.; Dustin, M. K.; Kiss, A. M.; Kohli, A. H.; Thomas, D.; Joe-Wong, C. M.; Brown, G. E.; Bargar, J.


    The extraction of oil and gas resources from low permeability shale reservoirs using hydraulic fracturing techniques has increased significantly in recent years. During hydraulic fracturing, large volumes of fluid are injected into subsurface shale formations, which drives substantial fluid-rock interaction that can release contaminants and alter rock permeability. Here, a combined experimental, imaging, and modeling approach was employed to systematically evaluate the impact of shale mineralogy on its physical and chemical alteration when exposed to fracturing fluids of different composition. Batch reactor experiments contained different shales with unique mineralogical compositions that were exposed to simulated hydraulic fracturing fluid. Experiments revealed that the balance between fluid acidity and acid neutralizing capacity of the rock was the strongest control on the evolution of fluid and rock chemistry. Carbonate mineral-rich shales rapidly recovered solution pH to circum-neutral conditions, whereas fluids in contact with carbonate mineral-poor shales remained acidic. The dissolution of shale minerals released metal contaminants, yet the precipitation of Fe(III)-bearing secondary phases helped to attenuate their release via co-precipitation or sorption. Post-reaction imaging illustrated that selective dissolution of carbonate minerals generated secondary porosity, the connectivity of which was dictated by initial carbonate distribution. Conversely, the precipitation of secondary Al- and Fe-bearing phases may occlude porosity, potentially inhibiting transport of water, contaminants, and hydrocarbons. The maturation of secondary Fe-bearing phases from amorphous to crystalline over time suggests that porosity will continue to evolve even after oxidation reactions have effectively ceased. These experiments reveal that the relative abundance and distribution of carbonate minerals is the master variable dictating both porosity alteration and contaminant release

  17. Predominance and Metabolic Potential of Halanaerobium spp. in Produced Water from Hydraulically Fractured Marcellus Shale Wells.

    Lipus, Daniel; Vikram, Amit; Ross, Daniel; Bain, Daniel; Gulliver, Djuna; Hammack, Richard; Bibby, Kyle


    Microbial activity in the produced water from hydraulically fractured oil and gas wells may potentially interfere with hydrocarbon production and cause damage to the well and surface infrastructure via corrosion, sulfide release, and fouling. In this study, we surveyed the microbial abundance and community structure of produced water sampled from 42 Marcellus Shale wells in southwestern Pennsylvania (well age ranged from 150 to 1,846 days) to better understand the microbial diversity of produced water. We sequenced the V4 region of the 16S rRNA gene to assess taxonomy and utilized quantitative PCR (qPCR) to evaluate the microbial abundance across all 42 produced water samples. Bacteria of the order Halanaerobiales were found to be the most abundant organisms in the majority of the produced water samples, emphasizing their previously suggested role in hydraulic fracturing-related microbial activity. Statistical analyses identified correlations between well age and biocide formulation and the microbial community, in particular, the relative abundance of Halanaerobiales We further investigated the role of members of the order Halanaerobiales in produced water by reconstructing and annotating a Halanaerobium draft genome (named MDAL1), using shotgun metagenomic sequencing and metagenomic binning. The recovered draft genome was found to be closely related to the species H. congolense, an oil field isolate, and Halanaerobium sp. strain T82-1, also recovered from hydraulic fracturing produced water. Reconstruction of metabolic pathways revealed Halanaerobium sp. strain MDAL1 to have the potential for acid production, thiosulfate reduction, and biofilm formation, suggesting it to have the ability to contribute to corrosion, souring, and biofouling events in the hydraulic fracturing infrastructure.IMPORTANCE There are an estimated 15,000 unconventional gas wells in the Marcellus Shale region, each generating up to 8,000 liters of hypersaline produced water per day

  18. In-situ stress and fracture characterization for planning of a hydraulic stimulation in the Desert Peak Geothermal Field, NV

    Hickman, S.; Davatzes, N. C.


    A suite of geophysical logs and a hydraulic fracturing stress measurement were conducted in well 27-15 in the Desert Peak Geothermal Field, Nevada, to constrain the state of stress and the geometry and relative permeability of natural fractures in preparation for development of an Enhanced Geothermal System (EGS) through hydraulic stimulation. Advanced Logic Technologies Borehole Televiewer (BHTV) and Schlumberger Formation MicroScanner (FMS) image logs reveal extensive drilling-induced tensile fractures, showing that the current minimum horizontal principal stress, Shmin, in the vicinity of well 27-15 is oriented 114 ± 17°. This orientation is consistent with down-dip extensional slip on a set of ESE and WNW dipping normal faults mapped at the surface. Similarly, all formations imaged in the BHTV and FMS logs include significant sub-populations of fractures that are well oriented for normal faulting given this direction of Shmin. Although the bulk permeability of the well is quite low, temperature and spinner flowmeter surveys reveal several minor flowing fractures. Some of these relatively permeable fractures are well oriented for normal faulting, in addition to fluid flow that is preferentially developed at low-angle formation boundaries. A hydraulic fracturing stress measurement conducted at the top of the intended stimulation interval (931 m) indicates that the magnitude of Shmin is 13.8 MPa, which is 0.609 of the calculated vertical (overburden) stress at this depth. Given the current water table depth (122 m below ground level), this Shmin magnitude is somewhat higher than expected for frictional failure on optimally oriented normal faults given typical laboratory measurements of sliding friction (Byerlee’s Law). Coulomb failure calculations assuming cohesionless pre-existing fractures with coefficients of friction of 0.6 or higher (consistent with Byerlee’s Law and with tests on representative core samples from nearby wells) indicate that shear

  19. Experimental study on the mechanism of hydraulic fracture growth in a glutenite reservoir

    Ma, Xinfang; Zou, Yushi; Li, Ning; Chen, Ming; Zhang, Yinuo; Liu, Zizhong


    Glutenite reservoirs are frequently significantly heterogeneous because of their unique depositional environment. The presence of gravel in this type of formation complicates the growth path of hydraulic fracture (HF). In this study, laboratory fracturing experiments were conducted on six large natural glutenite specimens (300 mm × 300 mm × 300 mm) using a true triaxial hydraulic fracturing system to investigate the growth law of HF in glutenite reservoirs. Before the experiments were performed, the rock properties of the gravel particles and matrix in the glutenite specimens were determined using various apparatuses. The effects of gravel size, horizontal differential stress, fracturing fluid type (or viscosity), and flow rate on the HF growth pattern, fracture width, and injection pressure were examined in detail. Similar to previous studies, four types of HF intersections with gravel particles, namely, termination, penetration, deflection, and attraction, were observed. The HF growth path in the glutenite specimens with large gravel (40 mm-100 mm) is likely branched and tortuous even under high horizontal differential stress. The HF growth path in the glutenite specimens with small gravel (less than 20 mm) is simple, but a process zone with multiple thin fractures may be created. Breakdown pressure may increase significantly when HF initiates from high-strength gravel particles, which are mainly composed of quartz. HF propagation is likely limited within high-strength gravel particles, thereby resulting in narrow fractures and even termination. The use of low-viscosity fluids, such as slickwater, and the low injection rate can further limit HF growth, particularly its width. As a response, high extension pressure builds up during fracturing.

  20. Microbial Community Changes in Hydraulic Fracturing Fluids and Produced Water from Shale Gas Extraction

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


    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.

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

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


    Successful economic production of oil and gas from nano-darcy-range permeability, tight shale reservoirs, is achieved via massive hydraulic fracturing. This is so despite their limited hydrocarbon in place, on per unit rock volume basis. As a reference, consider a typical average porosity of 6% and an average hydrocarbon saturation of 50% to 75%. The importance of tight shales results from their large areal extent and vertical thickness. For example, the areal extent of the Anwar field in Saudi Arabia of 3230 square miles (and 300 ft thick), while the Marcellus shale alone is over 100,000 square miles (and 70 to 150 ft thick). The low permeability of the rock matrix, the predominantly mineralized rock fabric, and the high capillary forces to both brines and hydrocarbons, restrict the mobility of pore fluids in these reservoirs. Thus, one anticipates that fluids do not move very far within tight shales. Successful production, therefore results from maximizing the surface area of contact with the reservoir by massive hydraulic fracturing from horizontal bore holes. This was the conceptual breakthrough of the previous decade and the one that triggered the emergence of gas shales, and recently oily shales, as important economic sources of energy. It is now understood that the process can be made substantially more efficient, more sustainable, and more cost effective by understanding the rock. This will be the breakthrough of this decade. Microseismic monitoring, mass balance calculations, and laboratory experiments of hydraulic fracturing on tight shales indicate the development of fracture complexity and fracture propagation that can not be explained in detail in this layered heterogeneous media. It is now clear that in tight shales the large-scale formation fabric is responsible for fracture complexity. For example, the presence and pervasiveness of mineralized fractures, bed interfaces, lithologic contacts, and other types of discontinuities, and their orientation

  2. A nonlocal model for fluid-structure interaction with applications in hydraulic fracturing

    Turner, Daniel Z


    Modeling important engineering problems related to flow-induced damage (in the context of hydraulic fracturing among others) depends critically on characterizing the interaction of porous media and interstitial fluid flow. This work presents a new formulation for incorporating the effects of pore pressure in a nonlocal representation of solid mechanics. The result is a framework for modeling fluid-structure interaction problems with the discontinuity capturing advantages of an integral based formulation. A number of numerical examples are used to show that the proposed formulation can be applied to measure the effect of leak-off during hydraulic fracturing as well as modeling consolidation of fluid saturated rock and surface subsidence caused by fluid extraction from a geologic reservoir. The formulation incorporates the effect of pore pressure in the constitutive description of the porous material in a way that is appropriate for nonlinear materials, easily implemented in existing codes, straightforward in i...

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

    Hopke, Jill E; Simis, Molly


    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.

  4. Estimating hydraulic conductivity of fractured rocks from high‐pressure packer tests with an Izbash's law‐based empirical model

    Chen, Yi‐Feng; Hu, Shao‐Hua; Hu, Ran; Zhou, Chuang‐Bing


    ...‐pressure groundwater flow conditions. The interpretation of the HPPT data, however, remains difficult due to the transition of flow conditions in the conducting structures and the hydraulic fracturing...

  5. 1PM TODAY: EPA to Hold Media Conference Call on Study of Hydraulic Fracturing Activities on Drinking Water Resources

    WASHINGTON - Environmental Protection Agency (EPA) officials will deliver remarks about the agency's study on potential impacts on drinking water resources in the United States from hydraulic fracturing activities, as requested by Congress, on a med

  6. The Role of Toxicological Science in Meeting the Challenges and Opportunities of Hydraulic Fracturing

    Goldstein, Bernard D.; Brooks, Bryan W.; Cohen, Steven D.; Gates, Alexander E.; Honeycutt, Michael E.; Morris, John B.; Orme-Zavaleta, Jennifer; Penning, Trevor M.; Snawder, John


    We briefly describe how toxicology can inform the discussion and debate of the merits of hydraulic fracturing by providing information on the potential toxicity of the chemical and physical agents associated with this process, individually and in combination. We consider upstream activities related to bringing chemical and physical agents to the site, on-site activities including drilling of wells and containment of agents injected into or produced from the well, and downstream activities inc...

  7. Regulation Of Hydraulic Fracturing In South Africa: A Project Life-Cycle Approach?

    Willemien du Plessis


    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.

  8. Pressure Responses of a Vertically Hydraulic Fractured Well in a Reservoir with Fractal Structure

    Razminia, Kambiz; Torres, Delfim F M


    We obtain an analytical solution for the pressure-transient behavior of a vertically hydraulic fractured well in a heterogeneous reservoir. The heterogeneity of the reservoir is modeled by using the concept of fractal geometry. Such reservoirs are called fractal reservoirs. According to the theory of fractional calculus, a temporal fractional derivative is applied to incorporate the memory properties of the fractal reservoir. The effect of different parameters on the computed wellbore pressure is fully investigated by various synthetic examples.

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

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


    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

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

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; Moridis, George J.


    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 towards conditions usually encountered in the Marcellus shale play in the Northeastern US at an approximate depth of 1500 m (~;;4,500 feet). Our modeling simulations indicate that when faults are present, micro-seismic events are possible, the magnitude of which is somewhat larger than the one associated with micro-seismic events originating from regular hydraulic fracturing because of the larger surface area that is available for rupture. The results of our simulations indicated fault rupture lengths of about 10 to 20 m, which, in rare cases can extend to over 100 m, depending on the fault permeability, the in situ stress field, and the fault strength properties. In addition to a single event rupture length of 10 to 20 m, repeated events and aseismic slip amounted to a total rupture length of 50 m, along with a shear offset displacement of less than 0.01 m. This indicates that the possibility of hydraulically induced fractures at great depth (thousands of meters) causing activation of faults and creation of a new flow path that can reach shallow groundwater resources (or even the surface) is remote. The expected low permeability of faults in producible shale is clearly a limiting factor for the possible rupture length and seismic magnitude. In fact, for a fault that is initially nearly-impermeable, the only possibility of larger fault slip event would be opening by hydraulic fracturing; this would allow pressure to penetrate the matrix along the fault and to reduce the frictional strength over a sufficiently large fault surface patch. However, our simulation results show that if the fault is initially impermeable, hydraulic fracturing along the fault results in numerous small micro-seismic events along with the propagation, effectively

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

    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)


    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)

  12. Estimates of hydraulic fracturing (Frac) sand production, consumption, and reserves in the United States

    Bleiwas, Donald I.


    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.

  13. The Critical Flow back Velocity in Hydraulic-Fracturing Shale Gas Wells

    Zheng Zhang


    Full Text Available The loss of prop pant during the flow back process in hydraulic fracturing treatments has been a problem for many years. The effectiveness of the fracture treatment is reduced. A well cleanup is often required to remove the unwanted proppant from the wellbore to re-establish production. Among several techniques available to reduce the prop pant loss, controlling flow back velocity within a critical range is an essential measure. The objective of this study is to determine the critical flow back velocity under different confining pressures in the propped fractures of different thicknesses. This objective is achieved based experimental studies conducted in a specially designed apparatus. For a fracture with a given width, the closure stress helps hold the proppant in place. This is due to the friction force that is proportional to the normal force created by the closure stress. The critical flow back velocity necessary to mobilize the proppant therefore increases with closure stress. However, the stress effect may be influenced by the shape of solid particles and friction coefficient of solid. Under the condition of constant closure stress, a narrow fracture holds proppant better than a wide fracture, resulting in increased critical flow back velocity. This is interpreted to be due to the “tighter” packing of proppant in narrow fractures.

  14. New P3D Hydraulic Fracturing Model Based on the Radial Flow

    鲁连军; 孙逢春; 肖海华; 安申法


    Pseudo three-dimension (P3D) hydraulic fracturing models often overpredict the fracture height for a poorly contained fracture. To solve this problem, a new method is presented in shaping the P3D fracture geometry on the basis of the fundamental theory and the original 1D fluid flow is replaced with a more representatively radial flow. The distribution of the fluid in the modified fluid field is analyzed and a sound explanation to the problem is given. Due to the consideration of the fluid flow in the vertical direction, the modified model can predict the fracture height much better. To validate the rationality of the radial fluid flow assumption, the distribution of the fluid in the modified fluid field is simulated with the plane potential flow by using finite element method. And the results agree effectively with those from the assumption. Through comparing with the full 3D model, the results show that this new P3D model can be used to aid the fracturing design and predict the fracture height under poorly contained situation.

  15. Biocides in hydraulic fracturing fluids: a critical review of their usage, mobility, degradation, and toxicity.

    Kahrilas, Genevieve A; Blotevogel, Jens; Stewart, Philip S; Borch, Thomas


    Biocides are critical components of hydraulic fracturing ("fracking") fluids used for unconventional shale gas development. Bacteria may cause bioclogging and inhibit gas extraction, produce toxic hydrogen sulfide, and induce corrosion leading to downhole equipment failure. The use of biocides such as glutaraldehyde and quaternary ammonium compounds has spurred a public concern and debate among regulators regarding the impact of inadvertent releases into the environment on ecosystem and human health. This work provides a critical review of the potential fate and toxicity of biocides used in hydraulic fracturing operations. We identified the following physicochemical and toxicological aspects as well as knowledge gaps that should be considered when selecting biocides: (1) uncharged species will dominate in the aqueous phase and be subject to degradation and transport whereas charged species will sorb to soils and be less bioavailable; (2) many biocides are short-lived or degradable through abiotic and biotic processes, but some may transform into more toxic or persistent compounds; (3) understanding of biocides' fate under downhole conditions (high pressure, temperature, and salt and organic matter concentrations) is limited; (4) several biocidal alternatives exist, but high cost, high energy demands, and/or formation of disinfection byproducts limits their use. This review may serve as a guide for environmental risk assessment and identification of microbial control strategies to help develop a sustainable path for managing hydraulic fracturing fluids.

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

    Hopke, Jill E; Simis, Molly


    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.

  17. The risk of hydraulic fracturing on public health in the UK and the UK's fracking legislation.

    Reap, Elisabeth


    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.

  18. Investigation of post hydraulic fracturing well cleanup physics in the Cana Woodford Shale

    Lu, Rong

    Hydraulic fracturing was first carried out in the 1940s and has gained popularity in current development of unconventional resources. Flowing back the fracturing fluids is critical to a frac job, and determining well cleanup characteristics using the flowback data can help improve frac design. It has become increasingly important as a result of the unique flowback profiles observed in some shale gas plays due to the unconventional formation characteristics. Computer simulation is an efficient and effective way to tackle the problem. History matching can help reveal some mechanisms existent in the cleanup process. The Fracturing, Acidizing, Stimulation Technology (FAST) Consortium at Colorado School of Mines previously developed a numerical model for investigating the hydraulic fracturing process, cleanup, and relevant physics. It is a three-dimensional, gas-water, coupled fracture propagation-fluid flow simulator, which has the capability to handle commonly present damage mechanisms. The overall goal of this research effort is to validate the model on real data and to investigate the dominant physics in well cleanup for the Cana Field, which produces from the Woodford Shale in Oklahoma. To achieve this goal, first the early time delayed gas production was explained and modeled, and a simulation framework was established that included all three relevant damage mechanisms for a slickwater fractured well. Next, a series of sensitivity analysis of well cleanup to major reservoir, fracture, and operational variables was conducted; five of the Cana wells' initial flowback data were history matched, specifically the first thirty days' gas and water producing rates. Reservoir matrix permeability, net pressure, Young's modulus, and formation pressure gradient were found to have an impact on the gas producing curve's shape, in different ways. Some moderately good matches were achieved, with the outcome of some unknown reservoir information being proposed using the

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

    Viswanathan, H. S.


    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.

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

    Bonneville, Alain; Jung, Hun Bok; Shao, Hongbo; Kabilan, Senthil; Um, Wooyong; Carroll, Kenneth C.; Varga, Tamas; Suresh, Niraj; Stephens, Sean A.; Fernandez, Carlos A.


    We have used an environmentally friendly and recyclable hydraulic fracturing fluid - diluted aqueous solutions of polyallylamine or PAA – for reservoir stimulation in Enhanced Geothermal System (EGS). This fluid undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at EGS temperatures. We are presenting here the results of laboratory-scale hydraulic fracturing experiment using the fluid on small cylindrical rock cores (1.59 cm in diameter and 5.08 cm in length) from the Coso geothermal field in California. Rock samples consisted of Mesozoic diorite metamorphosed to greenschist facies. The experiments were conducted on 5 samples for realistic ranges of pressures (up to 275 bar) and temperatures (up to 210 °C) for both the rock samples and the injected fluid. After fracturing, cores were subjected to a CO2 leakage test, injection of KI solution, and X-ray microtomography (XMT) scanning to examine the formation and distribution of fractures. The design and conduct of these experiments will be presented and discussed in details. Based on the obtained XMT images, Computational Fluid Dynamics (CFD) simulations were then performed to visualize hydraulic fractures and compute the bulk permeability. OpenFOAM (OpenCFD Ltd., Reading, UK), was used to solve the steady state simulation. The flow predictions, based upon the laminar, 3-D, incompressible Navier-Stokes equations for fluid mass and momentum, show the remarkable stimulation of the permeability in the core samples and demonstrate the efficiency of such a CO2 triggered fluid in EGS.

  1. Edit paper Methods for Large Scale Hydraulic Fracture Monitoring

    Ely, Gregory


    In this paper we propose computationally efficient and robust methods for estimating the moment tensor and location of micro-seismic event(s) for large search volumes. Our contribution is two-fold. First, we propose a novel joint-complexity measure, namely the sum of nuclear norms which while imposing sparsity on the number of fractures (locations) over a large spatial volume, also captures the rank-1 nature of the induced wavefield pattern. This wavefield pattern is modeled as the outer-product of the source signature with the amplitude pattern across the receivers from a seismic source. A rank-1 factorization of the estimated wavefield pattern at each location can therefore be used to estimate the seismic moment tensor using the knowledge of the array geometry. In contrast to existing work this approach allows us to drop any other assumption on the source signature. Second, we exploit the recently proposed first-order incremental projection algorithms for a fast and efficient implementation of the resulting...

  2. Water usage for natural gas production through hydraulic fracturing in the United States from 2008 to 2014.

    Chen, Huan; Carter, Kimberly E


    Hydraulic fracturing has promoted the exploitation of shale oil and natural gas in the United States (U.S.). However, the large amounts of water used in hydraulic fracturing may constrain oil and natural gas production in the shale plays. This study surveyed the amounts of freshwater and recycled produced water used to fracture wells from 2008 to 2014 in Arkansas, California, Colorado, Kansas, Louisiana, Montana, North Dakota, New Mexico, Ohio, Oklahoma, Pennsylvania, Texas, West Virginia, and Wyoming. Results showed that the annual average water volumes used per well in most of these states ranged between 1000 m(3) and 30,000 m(3). The highest total amount of water was consumed in Texas with 457.42 Mm(3) of water used to fracture 40,521 wells, followed by Pennsylvania with 108.67 Mm(3) of water used to treat 5127 wells. Water usages ranged from 96.85 Mm(3) to 166.10 Mm(3) annually in Texas from 2012 to 2014 with more than 10,000 wells fractured during that time. The percentage of water used for hydraulic fracturing in each state was relatively low compared to water usages for other industries. From 2009 to 2014, 6.55% (median) of the water volume used in hydraulic fracturing contained recycled produced water or recycled hydraulic fracturing wastewater. 10.84% (median) of wells produced by hydraulic fracturing were treated with recycled produced water. The percentage of wells where recycled wastewater was used was lower, except in Ohio and Arkansas, where more than half of the wells were fractured using recycled produced water. The median recycled wastewater volume in produced wells was 7127 m(3) per well, more than half the median value in annual water used per well 11,259 m(3). This indicates that, for wells recycling wastewater, more than half of their water use consisted of recycled wastewater.

  3. Hydraulic fracturing fluid migration in the subsurface: A review and expanded modeling results

    Birdsell, Daniel T.; Rajaram, Harihar; Dempsey, David; Viswanathan, Hari S.


    Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated. Topographically driven flow, overpressured shale reservoirs, permeable pathways such as faults or leaky wellbores, the increased formation pressure due to HF fluid injection, and the density contrast of the HF fluid to the surrounding brine can encourage upward HF fluid migration. In contrast, the very low shale permeability and capillary imbibition of water into partially saturated shale may sequester much of the HF fluid, and well production will remove HF fluid from the subsurface. We review the literature on important aspects of HF fluid migration. Single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore with flowback and produced water, how much reaches overlying aquifers, and how much is permanently sequestered by capillary imbibition, which is treated as a sink term based on a semianalytical, one-dimensional solution for two-phase flow. These simulations include all of the important aspects of HF fluid migration identified in the literature review and are performed in five stages to faithfully represent the typical operation of a hydraulically fractured well. No fracturing fluid reaches the aquifer without a permeable pathway. In the presence of a permeable pathway, 10 times more fracturing fluid reaches the aquifer if well production and capillary imbibition are not included in the model.

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

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


    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

  5. Hydraulic fracturing research in east Texas; Third GRI staged field experiment

    Robinson, B.M. (S.A. Holditch and Associates, Inc. (US))


    This paper presents results from results from research conducted on the third Gas Research inst. (GRI) staged field experiment (SFE) well. Research well SFE No. 3 was drilled as part of a field-based research program conducted in east Texas during the past 7 years. Most of the work before SFE No. 3 involved the Travis Peak formation; however, the Cotton Valley sandstone was the primary research target for this well. SFE no. 3 is the last in a series of research wells planned for east Texas. A fourth SFE is being conducted in the Frontier formation of southwestern Wyoming. Data on SFE wells are collected from whole cores, openhole geophysical logs, in-situ stress measurements, production and pressure-transient tests, fracture stimulation treatments, fracture-diagnostic measurements, and postfracture performance tests. Test data then are analyzed by research scientists, geologists, and engineers to describe the reservoir and hydraulic fracture fully.

  6. Environmentally Friendly, Rheoreversible, Hydraulic-fracturing Fluids for Enhanced Geothermal Systems

    Shao, Hongbo; Kabilan, Senthil; Stephens, Sean A.; Suresh, Niraj; Beck, Anthon NR; Varga, Tamas; Martin, Paul F.; Kuprat, Andrew P.; Jung, Hun Bok; Um, Wooyong; Bonneville, Alain; Heldebrant, David J.; Carroll, KC; Moore, Joseph; Fernandez, Carlos A.


    Cost-effective creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the feasibility of enhanced geothermal systems (EGS). Current reservoir stimulation entails adverse environmental impacts and substantial economic costs due to the utilization of large volumes of water “doped” with chemicals including rheology modifiers, scale and corrosion inhibitors, biocides, friction reducers among others where, typically, little or no information of composition and toxicity is disclosed. An environmentally benign, CO2-activated, rheoreversible fracturing fluid has recently been developed that significantly enhances rock permeability at effective stress significantly lower than current technology. We evaluate the potential of this novel fracturing fluid for application on geothermal sites under different chemical and geomechanical conditions, by performing laboratory-scale fracturing experiments with different rock sources under different confining pressures, temperatures, and pH environments. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable Polyallylamine (PAA) represent a highly versatile fracturing fluid technology. This fracturing fluid creates/propagates fracture networks through highly impermeable crystalline rock at significantly lower effective stress as compared to control experiments where no PAA was present, and permeability enhancement was significantly increased for PAA compared to conventional hydraulic fracturing controls. This was evident in all experiments, including variable rock source/type, operation pressure and temperature (over the entire range for EGS applications), as well as over a wide range of formation-water pH values. This versatile novel fracturing fluid technology represents a great alternative to industrially available fracturing fluids for cost-effective and competitive geothermal energy production.

  7. Development and implementation of a fluid flow code to evaluate block hydraulic behaviors of the fractured rock masses

    Um, Jeong-Gi; Han, Jisu; Lee, Dahye; Cho, Taechin


    A computer program code was developed to estimate the hydraulic head distribution through the 2-D DFN(discrete fracture network) blocks considering hydraulic aperture of the individual fractures, and to determine flow quantity, directional block hydraulic conductivity and principal hydraulic conductivity tensor according to fracture geometry such as orientation, frequency and size of the fracture network systems. The generated stochastic DFN system is assumed to have a network structure in which the equivalent flow pipe composed linear fractures is complexly connected. DFN systems often include individual or group of sub-network that are isolated from a network that can act as fluid flow passages from one flow boundary to another, and the fluid flow is completely blocked due to lack of connectivity. Fractures that are completely or partially isolated in the DFN system do not contribute to the overall fluid flow through the DFN system and add to the burden of numerical computation. This sometimes leads to numerical instability and failure to provide a solution. In this study, geometric and mathematical routines were designed and implemented to classify and eliminate such sub-networks. The developed program code can calculate the total head at each node connected to the flow path with various aperture as well as hydraulic conductivity of the individual flow pipe using the SOR method. Numerical experiments have been carried out to explore the applicability of the developed program code. A total of 108 stochastic 2-D DFN blocks of 20 m×20 m with various hydraulic aperture were prepared using two joint sets with fixed input parameters of fracture orientation, frequency and size distribution. The hydraulic anisotropy and the chance for equivalent continuum behavior of the DFN system were found to depend on the variability of fracture aperture.

  8. Modeling Atmospheric Emissions and Calculating Mortality Rates Associated with High Volume Hydraulic Fracturing Transportation

    Mathews, Alyssa

    Emissions from the combustion of fossil fuels are a growing pollution concern throughout the global community, as they have been linked to numerous health issues. The freight transportation sector is a large source of these emissions and is expected to continue growing as globalization persists. Within the US, the expanding development of the natural gas industry is helping to support many industries and leading to increased transportation. The process of High Volume Hydraulic Fracturing (HVHF) is one of the newer advanced extraction techniques that is increasing natural gas and oil reserves dramatically within the US, however the technique is very resource intensive. HVHF requires large volumes of water and sand per well, which is primarily transported by trucks in rural areas. Trucks are also used to transport waste away from HVHF well sites. This study focused on the emissions generated from the transportation of HVHF materials to remote well sites, dispersion, and subsequent health impacts. The Geospatial Intermodal Freight Transport (GIFT) model was used in this analysis within ArcGIS to identify roadways with high volume traffic and emissions. High traffic road segments were used as emissions sources to determine the atmospheric dispersion of particulate matter using AERMOD, an EPA model that calculates geographic dispersion and concentrations of pollutants. Output from AERMOD was overlaid with census data to determine which communities may be impacted by increased emissions from HVHF transport. The anticipated number of mortalities within the impacted communities was calculated, and mortality rates from these additional emissions were computed to be 1 in 10 million people for a simulated truck fleet meeting stricter 2007 emission standards, representing a best case scenario. Mortality rates due to increased truck emissions from average, in-use vehicles, which represent a mixed age truck fleet, are expected to be higher (1 death per 341,000 people annually).

  9. Laboratory Hydraulic Fracturing Experiments for Determining Reopening and Closing Pressures of Fractures

    IMAI, Tadao; KAMOSHIDA, Naoto; KATO, Harumi; SUGIMOTO, Fumio


    ... in the borehole wall and the triggering of acoustic emissions.In the experiments, we measured the pressures during the reopening and closing of a fracture caused by elastic restitution in a block of rock not subjected to compressive load...

  10. Thermal hydraulics analysis of the Advanced High Temperature Reactor

    Wang, Dean, E-mail: [University of Massachusetts Lowell, One University Avenue, Lowell, MA 01854 (United States); Yoder, Graydon L.; Pointer, David W.; Holcomb, David E. [Oak Ridge National Laboratory, 1 Bethel Valley RD #6167, Oak Ridge, TN 37831 (United States)


    Highlights: • The TRACE AHTR model was developed and used to define and size the DRACS and the PHX. • A LOFF transient was simulated to evaluate the reactor performance during the transient. • Some recommendations for modifying FHR reactor system component designs are discussed. - Abstract: The Advanced High Temperature Reactor (AHTR) is a liquid salt-cooled nuclear reactor design concept, featuring low-pressure molten fluoride salt coolant, a carbon composite fuel form with embedded coated particle fuel, passively triggered negative reactivity insertion mechanisms, and fully passive decay heat rejection. This paper describes an AHTR system model developed using the Nuclear Regulatory Commission (NRC) thermal hydraulic transient code TRAC/RELAP Advanced Computational Engine (TRACE). The TRACE model includes all of the primary components: the core, downcomer, hot legs, cold legs, pumps, direct reactor auxiliary cooling system (DRACS), the primary heat exchangers (PHXs), etc. The TRACE model was used to help define and size systems such as the DRACS and the PHX. A loss of flow transient was also simulated to evaluate the performance of the reactor during an anticipated transient event. Some initial recommendations for modifying system component designs are also discussed. The TRACE model will be used as the basis for developing more detailed designs and ultimately will be used to perform transient safety analysis for the reactor.

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

    Ingrid Tomac


    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.

  12. The Functional Potential of Microbial Communities in Hydraulic Fracturing Source Water and Produced Water from Natural Gas Extraction Characterized by Metagenomic Sequencing

    Arvind Murali Mohan; Bibby, Kyle J.; Daniel Lipus; Hammack, Richard W.; Gregory, Kelvin B


    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 anaerobi...

  13. Simulating the hydraulic stimulation of multiple fractures in an anisotropic stress field applying the discrete element method

    Zeeb, Conny; Frühwirt, Thomas; Konietzky, Heinz


    Key to a successful exploitation of deep geothermal reservoirs in a petrothermal environment is the hydraulic stimulation of the host rock to increase permeability. The presented research investigates the fracture propagation and interaction during hydraulic stimulation of multiple fractures in a highly anisotropic stress field. The presented work was conducted within the framework of the OPTIRISS project, which is a cooperation of industry partners and universities in Thuringia and Saxony (Federal States of Germany) and was funded by the European Fond for Regional Development. One objective was the design optimization of the subsurface geothermal heat exchanger (SGHE) by means of numerical simulations. The presented simulations were conducted applying 3DEC (Itasca™), a software tool based on the discrete element method. The simulation results indicate that the main direction of fracture propagation is towards lower stresses and thus towards the biosphere. Therefore, barriers might be necessary to limit fracture propagation to the designated geological formation. Moreover, the hydraulic stimulation significantly alters the stresses in the vicinity of newly created fractures. Especially the change of the minimum stress component affects the hydraulic stimulation of subsequent fractures, which are deflected away from the previously stimulated fractures. This fracture deflection can render it impossible to connect all fractures with a second borehole for the later production. The results of continuative simulations indicate that a fracture deflection cannot be avoided completely. Therefore, the stage alignment was modified to minimize fracture deflection by varying (1) the pauses between stages, (2) the spacing's between adjacent stages, and (3) the angle between stimulation borehole and minimum stress component. An optimum SGHE design, which implies that all stimulated fractures are connected to the production borehole, can be achieved by aligning the stimulation

  14. A Hydraulic Tomography Experiment in Fractured Sedimentary Rocks, Newark Basin, New Jersey, USA

    Tiedeman, C. R.; Barrash, W.; Thrash, C. J.; Johnson, C. D.


    Hydraulic tomography was performed in July 2015 in contaminated fractured mudstone beds at the former Naval Air Warfare Center (NAWC) in the Newark Basin near Trenton, NJ using seven existing wells. The spatial arrangement of wells (in a circle of 9 m radius with one central well), the use of packers to divide the wells into multiple monitoring intervals, and the deployment of fiber optic pressure transducers enabled collection of a hydraulic tomography dataset comprising high-resolution drawdown observations at an unprecedented level of spatial detail for fractured rocks. The experiment involved 45-minute cross-hole aquifer tests, conducted by pumping from a given packer-isolated well interval and continuously monitoring drawdowns in all other well intervals. The collective set of drawdown data from all tests and intervals displays a wide range of behavior suggestive of highly heterogeneous hydraulic conductivity (K) within the tested volume, such as: drawdown curves for different well intervals crossing one another on drawdown-time plots; variable drawdown curve shapes, including linear segments on log-log plots; variable order and magnitude of time-lag and/or drawdown for intervals of a given well in response to pumping from similar fractures or stratigraphic units in different wells; and variable groupings of wells and intervals showing similar responses for different pumping tests. The observed behavior is consistent with previous testing at the NAWC indicating that K within and across individual mudstone beds can vary by orders of magnitude over scales of meters. Preliminary assessment of the drawdown data together with a rich set of geophysical logs suggests an initial conceptual model that includes densely distributed fractures of moderate K at the shallowest depths of the tested volume, connected high-K bedding-plane-parting fractures at intermediate depths, and sparse low-K fractures in the deeper rocks. Future work will involve tomographic inversion of

  15. Predominance and Metabolic Potential of Halanaerobium spp. in Produced Water from Hydraulically Fractured Marcellus Shale Wells

    Lipus, Daniel; Vikram, Amit; Ross, Daniel; Bain, Daniel; Gulliver, Djuna; Hammack, Richard; Bibby, Kyle; Stams, Alfons J. M.



    Microbial activity in the produced water from hydraulically fractured oil and gas wells may potentially interfere with hydrocarbon production and cause damage to the well and surface infrastructure via corrosion, sulfide release, and fouling. In this study, we surveyed the microbial abundance and community structure of produced water sampled from 42 Marcellus Shale wells in southwestern Pennsylvania (well age ranged from 150 to 1,846 days) to better understand the microbial diversity of produced water. We sequenced the V4 region of the 16S rRNA gene to assess taxonomy and utilized quantitative PCR (qPCR) to evaluate the microbial abundance across all 42 produced water samples. Bacteria of the orderHalanaerobialeswere found to be the most abundant organisms in the majority of the produced water samples, emphasizing their previously suggested role in hydraulic fracturing-related microbial activity. Statistical analyses identified correlations between well age and biocide formulation and the microbial community, in particular, the relative abundance ofHalanaerobiales. We further investigated the role of members of the orderHalanaerobialesin produced water by reconstructing and annotating aHalanaerobiumdraft genome (named MDAL1), using shotgun metagenomic sequencing and metagenomic binning. The recovered draft genome was found to be closely related to the speciesH. congolense, an oil field isolate, andHalanaerobiumsp. strain T82-1, also recovered from hydraulic fracturing produced water. Reconstruction of metabolic pathways

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

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


    In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole

  17. Assessment of the Acute and Chronic Health Hazards of Hydraulic Fracturing Fluids.

    Wattenberg, Elizabeth V; Bielicki, Jeffrey M; Suchomel, Ashley E; Sweet, Jessica T; Vold, Elizabeth M; Ramachandran, Gurumurthy


    There is growing concern about how hydraulic fracturing affects public health because this activity involves handling large volumes of fluids that contain toxic and carcinogenic constituents, which are injected under high pressure through wells into the subsurface to release oil and gas from tight shale formations. The constituents of hydraulic fracturing fluids (HFFs) present occupational health risks because workers may be directly exposed to them, and general public health risks because of potential air and water contamination. Hazard identification, which focuses on the types of toxicity that substances may cause, is an important step in the complex health risk assessment of hydraulic fracturing. This article presents a practical and adaptable tool for the hazard identification of HFF constituents, and its use in the analysis of HFF constituents reported to be used in 2,850 wells in North Dakota between December 2009 and November 2013. Of the 569 reported constituents, 347 could be identified by a Chemical Abstract Service Registration Number (CASRN) and matching constituent name. The remainder could not be identified either because of trade secret labeling (210) or because of an invalid CASRN (12). Eleven public databases were searched for health hazard information on thirteen health hazard endpoints for 168 identifiable constituents that had at least 25 reports of use. Health hazard counts were generated for chronic and acute endpoints, including those associated with oral, inhalation, ocular, and dermal exposure. Eleven of the constituents listed in the top 30 by total health hazard count were also listed in the top 30 by reports of use. This includes naphthalene, which along with benzyl chloride, has the highest health hazard count. The top 25 constituents reportedly used in North Dakota largely overlap with those reported for Texas and Pennsylvania, despite different geologic formations, target resources (oil vs. gas), and disclosure requirements

  18. A time step criterion for the stable numerical simulation of hydraulic fracturing

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


    The process of propagating or widening cracks in rock formations by means of fluid flow, known as hydraulic fracturing, has been gaining attention in the last couple of decades. There is growing interest in its numerical simulation to make predictions. Due to the complexity of the processes taking place, e.g. solid deformation, fluid flow in an open channel, fluid flow in a porous medium and crack propagation, this is a challenging task. Hydraulic fracturing has been numerically simulated for some years now [1] and new methods to take more of its processes into account (increasing accuracy) while modeling in an efficient way (lower computational effort) have been developed in recent years. An example is the use of the Extended Finite Element Method (XFEM), whose application originated within the framework of solid mechanics, but is now seen as an effective method for the simulation of discontinuities with no need for re-meshing [2]. While more focus has been put to the correct coupling of the processes mentioned above, less attention has been paid to the stability of the model. When using a quasi-static approach for the simulation of hydraulic fracturing, choosing an adequate time step is not trivial. This is in particular true if the equations are solved in a staggered way. The difficulty lies within the inconsistency between the static behavior of the solid and the dynamic behavior of the fluid. It has been shown that too small time steps may lead to instabilities early into the simulation time [3]. While the solid reaches a stationary state instantly, the fluid is not able to achieve equilibrium with its new surrounding immediately. This is why a time step criterion has been developed to quantify the instability of the model concerning the time step. The presented results were created with a 2D poroelastic model, using the XFEM for both the solid and the fluid phases. An embedded crack propagates following the energy release rate criteria when the fluid pressure

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

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamidreza M.


    Aperture has a controlling impact on porosity and permeability and is a source of uncertainty in modeling of naturally fractured reservoirs. This uncertainty results from difficulties in accurately quantifying aperture in the subsurface and from a limited fundamental understanding of the mechanical and diagenetic processes that control aperture. In the absence of cement bridges and high pore pressure, fractures in the subsurface are generally considered to be closed. However, experimental work, outcrop analyses and subsurface data show that some fractures remain open, and that aperture varies even along a single fracture. However, most fracture flow models consider constant apertures for fractures. We create a stress-dependent heterogeneous aperture by combining Finite Element modeling of discrete fracture networks with an empirical aperture model. Using a modeling approach that considers fractures 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 σ1 has a controlling impact on aperture and permeability, where hydraulic opening is maximum for an angle of 15°. At this angle, the fracture experiences a minor amount of shear displacement that allows the fracture to remain open even when fluid pressure is lower than the local normal stress. Averaging the heterogeneous aperture to scale up permeability probably results in an underestimation of flow, indicating the need to incorporate full aperture distributions rather than simplified aperture models in reservoir-scale flow models.

  20. Experimental Study of Crack Initiation and Extension Induced by Hydraulic Fracturing in a Tree-Type Borehole Array

    Yiyu Lu


    Full Text Available High-pressure hydraulic fracturing technology in coal and coal bed methane mines can lead to roof and floor damage, and fracture initiation disorder that leads to a “blank area”, and other issues. A new method of hydraulic fracturing is proposed to increase the homogeneous permeability of coal in underground coalmines. Numerical and other simulation tests for different forms of a tree-type, branched borehole model are presented. The results show that the branched array causes cracks to initiate from the bottom of the array, and these extend along the direction of the adjacent boreholes. Generally, as the number of branched boreholes increases, the coal seam fracture network also increase, improving the distribution of the fracture network, making the fracturing effect better. The branched boreholes appear to reduce initiation pressure and, with increasing branches, the initiation pressure decreases. A model with four tree-type, branched boreholes leads to a reduction in initiation pressure of 69%. In terms of permeability improvement technology in underground coalmines, a branched hydraulic fracturing borehole array has the advantages of reducing initiation pressure, controlling crack initiation and extension, enhancing the fracturing effect and reducing the destruction of the roof and floor.

  1. Advancements in classification, treatment and outcome of radial head fractures

    Guitton, T.G.


    This thesis shows that advancements in technical head fractures analysis, imaging modalities, increased interest in psychosocial aspects of treatment and the availability of long-term outcome data can help improve classification, treatment and outcome in fractures of the radial head. It is science

  2. Robust Hydraulic Fracture Monitoring (HFM) of Multiple Time Overlapping Events Using a Generalized Discrete Radon Transform

    Ely, Gregory


    In this work we propose a novel algorithm for multiple-event localization for Hydraulic Fracture Monitoring (HFM) through the exploitation of the sparsity of the observed seismic signal when represented in a basis consisting of space time propagators. We provide explicit construction of these propagators using a forward model for wave propagation which depends non-linearly on the problem parameters - the unknown source location and mechanism of fracture, time and extent of event, and the locations of the receivers. Under fairly general assumptions and an appropriate discretization of these parameters we first build an over-complete dictionary of generalized Radon propagators and assume that the data is well represented as a linear superposition of these propagators. Exploiting this structure we propose sparsity penalized algorithms and workflow for super-resolution extraction of time overlapping multiple seismic events from single well data.

  3. Bench-mark solution for a penny-shaped hydraulic fracture driven by a thinning fluid

    Linkov, Aleksandr


    The paper presents a solution for axisymmetric propagation of a penny-shaped crack driven by a thinning fluid. The solution to the accuracy of four significant digits, at least, is obtained on the basis of the modified formulation of hydraulic fracture problem by employing the particle velocity, rather than conventionally used flux. This serves to properly organize iterations in the opening after reducing the problem to the self-similar form. Numerical results obtained show relatively small dependence of self-similar quantities (fracture radius, propagation speed, opening, particle velocity, pressure, flux) on the behavior index of a thinning fluid. The results provide bench marks for the accuracy control of truly 3D simulators and they serve for assigning an apparent viscosity when simulating the action of a thinning fluid by replacing it with an equivalent Newtonian fluid.

  4. An approximate solution for a penny-shaped hydraulic fracture that accounts for fracture toughness, fluid viscosity and leak-off

    Dontsov, E. V.


    This paper develops a closed-form approximate solution for a penny-shaped hydraulic fracture whose behaviour is determined by an interplay of three competing physical processes that are associated with fluid viscosity, fracture toughness and fluid leak-off. The primary assumption that permits one to construct the solution is that the fracture behaviour is mainly determined by the three-process multiscale tip asymptotics and the global fluid volume balance. First, the developed approximation is compared with the existing solutions for all limiting regimes of propagation. Then, a solution map, which indicates applicability regions of the limiting solutions, is constructed. It is also shown that the constructed approximation accurately captures the scaling that is associated with the transition from any one limiting solution to another. The developed approximation is tested against a reference numerical solution, showing that accuracy of the fracture width and radius predictions lie within a fraction of a per cent for a wide range of parameters. As a result, the constructed approximation provides a rapid solution for a penny-shaped hydraulic fracture, which can be used for quick fracture design calculations or as a reference solution to evaluate accuracy of various hydraulic fracture simulators.

  5. An Analytical Solution of Partially Penetrating Hydraulic Fractures in a Box-Shaped Reservoir

    He Zhang


    Full Text Available This paper presents a new method to give an analytical solution in Laplace domain directly that is used to describe pressure transient behavior of partially penetrating hydraulic fractures in a box-shaped reservoir with closed boundaries. The basic building block of the method is to solve diffusivity equation with the integration of Dirac function over the distance that is presented for the first time. Different from the traditional method of using the source solution and Green’s function presented by Gringarten and Ramey, this paper uses Laplace transform and Fourier transform to solve the diffusivity equation and the analytical solution obtained is accurate and simple. The effects of parameters including fracture height, fracture length, the position of the fracture, and reservoir width on the pressure and pressure derivative are fully investigated. The advantage of the analytical solution is easy to incorporate storage coefficient and skin factor. It can also reduce the amount of computation and compute efficiently and quickly.

  6. Flexible parallel implicit modelling of coupled thermal-hydraulic-mechanical processes in fractured rocks

    Cacace, Mauro; Jacquey, Antoine B.


    Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture-solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact Newton-Krylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

  7. A Graph Theoretic Approach for Hydraulic Fracturing and Wellbore Leakage Risk Modeling

    Glosser, D.; Rose, K.; Bauer, J. R.; Warner, T.


    Recent large scale development of unconventional formations for fossil energy has raised concerns over the potential for fluid leakage between subsurface systems and wellbores. This is particularly true in regions with extensive drilling history, where spatial densities of wellbores are higher, and where significant uncertainties in the location and mechanical integrity of such wellbores exist. The generation of induced fracture networks during hydraulic fracturing may increase subsurface connectivity, and create the potential for unwanted fluid migration between operational and legacy wellbores and subsurface fracture networks. We present a graph theoretic approach for identifying geospatial regions and wellbores at increased risk for subsurface connectivity based on wellbore proximity and local geologic characteristics. The algorithm transforms user inputted geospatial data (geologic and wellbore x,y,z) to graph structure, where wellbores are represented as nodes, and where potential overlapping fracture network zones are represented as edges. The algorithm can be used to complement existing fracture models to better account for the reach of induced fractures, and to identify spatial extents at increased risk for unwanted subsurface connectivity. Additionally, the model can be used to identify regions in need of geophysical detection methods for locating undocumented wells. As a result, the method can be part of a cumulative strategy to reduce uncertainty inherent to combined geologic and engineered systems. The algorithm has been successfully tested against a known leakage scenario in Pennsylvania. In addition to identifying wells associated with the leakage event, the algorithm identified two other higher risk networks in the region. The algorithm output provides valuable information for industry to develop environmentally safe drilling and injection plans; and for regulators to identify specific wellbores at greater risk for leakage, and to develop targeted

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

    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.


    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.

  9. Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas

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


    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.

  10. Contesting Technologies in the Networked Society: A Case Study of Hydraulic Fracturing and Shale Development

    Hopke, Jill E.

    In this dissertation, I study the network structure and content of a transnational movement against hydraulic fracturing and shale development, Global Frackdown. I apply a relational perspective to the study of role of digital technologies in transnational political organizing. I examine the structure of the social movement through analysis of hyperlinking patterns and qualitative analysis of the content of the ties in one strand of the movement. I explicate three actor types: coordinator, broker, and hyper-local. This research intervenes in the paradigm that considers international actors as the key nodes to understanding transnational advocacy networks. I argue this focus on the international scale obscures the role of globally minded local groups in mediating global issues back to the hyper-local scale. While international NGOs play a coordinating role, local groups with a global worldview can connect transnational movements to the hyper-local scale by networking with groups that are too small to appear in a transnational network. I also examine the movement's messaging on the social media platform Twitter. Findings show that Global Frackdown tweeters engage in framing practices of: movement convergence and solidarity, declarative and targeted engagement, prefabricated messaging, and multilingual tweeting. The episodic, loosely-coordinated and often personalized, transnational framing practices of Global Frackdown tweeters support core organizers' goal of promoting the globalness of activism to ban fracking. Global Frackdown activists use Twitter as a tool to advance the movement and to bolster its moral authority, as well as to forge linkages between localized groups on a transnational scale. Lastly, I 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). I analyze the top actors tweeting using the #fracking

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

    Guoxiang Chi


    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

  12. New development of hydraulic fracturing technique for in-situ stress measurement at great depth of mines


    In-situ stress measurement using the hydraulic fracturing technique was made at Wanfu Coal Mine in Shandong Province,China.To solve problems caused by great measuring depth and extra thick overburden soil layers in the mine,a series of improved techniques were developed for the traditional hydraulic fracturing technique and equipment to increase their pressure-enduring ability and to ensure safe and flexible removal of the sealing packers with other experimental apparatus.Successful in-situ stress measurement at 37 points within 7 boreholes,which were mostly over 1000 m deep,was completed.Through the measurement,detailed in

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

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid


    Aperture has a controlling impact on porosity and permeability and is a source of uncertainty in modeling of naturally fractured reservoirs. This uncertainty results from difficulties in accurately quantifying aperture in the subsurface and from a limited fundamental understanding of the mechanical...... 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...... and permeability, where hydraulic opening is maximum for an angle of 15°. At this angle, the fracture experiences a minor amount of shear displacement that allows the fracture to remain open even when fluid pressure is lower than the local normal stress. Averaging the heterogeneous aperture to scale up...

  14. Complementary hydro-mechanical coupled finite/discrete element and microseismic modelling to predict hydraulic fracture propagation in tight shale reservoirs

    Profit, Matthew; Dutko, Martin; Yu, Jianguo; Cole, Sarah; Angus, Doug; Baird, Alan


    This paper presents a novel approach to predict the propagation of hydraulic fractures in tight shale reservoirs. Many hydraulic fracture modelling schemes assume that the fracture direction is pre-seeded in the problem domain discretisation. This is a severe limitation as the reservoir often contains large numbers of pre-existing fractures that strongly influence the direction of the propagating fracture. To circumvent these shortcomings, a new fracture modelling treatment is proposed where the introduction of discrete fracture surfaces is based on new and dynamically updated geometrical entities rather than the topology of the underlying spatial discretisation. Hydraulic fracturing is an inherently coupled engineering problem with interactions between fluid flow and fracturing when the stress state of the reservoir rock attains a failure criterion. This work follows a staggered hydro-mechanical coupled finite/discrete element approach to capture the key interplay between fluid pressure and fracture growth. In field practice, the fracture growth is hidden from the design engineer and microseismicity is often used to infer hydraulic fracture lengths and directions. Microseismic output can also be computed from changes of the effective stress in the geomechanical model and compared against field microseismicity. A number of hydraulic fracture numerical examples are presented to illustrate the new technology.

  15. Advances and disputes of posterior malleolus fracture

    FU Su; ZOU Zhen-yu; MEI Gang; JIN Dan


    Objective The objective of this article is to summarize the development of evaluation and treatment of posterior malleolus fracture (PMF).Data sources Data used in this review were mainly from English literature of PubMed data base.Study selection Articles were included in this review if they were related to the PMF or trimalleolar fracture.Results No consensus was found regarding what sizes of posterior malleolus fragments would lead to ankle instability thus affecting prognosis and should be fixed.Ⅹ-ray measurement is unreliable,while CT scan is widely recommended and it can recognize the occult posterior malleolus fractures associated with tibia shaft fractures,which are always undetected previously.Direct posterior malleolus fixation is suitable to stabilize syndesmotic injury.The basic and clinical researches support direct reduction and buttress plate fixation of posterior malleolus fracture through the posterolateral approach.Operative indications and timing of weight bearing are still in discussion.Conclusions Knowing whether ankle instability occurs and the proper methods to diagnose,evaluate,and operate can help manage the fracture.Further biomechanical research on ankle stability and clinical study to compare various treatment methods are required.

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

    Xiangchong Liu


    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.

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

    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)


    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)

  18. Sustainable Management of Flowback Water during Hydraulic Fracturing of Marcellus Shale for Natural Gas Production

    Vidic, Radisav [Univ. of Pittsburgh, PA (United States)


    This study evaluated the feasibility of using abandoned mine drainage (AMD) as make- up water for the reuse of produced water for hydraulic fracturing. There is an abundance of AMD sources near permitted gas wells as documented in this study that can not only serve as makeup water and reduce the demand on high quality water resources but can also as a source of chemicals to treat produced water prior to reuse. The assessment of AMD availability for this purpose based on proximity and relevant regulations was accompanied by bench- and pilot-scale studies to determine optimal treatment to achieve desired water quality for use in hydraulic fracturing. Sulfate ions that are often present in AMD at elevated levels will react with Ba²⁺ and Sr²⁺ in produced water to form insoluble sulfate compounds. Both membrane microfiltration and gravity separation were evaluated for the removal of solids formed as a result of mixing these two impaired waters. Laboratory studies revealed that neither AMD nor barite formed in solution had significant impact on membrane filtration but that some produced waters contained submicron particles that can cause severe fouling of microfiltration membrane. Coagulation/flocculation was found to be an effective process for the removal of suspended solids and both bench- and pilot-scale studies revealed that optimal process conditions can consistently achieve the turbidity of the finished water below 5 NTU. Adjusting the blending ratio of AMD and produced water can achieve the desired effluent sulfate concentration that can be accurately predicted by chemical thermodynamics. Co-treatment of produced water and AMD will result in elevated levels of naturally occurring radioactive materials (NORM) in the solid waste generated in this process due to radium co-precipitation with barium sulfate. Laboratory studies revealed that the mobility of barite that may form in the subsurface due to the presence of sulfate in the fracturing fluid can be

  19. Draft Genome Sequence of Pseudomonas sp. BDAL1 Reconstructed from a Bakken Shale Hydraulic Fracturing-Produced Water Storage Tank Metagenome

    Lipus, Daniel; Ross, Daniel; Bibby, Kyle; Gulliver, Djuna



    We report the 5,425,832 bp draft genome ofPseudomonassp. strain BDAL1, recovered from a Bakken shale hydraulic fracturing-produced water tank metagenome. Genome annotation revealed several key biofilm formation genes and osmotic stress response mechanisms necessary for survival in hydraulic fracturing-produced water.

  20. A hybrid inverse method for hydraulic tomography in fractured and karstic media

    Wang, Xiaoguang; Jardani, Abderrahim; Jourde, Hervé


    We apply a stochastic Newton (SN) approach to solve a high-dimensional hydraulic inverse problem in highly heterogeneous geological media. By recognizing the connection between the cost function of deterministic optimizations and the posterior probability density of stochastic inversions, the Markov chain Monte Carlo (MCMC) sampler of SN is constructed by two parts: a deterministic part, which corresponds to a Newton step of deterministic optimization, and a stochastic part, which is a Gaussian distribution with the inverse of the local Hessian as the covariance matrix. The hybrid inverse method exploits the efficient tools for fast solution of deterministic inversions to improve the efficiency of the MCMC sampler. To address the ill-posedness of the inverse problem, a priori models, generated by a transition-probability geostatistical method, and conditioned to inter-well connection data, are used as regularization constraints. The effectiveness of the stochastic Newton method is first demonstrated by a synthetic test. The transmissivity field of the synthetic model is highly heterogeneous, and includes sharp variations. The inverse approach was then applied to a field hydraulic tomography investigation in a fractured and karstified aquifer to reconstruct its transmissivity field from a collection of real hydraulic head measurements. From the inversions, a series of transmissivity fields that produce good correlations between the inverted and the measured hydraulic heads were obtained. The inverse approach produced slightly different a posteriori transmissivity patterns for different a priori structure models of transmissivity; however, the trend and location of the high-transmissivity channels are consistent among various realizations. In addition, the uncertainty associated with each realization of the inverted transmissivity fields was quantified.

  1. Measuring water quality from individual fractures in open wellbores using hydraulic isolation and the dissolved oxygen alteration method

    Vitale, Sarah A.; Robbins, Gary A.


    This study describes a low-cost method for sampling individual fractures in open wellbores in crystalline bedrock utilizing naturally occurring flow conditions in the well. The method entails using the dissolved oxygen alteration method (DOAM) to identify transmissive fractures and vertical flow direction. After obtaining information about relative hydraulic gradients, flow direction in the well is modified using a single control pump to isolate fractures of interest for sampling. Additional dissolved oxygen, injected during the DOAM procedure, serves as a tracer to ensure the water quality in the sampling zone is characteristic of the fracture of interest by requiring a tracer-free zone prior to sampling. Sampling procedures are described conceptually for nine bedrock wells with varying flow conditions containing one, two, or three transmissive inflowing fractures. The method was demonstrated in two crystalline bedrock wells containing one and two transmissive inflowing fractures.

  2. Proppant backproduction during hydraulic fracturing -- A new failure mechanism for resin-coated proppants

    Vreeburg, R.J.; Roodhart, L.P.; Davies, D.R.; Penny, G.S. (STIM-LAB Inc., Duncan, OK (United States))


    Backproduction of proppant from hydraulically fractured wells, particularly those completed in the northern European Rotliegend formation, is a major operational problem, necessitating costly and manpower-intensive surface-handling procedures. Further, the development of unmanned platform operations offshore, required in today's economic climate, is impossible as long as this problem remains unsolved. The most cost-effective potential solution to this problem is provided by curable resin-coated proppant (RCP), which consolidates in the fracture. Early field trials with RCP's, however, were not completely effective in stopping the backproduction of proppant. Typically, some 10% of the total volume of RCP placed in the fracture was backproduced. The authors performed a laboratory study to help clarify the effect of curing temperature, water production rate, proppant size, and stress cycling on the integrity of RCP packs. The experiments confirmed the field experience that stress cycling has a dramatic effect on proppant backproduction of commercial RCP packs. The number of applied stress cycles (i.e., the number of times the well is shut in) and the initial RCP pack strength appear to be the dominant factors that govern proppant backproduction. Dedicated experiments are therefore required to evaluate the use of RCP's to eliminate proppant backproduction for a particular field application.

  3. Characterization of hydraulic fracturing flowback water in Colorado: Implications for water treatment

    Lester, Yaal; Ferrer, Imma; Thurman, E. Michael; Sitterley, Kurban A.; Korak, Julie A.; Aiken, George R.; Linden, Karl G.


    A suite of analytical tools was applied to thoroughly analyze the chemical composition of an oil/gas well flowback water from the Denver–Julesburg (DJ) basin in Colorado, and the water quality data was translated to propose effective treatment solutions tailored to specific reuse goals. Analysis included bulk quality parameters, trace organic and inorganic constituents, and organic matter characterization. The flowback sample contained salts (TDS = 22,500 mg/L), metals (e.g., iron at 81.4 mg/L) and high concentration of dissolved organic matter (DOC = 590 mgC/L). The organic matter comprised fracturing fluid additives such as surfactants (e.g., linear alkyl ethoxylates) and high levels of acetic acid (an additives' degradation product), indicating the anthropogenic impact on this wastewater. Based on the water quality results and preliminary treatability tests, the removal of suspended solids and iron by aeration/precipitation (and/or filtration) followed by disinfection was identified as appropriate for flowback recycling in future fracturing operations. In addition to these treatments, a biological treatment (to remove dissolved organic matter) followed by reverse osmosis desalination was determined to be necessary to attain water quality standards appropriate for other water reuse options (e.g., crop irrigation). The study provides a framework for evaluating site-specific hydraulic fracturing wastewaters, proposing a suite of analytical methods for characterization, and a process for guiding the choice of a tailored treatment approach.

  4. Capturing the complex behavior of hydraulic fracture stimulation through multi-physics modeling, field-based constraints, and model reduction

    Johnson, S.; Chiaramonte, L.; Cruz, L.; Izadi, G.


    Advances in the accuracy and fidelity of numerical methods have significantly improved our understanding of coupled processes in unconventional reservoirs. However, such multi-physics models are typically characterized by many parameters and require exceptional computational resources to evaluate systems of practical importance, making these models difficult to use for field analyses or uncertainty quantification. One approach to remove these limitations is through targeted complexity reduction and field data constrained parameterization. For the latter, a variety of field data streams may be available to engineers and asset teams, including micro-seismicity from proximate sites, well logs, and 3D surveys, which can constrain possible states of the reservoir as well as the distributions of parameters. We describe one such workflow, using the Argos multi-physics code and requisite geomechanical analysis to parameterize the underlying models. We illustrate with a field study involving a constraint analysis of various field data and details of the numerical optimizations and model reduction to demonstrate how complex models can be applied to operation design in hydraulic fracturing operations, including selection of controllable completion and fluid injection design properties. The implication of this work is that numerical methods are mature and computationally tractable enough to enable complex engineering analysis and deterministic field estimates and to advance research into stochastic analyses for uncertainty quantification and value of information applications.

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

    Schneider F.


    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

  6. Implementing ground surface deformation tools to characterize field-scale properties of a fractured aquifer during a short hydraulic test

    Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Boudin, Frédérick; Durand, Stéphane


    In naturally fractured reservoirs, fluid flow is governed by the structural and hydromechanical properties of fracture networks or conductive fault zones. In order to ensure a sustained exploitation of resources or to assess the safety of underground storage, it is necessary to evaluate these properties. As they generally form highly heterogeneous and anisotropic reservoirs, fractured media may be well characterized by means of several complementary experimental methods or sounding techniques. In this framework, the observation of ground deformation has been proved useful to gain insight of a fractured reservoir's geometry and hydraulic properties. Commonly, large conductive structures like faults can be studied from surface deformation from satellite methods at monthly time scales, whereas meter scale fractures have to be examined under short-term in situ experiments using high accuracy intruments like tiltmeters or extensometers installed in boreholes or at the ground's surface. To the best of our knowledge, the feasability of a field scale (~ 100 m) characterization of a fractured reservoir with geodetic tools in a short term experiment has not yet been addressed. In the present study, we implement two complementary ground surface geodetic tools, namely tiltmetry and optical leveling, to monitor the deformation induced by a hydraulic recovery test at the Ploemeur hydrological observatory (France). Employing a simple purely elastic modeling approach, we show that the joint use of time constraining data (tilt) and spatially constraining data (vertical displacement) makes it possible to evaluate the geometry (dip, root depth and lateral extent) and the storativity of a hydraulically active fault zone, in good agreement with previous studies. Hence we demonstrate that the adequate use of two complementary ground surface deformation methods offer a rich insight of large conductive structure's properties using a single short term hydraulic load. Ground surface

  7. Comparison of Heterogeneously-Propped Hydraulic Fractures for Vertical and Lateral Wells

    Morris, J.; Chugunov, N.


    Heterogeneous proppant placement (HPP) technologies offer improved hydraulic fracturing performance through the creation of channels within propped fractures (see figure). Such schemes, however, can suffer from reduced performance due to uncertainty in reservoir properties (e.g.: embedment and moduli). This is particularly true of unconventional reservoirs where properties can be highly heterogeneous. We demonstrate that the mechanisms controlling uncertainty in HPP performance differ between vertical and lateral wells. For computational efficiency, we combine the boundary element method to simulate formation deformation with a detailed discretization of the proppant within the fracture to predict conductivity of the HPP channels. We performed an extensive parameter study with thousands of scenarios relevant to HPP, including placement geometries consistent with both vertical and lateral wells. Global sensitivity analysis (GSA) was then applied to quantify and rank contributions from uncertain input parameters to variance in fracture conductivity. We were able to rigorously quantify the impact of parametric uncertainty. We found that for lateral wells the uncertainty in the conductivity is dominated by the uncertainty in diffusion of the proppant. For vertical wells, the dominant factors causing uncertainty in the performance change with stress. At low stress, performance is controlled by factors that dictate pillar geometry. At high stress, parameters that help preserve channels against closure stress control conductivity. Our results highlight the robustness of the HPP concept and quantify the sources of uncertainty in HPP performance. Further, we can clearly identify the fundamental parameters that control HPP conductivity and reveal that they are different for wellbore geometries that are typical of unconventional wells in North America. This implies that optimal HPP strategies will differ between vertical and lateral wells.

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

    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


    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.

  9. Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, volumes, and physical-chemical properties of chemicals

    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...

  10. Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources (ERD)

    In this report, EPA reviews and synthesizes scientific literature to assess the potential for hydraulic fracturing for oil and gas to change the quality or quantity of drinking water resources. This report also identifies factors affecting the frequency or severity of any potenti...

  11. Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources (External Review Draft)

    This assessment provides a review and synthesis of available scientific literature and data to assess the potential for hydraulic fracturing for oil and gas to impact the quality or quantity of drinking water resources, and identifies factors affecting the frequency or severity o...

  12. Community-based risk assessment of water contamination from high-volume horizontal hydraulic fracturing.

    Penningroth, Stephen M; Yarrow, Matthew M; Figueroa, Abner X; Bowen, Rebecca J; Delgado, Soraya


    The risk of contaminating surface and groundwater as a result of shale gas extraction using high-volume horizontal hydraulic fracturing (fracking) has not been assessed using conventional risk assessment methodologies. Baseline (pre-fracking) data on relevant water quality indicators, needed for meaningful risk assessment, are largely lacking. To fill this gap, the nonprofit Community Science Institute (CSI) partners with community volunteers who perform regular sampling of more than 50 streams in the Marcellus and Utica Shale regions of upstate New York; samples are analyzed for parameters associated with HVHHF. Similar baseline data on regional groundwater comes from CSI's testing of private drinking water wells. Analytic results for groundwater (with permission) and surface water are made publicly available in an interactive, searchable database. Baseline concentrations of potential contaminants from shale gas operations are found to be low, suggesting that early community-based monitoring is an effective foundation for assessing later contamination due to fracking.

  13. The Use of Hydraulic Head and Atmospheric Tritium to Identify Presence of Fractures in Clayey Aquitards: Numerical Analysis

    Farah, E. A.; Parker, B. L.; Cherry, J. A.


    Surficial clayey aquitards can provide underlying aquifers with strong protection from contamination if vertically connected open fractures are absent. Hence, methods are needed to identify such contaminant pathways. An existing two-dimensional model for steady-state groundwater flow and solute transport (FRACTRAN) was used for cross-sectional simulations to assess the prospects for using field measurements of hydraulic head and atmospheric (i.e. bomb) tritium in surficial aquitards to determine presence and nature of hydraulically connected fractures. Simulations for a 15-m thick horizontal aquitard, with shallow water table and downward groundwater flow, show that field measurements of head and tritium at points appropriately spaced along a horizontal line at the lower part of the aquitard provide unique insight since they offer the highest chance for detecting vertical fractures. Simulations represented sets of predominant vertical and horizontal fractures of uniform aperture (25 æm) and variable length. The simulations focused on fracture-network features assigned based on the literature of field investigations. The horizontal profiles show peaks and troughs for head, and always peaks for tritium concentrations at fracture localities. Use of only head or tritium alone may locate fractures, but may not discover whether each fracture is connected to the ground surface or aquifer top, or both. On the other hand, the coupled patterns of head and tritium can be used to identify fractures more accurately. For example, a head trough and a tritium sharp peak represent a fully penetrating fracture, while a head peak and a rounded-tip tritium peak represent a partially penetrating fracture. Moreover, these two are easily differentiated from an embedded fracture that is represented by a relatively small head trough and a short sharp tritium peak. The method of monitoring along a horizontal line was applied to the conceptual 15-m thick aquitard imitating horizontal

  14. Assessing the induced seismicity by hydraulic fracturing at the Wysin site (Poland)

    Ángel López Comino, José; Cesca, Simone; Kriegerowski, Marius; Heimann, Sebastian; Dahm, Torsten; Mirek, Janusz; Lasocky, Stanislaw


    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.

  15. Thermal-Hydraulic Experiments and Modelling for Advanced Nuclear Reactor Systems

    Song, C. H.; Chung, M. K.; Park, C. K. and others


    The objectives of the project are to study thermal hydraulic characteristics of reactor primary system for the verification of the reactor safety and to evaluate new safety concepts of new safety design features. To meet the research goal, several thermal hydraulic experiments were performed and related thermal hydraulic models were developed with the experimental data which were produced through the thermal hydraulic experiments. Followings are main research topics; - Multi-dimensional Phenomena in a Reactor Vessel Downcomer - Condensation Load and Thermal Mixing in the IRWST - Development of Thermal-Hydraulic Models for Two-Phase Flow - Development of Measurement Techniques for Two-Phase Flow - Supercritical Reactor T/H Characteristics Analysis From the above experimental and analytical studies, new safety design features of the advanced power reactors were verified and lots of the safety issues were also resolved.

  16. A decision analysis framework for estimating the potential hazards for drinking water resources of chemicals used in hydraulic fracturing fluids.

    Yost, Erin E; Stanek, John; Burgoon, Lyle D


    Despite growing concerns over the potential for hydraulic fracturing to impact drinking water resources, there are limited data available to identify chemicals used in hydraulic fracturing fluids that may pose public health concerns. In an effort to explore these potential hazards, a multi-criteria decision analysis (MCDA) framework was employed to analyze and rank selected subsets of these chemicals by integrating data on toxicity, frequency of use, and physicochemical properties that describe transport in water. Data used in this analysis were obtained from publicly available databases compiled by the United States Environmental Protection Agency (EPA) as part of a larger study on the potential impacts of hydraulic fracturing on drinking water. Starting with nationwide hydraulic fracturing chemical usage data from EPA's analysis of the FracFocus Chemical Disclosure Registry 1.0, MCDAs were performed on chemicals that had either noncancer toxicity values (n=37) or cancer-specific toxicity values (n=10). The noncancer MCDA was then repeated for subsets of chemicals reported in three representative states (Texas, n=31; Pennsylvania, n=18; and North Dakota, n=20). Within each MCDA, chemicals received scores based on relative toxicity, relative frequency of use, and physicochemical properties (mobility in water, volatility, persistence). Results show a relative ranking of these chemicals based on hazard potential, and provide preliminary insight into chemicals that may be more likely than others to impact drinking water resources. Comparison of nationwide versus state-specific analyses indicates regional differences in the chemicals that may be of more concern to drinking water resources, although many chemicals were commonly used and received similar overall hazard rankings. Several chemicals highlighted by these MCDAs have been reported in groundwater near areas of hydraulic fracturing activity. This approach is intended as a preliminary analysis, and represents one

  17. Influences of hydraulic gradient, surface roughness, intersecting angle, and scale effect on nonlinear flow behavior at single fracture intersections

    Li, Bo; Liu, Richeng; Jiang, Yujing


    Fluid flow tests were conducted on two crossed fracture models for which the geometries of fracture segments and intersections were measured by utilizing a visualization technique using a CCD (charged coupled device) camera. Numerical simulations by solving the Navier-Stokes equations were performed to characterize the fluid flow at fracture intersections. The roles of hydraulic gradient, surface roughness, intersecting angle, and scale effect in the nonlinear fluid flow behavior through single fracture intersections were investigated. The simulation results of flow rate agreed well with the experimental results for both models. The experimental and simulation results showed that with the increment of the hydraulic gradient, the ratio of the flow rate to the hydraulic gradient, Q/J, decreases and the relative difference of Q/J between the calculation results employing the Navier-Stokes equations and the cubic law, δ, increases. When taking into account the fracture surface roughness quantified by Z2 ranging 0-0.42 for J = 1, the value of δ would increase by 0-10.3%. The influences of the intersecting angle on the normalized flow rate that represents the ratio of the flow rate in a segment to the total flow rate, Ra, and the ratio of the hydraulic aperture to the mechanical aperture, e/E, are negligible when J 10-2. Based on the regression analysis on simulation results, a mathematical expression was proposed to quantify e/E, involving variables of J and Rr, where Rr is the radius of truncating circles centered at an intersection. For E/Rr > 10-2, e/E varies significantly and the scale of model has large impacts on the nonlinear flow behavior through intersections, while for E/Rr < 10-3, the scale effect is negligibly small. Finally, a necessary condition to apply the cubic law to fluid flow through fracture intersections is suggested as J < 10-3, E/Rr < 10-3, and Z2 = 0.

  18. Hydraulic fracturing in unconventional reservoirs - Identification of hazards and strategies for a quantitative risk assessment

    Helmig, R.; Kissinger, A.; Class, H.; Ebigbo, A.


    fractured reservoir, fracture propagation, fault zones and their role in regard to fluid migration into shallow aquifers). A quantitative risk assessment which should be the main aim of future work in this field has much higher demands, especially on site specific data, as the estimation of statistical parameter uncertainty requires site specific parameter distributions. There is already ongoing research on risk assessment in related fields like CO2 sequestration. We therefore propose these methodologies to be transferred to risk estimation relating to the use of the hydraulic fracking method, be it for unconventional gas or enhanced geothermal energy production. The overall aim should be to set common and transparent standards for different uses of the subsurface and their involved risks and communicate those to policy makers and stake holders.

  19. Injection of radioactive waste by hydraulic fracturing at West Valley, New York. Volume 2. Text


    Results of a preliminary study are presented of the technical feasibility of radioactive waste disposal by hydraulic fracturing and injection into shale formations below the Nuclear Fuel Services Incorporated site at West Valley, New York. At this time there are approximately 600,000 gallons of high level neutralized Purex waste, including both the supernate (liquid) and sludge, and a further 12,000 gallons of acidic Thorex waste stored in tanks at the West Valley facilities. This study assesses the possibility of combining these wastes in a suitable grout mixture and then injecting them into deep shale formations beneath the West Valley site as a means of permanent disposal. The preliminary feasibility assessment results indicated that at the 850 to 1,250 feet horizons, horizontal fracturing and injection could be effectively achieved. However, a detailed safety analysis is required to establish the acceptability of the degree of isolation. The principal concerns regarding isolation are due to existing and possible future water supply developments within the area and the local effects of the buried valley. In addition, possible future natural gas developments are of concern. The definition of an exclusion zone may be appropriate to avoid problems with these developments. The buried valley may require the injections to be limited to the lower horizon depending on the results of further investigations.

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

    Qi Zhao; Andrea Lisjak; Omid Mahabadi; Qinya Liu; Giovanni Grasselli


    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 eval-uate 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.

  1. Hydraulic fracturing offers view of microbial life in the deep terrestrial subsurface.

    Mouser, Paula J; Borton, Mikayla; Darrah, Thomas H; Hartsock, Angela; Wrighton, Kelly C


    Horizontal drilling and hydraulic fracturing are increasingly used for recovering energy resources in black shales across the globe. Although newly drilled wells are providing access to rocks and fluids from kilometer depths to study the deep biosphere, we have much to learn about microbial ecology of shales before and after 'fracking'. Recent studies provide a framework for considering how engineering activities alter this rock-hosted ecosystem. We first provide data on the geochemical environment and microbial habitability in pristine shales. Next, we summarize data showing the same pattern across fractured shales: diverse assemblages of microbes are introduced into the subsurface, eventually converging to a low diversity, halotolerant, bacterial and archaeal community. Data we synthesized show that the shale microbial community predictably shifts in response to temporal changes in geochemistry, favoring conservation of key microorganisms regardless of inputs, shale location or operators. We identified factors that constrain diversity in the shale and inhibit biodegradation at the surface, including salinity, biocides, substrates and redox. Continued research in this engineered ecosystem is required to assess additive biodegradability, quantify infrastructure biocorrosion, treat wastewaters that return to the surface and potentially enhance energy production through in situ methanogenesis.

  2. Identification of polypropylene glycols and polyethylene glycol carboxylates in flowback and produced water from hydraulic fracturing.

    Thurman, E Michael; Ferrer, Imma; Rosenblum, James; Linden, Karl; Ryan, Joseph N


    The purpose of the study was to separate and identify the unknown surfactants present in flowback and produced water from oil and gas wells in the Denver-Julesburg Basin (Niobrara Formation) in Weld County, Colorado, USA. Weld County has been drilled extensively during the last five years for oil and gas between 7000-8000 feet below land-surface. Polypropylene glycols (PPGs) and polyethylene glycols carboxylates (PEG-Cs) were found for the first time in these flowback and produced water samples. These ethoxylated surfactants may be used as friction reducers, clay stabilizers, and surfactants. Ultrahigh-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC/QTOF-MS) was used to separate and identify the different classes of PPGs, PEG-Cs, and their isomers. The Kendrick mass scale was applied along with mass spectrometry/mass spectrometry (MS-MS) with accurate mass for rapid and unequivocal identification. The PPGs and their isomers occur at the ppm concentration range and may be useful as "fingerprints" of hydraulic-fracturing. Comparing these detections to the compounds used in the fracturing process from FracFocus 3.0 (, it appears that both PPGs and polyethylene glycols (PEGs) are commonly named as additives, but the PEG-Cs have not been reported. The PEG-Cs may be trace impurities or degradation products of PEGs.

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

    Qi Zhao


    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.

  4. Advances in thermal-hydraulic studies of a transmutation advanced device for sustainable energy applications

    Fajardo, Laura Garcia, E-mail: [European Organization for Nuclear Research (CERN), Geneva (Switzerland). Technology Department; Hernandez, Carlos Garcia; Mazaira, Leorlen Rojas, E-mail:, E-mail: [Higher Institute of Technologies and Applied Sciences (INSTEC), Habana (Cuba); Castells, Facundo Alberto Escriva, E-mail: [University of Valencia (UV), Valencia (Spain). Energetic Engineering Institute; Lira, Carlos Brayner de Olivera, E-mail: [Universidade Federal de Pernambuco (UFPE), Recife, PE (BRazil). Dept. de Engenharia Nuclear


    The Transmutation Advanced Device for Sustainable Energy Applications (TADSEA) is a pebble-bed Accelerator Driven System (ADS) with a graphite-gas configuration, designed for nuclear waste trans- mutation and for obtaining heat at very high temperatures to produce hydrogen. In previous work, the TADSEA's nuclear core was considered as a porous medium performed with a CFD code and thermal-hydraulic studies of the nuclear core were presented. In this paper, the heat transfer from the fuel to the coolant was analyzed for three core states during normal operation. The heat transfer inside the spherical fuel elements was also studied. Three critical fuel elements groups were defined regarding their position inside the core. Results were compared with a realistic CFD model of the critical fuel elements groups. During the steady state, no critical elements reached the limit temperature of this type of fuel. (author)

  5. Reactivity of Dazomet, a Hydraulic Fracturing Additive: Hydrolysis and Interaction with Pyrite

    Consolazio, N.; Lowry, G. V.; Karamalidis, A.; Hakala, A.


    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

  6. Linking advanced fracture models to structural analysis

    Chiesa, Matteo


    Shell structures with defects occur in many situations. The defects are usually introduced during the welding process necessary for joining different parts of the structure. Higher utilization of structural materials leads to a need for accurate numerical tools for reliable prediction of structural response. The direct discretization of the cracked shell structure with solid finite elements in order to perform an integrity assessment of the structure in question leads to large size problems, and makes such analysis infeasible in structural application. In this study a link between local material models and structural analysis is outlined. An ''ad hoc'' element formulation is used in order to connect complex material models to the finite element framework used for structural analysis. An improved elasto-plastic line spring finite element formulation, used in order to take cracks into account, is linked to shell elements which are further linked to beam elements. In this way one obtain a global model of the shell structure that also accounts for local flexibilities and fractures due to defects. An important advantage with such an approach is a direct fracture mechanics assessment e.g. via computed J-integral or CTOD. A recent development in this approach is the notion of two-parameter fracture assessment. This means that the crack tip stress tri-axiality (constraint) is employed in determining the corresponding fracture toughness, giving a much more realistic capacity of cracked structures. The present thesis is organized in six research articles and an introductory chapter that reviews important background literature related to this work. Paper I and II address the performance of shell and line spring finite elements as a cost effective tool for performing the numerical calculation needed to perform a fracture assessment. In Paper II a failure assessment, based on the testing of a constraint-corrected fracture mechanics specimen under tension, is

  7. Radiological issues associated with the recent boom in oil and gas hydraulic fracturing

    Lopez, Alejandro [AMEC Environment and Infrastructure, 800 North Bell Ave., Pittsburgh, PA 15106 (United States)


    As the worldwide hydraulic fracturing 'fracking' market continued to grow to an estimated $37 Billion in 2012, the need to understand and manage radiological issues associated with fracking is becoming imperative. Fracking is a technique that injects pressurized fluid into rock layer to propagate fractures that allows natural gas and other petroleum products to be more easily extracted. Radioactivity is associated with fracking in two ways. Radioactive tracers are frequently a component of the injection fluid used to determine the injection profile and locations of fractures. Second, because there are naturally-occurring radioactive materials (NORM) in the media surrounding and containing oil and gas deposits, the process of fracking can dislodge radioactive materials and transport them to the surface in the wastewater and gases. Treatment of the wastewater to remove heavy metals and other contaminates can concentrate the NORM into technologically-enhanced NORM (TENORM). Regulations to classify, transport, and dispose of the TENORM and other radioactive waste can be complicated and cumbersome and vary widely in the international community and even between states/provinces. In many cases, regulations on NORM and TENORM do not even exist. Public scrutiny and regulator pressure will only continue to increase as the world demands on oil and gas continue to rise and greater quantities of TENORM materials are produced. Industry experts, health physicists, regulators, and public communities must work together to understand and manage radiological issues to ensure reasonable and effective regulations protective of the public, environment, and worker safety and health are implemented. (authors)

  8. Infiltration and hydraulic connections from the Niagara River to a fractured-dolomite aquifer in Niagara Falls, New York

    Yager, Richard M.; Kappel, William M.


    The spatial distribution of hydrogen and oxygen stable-isotope values in groundwater can be used to distinguish different sources of recharge and to trace groundwater flow directions from recharge boundaries. This method can be particularly useful in fractured-rock settings where multiple lines of evidence are required to delineate preferential flow paths that result from heterogeneity within fracture zones. Flow paths delineated with stable isotopes can be combined with hydraulic data to form a more complete picture of the groundwater flow system. In this study values of δD and δ 18O were used to delineate paths of river-water infiltration into the Lockport Group, a fractured dolomite aquifer, and to compute the percentage of river water in groundwater samples from shallow bedrock wells. Flow paths were correlated with areas of high hydraulic diffusivity in the shallow bedrock that were delineated from water-level fluctuations induced by diurnal stage fluctuations in man-made hydraulic structures. Flow paths delineated with the stable-isotope and hydraulic data suggest that river infiltration reaches an unlined storm sewer in the bedrock through a drainage system that surrounds carrying river water to hydroelectric power plants. This findings is significant because the storm sewer is the discharge point for contaminated groundwater from several chemical waste-disposal sites and the cost of treating the storm sewer's discharge could be reduced if the volume of infiltration from the river were decreased.

  9. Engineering geological characteristics and the hydraulic fracture propagation mechanism of the sand-shale interbedded formation in the Xu5 reservoir

    Lu, Cong; Li, Mei; Guo, Jian-Chun; Tang, Xu-Hai; Zhu, Hai-Yan; Yong-Hui, Wang; Liang, Hao


    In the Xu5 formation the sandstone reservoir and the shale reservoir are interbedded with each other. The average thickness of each formation is about 8 m, which increases the difficulty of the hydraulic fracturing treatment. The shale thickness ratio (the ratio of shale thickness to formation thickness) is 55-62.5%. The reservoir is characterized by ultra-low porosity and permeability. The brittleness index of sandstone is 0.5-0.8, and the brittleness index of shale is 0.3-0.8. Natural fractures are poorly developed and are mainly horizontal and at a low angle. The formation strength is medium and the reservoir is of the hybrid strike-slip fault and reverse fault stress regime. The difference between the minimum principal stress and the vertical stress is small, and the maximum horizontal principal stress is 20 MPa higher than the minimum horizontal principal stress and vertical stress. A mechanical model of a hydraulic fracture encountering natural fractures is built according to geological characteristics. Fracture mechanics theory is then used to establish a hydraulic fracturing model coupling the seepage-stress-damage model to simulate the initiation and propagation of a fracture. The hydraulic fracture geometry is mainly I-shaped and T-shaped, horizontal propagation dominates the extension, and vertical propagation is limited. There is a two to three meter stress diversion area around a single hydraulic fracture. The stress diversion between a hydraulic fracture and a natural fracture is advantageous in forming a complex fracture. The research results can provide theoretical guidance for tight reservoir fracturing design.

  10. FAST TRACK PAPER: The creation of an asymmetric hydraulic fracture as a result of driving stress gradients

    Fischer, T.; Hainzl, S.; Dahm, T.


    Hydraulic fracture stimulation is frequently performed in hydrocarbon reservoirs and geothermal systems to increase the permeability of the rock formation. These hydraulic fractures are often mapped by hypocentres of induced microearthquakes. In some cases microseismicity exhibits asymmetry relative to the injection well, which can be interpreted by unequal conditions for fracture growth at opposite sides of the well or by observation effects. Here we investigate the role of the lateral change of the minimum compressive stress. We use a simple model to describe the relation among the lateral stress gradient, the mean viscous pressure gradients in the fracture wings, the fracture geometry, and the net pressure in the fracture. Our model predicts a faster fracture growth in the direction of decreasing stress and a limited growth in the opposite direction. We derive a simple relationship to estimate the lateral stress gradient from the injection pressure and the shape of the seismic hypocentre cloud. The model is tested by microseismic data obtained during stimulation of a Canyon Sands gas field in West Texas. Using a maximum likelihood method we fit the parameters of the asymmetric fracture model to the space-time pattern of hypocentres. The estimated stress gradients per metre are in the range from 0.008 to 0.010 times the bottom-hole injection overpressure (8-10 kPam-1 assuming the net pressure of 1 MPa). Such large horizontal gradients in the order of the hydrostatic gradient could be caused by the inhomogeneous extraction of gas resulting in a lateral change of the effective normal stress acting normal to the fracture wall.

  11. Determination of hydraulic conductivity of fractured rock masses:A case study for a rock cavern project in Singapore

    Zhipeng Xu; Zhiye Zhao; Jianping Sun; Ming Lu


    In order to reduce the risk associated with water seepage in an underground rock cavern project in Singapore, a reliable hydro-geological model should be established based on the in situ investigation data. The key challenging issue in the hydro-geological model building is how to integrate limited geological and hydro-geological data to determine the hydraulic conductivity of the fractured rock masses. Based on the data obtained from different stages (feasibility investigation stage, construction stage, and post-construction stage), suitable models and methods are proposed to determine the hy-draulic conductivities at different locations and depths, which will be used at other locations in the future.

  12. Pore pressure migration during hydraulic stimulation due to permeability enhancement by low-pressure subcritical fracture slip

    Mukuhira, Yusuke; Moriya, Hirokazu; Ito, Takatoshi; Asanuma, Hiroshi; Häring, Markus


    Understanding the details of pressure migration during hydraulic stimulation is important for the design of an energy extraction system and reservoir management, as well as for the mitigation of hazardous-induced seismicity. Based on microseismic and regional stress information, we estimated the pore pressure increase required to generate shear slip on an existing fracture during stimulation. Spatiotemporal analysis of pore pressure migration revealed that lower pore pressure migrates farther and faster and that higher pore pressure migrates more slowly. These phenomena can be explained by the relationship between fracture permeability and stress state criticality. Subcritical fractures experience shear slip following smaller increases of pore pressure and promote migration of pore pressure because of their enhanced permeability. The difference in migration rates between lower and higher pore pressures suggests that the optimum wellhead pressure is the one that can stimulate relatively permeable fractures, selectively. Its selection optimizes economic benefits and minimizes seismic risk.

  13. Air monitoring of volatile organic compounds at relevant receptors during hydraulic fracturing operations in Washington County, Pennsylvania.

    Maskrey, Joshua R; Insley, Allison L; Hynds, Erin S; Panko, Julie M


    A 3-month air monitoring study was conducted in Washington County, Pennsylvania, at the request of local community members regarding the potential risks resulting from air emissions of pollutants related to hydraulic fracturing operations. Continuous air monitoring for total volatile organic compounds was performed at two sampling sites, including a school and a residence, located within 900 m of a hydraulic fracturing well pad that had been drilled prior to the study. Intermittent 24-hour air samples for 62 individual volatile organic compounds were also collected. The ambient air at both sites was monitored during four distinct periods of unconventional natural gas extraction activity: an inactive period prior to fracturing operations, during fracturing operations, during flaring operations, and during another inactive period after operations. The results of the continuous monitoring during fracturing and flaring sampling periods for total volatile organic compounds were similar to the results obtained during inactive periods. Total volatile organic compound 24-hour average concentrations ranged between 0.16 and 80 ppb during all sampling periods. Several individual volatile compounds were detected in the 24-hour samples, but they were consistent with background atmospheric levels measured previously at nearby sampling sites and in other areas in Washington County. Furthermore, a basic yet conservative screening level evaluation demonstrated that the detected volatile organic compounds were well below health-protective levels. The primary finding of this study was that the operation of a hydraulic fracturing well pad in Washington County did not substantially affect local air concentrations of total and individual volatile organic compounds.

  14. Reflection seismic imaging of a hydraulically conductive fracture zone in a high noise area, Forsmark, Sweden

    Juhlin, C.; Stephens, M. B.; Cosma, C.


    High resolution reflection seismic methods have proven to be useful tools for locating fracture zones in crystalline rock. Siting of potential high-level nuclear waste repositories is a particularly important application of these methods. By using small explosive sources (15-75 grams), high resolution images of the sub-surface have been obtained in the depth range 100 m to 2 km in Sweden, Canada and elsewhere. Although ambient noise conditions in areas such as the Fennoscandian and Canadian shields are generally low, industrial noise can be high in some areas, particularly at potential sites suitable for repositories, since these are often close to existing infrastructure. In addition, the presence of this infrastructure limits the choice of sources available to the geophysicist. Forsmark, located about 140 km north of Stockholm, is one such potential site where reflection seismics have been carried out. Existing infrastructure includes nuclear reactors for power generation and a low- level waste repository. In the vicinity of the reactors, it was not possible to use an explosive source due to permitting restrictions. Instead, a VIBSIST system consisting of a tractor mounted hydraulic hammer was used in the vicinity of the reactors. By repeatedly hitting the pavement, without breaking it, at predefined sweeps and then stacking the signals, shot records comparable to explosive data could be generated. These shot records were then processed using standard methods to produce stacked sections along 3 profiles within the reactor area. Clear reflections are seen in the uppermost 600 m along 3 of these profiles. Correlation of crossing profiles shows that the strongest reflection (B8) is generated by a gently east-southeast dipping interface. Prior to construction of the reactors, several boreholes were drilled to investigate the bedrock in the area. One of these boreholes was located close to where two of the profiles cross. Projection of the B8 reflection into the

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

    Yu Wang


    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.

  16. Geochemical simulation of fluid rock interactions to predict flowback water compostions during hydraulic fracturing

    Kühn, Michael; Vieth-Hillebrand, Andrea; Wilke, Franziska D. H.


    Black shales are a heterogeneous mixture of minerals, organic matter and formation water and little is actually known about the fluid-rock interactions during hydraulic fracturing and their effects on composition of flowback and produced water. Geochemical simulations have been performed based on the analyses of "real" flowback water samples and artificial stimulation fluids from lab experiments with the aim to set up a chemical process model for shale gas reservoirs. Prediction of flowback water compositions for potential or already chosen sites requires validated and parameterized geochemical models. For the software "Geochemist's Workbench" (GWB) data bases are adapted and amended based on a literature review. Evaluation of the system has been performed in comparison with the results from laboratory experiments. Parameterization was done in regard to field data provided. Finally, reaction path models are applied for quantitative information about the mobility of compounds in specific settings. Our work leads to quantitative estimates of reservoir compounds in the flowback based on calibrations by laboratory experiments. Such information is crucial for the assessment of environmental impacts as well as to estimate human- and ecotoxicological effects of the flowback waters from a variety of natural gas shales. With a comprehensive knowledge about potential composition and mobility of flowback water, selection of water treatment techniques will become easier.

  17. Identifying chemicals of concern in hydraulic fracturing fluids used for oil production.

    Stringfellow, William T; Camarillo, Mary Kay; Domen, Jeremy K; Sandelin, Whitney L; Varadharajan, Charuleka; Jordan, Preston D; Reagan, Matthew T; Cooley, Heather; Heberger, Matthew G; Birkholzer, Jens T


    Chemical additives used for hydraulic fracturing and matrix acidizing of oil reservoirs were reviewed and priority chemicals of concern needing further environmental risk assessment, treatment demonstration, or evaluation of occupational hazards were identified. We evaluated chemical additives used for well stimulation in California, the third largest oil producing state in the USA, by the mass and frequency of use, as well as toxicity. The most frequently used chemical additives in oil development were gelling agents, cross-linkers, breakers, clay control agents, iron and scale control agents, corrosion inhibitors, biocides, and various impurities and product stabilizers used as part of commercial mixtures. Hydrochloric and hydrofluoric acids, used for matrix acidizing and other purposes, were reported infrequently. A large number and mass of solvents and surface active agents were used, including quaternary ammonia compounds (QACs) and nonionic surfactants. Acute toxicity was evaluated and many chemicals with low hazard to mammals were identified as potentially hazardous to aquatic environments. Based on an analysis of quantities used, toxicity, and lack of adequate hazard evaluation, QACs, biocides, and corrosion inhibitors were identified as priority chemicals of concern that deserve further investigation.

  18. Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations

    Forghani-Arani, Farnoush; Willis, Mark; Snieder, Roel; Haines, Seth S.; Behura, Jyoti; Batzle, Mike; Davidson, Michael


    Surface-wave dispersion analysis is useful for estimating near-surface shear-wave velocity models, designing receiver arrays, and suppressing surface waves. Here, we analyze whether passive seismic noise generated during hydraulic-fracturing operations can be used to extract surface-wave dispersion characteristics. Applying seismic interferometry to noise measurements, we extract surface waves by cross-correlating several minutes of passive records; this approach is distinct from previous studies that used hours or days of passive records for cross-correlation. For comparison, we also perform dispersion analysis for an active-source array that has some receivers in common with the passive array. The active and passive data show good agreement in the dispersive character of the fundamental-mode surface-waves. For the higher mode surface waves, however, active and passive data resolve the dispersive properties at different frequency ranges. To demonstrate an application of dispersion analysis, we invert the observed surface-wave dispersion characteristics to determine the near-surface, one-dimensional shear-wave velocity.

  19. Ground gas monitoring: implications for hydraulic fracturing and CO2 storage.

    Teasdale, Christopher J; Hall, Jean A; Martin, John P; Manning, David A C


    Understanding the exchange of carbon dioxide (CO2) and methane (CH4) between the geosphere and atmosphere is essential for the management of anthropogenic emissions. Human activities such as carbon capture and storage and hydraulic fracturing ("fracking") affect the natural system and pose risks to future global warming and to human health and safety if not engineered to a high standard. In this paper an innovative approach of expressing ground gas compositions is presented, using data derived from regulatory monitoring of boreholes in the unsaturated zone at infrequent intervals (typically 3 months) with data from a high frequency monitoring instrument deployed over periods of weeks. Similar highly variable trends are observed for time scales ranging from decades to hourly for boreholes located close to sanitary landfill sites. Additionally, high frequency monitoring data confirm the effect of meteorological controls on ground gas emissions; the maximum observed CH4 and CO2 concentrations in a borehole monitored over two weeks were 40.1% v/v and 8.5% v/v respectively, but for 70% of the monitoring period only air was present. There is a clear weakness in current point monitoring strategies that may miss emission events and this needs to be considered along with obtaining baseline data prior to starting any engineering activity.

  20. The Water Risks of Hydraulic Fracturing (Fracking): Key Issues from the New California Assessment

    Gleick, P. H.


    A key component of the Water-Energy Nexus is the effort over the past decade or so to quantify the volumes and form of water required for the energy fuel cycle from extraction to generation to waste disposal. The vast majority of the effort in this area has focused on the water needs of electricity generation, but other fuel-cycle components also entail significant water demands and threats to water quality. Recent work for the State of California (managed by the California Council on Science and Technology - CCST) has produced a new state-of-the-art assessment of a range of potential water risks associated with hydraulic fracturing and related oil and gas extraction, including volumetric water demands, methods of disposal of produced water, and aquifer contamination. For example, this assessment produced new information on the disposal of produced water in surface percolation pits and the potential for contamination of local groundwater (see Figure). Understanding these risks raises questions about current production and future plans to expand production, as well as tools used by state and federal agencies to manage these risks. This talk will summarize the science behind the CCST assessment and related policy recommendations for both water and energy managers.

  1. Source and fate of hydraulic fracturing water in the Barnett Shale: a historical perspective.

    Nicot, Jean-Philippe; Scanlon, Bridget R; Reedy, Robert C; Costley, Ruth A


    Considerable controversy continues about water availability for and potential impacts of hydraulic fracturing (HF) of hydrocarbon assets on water resources. Our objective was to quantify HF water volume in terms of source, reuse, and disposal, using the Barnett Shale in Texas as a case study. Data were obtained from commercial and state databases, river authorities, groundwater conservation districts, and operators. Cumulative water use from ∼ 18,000 (mostly horizontal) wells since 1981 through 2012 totaled ∼ 170,000 AF (210 Mm(3)); ∼ 26 000 AF (32 Mm(3)) in 2011, representing 32% of Texas HF water use and ∼ 0.2% of 2011 state water consumption. Increase in water use per well by 60% (from 3 to 5 Mgal/well; 0.011-0.019 Mm(3)) since the mid-2000s reflects the near-doubling of horizontal-well lengths (2000-3800 ft), offset by a reduction in water-use intensity by 40% (2000-1200 gal/ft; 2.5-1.5 m(3)/m). Water sources include fresh surface water and groundwater in approximately equal amounts. Produced water amount is inversely related to gas production, exceeds HF water volume, and is mostly disposed in injection wells. Understanding the historical evolution of water use in the longest-producing shale play is invaluable for assessing its water footprint for energy production.

  2. Potential water resource impacts of hydraulic fracturing from unconventional oil production in the Bakken shale.

    Shrestha, Namita; Chilkoor, Govinda; Wilder, Joseph; Gadhamshetty, Venkataramana; Stone, James J


    Modern drilling techniques, notably horizontal drilling and hydraulic fracturing, have enabled unconventional oil production (UOP) from the previously inaccessible Bakken Shale Formation located throughout Montana, North Dakota (ND) and the Canadian province of Saskatchewan. The majority of UOP from the Bakken shale occurs in ND, strengthening its oil industry and businesses, job market, and its gross domestic product. However, similar to UOP from other low-permeability shales, UOP from the Bakken shale can result in environmental and human health effects. For example, UOP from the ND Bakken shale generates a voluminous amount of saline wastewater including produced and flowback water that are characterized by unusual levels of total dissolved solids (350 g/L) and elevated levels of toxic and radioactive substances. Currently, 95% of the saline wastewater is piped or trucked onsite prior to disposal into Class II injection wells. Oil and gas wastewater (OGW) spills that occur during transport to injection sites can potentially result in drinking water resource contamination. This study presents a critical review of potential water resource impacts due to deterministic (freshwater withdrawals and produced water management) and probabilistic events (spills due to leaking pipelines and truck accidents) related to UOP from the Bakken shale in ND.

  3. Temporal Trends in Freshwater Withdrawals for Hydraulic Fracturing in the Marcellus Shale

    Barth-Naftilan, E.; Saiers, J. E.


    Development of the Marcellus Shale, the nation's largest shale gas producing formation, is estimated to use two to seven million gallons of water per well. Because Marcellus Shale wells are located in relatively water-rich areas, there has been less pressure in the region to recycle and reuse freshwater sourced from surface water streams for stimulating new wells. We review trends in actual freshwater withdrawals from surface water streams over time, and examine which regulations are most protective of flows intra- and inter-annually. Pass-by flow protective requirements appear to be most effective when set based on monthly flows, rather than annual flows, though not all regulatory agencies are using this protective mechanism. Total water use by industry in a shale play doesn't appear to follow trends of seasonal availability until three to five years after development begins in that play, and intensity of water use from surface water withdrawal sites appears to decrease over time. Trends in water use can be tied to a number of factors including changing gas prices and demand (number of wells hydraulically fractured), increasing length of laterals, increasing recycling rates, increasing industrial efficiency, and others.

  4. A systematic evaluation of chemicals in hydraulic-fracturing fluids and wastewater for reproductive and developmental toxicity.

    Elliott, Elise G; Ettinger, Adrienne S; Leaderer, Brian P; Bracken, Michael B; Deziel, Nicole C


    Hydraulic-fracturing fluids and wastewater from unconventional oil and natural gas development contain hundreds of substances with the potential to contaminate drinking water. Challenges to conducting well-designed human exposure and health studies include limited information about likely etiologic agents. We systematically evaluated 1021 chemicals identified in hydraulic-fracturing fluids (n=925), wastewater (n=132), or both (n=36) for potential reproductive and developmental toxicity to triage those with potential for human health impact. We searched the REPROTOX database using Chemical Abstract Service registry numbers for chemicals with available data and evaluated the evidence for adverse reproductive and developmental effects. Next, we determined which chemicals linked to reproductive or developmental toxicity had water quality standards or guidelines. Toxicity information was lacking for 781 (76%) chemicals. Of the remaining 240 substances, evidence suggested reproductive toxicity for 103 (43%), developmental toxicity for 95 (40%), and both for 41 (17%). Of these 157 chemicals, 67 had or were proposed for a federal water quality standard or guideline. Our systematic screening approach identified a list of 67 hydraulic fracturing-related candidate analytes based on known or suspected toxicity. Incorporation of data on potency, physicochemical properties, and environmental concentrations could further prioritize these substances for future drinking water exposure assessments or reproductive and developmental health studies.

  5. A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

    Mallants, Dirk; Simunek, Jirka; Gerke, Kirill


    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.

  6. Advanced studies on Simulation Methodologies for very Complicated Fracture Phenomena

    Nishioka, Toshihisa


    Although nowadays, computational techniques are well developed, for Extremely Complicated Fracture Phenomena, they are still very difficult to simulate, for general engineers, researchers. To overcome many difficulties in those simulations, we have developed not only Simulation Methodologies but also theoretical basis and concepts. We sometimes observe extremely complicated fracture patterns, especially in dynamic fracture phenomena such as dynamic crack branching, kinking, curving, etc. For examples, although the humankind, from primitive men to modern scientists such as Albert Einstein had watched the post-mortem patterns of dynamic crack branching, the governing condition for the onset of the phenomena had been unsolved until our experimental study. From in these studies, we found the governing condition of dynamic crack bifurcation, as follows. When the total energy flux per unit time into a propagating crack tip reaches the material crack resistance, the crack braches into two cracks [total energy flux criterion]. The crack branches many times whenever the criterion is satisfied. Furthermore, the complexities also arise due to their time-dependence and/or their-deformation dependence. In order to make it possible to simulate such extremely complicated fracture phenomena, we developed many original advanced computational methods and technologies. These are (i)moving finite element method based on Delaunay automatic triangulation (MFEMBOAT), path independent,(ii) equivalent domain integral expression of the dynamic J integral associated with a continuous auxiliary function,(iii) Mixed phase path-prediction mode simulation, (iv) implicit path prediction criterion. In this paper, these advanced computational methods are thoroughly explained together with successful comparison with the experimental results. Since multiple dynamic crack branching phenomena may be most complicated fracture due to complicated fracture paths, and its time dependence (transient), this

  7. Advances in thermal hydraulic and neutronic simulation for reactor analysis and safety

    Tentner, A.M.; Blomquist, R.N.; Canfield, T.R.; Ewing, T.F.; Garner, P.L.; Gelbard, E.M.; Gross, K.C.; Minkoff, M.; Valentin, R.A.


    This paper describes several large-scale computational models developed at Argonne National Laboratory for the simulation and analysis of thermal-hydraulic and neutronic events in nuclear reactors and nuclear power plants. The impact of advanced parallel computing technologies on these computational models is emphasized.

  8. Numerical simulation of hydraulic fracturing using a three-dimensional fracture model coupled with an adaptive mesh fluid model

    Xiang, G.L.; Vire, A.; Pavlidis, D.; Pain, C.


    A three-dimensional fracture model developed in the context of the combined finite-discrete element method is incorporated into a two-way fluid-solid coupling model. The fracture model is capable of simulating the whole fracturing process. It includes pre-peak hardening deformation, post-peak strain

  9. Status of the art: hydraulic conductivity of acid- fractures; Condutividade hidraulica de fratura acida: estado da arte

    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:


    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)

  10. GHGfrack: An Open-Source Model for Estimating Greenhouse Gas Emissions from Combustion of Fuel during Drilling and Hydraulic Fracturing.

    Vafi, Kourosh; Brandt, Adam


    This paper introduces GHGfrack, an open-source engineering-based model that estimates energy consumption and associated GHG emissions from drilling and hydraulic fracturing operations. We describe verification and calibration of GHGfrack against field data for energy and fuel consumption. We run GHGfrack using data from 6927 wells in Eagle Ford and 4431 wells in Bakken oil fields. The average estimated energy consumption in Eagle Ford wells using lateral hole diameters of 8 (3)/4 and 6 (1)/8 in. are 2.25 and 2.73 TJ/well, respectively. The average estimated energy consumption in Bakken wells using hole diameters of 6 in. for horizontal section is 2.16 TJ/well. We estimate average greenhouse gas (GHG) emissions of 419 and 510 tonne of equivalent CO2 per well (tonne of CO2 eq/well) for the two aforementioned assumed geometries in Eagle Ford, respectively, and 417 tonne of CO2 eq/well for the case of Bakken. These estimates are limited only to GHG emissions from combustion of diesel fuel to supply energy only for rotation of drill string, drilling mud circulation, and fracturing pumps. Sensitivity analysis of the model shows that the top three key variables in driving energy intensity in drilling are the lateral hole diameter, drill pipe internal diameter, and mud flow rate. In hydraulic fracturing, the top three are lateral casing diameter, fracturing fluid volume, and length of the lateral.

  11. Spatial and temporal correlation of water quality parameters of produced waters from devonian-age shale following hydraulic fracturing.

    Barbot, Elise; Vidic, Natasa S; Gregory, Kelvin B; Vidic, Radisav D


    The exponential increase in fossil energy production from Devonian-age shale in the Northeastern United States has highlighted the management challenges for produced waters from hydraulically fractured wells. Confounding these challenges is a scant availability of critical water quality parameters for this wastewater. Chemical analyses of 160 flowback and produced water samples collected from hydraulically fractured Marcellus Shale gas wells in Pennsylvania were correlated with spatial and temporal information to reveal underlying trends. Chloride was used as a reference for the comparison as its concentration varies with time of contact with the shale. Most major cations (i.e., Ca, Mg, Sr) were well-correlated with chloride concentration while barium exhibited strong influence of geographic location (i.e., higher levels in the northeast than in southwest). Comparisons against brines from adjacent formations provide insight into the origin of salinity in produced waters from Marcellus Shale. Major cations exhibited variations that cannot be explained by simple dilution of existing formation brine with the fracturing fluid, especially during the early flowback water production when the composition of the fracturing fluid and solid-liquid interactions influence the quality of the produced water. Water quality analysis in this study may help guide water management strategies for development of unconventional gas resources.

  12. Final design of a free-piston hydraulic advanced Stirling conversion system

    Wallace, D. A.; Noble, J. E.; Emigh, S. G.; Ross, B. A.; Lehmann, G. A.


    Under the US Department of Energy's (DOEs) Solar Thermal Technology Program, Sandia National Laboratories is evaluating heat engines for solar distributed receiver systems. The final design is described of an engineering prototype advanced Stirling conversion system (ASCS) with a free-piston hydraulic engine output capable of delivering about 25 kW of electric power to a utility grid. The free-piston Stirling engine has the potential for a highly reliable engine with long life because it has only a few moving parts, has noncontacting bearings, and can be hermetically sealed. The ASCS is designed to deliver maximum power per year over a range of solar input with a design life of 30 years (60,000 h). The system includes a liquid Nak pool boiler heat transport system and a free-piston Stirling engine with high-pressure hydraulic output, coupled with a bent axis variable displacement hydraulic motor and a rotary induction generator.

  13. Investigating the traffic-related environmental impacts of hydraulic-fracturing (fracking) operations.

    Goodman, Paul S; Galatioto, Fabio; Thorpe, Neil; Namdeo, Anil K; Davies, Richard J; Bird, Roger N


    Hydraulic fracturing (fracking) has been used extensively in the US and Canada since the 1950s and offers the potential for significant new sources of oil and gas supply. Numerous other countries around the world (including the UK, Germany, China, South Africa, Australia and Argentina) are now giving serious consideration to sanctioning the technique to provide additional security over the future supply of domestic energy. However, relatively high population densities in many countries and the potential negative environmental impacts that may be associated with fracking operations has stimulated controversy and significant public debate regarding if and where fracking should be permitted. Road traffic generated by fracking operations is one possible source of environmental impact whose significance has, until now, been largely neglected in the available literature. This paper therefore presents a scoping-level environmental assessment for individual and groups of fracking sites using a newly-created Traffic Impacts Model (TIM). The model produces estimates of the traffic-related impacts of fracking on greenhouse gas emissions, local air quality emissions, noise and road pavement wear, using a range of hypothetical fracking scenarios to quantify changes in impacts against baseline levels. Results suggest that the local impacts of a single well pad may be short duration but large magnitude. That is, whilst single digit percentile increases in emissions of CO2, NOx and PM are estimated for the period from start of construction to pad completion (potentially several months or years), excess emissions of NOx on individual days of peak activity can reach 30% over baseline. Likewise, excess noise emissions appear negligible (fracking water and flowback waste requirements. The TIM model is designed to be adaptable to any geographic area where the required input data are available (such as fleet characteristics, road type and quality), and we suggest could be deployed as a

  14. A Biofilm Treatment Approach for Produced Water from Hydraulic Fracturing Using Engineered Microbial Mats

    Akyon, B.; Stachler, E.; Bibby, K. J.


    Hydraulic fracturing results in large volumes of wastewater, called "produced water". Treatment of produced water is challenged by its high salt, organic compound, and radionuclide concentrations. Current disposal approaches include deep well injection and physical-chemical treatment for surface disposal; however, deep well injection has been recently linked to induced seismicity and physical-chemical treatments suffer from fouling and high cost. The reuse of the produced water has emerged as a desirable management option; however, this requires pretreatment to generate a water of usable quality and limit microbial activity. Biological treatment is an underexplored area in produced water management and has the potential to remove organics and reduce overall costs for physiochemical treatment or reuse. Suspended growth biological treatment techniques are known to be limited by salinity motivating a more robust biofilm approach: 'microbial mats'. In this study, we used engineered microbial mats as a biofilm treatment for the produced water. Evaluation of the biodegradation performance of microbial mats in synthetic and real produced waters showed microbial activity at up to 100,000 mg/L TDS concentration (three times the salt concentration of the ocean). Organic removal rates reached to 1.45 mg COD/gramwet-day at 91,351 mg/L TDS in real produced water samples and initial evaluation demonstrated the potential for field-scale application. Metagenomic analyses of microbial mats demonstrated an adaptive shift in the microbial community treating different samples, suggesting the wide applicability of this treatment approach for produced waters with varying chemical composition. On-going studies focus on the evaluation of the removal of the organics and the contaminants of high concern in produced water using microbial mats as well as the effect of the biofilm growth conditions on the biodegradation in changing salt concentrations.

  15. Addressing the challenges of GRACE application in basins with hydraulic fracturing activity

    Read, L.; Ruybal, C.; Hogue, T. S.; Hinojosa, M. P.


    Despite the growing number of studies that employ GRACE to quantify groundwater resources we have found no published studies on whether GRACE is also accounting for subsurface mass redistributions related to energy development activities from oil production, water production, and wastewater injection. Given the similar densities of water and crude oil (water is 1.0g/cc, crude oil is 0.8-0.9g/cc) and the fact that large volumes of oil and water are extracted on a monthly basis for hydraulic fracturing or reinjected as a means of waste disposal, it is important to determine whether GRACE is detecting mass redistributions from energy development to be able to correctly infer changes in water mass. The purpose of this study is to investigate whether GRACE measurements are impacted by energy development activities and offer a methodology for determining whether this activity should be considered when evaluating changes in terrestrial water storage, groundwater storage, or any other prediction involving quantification of groundwater. To address this question we compiled a dataset from the Bakken Play in North Dakota to use as a case study, where oil production was significant and increased exponentially from 2002-2015, and groundwater withdrawals for agriculture were relatively stable and limited. Preliminary results indicate that oil and gas production is of a similar scale and thus important to include when calculating groundwater changes. Broadly, this research addresses the challenges and uncertainties in applying GRACE to quantify groundwater or terrestrial water changes in energy-active basins, namely in accounting for oil reservoir changes, production, and injection rates, as well as the process of data collection in proprietary systems.

  16. Will water scarcity in semiarid regions limit hydraulic fracturing of shale plays?

    Scanlon, Bridget R.; Reedy, Robert C.; Nicot, Jean Philippe


    There is increasing concern about water constraints limiting oil and gas production using hydraulic fracturing (HF) in shale plays, particularly in semiarid regions and during droughts. Here we evaluate HF vulnerability by comparing HF water demand with supply in the semiarid Texas Eagle Ford play, the largest shale oil producer globally. Current HF water demand (18 billion gallons, bgal; 68 billion liters, bL in 2013) equates to ˜16% of total water consumption in the play area. Projected HF water demand of ˜330 bgal with ˜62 000 additional wells over the next 20 years equates to ˜10% of historic groundwater depletion from regional irrigation. Estimated potential freshwater supplies include ˜1000 bgal over 20 yr from recharge and ˜10 000 bgal from aquifer storage, with land-owner lease agreements often stipulating purchase of freshwater. However, pumpage has resulted in excessive drawdown locally with estimated declines of ˜100-200 ft in ˜6% of the western play area since HF began in 2009-2013. Non-freshwater sources include initial flowback water, which is ≤5% of HF water demand, limiting reuse/recycling. Operators report shifting to brackish groundwater with estimated groundwater storage of 80 000 bgal. Comparison with other semiarid plays indicates increasing brackish groundwater and produced water use in the Permian Basin and large surface water inputs from the Missouri River in the Bakken play. The variety of water sources in semiarid regions, with projected HF water demand representing ˜3% of fresh and ˜1% of brackish water storage in the Eagle Ford footprint indicates that, with appropriate management, water availability should not physically limit future shale energy production.

  17. Spatial Risk Analysis of Hydraulic Fracturing near Abandoned and Converted Oil and Gas Wells.

    Brownlow, Joshua W; Yelderman, Joe C; James, Scott C


    Interaction between hydraulically generated fractures and existing wells (frac hits) could represent a potential risk to groundwater. In particular, frac hits on abandoned oil and gas wells could lead to upward leakage into overlying aquifers, provided migration pathways are present along the abandoned well. However, potential risk to groundwater is relatively unknown because few studies have investigated the probability of frac hits on abandoned wells. In this study, actual numbers of frac hits were not determined. Rather, the probability for abandoned wells to intersect hypothetical stimulated reservoir sizes of horizontal wells was investigated. Well data were compiled and analyzed for location and reservoir information, and sensitivity analyses were conducted by varying assumed sizes of stimulated reservoirs. This study used public and industry data for the Eagle Ford Shale play in south Texas, with specific attention paid to abandoned oil and gas wells converted into water wells (converted wells). In counties with Eagle Ford Shale activity, well-data analysis identified 55,720 abandoned wells with a median age of 1983, and 2400 converted wells with a median age of 1954. The most aggressive scenario resulted in 823 abandoned wells and 184 converted wells intersecting the largest assumed stimulated reservoir size. Analysis showed abandoned wells have the potential to be intersected by multiple stimulated reservoirs, and risks for intersection would increase if currently permitted horizontal wells in the Eagle Ford Shale are actually completed. Results underscore the need to evaluate historical oil and gas activities in areas with modern unconventional oil and gas activities. © 2016, National Ground Water Association.

  18. Hydraulic Properties of Fractured Rock Samples at In-Situ Conditions - Insights from Lab Experiments Using X-Ray Tomography

    Nehler, Mathias; Stöckhert, Ferdinand; Duda, Mandy; Renner, Jörg; Bracke, Rolf


    The hydraulic properties of low-porosity rock formations are controlled by the geometry of open fractures, joints and faults. Aperture, surface roughness, accessible length, and thus, the volume available for fluids associated of such interfaces are strongly affected by their state of stress. Moreover, these properties may evolve with time in particular due to processes involving chemically active fluids. Understanding the physico-chemical interactions of rocks with fluids at reservoir conditions will help to predict the long-term reservoir development and to increase the efficiency of geothermal power plants. We designed an x-ray transparent flow-through cell. Confining pressure can be up to 50 MPa and pore fluid can currently be circulated through the sample with pressures of up to 25 MPa. All wetted parts are made of PEEK to avoid corrosion when using highly saline fluids. Laboratory experiments were performed to investigate hydraulic properties of fractured low-porosity samples under reservoir conditions while x-rays transmit the sample. The cell is placed inside a µCT scanner with a 225 kV multifocal x-ray tube for high resolution x-ray tomography. Samples measure 10 mm in diameter and 25 mm in length resulting in a voxel resolution of approximately 10 µm. Samples with single natural as well as artificial fractures were subjected to various confining pressures ranging from 2.5 MPa to 25 MPa. At each pressure level, effective permeability was determined from steady-state flow relying on Darcy's law. In addition, a full 3D image was recorded by the µCT scanner to gain information on the fracture aperture and geometry. Subvolumes (400x400x400 voxels) of the images were analyzed to reduce computational cost. The subvolumes were filtered in 3D with an edge preserving non-local means filter. Further quantification algorithms were implemented in Matlab. Segmentation into pore space and minerals was done automatically for all datasets by a peak finder algorithm

  19. Estimation of the fluid excess pressure of hydraulic fractures in paleo geothermal reservoirs; Abschaetzung des Fluidueberdrucks von hydraulischen Bruechen in palaeogeothermischen Reservoiren

    Philipp, Sonja L. [Goettingen Univ. (Germany). Geowissenschaftliches Zentrum


    In many geothermal reservoirs to low natural permeabilities have to be enhanced by opening or shearing the existing fractures or by generating artificial hydraulic fractures (reservoir stimulation). Such hydraulic fractures can also occur naturally and will remain in paleo geothermal reservoirs. Using the example of calcite passages in a Jurassic limestone-marl alternations in southwest England the author of the contribution under consideration shows that the fault zones (mainly normal faults) were used as fluid transport pathways for calcium carbonate containing water which was injected as hydraulic fractures in the host rock. Overall, in consensus with isotopic studies it was shown that geothermal waters with relatively local origin were within the sedimentary basin and did not come from great depths. The pore fluid pressure within the limestone beds is not sufficient as a reason for the formation of calcite passages.

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

    Mohan, Arvind Murali; Bibby, Kyle J; Lipus, Daniel; Hammack, Richard W; Gregory, Kelvin B


    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.

  1. XFEM-Based CZM for the Simulation of 3D Multiple-Cluster Hydraulic Fracturing in Quasi-Brittle Shale Formations

    Haddad, Mahdi; Sepehrnoori, Kamy


    The cohesive zone model (CZM) honors the softening effects and plastic zone at the fracture tip in a quasi-brittle rock, e.g., shale, which results in a more precise fracture geometry and pumping pressure compared to those from linear elastic fracture mechanics. Nevertheless, this model, namely the planar CZM, assumes a predefined surface on which the fractures propagate and therefore restricts the fracture propagation direction. Notably, this direction depends on the stress interactions between closely spaced fractures and can be acquired by integrating CZM as the segmental contact interaction model with a fully coupled pore pressure-displacement model based on extended finite element method (XFEM). This integrated model, called XFEM-based CZM, simulates the fracture initiation and propagation along an arbitrary, solution-dependent path. In this work, we modeled a single stage of 3D hydraulic fracturing initiating from three perforation clusters in a single-layer, quasi-brittle shale formation using planar CZM and XFEM-based CZM including slit flow and poroelasticity for fracture and matrix spaces, respectively, in Abaqus. We restricted the XFEM enrichment zones to the stimulation regions as enriching the whole domain leads to extremely high computational expenses and unrealistic fracture growths around sharp edges. Moreover, we validated our numerical technique by comparing the solution for a single fracture with KGD solution and demonstrated several precautionary measures in using XFEM in Abaqus for faster solution convergence, for instance the initial fracture length and mesh refinement. We demonstrated the significance of the injection rate and stress contrast in fracture aperture, injection pressure, and the propagation direction. Moreover, we showed the effect of the stress distribution on fracture propagation direction comparing the triple-cluster fracturing results from planar CZM with those from XFEM-based CZM. We found that the stress shadowing effect of

  2. Hydraulic Fracturing Design of Coal-bed Gas Well%煤层气井水力压裂设计

    张志全; 张军; 许弟龙; 胡东; 张保国; 唐艳


    针对煤层气井储层特性和压裂的特殊性,选择了拟三维模型进行水力压裂设计。针对一口具体井的资料进行了模拟计算,计算结果合理。同时就地面注液排量、压裂液稠度系数和地应力差值对裂缝几何形态的影响进行了计算和分析,并提出了相应的建议。%In consideration of reservoir charateristics and particalarity of fracturing of coal-bed gas well,a psuedo 3D fracture model is selected to design the hydraulic fracturing.A simulation calculation is performed with data from a specific well,of which the result is reasonable,at the same time calculation and analysis are conducted on the geometry of fractures based on the displacement of surface injected fluid,density coefficient of fracturing fluid and differential value of earth stress,thus related proposals are made.

  3. In-situ stress measurements and stress change monitoring to monitor overburden caving behaviour and hydraulic fracture pre-conditioning

    Puller Jesse W.; Mills Ken W.; Jeffrey Rob G.; Walker Rick J.


    A coal mine in New South Wales is longwall mining 300 m wide panels at a depth of 160–180 m directly below a 16–20 m thick conglomerate strata. As part of a strategy to use hydraulic fracturing to manage potential windblast and periodic caving hazards associated with these conglomerate strata, the in-situ stresses in the conglomerate were measured using ANZI strain cells and the overcoring method of stress relief. Changes in stress associated with abutment loading and placement of hydraulic fractures were also measured using ANZI strain cells installed from the surface and from underground. Overcore stress mea-surements have indicated that the vertical stress is the lowest principal stress so that hydraulic fractures placed ahead of mining form horizontally and so provide effective pre-conditioning to promote caving of the conglomerate strata. Monitoring of stress changes in the overburden strata during longwall retreat was undertaken at two different locations at the mine. The monitoring indicated stress changes were evi-dent 150 m ahead of the longwall face and abutment loading reached a maximum increase of about 7.5 MPa. The stresses ahead of mining change gradually with distance to the approaching longwall and in a direction consistent with the horizontal in-situ stresses. There was no evidence in the stress change monitoring results to indicate significant cyclical forward abutment loading ahead of the face. The for-ward abutment load determined from the stress change monitoring is consistent with the weight of over-burden strata overhanging the goaf indicated by subsidence monitoring.

  4. Relationship of Shallow Groundwater Quality to Hydraulic Fracturing Activities in Antrim and Kalkaska Counties, MI

    Stefansky, J. N.; Robertson, W. M.; Chappaz, A.; Babos, H.; Israel, S.; Groskreutz, L. M.


    Hydraulic fracturing (fracking) of oil and natural gas (O&G) wells is a widely applied technology that can increase yields from tight geologic formations. However, it is unclear how fracking may impact shallow groundwater; previous research into its effects has produced conflicting results. Much of the worry over potential impacts to water quality arises from concerns about the produced water. The water produced from O&G formations is often salty, contains toxic dissolved elements, and can be radioactive. If fracking activities cause or increase connectivity between O&G formations and overlying groundwater, there may be risks to aquifers. As one part of a groundwater quality study in Antrim and Kalkaska Counties, MI, samples were collected from the unconfined glacial aquifer (3-300 m thick) and produced water from the underlying Antrim formation, a shallow (180-670 m deep) natural gas producing black shale. Groundwater samples were collected between 200 to 10,000 m distance from producing Antrim gas wells and from a range of screened intervals (15-95 m). Samples were analyzed for major constituents (e.g., Br, Cl), pH, conductivity, and dissolved oxygen (DO). The specific conductance of groundwater samples ranged from 230-1020 μS/cm; DO ranged from 0.4-100% saturation. Preliminary results show a slight inverse correlation between specific conductance and proximity to producing Antrim wells. The observed range of DO saturation in glacial aquifer groundwater appears to be related to both screened depth of the water wells and proximity to Antrim wells. During sampling, some well owners expressed concerns about the effects of fracking on groundwater quality and reported odd smells and tastes in their water after O&G drilling occurred near their homes. The results of this study and reported observations provide evidence to suggest a potential hydrogeological connection between the Antrim formation and the overlying glacial aquifer in some locations; it also raises

  5. Biocides in hydraulic fracturing: hazard and vulnerability with respect to potential groundwater pollution

    Worrall, Fred; Wilson, Miles; Davies, Richard


    Biocides are one possible chemical additive to frack fluids and their role is to control bacterial growth. Bacterial growth might lead to biofilm build up; and acid sulfide species and hydrogen sulfide (H2S) production: biofilm build up may reduce formation permeability and hinder gas extraction. Kahrilas et al. (2014) published a review of common biocides used in fracking in the USA. The biocides assessed in the review were the sixteen most commonly used in the USA, based on the hydraulic fracturing chemical registry Frac Focus (Frac Focus, 2015). However, the review of Kahrilas et al. (2014) contained no data or observations and so the objective of this study was to consider whether biocides proposed for use in hydrofacturing could be a threat to English groundwater. The study considered all groundwater samples analysed for biocides in English groundwater between 2005 and 2014. The monitoring records were compared to: records of application (both amount and area); and chemical and molecular data for the biocides. The study did not use traditional adsorption and degradation data as these parameters are to prone to variability and are not pure molecular parameters. The study then used the approach of Worrall and Thomsen (2004) to consider the hazard represented by proposed frack biocides and the approach of Worrall and Kolpin (2003) to consider the vulnerability of the areas of potential shale gas exploitation. The study showed that of the 113 biocides tested for in English groundwaters in the decade 2005 - 2014 that 95 were detected above 0.1 g/l . Of these 95, 41 were compounds that were not recorded as being applied during the period of record and the detection of these 41 compounds did not decline over the 10 year period which implies very long residence times and that once compounds do pollute an aquifer then they will be a persistent problem. Furthermore, the solubility of the range of biocides used in frack fluids would imply a potentially higher hazard

  6. Nanoscale zero-valent iron for metal/metalloid removal from model hydraulic fracturing wastewater.

    Sun, Yuqing; Lei, Cheng; Khan, Eakalak; Chen, Season S; Tsang, Daniel C W; Ok, Yong Sik; Lin, Daohui; Feng, Yujie; Li, Xiang-Dong


    Nanoscale zero-valent iron (nZVI) was tested for the removal of Cu(II), Zn(II), Cr(VI), and As(V) in model saline wastewaters from hydraulic fracturing. Increasing ionic strength (I) from 0.35 to 4.10 M (Day-1 to Day-90 wastewaters) increased Cu(II) removal (25.4-80.0%), inhibited Zn(II) removal (58.7-42.9%), slightly increased and then reduced Cr(VI) removal (65.7-44.1%), and almost unaffected As(V) removal (66.7-75.1%) by 8-h reaction with nZVI at 1-2 g L(-1). The removal kinetics conformed to pseudo-second-order model, and increasing I decreased the surface area-normalized rate coefficient (ksa) of Cu(II) and Cr(VI), probably because agglomeration of nZVI in saline wastewaters restricted diffusion of metal(loid)s to active surface sites. Increasing I induced severe Fe dissolution from 0.37 to 0.77% in DIW to 4.87-13.0% in Day-90 wastewater; and Fe dissolution showed a significant positive correlation with Cu(II) removal. With surface stabilization by alginate and polyvinyl alcohol, the performance of entrapped nZVI in Day-90 wastewater was improved for Zn(II) and Cr(VI), and Fe dissolution was restrained (3.20-7.36%). The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in removal trends from Day-1 to Day-90 wastewaters was attributed to: (i) distinctive removal mechanisms of Cu(II) and Cr(VI) (adsorption, (co-)precipitation, and reduction), compared to Zn(II) (adsorption) and As(V) (bidentate inner-sphere complexation); and (ii) changes in solution speciation (e.g., from Zn(2+) to ZnCl3(-) and ZnCl4(2-); from CrO4(2-) to CaCrO4 complex). Bare nZVI was susceptible to variations in wastewater chemistry while entrapped nZVI was more stable and environmentally benign, which could be used to remove metals/metalloids before subsequent treatment for reuse/disposal. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

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


    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.

  8. Hydraulic fracturing and wellbore completion of coalbed methane wells in the Powder River Basin, Wyoming: Implications for water and gas production

    Colmenares, L.B.; Zoback, M.D. [Stanford University, Stanford, CA (United States). Dept. of Geophysics


    Excessive water production (more than 7000 bbl/month per well) from many coalbed methane (CBM) wells in the Powder River Basin of Wyoming is also associated with significant delays in the time it takes for gas production to begin. Analysis of about 550 water-enhancement activities carried out during well completion demonstrates that such activities result in hydraulic fracturing of the coal. Water-enhancement activities, consists of pumping 60 bbl of water/min into the coal seam during approximately 15 min. This is done to clean the well-bore and to enhance CBM production. Hydraulic fracturing is of concern because vertical hydraulic fracture growth could extend into adjacent formations and potentially result in excess CBM water production and inefficient depressurization of coals. Analysis of the pressure-time records of the water-enhancement tests enabled us to determine the magnitude of the least principal stress (S{sub 3}) in the coal seams of 372 wells. These data reveal that because S{sub 3} switches between the minimum horizontal stress and the overburden at different locations, both vertical and horizontal hydraulic fracture growth is inferred to occur in the basin, depending on the exact location and coal layer. Relatively low water production is observed for wells with inferred horizontal fractures, whereas all of the wells associated with excessive water production are characterized by inferred vertical hydraulic fractures. The reason wells with exceptionally high water production show delays in gas production appears to be inefficient depressurization of the coal caused by water production from the formations outside the coal. To minimize CBM water production, we recommend that in areas of known vertical fracture propagation, the injection rate during the water-enhancement tests should be reduced to prevent the propagation of induced fractures into adjacent water-bearing formations.


    Mukul M. Sharma


    The primary objective of this research was to improve completion and fracturing practices in gas reservoirs in marginal plays in the continental United States. The Bossier Play in East Texas, a very active tight gas play, was chosen as the site to develop and test the new strategies for completion and fracturing. Figure 1 provides a general location map for the Dowdy Ranch Field, where the wells involved in this study are located. The Bossier and other tight gas formations in the continental Unites States are marginal plays in that they become uneconomical at gas prices below $2.00 MCF. It was, therefore, imperative that completion and fracturing practices be optimized so that these gas wells remain economically attractive. The economic viability of this play is strongly dependent on the cost and effectiveness of the hydraulic fracturing used in its well completions. Water-fracs consisting of proppant pumped with un-gelled fluid is the type of stimulation used in many low permeability reservoirs in East Texas and throughout the United States. The use of low viscosity Newtonian fluids allows the creation of long narrow fractures in the reservoir, without the excessive height growth that is often seen with cross-linked fluids. These low viscosity fluids have poor proppant transport properties. Pressure transient tests run on several wells that have been water-fractured indicate a long effective fracture length with very low fracture conductivity even when large amounts of proppant are placed in the formation. A modification to the water-frac stimulation design was needed to transport proppant farther out into the fracture. This requires suspending the proppant until the fracture closes without generating excessive fracture height. A review of fracture diagnostic data collected from various wells in different areas (for conventional gel and water-fracs) suggests that effective propped lengths for the fracture treatments are sometimes significantly shorter than those

  10. Fracture hydraulic conductivity in the Mexico City clayey aquitard: Field piezometer rising-head tests

    Vargas, Carlos; Ortega-Guerrero, Adrián

    A regional lacustrine aquitard covers the main aquifer of the metropolitan area of Mexico City. The aquitard's hydraulic conductivity (K') is fundamental for evaluating the natural protection of the aquifer against a variety of contaminants present on the surface and its hydraulic response. This study analyzes the distribution and variation of K' in the plains of Chalco, Texcoco and Mexico City (three of the six former lakes that existed in the Basin of Mexico), on the basis of 225 field-permeability tests, in nests of existing piezometers located at depths of 2-85 m. Tests were interpreted using the Hvorslev method and some by the Bouwer-Rice method. Results indicate that the distribution of K' fits log-Gaussian regression models. Dominant frequencies for K' in the Chalco and Texcoco plains range between 1E-09 and 1E-08 m/s, with similar population means of 1.19E-09 and 1.7E-09 m/s, respectively, which are one to two orders of magnitude higher than the matrix conductivity. In the Mexico City Plain the population mean is near by one order of magnitude lower; K'=2.6E-10 m/s. The contrast between the measured K' and that of the matrix is attributed to the presence of fractures in the upper 25-40 m, which is consistent with the findings of previous studies on solute migration in the aquitard. Un imperméable régional d'origine lacustre recouvre le principal aquifère de la zone urbaine de la ville de Mexico. La conductivité hydraulique K' de cet imperméable est fondamentale pour évaluer la protection naturelle de l'aquifère, contre les différents contaminants présents en surface, et sa réponse hydraulique. Cette étude analyse et les variations de K' dans les plaines de Chalco, Texcoco et Mexico (trois des six anciens lacs qui existaient dans le Bassin de Mexico), sur la base de 225 essais de perméabilité sur le terrain, réalisés en grappes dans des piézomètres existants entre 2 et 85 m de profondeur. Les essais ont été interprétés avec la m

  11. Strategic Need for Multi-Purpose Thermal Hydraulic Loop for Support of Advanced Reactor Technologies

    James E. O' Brien; Piyush Sabharwall; Su-Jong Yoon; Gregory K. Housley


    This report presents a conceptual design for a new high-temperature multi fluid, multi loop test facility for the INL to support thermal hydraulic, materials, and thermal energy storage research for nuclear and nuclear-hybrid applications. In its initial configuration, the facility will include a high-temperature helium loop, a liquid salt loop, and a hot water/steam loop. The three loops will be thermally coupled through an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX). Research topics to be addressed with this facility include the characterization and performance evaluation of candidate compact heat exchangers such as printed circuit heat exchangers (PCHEs) at prototypical operating conditions, flow and heat transfer issues related to core thermal hydraulics in advanced helium-cooled and salt-cooled reactors, and evaluation of corrosion behavior of new cladding materials and accident-tolerant fuels for LWRs at prototypical conditions. Based on its relevance to advanced reactor systems, the new facility has been named the Advanced Reactor Technology Integral System Test (ARTIST) facility. Research performed in this facility will advance the state of the art and technology readiness level of high temperature intermediate heat exchangers (IHXs) for nuclear applications while establishing the INL as a center of excellence for the development and certification of this technology. The thermal energy storage capability will support research and demonstration activities related to process heat delivery for a variety of hybrid energy systems and grid stabilization strategies. Experimental results obtained from this research will assist in development of reliable predictive models for thermal hydraulic design and safety codes over the range of expected advanced reactor operating conditions. Proposed/existing IHX heat transfer and friction correlations and criteria will be assessed with information on materials compatibility and instrumentation

  12. Strategic need for a multi-purpose thermal hydraulic loop for support of advanced reactor technologies

    O' Brien, James E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States); Yoon, Su -Jong [Idaho National Lab. (INL), Idaho Falls, ID (United States); Housley, Gregory K. [Idaho National Lab. (INL), Idaho Falls, ID (United States)


    This report presents a conceptual design for a new high-temperature multi fluid, multi loop test facility for the INL to support thermal hydraulic, materials, and thermal energy storage research for nuclear and nuclear-hybrid applications. In its initial configuration, the facility will include a high-temperature helium loop, a liquid salt loop, and a hot water/steam loop. The three loops will be thermally coupled through an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX). Research topics to be addressed with this facility include the characterization and performance evaluation of candidate compact heat exchangers such as printed circuit heat exchangers (PCHEs) at prototypical operating conditions, flow and heat transfer issues related to core thermal hydraulics in advanced helium-cooled and salt-cooled reactors, and evaluation of corrosion behavior of new cladding materials and accident-tolerant fuels for LWRs at prototypical conditions. Based on its relevance to advanced reactor systems, the new facility has been named the Advanced Reactor Technology Integral System Test (ARTIST) facility. Research performed in this facility will advance the state of the art and technology readiness level of high temperature intermediate heat exchangers (IHXs) for nuclear applications while establishing the INL as a center of excellence for the development and certification of this technology. The thermal energy storage capability will support research and demonstration activities related to process heat delivery for a variety of hybrid energy systems and grid stabilization strategies. Experimental results obtained from this research will assist in development of reliable predictive models for thermal hydraulic design and safety codes over the range of expected advanced reactor operating conditions. Proposed/existing IHX heat transfer and friction correlations and criteria will be assessed with information on materials compatibility and instrumentation

  13. Estimation of the hydraulic conductivity of a two-dimensional fracture network using effective medium theory and power-law averaging

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


    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.

  14. Numerical Model of Hydraulic Fracturing Fluid Transport in the Subsurface with Pressure Transient, Density Effects, and Imbibition

    Birdsell, D.; Rajaram, H.; Dempsey, D.; Viswanathan, H.


    Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated from an environmental and public health perspective and to understand formation damage from an oil and gas production perspective. Upward pressure gradients, permeable pathways such as faults or improperly abandoned wellbores, and the density contrast of the HF fluid to the surrounding brine encourages upward HF fluid migration. In contrast, the very low shale permeability and the imbibition of water into partially-saturated shale may sequester much of the HF fluid. Using the Finite Element Heat and Mass Transfer Code (FEHM), single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore as flowback and produced water and how much reaches overlying aquifers; imbibition is calculated with a semi-analytical one-dimensional solution and treated as a sink term. The travel time for HF fluid to reach the shallow aquifers is highly dependent on the amount of water imbibed and the suction applied to the well. If imbibition rates and suction are small, the pressure transient due to injection and the density contrast allows rapid upward plume migration at early times. The density contrast diminishes considerably within tens to hundreds of years as mixing occurs. We present estimates of HF fluid migration to shallow aquifers during the first 1,000 years after hydraulic fracturing begins for ranges of subsurface properties.

  15. Adsorption of hydraulic fracturing fluid components 2-butoxyethanol and furfural onto granular activated carbon and shale rock.

    Manz, Katherine E; Haerr, Gregory; Lucchesi, Jessica; Carter, Kimberly E


    The objective of this study was to understand the adsorption ability of a surfactant and a non-surfactant chemical additive used in hydraulic fracturing onto shale and GAC. Experiments were performed at varying temperatures and sodium chloride concentrations to establish these impacts on the adsorption of the furfural (a non-surfactant) and 2-Butoxyethanol (2-BE) (a surfactant). Experiments were carried out in continuously mixed batch experiments with Langmuir and Freundlich isotherm modeling. The results of the experiments showed that adsorption of these compounds onto shale does not occur, which may allow these compounds to return to the surface in flowback and produced waters. The adsorption potential for these chemicals onto GAC follows the assumptions of the Langmuir model more strongly than those of the Freundlich model. The results show uptake of furfural and 2-BE occurs within 23 h in the presence of DI water, 0.1 mol L(-1) sodium chloride, and in lab synthesized hydraulic fracturing brine. Based on the data, 83% of the furfural and 62% of the 2-BE was adsorbed using GAC.

  16. Development of a data-driven forecasting tool for hydraulically fractured, horizontal wells in tight-gas sands

    Kulga, B.; Artun, E.; Ertekin, T.


    Tight-gas sand reservoirs are considered to be one of the major unconventional resources. Due to the strong heterogeneity and very low permeability of the formation, and the complexity of well trajectories with multiple hydraulic fractures; there are challenges associated with performance forecasting and optimum exploitation of these resources using conventional modeling approaches. In this study, it is aimed to develop a data-driven forecasting tool for tight-gas sands, which are based on artificial neural networks that can complement the physics-driven modeling approach, namely numerical-simulation models. The tool is designed to predict the horizontal-well performance as a proxy to the numerical model, once the initial conditions, operational parameters, reservoir/hydraulic-fracture characteristics are provided. The data-driven model, that the forecasting tool is based on, is validated with blind cases by estimating the cumulative gas production after 10 years with an average error of 3.2%. A graphical-user-interface application is developed that allows the practicing engineer to use the developed tool in a practical manner by visualizing estimated performance for a given reservoir within a fraction of a second. Practicality of the tool is demonstrated with a case study for the Williams Fork Formation by assessing the performance of various well designs and by incorporating known uncertainties through Monte Carlo simulation. P10, P50 and P90 estimates of the horizontal-well performance are quickly obtained within acceptable accuracy levels.

  17. Regulation of Water Pollution from Hydraulic Fracturing in Horizontally-Drilled Wells in the Marcellus Shale Region, USA

    Heather Hatzenbuhler


    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.

  18. Rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system — Concepts and field results

    Zimmermann, Günter; Blöcher, Guido; Reinicke, Andreas; Brandt, Wulf


    Enhanced geothermal systems (EGS) are engineered reservoirs developed to extract economic amounts of heat from low permeability and/or porosity geothermal resources. To enhance the productivity of reservoirs, a site specific concept is necessary to actively make reservoir conditions profitable using specially adjusted stimulation treatments, such as multi fracture concepts and site specific well path design. The results of previously performed stimulation treatments in the geothermal research well GtGrSk4/05 at Groß Schönebeck, Germany are presented. The reservoir is located at a 4100-4300 m depth within the Lower Permian of the NE German Basin with a bottom-hole temperature of 150 °C. The reservoir rock is classified by two lithological units from bottom to top: volcanic rocks (andesitic rocks) and siliciclastics ranging from conglomerates to fine-grained sandstones (fluvial sediments). The stimulation treatments included multiple hydraulic stimulations and an acid treatment. In order to initiate a cross-flow from the sandstone layer, the hydraulic stimulations were performed in different depth sections (two in the sandstone section and one in the underlying volcanic section). In low permeability volcanic rocks, a cyclic hydraulic fracturing treatment was performed over 6 days in conjunction with adding quartz in low concentrations to maintain a sustainable fracture performance. Flow rates of up to 150 l/s were realized, and a total of 13,170 m 3 of water was injected. A hydraulic connection to the sandstone layer was successfully achieved in this way. However, monitoring of the water level in the offsetting well EGrSk3/90, which is 475 m apart at the final depth, showed a very rapid water level increase due to the stimulation treatment. This can be explained by a connected fault zone within the volcanic rocks. Two gel-proppant treatments were performed in the slightly higher permeability sandstones to obtain long-term access to the reservoir rocks. During each

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

    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.


    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 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 management of produced water include reuse

  20. Mathematical study of fracture face skin in hydraulic fractures%人工裂缝缝壁表皮效应数学模型研究

    才博; 王晓冬; 王欣


    针对以往模型进行压裂设计与分析方法对结果偏差较大的实际情况,在对经典裂缝延伸和扩展PKN和KGD理论模型研究的基础上,运用断裂力学和流体耦合方法,建立新的缝壁表皮数学模型,获得新的裂缝缝壁表皮效应分段数学函数.将新模型与以往Cinco-Ley模型进行现场参数计算对比,结果表明:以往认为该表皮效应对产量影响只有5%,新模型表明该表皮效应对产量的影响可以达到50%,新模型揭示了以往认为高效压裂工艺下反而压后减产矛盾现象的真正原因.利用新模型指导压裂设计可降低裂缝缝壁表皮对产量的影响,增强压裂设计对储层的适应性和科学性.现场35井次试验表明,采用新模型后在降低成本的情况下,压裂效果增加1.5倍.%The results of hydraulic fracturing design and analysis were obviously mistaken by the former fracture face skin model.In order to reveal this skin effect more accurately,based on the classical theoretic models of perkins,kern and norgren(PKN) and khristianovic,geertsma and dekerk(KGD),a new mathematical model of fracture face skin with segmentation characteristic was established using fracture mechanics and fluid coupling method.Comparing the new model with the Cinco-Ley model through field data,the results show that the productivity of the Cinco-Ley model was influenced by only 5%,while that of the new model by 50%.This revealed the poor post-fracturing production with fracturing techniques that are regarded as most effective means by many designers.Using this new model,the influence of skin on productivity was reduced and made fracturing treatment more adaptable and scientific.Through field tests on 35 wells,the output was increased 1.5 times and the costs were dramatically cut by new model.

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

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


    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.

  2. Hydraulic Fracturing of 403 Shallow Diatomite Wells in South Belridge Oil Field, Kern County, California, in 2014

    Wynne, D. B.; Agusiegbe, V.


    We examine all 403 Hydraulic Fracture (HF) jobs performed by Aera Energy, LLC, in the South Belridge oil field, Kern County, CA in 2014. HFs in the South Belridge oil field are atypical amongst North American plays because the reservoir is shallow and produced via vertical wells. Our data set constitutes 88% of all HF jobs performed in CA oil fields in calendar-2014. The South Belridge field produces 11% of California's oil and the shallow HFs performed here differ from most HFs performed elsewhere. We discuss fracture modeling and methods and summary statistics, and modelled dimensions of fractures and their relationships to depth and reservoir properties. The 403 HFs were made in the diatomite-dominated Reef Ridge member of the Monterey Formation. The HFs began at an average depth of 1047 feet below ground (ft TVD) and extended an average of 626 ft vertically downward. The deepest initiation of HF was at 2380 ft and the shallowest cessation was at 639 ft TVD. The average HF was performed using 1488 BBL (62,496 gallons) of water. The HFs were performed in no more than 6 stages and nearly all were completed within one day. We (1) compare metrics of the South Belridge sample group with recent, larger "all-CA" and nationwide samples; and (2) conclude that if relationships of reservoir properties, well completion and HF are well understood, shallow diatomite HF may be optimized to enhance production while minimizing environmental impact.

  3. Mechanical interactions between proppants and rock and their effect on hydraulic fracture performance

    Legarth, B.A.; Raab, S.; Huenges, E. [GeoForschungsZentrum Potsdam (Germany)


    Proppants interact mechanically with the rock matrix. This causes damage to the fracture face and influences propped fracture performance. Therefore, proppant embedment and proppant crushing phenomena were analysed in laboratory under simulated in situ conditions. The embedment tests were performed in a conductivity cell using reassembled core halves. Embedment features in the rock matrix were optically analyzed. In a separate unit single grain strength tests were performed on a wide range of ceramic proppant types (AI203-based, coated/uncoated) and sizes (diameter 0,2-1,6 mm). The experiment showed that areas in the fracture with low proppant concentration revealed severe proppant crushing and embedment that occurred already at low effective stress. Punctual loading was identified as reason for premature proppant failure. Grain strength testing showed that compressive fracture force increases with grain diameter, is influenced by the presence of a coating and might be additionally controlled by grain surface structure. Compressive fracture strength is largely independent from size for same proppant types. A contact model introduced by Hertz was applied to retrieve the stress magnitudes at grain failure. Proppant crushing leads to generation of fines in the matrix and the proppant pack. These fines can be transported and plug pore-throats and flow channels. Dependent on completion type and expected fracture widths proppant grain size should be maximized for higher fracture conductivity. Proppant crushing and embedment processes are enforced by decreasing proppant concentration. Considering natural conditions in a fracture - rough surfaces, tortuous-twisted paths that hinder even proppant distribution - low proppant concentrations appear to be very real, maybe even the normal case in nature. Thus, high proppant concentration is the key issue to mitigate fracture impairment. (orig.)

  4. XFEM-Based CZM for the Simulation of 3D Multiple-Stage Hydraulic Fracturing in Quasi-brittle Shale Formations

    Haddad, M.; Sepehrnoori, K.


    The Cohesive Zone Model (CZM) engages the plastic zone and softening effects at the fracture tip in a quasi-brittle rock, e.g. shale, which concludes a more precise fracture geometry and pumping pressure compared to those from Linear Elastic Fracture Mechanics. Nevertheless, this model, namely planar CZM, assumes a predefined surface on which the fractures propagate and therefore, restricts the fracture propagation direction. Notably, this direction depends on the stress interactions between closely spaced fractures and can be acquired integrating CZM as the segmental contact interaction model with a fully coupled pore pressure-displacement, extended finite element model (XFEM). This later model simulates the fracture initiation and propagation along an arbitrary, solution-dependent path. In this work, we modeled double- and triple-cluster 3D hydraulic fracturing in a single-layer, quasi-brittle shale formation using planar CZM and XFEM-based CZM including slit flow and poro-elasticity for fracture and matrix spaces, respectively, in Abaqus. Our fully-coupled pore pressure-stress Geomechanics model includes leak-off as a continuum-based fluid flow component coupled with the other unknowns in the problem. Having compared the triple-cluster fracturing results from planar CZM with those from XFEM-based CZM, we found that the stress shadowing effect of multiple hydraulic fractures on each other can cause these fractures to rationally propagate out of plane; this also demonstrates the advantages of the second method compared to the first one. We investigated the effect of this arbitrary propagation direction on not only the fractures' length, aperture, and the required injection pressure, but also fractures' connection to the wellbore. Depending on the spacing and the number of clusters per stage, this connection can be gradually disrupted with time due to the near-wellbore fracture closure which may embed proppant particles on the fracture wall, or screen out the

  5. Depth-discrete specific storage in fractured sedimentary rock using steady-state and transient single-hole hydraulic tests

    Quinn, Patryk M.; Cherry, John A.; Parker, Beth L.


    A method is presented for obtaining depth-discrete values of specific storage (Ss) from single-hole hydraulic tests in fractured rock boreholes using straddle packers (1.5-17 m test intervals). Low flow constant head (CH) step tests analyzed using the Thiem method provide transmissivity (T) values free from non-Darcian error. Short-term, constant-rate pumping tests (0.5-2 h) analyzed using the Cooper-Jacob approximation of the Theis method provide S from the hydraulic diffusivity using the Darcian T value from the CH step test. This synergistic use of two types of hydraulic tests avoids the common source of error when pumping tests (injection or withdrawal) are conducted at higher flow rates and thereby induce non-Darcian flow resulting in the underestimation of T. Other errors, such as well bore storage and leakage, can also substantially influence S by causing a shift in the time axis of the Cooper-Jacob semi-log plot. In this approach, the Darcian T values from the CH step tests are used in the analysis of the transient pumping test data for calculating S throughout the pumping test using the Cooper-Jacob approximation to minimize all of the aforementioned errors, resulting in more representative S values. The effect of these non-idealities on the measured drawdown is illustrated using the Theis equation with the Darcian T and S values to calculate drawdown for comparison to measured data. The Ss values for tests in sandstone obtained from this approach are more consistent with confined aquifer conditions than values derived from the traditional Cooper-Jacob method, and are within the range of field and lab values presented from a compilation of literature values for fractured sandstone. (10-7-10-5 m-1) This method for obtaining Ss values from short-interval, straddle packer tests improves the estimation of both K and Ss and provides opportunity to study their spatial distribution in fractured rock.

  6. 顶板穿层钻孔水力压裂现场数值模拟研究%Roof Layer Drilling Hydraulic Fracturing Field Numerical Simulation Research



    Based on the theory of hydraulic fracturing antireflection mechanism,take Henan Energy Chemical Group of Jiaozuo Mining Group 21 Coal Seam as a parameter to the actual measured data,to play 22111 transportation lane roof extraction layer drilling to hy-draulic fracturing of coal body,and using RFPA2D -Flow hydraulic fracturing field simulation software in Mazhuang Coal Mine. Ana-lyzed the produce of the coal seam in the process of hydraulic fracturing fracture and well versed in,and around the borehole after frac-turing principal stress and the change of permeability coefficient,known around the borehole after fracturing coal principal stress is sig-nificantly reduced and the permeability coefficient increased significantly. And through the on-site hydraulic fracturing extraction data analysis:the hiatal area of influence puckering average daily drainage is pure gas flow pressure in no impact on regional group extraction holes per 35. 35 times that of the gas extraction from pure flow extraction pore gas concentration to increase 1. 34 times on average. Hy-draulic fracturing can significantly increase the extraction effect.%以水力压裂增透机理为理论基础,以河南能源化工集团焦作煤业集团二1 煤层的现场实测数据为参数,对演马庄矿22111运输巷顶板抽采巷打顶板穿层钻孔对煤体进行水力压裂,并运用 RFPA2D -Flow软件进行水力压裂现场模拟.通过分析水力压裂过程中煤层裂隙的产生和贯通,以及压裂后钻孔周围主应力和渗透系数的变化,可知压裂后钻孔周围煤层主应力得到明显降低和渗透系数得到显著增加.并通过现场水力压裂抽采数据分析得出:压裂孔影响区域单孔日均抽放纯瓦斯流量是压裂孔未影响区域组抽采孔日均瓦斯抽采纯流量的35. 35倍,抽采孔瓦斯浓度平均要提高1. 34倍.水力压裂能显著增加抽采效果.

  7. Integrated Experimental and Computational Study of Hydraulic Fracturing and the Use of Alternative Fracking Fluids

    Viswanathan, H.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Zhang, D.; Makedonska, N.; Middleton, R. S.; Currier, R.; Gupta, R.; Lei, Z.; Kang, Q.; O'Malley, D.; Hyman, J.


    Shale gas is an unconventional fossil energy resource that is already having a profound impact on US energy independence and is projected to last for at least 100 years. Production of methane and other hydrocarbons from low permeability shale involves hydrofracturing 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. This project uses innovative high-pressure microfluidic and triaxial core flood experiments on shale to explore fracture-permeability relations and the extraction of hydrocarbon. These data are integrated with simulations including lattice Boltzmann modeling of pore-scale processes, finite-element/discrete element models of fracture development in the near-well environment, discrete-fracture modeling of the reservoir, and system-scale models to assess the economics of alternative fracturing fluids. The ultimate goal is to make the necessary measurements to 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.

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

    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)


    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.


    David S. Schechter


    The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, we divided the report into two chapters. The first chapter was to image and perform experimental investigation of transfer mechanisms during CO{sub 2} flooding in NFR and HFR using X-ray CT scanner. In this chapter, we emphasized our work on understanding the connection between fracture properties and fundamentals of transfer mechanism from matrix to fractures and fluid flow through fracture systems. We started our work by investigating the effect of different overburden pressures and stress-state conditions on rock properties and fluid flow. Since the fracture aperture is one of important parameter that governs the fluid flow through the fracture systems, the average fracture aperture from the fluid flow experiments and fracture aperture distribution derived from X-ray CT scan were estimated for our modeling purposes. The fracture properties and fluid flow have significant changes in response to different overburden pressures and stress-state conditions. The fracture aperture distribution follows lognormal distribution even at elevated stress conditions. Later, we also investigated the fluid transfers between matrix and fracture that control imbibition process. We evaluated dimensionless time for validating the scheme of upscaling laboratory experiments to field dimensions. In CO{sub 2} injection experiments, the use of X-ray CT has allowed us to understand the mechanisms of CO{sub 2} flooding process in fractured system and to take important steps in reducing oil bypassed. When CO{sub 2} flooding experiments were performed on a short core with a fracture at the center of the core, the gravity plays an important role in the recovery of oil

  10. Upfront predictions of hydraulic fracturing and gas production in underexplored shale gas basins: Example of the posidonia shale formation in the Netherlands

    TerHeege, J.H.; Zijp, M.; DeBruin, G.; Buijze, L.


    Upfront predictions of hydraulic fracturing and gas production of potential shale gas targets in Europe are important as often large potential resources are deduced without detailed knowledge on the potential for successful stimulation. Such predictions are challenging as they need to be based on li

  11. Data regarding hydraulic fracturing distributions and treatment fluids, additives, proppants, and water volumes applied to wells drilled in the United States from 1947 through 2010

    Gallegos, Tanya J.; Varela, Brian A.


    Comprehensive, published, and publicly available data regarding the extent, location, and character of hydraulic fracturing in the United States are scarce. The objective of this data series is to publish data related to hydraulic fracturing in the public domain. The spreadsheets released with this data series contain derivative datasets aggregated temporally and spatially from the commercial and proprietary IHS database of U.S. oil and gas production and well data (IHS Energy, 2011). These datasets, served in 21 spreadsheets in Microsoft Excel (.xlsx) format, outline the geographical distributions of hydraulic fracturing treatments and associated wells (including well drill-hole directions) as well as water volumes, proppants, treatment fluids, and additives used in hydraulic fracturing treatments in the United States from 1947 through 2010. This report also describes the data—extraction/aggregation processing steps, field names and descriptions, field types and sources. An associated scientific investigation report (Gallegos and Varela, 2014) provides a detailed analysis of the data presented in this data series and comparisons of the data and trends to the literature.

  12. School and Community Impacts of Hydraulic Fracturing within Pennsylvania's Marcellus Shale Region, and the Dilemmas of Educational Leadership in Gasfield Boomtowns

    Schafft, Kai A.; Biddle, Catharine


    Innovations associated with gas and oil drilling technology, including new hydraulic fracturing and horizontal drilling techniques, have recently led to dramatic boomtown development in many rural areas that have endured extended periods of economic decline. The Marcellus Shale play, one of the world's largest gas-bearing shale formations,…

  13. Sweet spots for hydraulic fracturing oil or gas production in underexplored shales using key performance indicators: Example of the Posidonia Shale formation in the Netherlands

    Heege, J.H. ter; Zijp, M.H.A.A.; Nelkamp, S.


    While extensive data and experiences are available for hydraulic fracturing and hydrocarbon production from shales in the U.S.A., such a record is lacking in many underexplored shale basins worldwide. As limited data is usually available in these basins, analysis of shale prospectivity and identific

  14. Environmental concerns and regulatory initiatives related to hydraulic fracturing in shale gas formations: potential implications for North American gas supply

    Sumi, Lisa [Earthworks (Canada)


    Shale gas resources have been referred to as a game changer for North America and it is expected that shale gas will account for over 30% of the natural gas production in North America by 2020. However, the development of this resource has raised several concerns, notably in terms of water use and contamination; more stringent regulations could be implemented in the coming years. The aim of this paper is to present the effect that more stringent regulations would have on gas development in the Marcellus shale, which accounts for 20% of North American shale gas production. Information on hydraulic fracturing and its environmental impacts is provided herein, along with information on the regulatory initiatives underway in the Marcellus shale region. This paper pointed out that novel regulations relating to shale gas development could significantly reduce the growth in shale gas production.

  15. Detection of water contamination from hydraulic fracturing wastewater: a μPAD for bromide analysis in natural waters.

    Loh, Leslie J; Bandara, Gayan C; Weber, Genevieve L; Remcho, Vincent T


    Due to the rapid expansion in hydraulic fracturing (fracking), there is a need for robust, portable and specific water analysis techniques. Early detection of contamination is crucial for the prevention of lasting environmental damage. Bromide can potentially function as an early indicator of water contamination by fracking waste, because there is a high concentration of bromide ions in fracking wastewaters. To facilitate this, a microfluidic paper-based analytical device (μPAD) has been developed and optimized for the quantitative colorimetric detection of bromide in water using a smartphone. A paper microfluidic platform offers the advantages of inexpensive fabrication, elimination of unstable wet reagents, portability and high adaptability for widespread distribution. These features make this assay an attractive option for a new field test for on-site determination of bromide.

  16. Automated method for determining the flow of surface functionalized nanoparticles through a hydraulically fractured mineral formation using plasmonic silver nanoparticles.

    Maguire-Boyle, Samuel J; Garner, David J; Heimann, Jessica E; Gao, Lucy; Orbaek, Alvin W; Barron, Andrew R


    Quantifying nanoparticle (NP) transport within porous geological media is imperative in the design of tracers and sensors to monitor the environmental impact of hydraulic fracturing that has seen increasing concern over recent years, in particular the potential pollution and contamination of aquifers. The surface chemistry of a NP defining many of its solubility and transport properties means that there is a wide range of functionality that it is desirable to screen for optimum transport. Most prior transport methods are limited in determining if significant adsorption occurs of a NP over a limited column distance, however, translating this to effects over large distances is difficult. Herein we report an automated method that allows for the simulation of adsorption effects of a dilute nanoparticle solution over large distances under a range of solution parameters. Using plasmonic silver NPs and UV-visible spectroscopic detection allows for low concentrations to be used while offering greater consistency in peak absorbance leading to a higher degree of data reliability and statistics. As an example, breakthrough curves were determined for mercaptosuccinic acid (MSA) and cysteamine (CYS) functionalized Ag NPs passing through Ottawa sand (typical proppant material) immobile phase (C) or bypassing the immobile phase (C0). Automation allows for multiple sequences such that the absorption plateau after each breakthrough and the rate of breakthrough can be compared for multiple runs to provide statistical analysis. The mobility of the NPs as a function of pH is readily determined. The stickiness (α) of the NP to the immobile phase calculated from the C/C0 ratio shows that MSA-Ag NPs show good mobility, with a slight decrease around neutral pH, while CYS-Ag NPs shows an almost sinusoidal variation. The automated process described herein allows for rapid screening of NP functionality, as a function of immobile phase (proppant versus reservoir material), hydraulic

  17. The Pennsylvania Experience with Hydraulic Fracturing for Shale Gas Development: Relatively Infrequent Water Quality Incidents with Lots of Public Attention

    Brantley, S. L.; Li, Z.; Yoxtheimer, D.; Vidic, R.


    New techniques of hydraulic fracturing - "fracking" - have changed the United States over the last 10 years into a leading producer of natural gas extraction from shale. The first such gas well in Pennsylvania was drilled and completed using high-volume hydraulic fracturing in 2004. By late 2014, more than 8500 of these gas wells had been drilled in the Marcellus Shale gas field in Pennsylvania alone. Almost 1000 public complaints about groundwater quality were logged by the PA Department of Environmental Protection (PA DEP) between 2008 and 2012. Only a fraction of these were attributed to unconventional gas development. The most common problem was gas migration into drinking water, but contamination incidents also included spills, seepage, or leaks of fracking fluids, brine salts, or very occasionally, radioactive species. Many problems of gas migration were from a few counties in the northeastern part of the state. However, sometimes one gas well contaminated multiple water wells. For example, one gas well was reported by the state regulator to have contaminated 18 water wells with methane near Dimock PA. It can be argued that such problems at a relatively small fraction of gas wells initiated pockets of pushback against fracking worldwide. This resistance to fracking has grown even though fracking has been in use in the U.S.A. since the 1940s. We have worked as part of an NSF-funded project (the Shale Network) to share water quality data and publish it online using the CUAHSI Hydrologic Information System. Sharing data has led to collaborative investigation of specific contamination incidents to understand how problems can occur, and to efforts to quantify the frequency of impacts. The Shale Network efforts have also highlighted the need for more transparency with water quality data in the arena related to the energy-water nexus. As more data are released, new techniques of data analysis will allow better understanding of how to tune best practices to be

  18. Analysis of the hydraulic data from the MI fracture zone at the Grimsel Rock Laboratory, Switzerland

    Davey, A.; Karasaki, K.; Long, J.C.S.; Landsfeld, M.; Mensch, A.; Martel, S.J.


    One of the major problems in analyzing flow and transport in fractured rock is that the flow may be largely confined to a poorly connected network of fractures. In order to overcome some of this problem, Lawrence Berkeley Laboratory (LBL) has been developing a new type of fracture hydrology model called an equivalent discontinuum model. In this model the authors represent the discontinuous nature of the problem through flow on a partially filled lattice. A key component in constructing an equivalent discontinuum model from this lattice is removing some of the conductive elements such that the system is partially connected in the same manner as the fracture network. This is done through a statistical inverse technique called simulated annealing. The fracture network model is annealed by continually modifying a base model, or template such that the modified systems behave more and more like the observed system. In order to see how the simulated annealing algorithm works, the authors have developed a series of synthetic real cases. In these cases, the real system is completely known so that the results of annealing to steady state data can be evaluated absolutely. The effect of the starting configuration has been studied by varying the percent of conducting elements in the initial configuration. Results have shown that the final configurations converge to about the same percentage of conducting elements. An example using Nagra field data from the Migration Experiment (MI) at Grimsel Rock Laboratory in Switzerland is also analyzed. 24 refs., 33 figs., 3 tabs.

  19. Syn- and postkinematic cement textures in fractured carbonate rocks: Insights from advanced cathodoluminescence imaging

    Ukar, Estibalitz; Laubach, Stephen E.


    In calcite and dolomite deposits in fractures, transmitted light and optical cathodoluminescence methods detect crack-seal texture in some fractures, but scanning electron microscope-based cathodoluminescence (SEM-CL) combined with secondary-electron images and element maps, reveals crack-seal and cement growth textures where previous SEM-CL imaging methods found massive or featureless deposits. In a range of fractured carbonate rocks, patterns and textures of calcite and dolomite cements precipitated during and after fracture growth resemble complex accumulation patterns found in quartz in sandstone fractures, suggesting that some apparent differences between carbonate mineral and quartz deposits in fractures reflect the limits of previous imaging methods. Advances in delineating textures in widespread carbonate mineral deposits in fractures provide evidence for growth and occlusion of fracture porosity.

  20. A Site Characterization Protocol for Evaluating the Potential for Triggered or Induced Seismicity Resulting from Wastewater Injection and Hydraulic Fracturing

    Walters, R. J.; Zoback, M. D.; Gupta, A.; Baker, J.; Beroza, G. C.


    Regulatory and governmental agencies, individual companies and industry groups and others have recently proposed, or are developing, guidelines aimed at reducing the risk associated with earthquakes triggered by waste water injection or hydraulic fracturing. While there are a number of elements common to the guidelines proposed, not surprisingly, there are also some significant differences among them and, in a number of cases, important considerations that are not addressed. The goal of this work is to develop a comprehensive protocol for site characterization based on a rigorous scientific understanding of the responsible processes. Topics addressed will include the geologic setting (emphasizing faults that might be affected), historical seismicity, hydraulic characterization of injection and adjacent intervals, geomechanical characterization to identify potentially active faults, plans for seismic monitoring and reporting, plans for monitoring and reporting injection (pressure, volumes, and rates), other factors contributing to risk (potentially affected population centers, structures, and facilities), and implementing a modified Probabilistic Seismic Hazard Analysis (PSHA). The guidelines will be risk based and adaptable, rather than prescriptive, for a proposed activity and region of interest. They will be goal oriented and will rely, to the degree possible, on established best practice procedures, referring to existing procedures and recommendations. By developing a risk-based site characterization protocol, we hope to contribute to the development of rational and effective measures for reducing the risk posed by activities that potentially trigger earthquakes.

  1. Overcoming tortuosity in hydraulic fracture operations in the Pilar Field, Alagoas, Brazil; Operacoes de fraturamento hidraulico no Campo de Pilar, Alagoas

    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)


    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)

  2. Overcoming tortuosity in hydraulic fracture operations in the Pilar Field, Alagoas, Brazil; Operacoes de fraturamento hidraulico no Campo de Pilar, Alagoas

    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)


    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)

  3. Hydraulic transmissivity and heat exchange efficiency of open fractures: a model based on lowpass filtered apertures

    Neuville, Amélie; Schmittbuhl, Jean; 10.1111/j.1365-246X.2011.05126.x


    Natural open joints in rocks commonly present multi-scale self-affine apertures. This geometrical complexity affects fluid transport and heat exchange between the flow- ing fluid and the surrounding rock. In particular, long range correlations of self-affine apertures induce strong channeling of the flow which influences both mass and heat advection. A key question is to find a geometrical model of the complex aperture that describes at best the macroscopic properties (hydraulic conductivity, heat exchange) with the smallest number of parameters. Solving numerically the Stokes and heat equa- tions with a lubrication approximation, we show that a low pass filtering of the aperture geometry provides efficient estimates of the effective hydraulic and thermal properties (apertures). A detailed study of the influence of the bandwidth of the lowpass filtering on these transport properties is also performed. For instance, keeping the information of amplitude only of the largest Fourier length scales allows us to rea...

  4. Hydraulic fracturing of tight CBM reservoirs in the San Juan Basin, NM

    Goodwin, R. [Burlington Resources, Calgary, AB (Canada)


    Stimulation techniques, reservoir size and effects of stimulation, and regulatory compliance are described. The gas content, thickness, and pressure characteristics of San Juan Fruitland coal are considered. Cavitation, no proppant injection, sand-laden fluids, foamed fluids, sand control additives, coiled tubing fracturing, and breakdown have been tried, and better stimulation techniques are being pursued. Reduced pad size and minimal new road development to prevent surface damage, disposal of stimulation fluids in disposal wells, and surface casing and zonal isolation to protect surface waters has minimized damage to the environment during fracturing and disposal. 3 figs.

  5. Tap Water Hydraulic Control Systems - Design and Industrial Applications. Chapter 7 in Advances in Hydraulic Control Systems

    Conrad, Finn

    Deals with development and design of modern tap water hydraulic components and systems, in particalar the Danfoss Nessie-family of components and systems working with pure tap water without any kind of additives. Typical industrial applications are presented and the perspectives of new industrial...

  6. Viral Predation and Host Immunity Structure Microbial Communities in a Terrestrial Deep Subsurface, Hydraulically Fractured Shale System

    Daly, R. A.; Mouser, P. J.; Trexler, R.; Wrighton, K. C.


    Despite a growing appreciation for the ecological role of viruses in marine and gut systems, little is known about their role in the terrestrial deep (> 2000 m) subsurface. We used assembly-based metagenomics to examine the viral component in fluids from hydraulically fractured Marcellus shale gas wells. Here we reconstructed microbial and viral genomes from samples collected 7, 82, and 328 days post fracturing. Viruses accounted for 4.14%, 0.92% and 0.59% of the sample reads that mapped to the assembly. We identified 6 complete, circularized viral genomes and an additional 92 viral contigs > 5 kb with a maximum contig size of 73.6 kb. A BLAST comparison to NCBI viral genomes revealed that 85% of viral contigs had significant hits to the viral order Caudovirales, with 43% of sequences belonging to the family Siphoviridae, 38% to Myoviridae, and 12% to Podoviridae. Enrichment of Caudovirales viruses was supported by a large number of predicted proteins characteristic of tailed viruses including terminases (TerL), tape measure, tail formation, and baseplate related proteins. The viral contigs included evidence of lytic and temperate lifestyles, with the 7 day sample having the greatest number of detected lytic viruses. Notably in this sample, the most abundant virus was lytic and its inferred host, a member of the Vibrionaceae, was not detected at later time points. Analyses of CRISPR sequences (a viral and foreign DNA immune system in bacteria and archaea), linked 18 viral contigs to hosts. CRISPR linkages increased through time and all bacterial and archaeal genomes recovered in the final time point had genes for CRISPR-mediated viral defense. The majority of CRISPR sequences linked phage genomes to several Halanaerobium strains, which are the dominant and persisting members of the community inferred to be responsible for carbon and sulfur cycling in these shales. Network analysis revealed that several viruses were present in the 82 and 328 day samples; this viral

  7. Hydraulic fracturing to enhance geothermal energy recovery in deep and tight formations. Modell approach in petrothermy research project OPTIRISS

    Rafiee, M.M.; Schmitz, S.; Barsch, M. [DBI - Gastechnologisches Institut gGmbH, Freiberg (Germany)


    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

  8. Potential impact of flowback water from hydraulic fracturing on agricultural soil quality: Metal/metalloid bioaccessibility, Microtox bioassay, and enzyme activities.

    Chen, Season S; Sun, Yuqing; Tsang, Daniel C W; Graham, Nigel J D; Ok, Yong Sik; Feng, Yujie; Li, Xiang-Dong


    Hydraulic fracturing has advanced the development of shale gas extraction, while inadvertent spills of flowback water may pose a risk to the surrounding environment due to its high salt content, metals/metalloids (As, Se, Fe and Sr), and organic additives. This study investigated the potential impact of flowback water on four representative soils from shale gas regions in Northeast China using synthetic flowback solutions. The compositions of the solutions were representative of flowback water arising at different stages after fracturing well establishment. The effects of solution composition of flowback water on soil ecosystem were assessed in terms of metal mobility and bioaccessibility, as well as biological endpoints using Microtox bioassay (Vibrio fischeri) and enzyme activity tests. After one-month artificial aging of the soils with various flowback solutions, the mobility and bioaccessibility of As(V) and Se(VI) decreased as the ionic strength of the flowback solutions increased. The results inferred a stronger binding affinity of As(V) and Se(VI) with the soils. Nevertheless, the soil toxicity to Vibrio fischeri only presented a moderate increase after aging, while dehydrogenase and phosphomonoesterase activities were significantly suppressed with increasing ionic strength of flowback solutions. On the contrary, polyacrylamide in the flowback solutions led to higher dehydrogenase activity. These results indicated that soil enzyme activities were sensitive to the composition of flowback solutions. A preliminary human health risk assessment related to As(V) suggested a low level of cancer risk through exposure via ingestion, while holistic assessment of environmental implications is required.

  9. Hydraulic Shuttle Irradiation System (HSIS) Recently Installed in the Advanced Test Reactor (ATR)

    A. Joseph Palmer; Gerry L. McCormick; Shannon J. Corrigan


    2010 International Congress on Advances in Nuclear Power Plants (ICAPP’10) ANS Annual Meeting Imbedded Topical San Diego, CA June 13 – 17, 2010 Hydraulic Shuttle Irradiation System (HSIS) Recently Installed in the Advanced Test Reactor (ATR) Author: A. Joseph Palmer, Mechanical Engineer, Irradiation Test Programs, 208-526-8700, Affiliation: Idaho National Laboratory P.O. Box 1625, MS-3840 Idaho Falls, ID 83415 INL/CON-10-17680 ABSTRACT Most test reactors are equipped with shuttle facilities (sometimes called rabbit tubes) whereby small capsules can be inserted into the reactor and retrieved during power operations. With the installation of Hydraulic Shuttle Irradiation System (HSIS) this capability has been restored to the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). The general design and operating principles of this system were patterned after the hydraulic rabbit at Oak Ridge National Laboratory’s (ORNL) High Flux Isotope Reactor (HFIR), which has operated successfully for many years. Using primary coolant as the motive medium the HSIS system is designed to simultaneously transport fourteen shuttle capsules, each 16 mm OD x 57 mm long, to and from the B-7 position of the reactor. The B-7 position is one of the higher flux positions in the reactor with typical thermal and fast (>1 Mev) fluxes of 2.8E+14 n/cm2/sec and 1.9E+14 n/cm2/sec respectively. The available space inside each shuttle is approximately 14 mm diameter x 50 mm long. The shuttle containers are made from titanium which was selected for its low neutron activation properties and durability. Shuttles can be irradiated for time periods ranging from a few minutes to several months. The Send and Receive Station (SRS) for the HSIS is located 2.5 m deep in the ATR canal which allows irradiated shuttles to be easily moved from the SRS to a wet loaded cask, or transport pig. The HSIS system first irradiated (empty) shuttles in September 2009 and has since completed

  10. 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

    Gallegos, Tanya J.; Varela, Brian A.


    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.

  11. NATO Advanced Study Institute on Disorder and Fracture

    Roux, S; Guyon, E


    Fracture, and particularly brittle fracture, is a good example of an instability. For a homogeneous solid, subjected to a uniform stress field, a crack may appear anywhere in the structure once the threshold stress is reached. However, once a crack has been nucleated in some place, further damage in the solid will in most cases propagate from the initial crack, and not somewhere else in the solid. In this sense fracture is an unstable process. This property makes the process extremely sensitive to any heterogeneity present in the medium, which selects the location of the first crack nucleated. In particular, fracture appears to be very sensitive to disorder, which can favor or impede local cracks. Therefore, in most realistic cases, a good description of fracture mechanics should include the effect of disorder. Recently this need has motivated work in this direction starting from the usual description of fracture mechanics. Parallel with this first trend, statistical physics underwent a very important develop...

  12. Selection of finite-element mesh parameters in modeling the growth of hydraulic fracturing cracks

    Kurguzov, V. D.


    The effect of the mesh geometry on the accuracy of solutions obtained by the finite-element method for problems of linear fracture mechanics is investigated. The guidelines have been formulated for constructing an optimum mesh for several routine problems involving elements with linear and quadratic approximation of displacements. The accuracy of finite-element solutions is estimated based on the degree of the difference between the calculated stress-intensity factor (SIF) and its value obtained analytically. In problems of hydrofracturing of oil-bearing formation, the pump-in pressure of injected water produces a distributed load on crack flanks as opposed to standard fracture mechanics problems that have analytical solutions, where a load is applied to the external boundaries of the computational region and the cracks themselves are kept free from stresses. Some model pressure profiles, as well as pressure profiles taken from real hydrodynamic computations, have been considered. Computer models of cracks with allowance for the pre-stressed state, fracture toughness, and elastic properties of materials are developed in the MSC.Marc 2012 finite-element analysis software. The Irwin force criterion is used as a criterion of brittle fracture and the SIFs are computed using the Cherepanov-Rice invariant J-integral. The process of crack propagation in a linearly elastic isotropic body is described in terms of the elastic energy release rate G and modeled using the VCCT (Virtual Crack Closure Technique) approach. It has been found that the solution accuracy is sensitive to the mesh configuration. Several parameters that are decisive in constructing effective finite-element meshes, namely, the minimum element size, the distance between mesh nodes in the vicinity of a crack tip, and the ratio of the height of an element to its length, have been established. It has been shown that a mesh that consists of only small elements does not improve the accuracy of the solution.

  13. Rib Fracture Protocol Advancing the Care of the Elderly Patient.

    Leininger, Susan

    This article discusses unique factors associated with rib fractures in the elderly patient population and explains the process used in one facility to develop a revised protocol for the management of elderly patients with a rib fracture. The goals were to eliminate gaps in early trauma care management and employ a care routine that would improve outcomes for this vulnerable group of patients with fracture.

  14. Selection of the optimal completion of horizontal wells with multi-stage hydraulic fracturing of the low-permeable formation, field C

    Bozoev, A. M.; Demidova, E. A.


    At the moment, many fields of Western Siberia are in the later stages of development. In this regard, the multilayer fields are actually involved in the development of hard to recover reserves by conducting well interventions. However, most of these assets may not to be economical profitable without application of horizontal drilling and multi-stage hydraulic fracturing treatment. Moreover, location of frac ports in relative to each other, number of stages, volume of proppant per one stage are the main issues due to the fact that the interference effect could lead to the loss of oil production. The optimal arrangement of horizontal wells with multi-stage hydraulic fracture was defined in this paper. Several analytical approaches have been used to predict the started oil flow rate and chose the most appropriate for field C reservoir J1. However, none of the analytical equations could not take into account the interference effect and determine the optimum number of fractures. Therefore, the simulation modelling was used. Finally, the universal equation is derived for this field C, the reservoir J1. This tool could be used to predict the flow rate of the horizontal well with hydraulic fracturing treatment on the qualitative level without simulation model.

  15. Determining the hydraulic and fracture properties of the Coal Seam Gas well by numerical modelling and GLUE analysis

    Askarimarnani, Sara; Willgoose, Garry; Fityus, Stephen


    Coal seam gas (CSG) is a form of natural gas that occurs in some coal seams. Coal seams have natural fractures with dual-porosity systems and low permeability. In the CSG industry, hydraulic fracturing is applied to increase the permeability and extract the gas more efficiently from the coal seam. The industry claims that it can design fracking patterns. Whether this is true or not, the public (and regulators) requires assurance that once a well has been fracked that the fracking has occurred according to plan and that the fracked well is safe. Thus defensible post-fracking testing methodologies for gas generating wells are required. In 2009 a fracked well HB02, owned by AGL, near Broke, NSW, Australia was subjected to "traditional" water pump-testing as part of this assurance process. Interpretation with well Type Curves and simple single phase (i.e. only water, no gas) highlighted deficiencies in traditional water well approaches with a systemic deviation from the qualitative characteristic of well drawdown curves (e.g. concavity versus convexity of drawdown with time). Accordingly a multiphase (i.e. water and methane) model of the well was developed and compared with the observed data. This paper will discuss the results of this multiphase testing using the TOUGH2 model and its EOS7C constitutive model. A key objective was to test a methodology, based on GLUE monte-carlo calibration technique, to calibrate the characteristics of the frack using the well test drawdown curve. GLUE involves a sensitivity analysis of how changes in the fracture properties change the well hydraulics through and analysis of the drawdown curve and changes in the cone of depression. This was undertaken by changing the native coal, fracture, and gas parameters to see how changing those parameters changed the match between simulations and the observed well drawdown. Results from the GLUE analysis show how much information is contained in the well drawdown curve for estimating field scale

  16. Development of a steady thermal-hydraulic analysis code for the China Advanced Research Reactor

    TIAN Wenxi; QIU Suizheng; GUO Yun; SU Guanghui; JIA Dounan; LIU Tiancai; ZHANG Jianwei


    A multi-channel model steady-state thermalhydraulic analysis code was developed for the China Advanced Research Reactor (CARR). By simulating the whole reactor core, the detailed mass flow distribution in the core was obtained. The result shows that structure size plays the most important role in mass flow distribution, and the influence of core power could be neglected under singlephase flow. The temperature field of the fuel element under unsymmetrical cooling condition was also obtained, which is necessary for further study such as stress analysis, etc. Of the fuel element. At the same time, considering the hot channel effect including engineering factor and nuclear factor, calculation of the mean and hot channel was carried out and it is proved that all thermal-hydraulic parameters satisfy the "Safety design regulation of CARR".

  17. Thermo-hydraulic characterization of a fractured shallow reservoir in Bergen (Norway) to improve the efficiency of a BHE field

    Mandrone, Giuseppe; Giordano, Nicolò; Bastesen, Eivind; Wheeler, Walter; Chicco, Jessica


    Sustainable thermal energy production from GSHP systems is greatly dependent on the thermo-hydraulic field, yet there are few realistic case studies which capture the dynamics of such systems. Here we present initial work on the static model for one such case example. A BHE field consisting of 12 ground heat exchangers in fractured crystalline rock has been supplying thermal energy for the past 20 years to meet the heating needs of a school located in Bergen, Norway. In recent years the heat pump COP has significantly decreased, which has been ascribed to a depletion of the extractable energy surrounding the BHEs, that is, by extracting more energy in the heating season than is naturally replaced in the summer. A numerical model of the underground is constructed to show the thermal depletion and determine a sustainable thermal use of the shallow reservoir (0-200 m). At this stage, the model represents the geology and structure of the underground, which consists of metamorphic rocks of the Nordåsvatnet Complex (Minor Bergen Arc, Ordovician): amphibolites, micaschists, augen gneisses and quartz-schists depict the first 200 m below ground level. Preliminary well tests in some of these BHEs showed how complex and heterogeneous is the hydrogeological field. Some wells are clearly connected, others show hydraulic head difference of more than 15 m even though they are close by. Future flow tracer tests and down-hole fracture characterization will be carried out for in-depth representation of the flow field. Here we present and discuss laboratory thermal measurements on samples collected in the area, especially a comparison of two thermal conductivity measurement techniques. Thermal conductivity measurements were carried out with the thermal conductivity scanner by Lippmann and Rauen GbR and with the KD2 Pro by Decagon Devices. The optical scanning technology and the transient line source method were therefore compared to get the most valuable results. Electrical

  18. Environmental aspects of hydraulic fracturing - Main results and recommendations from two studies on behalf of the German Environment Agency

    Krischbaum, Bernd; Bertram, Andreas; Böttcher, Christian; Iyimen-Schwarz, Züleyha; Rechenberg, Jörg; Dannwolf, Uwe; Meiners, Georg


    The German Environment Agency (UBA) accompanies the debate on fracking for years. Two major reports on risks and environmental impacts regarding the exploration and exploitation of unconventional natural gas, in particular shale gas have been published. On the basis of these studies as well as on scientific evidence UBA considers ecological barriers as a sustainable means to minimize the risks to environment and human health. 1) Recent studies show that the contamination of shallow aquifers by rise of fluids through natural faults or artificially created fractures is extremely unlikely. However, activities on the surface and lack of wellbore integrity pose threats and substantial risks for the quality of shallow aquifers. 2) The need for thorough groundwater monitoring is fully accepted, yet its range and design is subject to discussion. 3) Formerly, analysis and mass balances of flowback and produced water have been insufficient, thus there is a lack of exact information on proportions of frac-fluids, flowback and formation water respectively, as well as data on possible reaction products. 4) Currently, neither on national nor on European level best reference techniques (BREF) for the treatment and disposal of flowback and produced water are available. 5) In addition, land consumption, emission of greenhouse gases, and induced seismicity are major issues. UBA recommends amongst others the implementation of an environmental impact assessment (EIA) for fracking activities, the prohibition of fracking in water protection areas as well as their catchments, and the disclosure of all frac-fluid chemicals within a national chemical registry. To achieve these objectives the German Environment Agency suggests a step-by-step approach. The paper will present the main results from the studies and the recommendations of the German Environment Agency regarding hydraulic fracturing for unconventional gas exploitation.

  19. [Treatment of children with femoral subtrochanteric fracture with advanced elastic intramedullary nail technology].

    Tan, Jia-chang; Yang, You-meng; Xu, Hong-yu; Luo, Yu; Wang, Hui


    To explore curative effects of advanced elastic intramedullary nail technology in treating children with femoral subtrochanteric fracture. Form March 2009 to December 2010, 16 children with femoral subtrochanteric fracture were treated with advanced elastic intramedullary nail technology. There were 12 males and 4 females ranging in age from 7 to 15 years old with a mean of 9.8 years old. According to fracture classification, 9 cases were stable fractures (traverse or short oblique type) and 7 cases were unstable fractures (comminuted or long oblique type). Radiographs and complications were retrospectively reviewed. Fracture healing were evaluated according to Flynn criteria. All children were followed up from 11 to 32 months with an average of 21 months. No incision infecton,bone nonunion and breakage of screw occurred. The fracture healing time was from 8 to 16 weeks with an average of 10.1 weeks. According to Flynn criteria, 14 cases got excellent results, 1 moderate and 1 poor. Advanced elastic intramedullary nail technology for the treatment of children with femoral subtrochanteric fracture is a safe and effective fixation, which is good for early mobilization, shorter the duration of hospital stays and reduce complications.

  20. Bed load proppant transport during slickwater hydraulic fracturing: insights from comparisons between published laboratory data and correlations for sediment and pipeline slurry transport

    McClure, Mark W


    Bed load transport is the movement of particles along the top of a bed through rolling, saltation, and suspension created by turbulent lift above the bed surface. In recent years, there has been a resurgence of interest in the idea that bed load transport is significant for proppant transport during hydraulic fracturing. However, scaling arguments suggest that bed load transport is only dominant in the laboratory and is negligible at the field scale. I review laboratory experiments that have been used to develop concepts of bed load transport in hydraulic fracturing. I also review the scaling arguments and laboratory results that have been used to argue that viscous drag, not bed load transport, is dominant at the field scale. I compare literature correlations for fluvial sediment transport and for pipeline slurry transport with published laboratory data on proppant transport in slot flow. The comparisons indicate that fluvial transport correlations are suitable for predicting the rate of sediment erosion due...

  1. Support to the identification of potential risks for the environment and human health arising from hydrocarbons operations involving hydraulic fracturing in Europe

    Broomfield, L.; Lelland, A.


    The potential risks for the environment and human health arising from shale gas production (hydraulic fracturing) in Europe are assessed. As readily accessible oil and gas reserves are becoming progressively limited, the energy supply industry is turning more to unconventional reserves, which were previously too complex or too expensive to extract, like shale gas. There are significant shale gas reserves in Europe. Permission is being sought in many EU Member States for exploratory works and to bring forward projects for hydraulic fracturing and extraction of shale gas. As with any drilling and extraction process, shale gas extraction brings environmental and health risks which need to be understood and addressed. CE Delft conducted the legal assessment on shale gas related EU legislation. Gaps and uncertainties have been addressed, but no real risks within the legislation have been discovered. A large part of the shale gas related legislation is part of the individual member states legislation and not directly addressed by EU legislation.

  2. Numerical simulation of the environmental impact of hydraulic fracturing of tight/shale gas reservoirs on near-surface ground water: background, base cases, shallow reservoirs, short-term gas and water transport

    Researchers examined gas and water transport between a deep tight shale gas reservoir and a shallow overlying aquifer in the two years following hydraulic fracturing, assuming a pre-existing connecting pathway.

  3. Research advances in fracturing mechanism of amorphous materials


    @@ The fracture behavior of brittle materials is a timehonored problem. Archeologists discover that prehistoric people created their primitive tools using this behavior. During the Stone Age, for example, they made simple wooden butchery implements by taking advantage of a sharp edge caused by the brittle fracture on flint. According to archeologists, the application of brittle fracture to the tool-making was one of monumental inventions to mark the very beginning of human civilization.Afterwards, ancient potters succeeded in decorating their works by having the surface of pottery inlaid with cracks and fissures.

  4. Modeling potential occupational inhalation exposures and associated risks of toxic organics from chemical storage tanks used in hydraulic fracturing using AERMOD.

    Chen, Huan; Carter, Kimberly E


    Various toxic chemicals used in hydraulic fracturing fluids may influence the inherent health risks associated with these operations. This study investigated the possible occupational inhalation exposures and potential risks related to the volatile organic compounds (VOCs) from chemical storage tanks and flowback pits used in hydraulic fracturing. Potential risks were evaluated based on radial distances between 5 m and 180 m from the wells for 23 contaminants with known inhalation reference concentration (RfC) or inhalation unit risks (IUR). Results show that chemicals used in 12.4% of the wells posed a potential acute non-cancer risks for exposure and 0.11% of the wells with may provide chronic non-cancer risks for exposure. Chemicals used in 7.5% of the wells were associated with potential acute cancer risks for exposure. Those chemicals used in 5.8% of the wells may be linked to chronic cancer risks for exposure. While eight organic compounds were associated with acute non-cancer risks for exposure (>1), methanol the major compound in the chemical storage tanks (1.00-45.49) in 7,282 hydraulic fracturing wells. Wells with chemicals additives containing formaldehyde exhibited both acute and chronic cancer risks for exposure with IUR greater than 10(-6), suggesting formaldehyde was the dominant contributor to both types of risks for exposure in hydraulic fracturing. This study also found that due to other existing on-site emission sources of VOCs and the geographically compounded air concentrations from other surrounding wells, chemical emissions data from storage tanks and flowback pits used in this study were lower than reported concentrations from field measurements where higher occupational inhalation risks for exposure may be expected.

  5. Particle velocity based universal algorithm for numerical simulation of hydraulic fractures

    Wrobel, Michal


    In the paper, we propose a new effective mathematical formulation and resulting universal numerical algorithm capable of tackling various HF models in the framework of a unified approach. The presented numerical scheme is not limited to any particular elasticity model or crack propagation regime. Its basic assumptions are: i) proper choice of independent and dependent variables (with the direct utilization of a new one - the reduced particle velocity), ii) tracing the fracture front by use of the speed equation which can be integrated in a closed form and sets an explicit relation between the crack propagation speed and the coefficients in the asymptotic expansion of the crack opening, iii) proper regularization techniques, iv) improved temporal approximation, v) modular algorithm architecture. The application of the new dependent variable, the reduced particle velocity, instead of the usual fluid flow rate, facilitates the computation of the crack propagation speed from the local relation based on the speed ...

  6. Advanced neutron source reactor thermal-hydraulic test loop facility description

    Felde, D.K.; Farquharson, G.; Hardy, J.H.; King, J.F.; McFee, M.T.; Montgomery, B.H.; Pawel, R.E.; Power, B.H.; Shourbaji, A.A.; Siman-Tov, M.; Wood, R.J.; Yoder, G.L.


    The Thermal-Hydraulic Test Loop (THTL) is a facility for experiments constructed to support the development of the Advanced Neutron Source Reactor (ANSR) at Oak Ridge National Laboratory. The ANSR is both cooled and moderated by heavy water and uses uranium silicide fuel. The core is composed of two coaxial fuel-element annuli, each of different diameter. There are 684 parallel aluminum-clad fuel plates (252 in the inner-lower core and 432 in the outer-upper core) arranged in an involute geometry that effectively creates an array of thin rectangular flow channels. Both the fuel plates and the coolant channels are 1.27 mm thick, with a span of 87 mm (lower core), 70 mm (upper core), and 507-mm heated length. The coolant flows vertically upwards at a mass flux of 27 Mg/m{sup 2}s (inlet velocity of 25 m/s) with an inlet temperature of 45{degrees}C and inlet pressure of 3.2 MPa. The average and peak heat fluxes are approximately 6 and 12 MW/m{sup 2}, respectively. The availability of experimental data for both flow excursion (FE) and true critical heat flux (CHF) at the conditions applicable to the ANSR is very limited. The THTL was designed and built to simulate a full-length coolant subchannel of the core, allowing experimental determination of thermal limits under the expected ANSR thermal-hydraulic conditions. For these experimental studies, the involute-shaped fuel plates of the ANSR core with the narrow 1.27-mm flow gap are represented by a narrow rectangular channel. Tests in the THTL will provide both single- and two-phase thermal-hydraulic information. The specific phenomena that are to be examined are (1) single-phase heat-transfer coefficients and friction factors, (2) the point of incipient boiling, (3) nucleate boiling heat-transfer coefficients, (4) two-phase pressure-drop characteristics in the nucleate boiling regime, (5) flow instability limits, and (6) CHF limits.

  7. Formability Prediction of Advanced High Strength Steel with a New Ductile Fracture Criterion

    Lou, Yanshan; Lim, Sungjun; Huh, Jeehyang; Huh, Hoon


    A ductile fracture criterion is newly proposed to accurately predict forming limit diagrams (FLD) of sheet metals. The new ductile fracture criterion is based on the effect of the non-dimensional stress triaxiality, the stress concentration factor and the effective plastic strain on the nucleation, growth and coalescence of voids. The new ductile fracture criterion has been applied to estimate the formability of four kind advanced high strength steels (AHSS): DP780, DP980, TRIP590, and TWIP980. FLDs predicted are compared with experimental results and those predicted by other ductile fracture criteria. The comparison demonstrates that FLDs predicted by the new ductile fracture criterion are in better agreement with experimental FLDs than those predicted by other ductile fracture criteria. The better agreement of FLDs predicted by the new ductile fracture criterion is because conventional ductile fracture criteria were proposed for fracture prediction in bulk metal forming while the new one is proposed to predict the onset of fracture in sheet metal forming processes.

  8. Evidence for hydraulic fracturing at Gale crater, Mars: Implications for burial depth of the Yellowknife Bay formation

    Caswell, Tess E.; Milliken, Ralph E.


    NASA's Curiosity rover identified a formerly habitable environment within strata informally known as the Yellowknife Bay formation. The stratigraphic relationship, and thus depositional age, of these rocks relative to other geologic units in Gale crater is not clear from orbital data alone. If part of lower Aeolis Mons (informally known as Mount Sharp), the Yellowknife Bay rocks have been deeply buried and exhumed prior to 3.2-3.3 Ga. If part of younger alluvial fan deposits, however, they likely have never experienced more than ∼100 m of burial. Knowledge of burial history can thus constrain the stratigraphic placement of Yellowknife Bay and the habitable environment preserved therein. The mechanics of natural hydraulic fractures observed in mudstone at YKB allow us to evaluate its burial history and imply a minimum burial depth of 1.2 km. This is consistent with burial by the entirety of lower Mount Sharp and a depositional age of ∼ 3.6- 3.8 Ga, providing observation-based evidence that Mount Sharp was once much more laterally extensive than its present form. Rocks of the Yellowknife Bay formation thus represent the oldest strata that Curiosity will encounter during its journey in Gale crater, and any additional habitable environments discovered along Curiosity's future path represent conditions at younger times.

  9. Microbial mats as a biological treatment approach for saline wastewaters: the case of produced water from hydraulic fracturing.

    Akyon, Benay; Stachler, Elyse; Wei, Na; Bibby, Kyle


    Treatment of produced water, i.e. wastewater from hydraulic fracturing, for reuse or final disposal is challenged by both high salinity and the presence of organic compounds. Organic compounds in produced water may foul physical-chemical treatment processes or support microbial corrosion, fouling, and sulfide release. Biological approaches have potential applications in produced water treatment, including reducing fouling of physical-chemical treatment processes and decreasing biological activity during produced water holding; however, conventional activated sludge treatments are intolerant of high salinity. In this study, a biofilm treatment approach using constructed microbial mats was evaluated for biodegradation performance, microbial community structure, and metabolic potential in both simulated and real produced water. Results demonstrated that engineered microbial mats are active at total dissolved solids (TDS) concentrations up to at least 100,000 mg/L, and experiments in real produced water showed a biodegradation capacity of 1.45 mg COD/gramwet-day at a TDS concentration of 91,351 mg/L. Additionally, microbial community and metagenomic analyses revealed an adaptive microbial community that shifted based upon the sample being treated and has the metabolic potential to degrade a wide array of contaminants, suggesting the potential of this approach to treat produced waters with varying composition.

  10. Estrogen and androgen receptor activities of hydraulic fracturing chemicals and surface and ground water in a drilling-dense region

    Kassotis, Christopher D.; Tillitt, Donald E.; Davis, J. Wade; Hormann, Anette M.; Nagel, Susan C.


    The rapid rise in natural gas extraction using hydraulic fracturing increases the potential for contamination of surface and ground water from chemicals used throughout the process. Hundreds of products containing more than 750 chemicals and components are potentially used throughout the extraction process, including more than 100 known or suspected endocrine-disrupting chemicals. We hypothesized thataselected subset of chemicalsusedin natural gas drilling operationsandalso surface and ground water samples collected in a drilling-dense region of Garfield County, Colorado, would exhibit estrogen and androgen receptor activities. Water samples were collected, solid-phase extracted, and measured for estrogen and androgen receptor activities using reporter gene assays in human cell lines. Of the 39 unique water samples, 89%, 41%, 12%, and 46% exhibited estrogenic, antiestrogenic, androgenic, and antiandrogenic activities, respectively. Testing of a subset of natural gas drilling chemicals revealed novel antiestrogenic, novel antiandrogenic, and limited estrogenic activities. The Colorado River, the drainage basin for this region, exhibited moderate levels of estrogenic, antiestrogenic, and antiandrogenic activities, suggesting that higher localized activity at sites with known natural gas–related spills surrounding the river might be contributing to the multiple receptor activities observed in this water source. The majority of water samples collected from sites in a drilling-dense region of Colorado exhibited more estrogenic, antiestrogenic, or antiandrogenic activities than reference sites with limited nearby drilling operations. Our data suggest that natural gas drilling operationsmayresult in elevated endocrine-disrupting chemical activity in surface and ground water.

  11. Comparative Analysis of Hydraulic Fracturing Wastewater Practices in Unconventional Shale Development: Newspaper Coverage of Stakeholder Concerns and Social License to Operate

    Joel Gehman


    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.

  12. A web-based multicriteria evaluation of spatial trade-offs between environmental and economic implications from hydraulic fracturing in a shale gas region in Ohio.

    Liu, X; Gorsevski, P V; Yacobucci, M M; Onasch, C M


    Planning of shale gas infrastructure and drilling sites for hydraulic fracturing has important spatial implications. The evaluation of conflicting and competing objectives requires an explicit consideration of multiple criteria as they have important environmental and economic implications. This study presents a web-based multicriteria spatial decision support system (SDSS) prototype with a flexible and user-friendly interface that could provide educational or decision-making capabilities with respect to hydraulic fracturing site selection in eastern Ohio. One of the main features of this SDSS is to emphasize potential trade-offs between important factors of environmental and economic ramifications from hydraulic fracturing activities using a weighted linear combination (WLC) method. In the prototype, the GIS-enabled analytical components allow spontaneous visualization of available alternatives on maps which provide value-added features for decision support processes and derivation of final decision maps. The SDSS prototype also facilitates nonexpert participation capabilities using a mapping module, decision-making tool, group decision module, and social media sharing tools. The logical flow of successively presented forms and standardized criteria maps is used to generate visualization of trade-off scenarios and alternative solutions tailored to individual user's preferences that are graphed for subsequent decision-making.

  13. Roof Weakening of Hydraulic Fracturing for Control of Hanging Roof in the Face End of High Gassy Coal Longwall Mining: A Case Study

    Huang, Bingxiang; Wang, Youzhuang


    The occurence of hanging roof commonly arises in the face end of longwall coal mining under hard roof conditions. The sudden break and subsequent caving of a hanging roof could result in the extrusion of gas in the gob to the face, causing gas concentrations to rise sharply and to increase to over a safety-limited value. A series of linear fracturing-holes of 32 mm diameter were drilled into the roof of the entries with an anchor rig. According to the theory that the gob should be fully filled with the fragmentized falling roof rock, the drilling depth is determined as being 3 5 times the mining height if the broken expansion coefficient takes an empirical value. Considering the general extension range of cracks and the supporting form of the entryway, the spacing distance between two drilling holes is determined as being 1 2 times the crack's range of extension. Using a mounting pipe, a high pressure resistant sealing device of a small diameter-size was sent to the designated location for the high-pressure hydraulic fracturing of the roof rock. The hydraulic fracturing created the main hydro-fracturing crack and airfoil branch cracks in the interior of the roof-rock, transforming the roof structure and weakening the strength of the roof to form a weak plane which accelerated roof caving, and eventually induced the full caving in of the roof in time with the help of ground pressure. For holes deeper than 4 m, retreating hydraulic fracturing could ensure the uniformity of crack extension. Tested and applied at several mines in Shengdong Mining District, the highest ruptured water pressure was found to be 55 MPa, and the hanging roof at the face end was reduced in length from 12 m to less than 1 2 m. This technology has eliminated the risk of the extrusion of gas which has accumulated in the gob.

  14. Proceedings of the International Symposium on Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances

    Faybishenko, B. (ed.)


    This publication contains extended abstracts of papers presented at the International Symposium ''Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances'' held at Ernest Orlando Lawrence Berkeley National Laboratory on February 10-12, 1999. This Symposium is organized in Honor of the 80th Birthday of Paul A. Witherspoon, who initiated some of the early investigations on flow and transport in fractured rocks at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory. He is a key figure in the development of basic concepts, modeling, and field measurements of fluid flow and contaminant transport in fractured rock systems. The technical problems of assessing fluid flow, radionuclide transport, site characterization, modeling, and performance assessment in fractured rocks remain the most challenging aspects of subsurface flow and transport investigations. An understanding of these important aspects of hydrogeology is needed to assess disposal of nu clear wastes, development of geothermal resources, production of oil and gas resources, and remediation of contaminated sites. These Proceedings of more than 100 papers from 12 countries discuss recent scientific and practical developments and the status of our understanding of fluid flow and radionuclide transport in fractured rocks. The main topics of the papers are: Theoretical studies of fluid flow in fractured rocks; Multi-phase flow and reactive chemical transport in fractured rocks; Fracture/matrix interactions; Hydrogeological and transport testing; Fracture flow models; Vadose zone studies; Isotopic studies of flow in fractured systems; Fractures in geothermal systems; Remediation and colloid transport in fractured systems; and Nuclear waste disposal in fractured rocks.

  15. Monitoring performance for hydraulic fracturing using synthetic microseismic catalogue at the Wysin site (Poland)

    Ángel López Comino, José; Cesca, Simone; Kriegerowski, Marius; Heimann, Sebastian; Dahm, Torsten; Mirek, Janusz; Lasocky, Stanislaw


    Previous analysis to assess the monitoring performance of a dedicated seismic network are always useful to determine its capability of detecting, locating and characterizing target seismicity. This work focuses on a hydrofracking experiment in Poland, which is monitored in the framework of the SHEER (SHale gas Exploration and Exploitation induced Risks) EU project. The seismic installation is located near Wysin (Poland), in the central-western part of the Peribaltic synclise at Pomerania. The network setup includes a distributed network of six broadband stations, three shallow borehole stations and three small-scale arrays. We assess the monitoring performance prior operations, using synthetic seismograms. Realistic full waveform are generated and combined with real noise before fracking operations, to produce either event based or continuous synthetic waveforms. Background seismicity is modelled by double couple (DC) focal mechanisms. Non-DC sources resemble induced tensile fractures opening in the direction of the minimal compressive stress and closing in the same direction after the injection. Microseismic sources are combined with a realistic crustal model, distribution of hypocenters, magnitudes and source durations. The network detection performance is then assessed in terms of Magnitude of Completeness (Mc) through two different techniques: i) using an amplitude threshold approach, taking into account a station dependent noise level and different values of signal-to-noise ratio (SNR) and ii) through the application of an automatic detection algorithm to the continuous synthetic dataset. In the first case, we compare the maximal amplitude of noise free synthetic waveforms with the different noise levels. Imposing the simultaneous detection at e.g. 4 stations for a robust detection, the Mc is assessed and can be adjusted by empirical relationships for different SNR values. We find that different source mechanisms have different detection threshold. The

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

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


    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

  17. Spatiotemporal Variability in Hydraulic Fracturing Water Use and Water Produced with Shale Gas in the U.S.

    Nicot, J. P.; Scanlon, B. R.; Reedy, R. C.


    Longer time series and increasing data availability allows more comprehensive assessment of spatiotemporal variability in hydraulic fracturing (HF) water use and flowback/produced (FP) water generation in shale plays in the U.S. In this analysis we quantified HF and FP water volumes for seven major shale gas plays in the U.S. using detailed well by well analyses through 2015. Well count ranges from 1,500 (Utica) to 20,200 (Barnett) with total cumulative? HF water use ranging from 12 billion gallons (bgal) (Utica) to 65 bgal (Barnett). HF water use/well has been increasing over time in many plays and currently ranges from 4.5 mgal/well (Fayetteville) to 10 mgal/well (Utica) (2015). Normalizing by lateral length results in a range of 900 gal/ft (Fayetteville) to 15,600 gal/ft (Marcellus) (2015). FP water volumes are also highly variable, lowest in the Utica and highest in the Barnett. Management of FP water is mostly through disposal into Class II salt water injection wells, with the exception of the Marcellus where >90% of the FP water is reused/recycled. Along the dramatic domestic gas production increase, electricity generation from natural gas has almost doubled since 2000. It is important to consider the water use for HF in terms of the lifecycle of natural gas with HF water consumption. It is equivalent to <10% of the water consumed in natural gas-fired power plants that usually require less water than coal-fired power plants, resulting in net water savings.

  18. Co-treatment of abandoned mine drainage and Marcellus Shale flowback water for use in hydraulic fracturing.

    He, Can; Zhang, Tieyuan; Vidic, Radisav D


    Flowback water generated during shale gas extraction in Pennsylvania is mostly reused for hydraulic fracturing operation. Abandoned mine drainage (AMD), one of the most widespread threats to water quality in Pennsylvania, can potentially serve as a make-up water source to enable flowback water reuse. This study demonstrated co-treatment of flowback water and AMD produced in northeastern Pennsylvania in a pilot-scale system consisting of rapid mix reactor, flocculation tank and sedimentation tank. Sulfate concentration in the finished water can be controlled at a desired level (i.e., below 100 mg/L) by adjusting the ratio of flowback water and AMD in the influent. Fe(3+) contained in the AMD can serve as a coagulant to enhance the removal of suspended solids, during which Fe(2+) is co-precipitated and the total iron is reduced to a desirable level. Solid waste generated in this process (i.e., barite) will incorporate over 99% of radium present in the flowback water, which offers the possibility to control the fate of naturally occurring radioactive materials (NORM) brought to the surface by unconventional gas extraction. Sludge recirculation in the treatment process can be used to increase the size of barite particles formed by mixing flowback water and AMD to meet specifications for use as a weighting agent in drilling fluid. This alternative management approach for NORM can be used to offset the treatment cost and promote flowback water reuse, reduce environmental impacts of AMD and reduce pressure on fresh water sources. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Measurement of field-saturated hydraulic conductivity on fractured rock outcrops near Altamura (Southern Italy) with an adjustable large ring infiltrometer

    Caputo, M.C.; de Carlo, L.; Masciopinto, C.; Nimmo, J.R.


    Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable diameter that can be fixed on-site. It thus allows an improved representation of the natural system's heterogeneity, while also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media. ?? 2009 Springer-Verlag.

  20. Hydraulic fracture model and diagnostics verification at GRI/DOE multi-site projects and tight gas sand program support. Final report, July 28, 1993--February 28, 1997

    Schroeder, J.E.


    The Mesaverde Group of the Piceance Basin in western Colorado has been a pilot study area for government-sponsored tight gas sand research for over twenty years. Early production experiments included nuclear stimulations and massive hydraulic fracture treatments. This work culminated in the US Department of Energy (DOE)`s Multiwell Experiment (MWX), a field laboratory designed to study the reservoir and production characteristics of low permeability sands. A key feature of MWX was an infrastructure which included several closely spaced wells that allowed detailed characterization of the reservoir through log and core analysis, and well testing. Interference and tracer tests, as well as the use of fracture diagnostics gave further information on stimulation and production characteristics. Thus, the Multiwell Experiment provided a unique opportunity for identifying the factors affecting production from tight gas sand reservoirs. The purpose of this operation was to support the gathering of field data that may be used to resolve the number of unknowns associated with measuring and modeling the dimensions of hydraulic fractures. Using the close-well infrastructure at the Multiwell Site near Rifle, Colorado, this operation focused primarily on the field design and execution of experiments. The data derived from the experiments were gathered and analyzed by DOE team contractors.

  1. Intelligent fracture creation for shale gas development

    Douglas, Craig C.


    Shale gas represents a major fraction of the proven reserves of natural gas in the United States and a collection of other countries. Higher gas prices and the need for cleaner fuels provides motivation for commercializing shale gas deposits even though the cost is substantially higher than traditional gas deposits. Recent advances in horizontal drilling and multistage hydraulic fracturing, which dramatically lower costs of developing shale gas fields, are key to renewed interest in shale gas deposits. Hydraulically induced fractures are quite complex in shale gas reservoirs. Massive, multistage, multiple cluster treatments lead to fractures that interact with existing fractures (whether natural or induced earlier). A dynamic approach to the fracturing process so that the resulting network of reservoirs is known during the drilling and fracturing process is economically enticing. The process needs to be automatic and done in faster than real-time in order to be useful to the drilling crews.

  2. Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1980-August 31, 1981

    Aki, K.


    Progress is reported on the following: interpretation of seismic data from hydraulic fracturing experiments at the Fenton Hill Hot Dry Rock Geothermal Site, interpretation of 3-D velocity anomalies in the western US with special attention to geothermal areas, theoretical and observational studies of scattering and attenuation of high-frequency seismic waves, theoretical and observational studies of volcanic tremors in relation to magma transport mechanisms, and deployment and maintenance of 9 event-recorders around Mt. St. Helens. Abstracts of papers submitted for publication are included. (MHR)

  3. Stimuli-Responsive/Rheoreversible Hydraulic Fracturing Fluids as a Greener Alternative to Support Geothermal and Fossil Energy Production

    Jung, Hun Bok; Carroll, KC; Kabilan, Senthil; Heldebrant, David J.; Hoyt, David W.; Zhong, Lirong; Varga, Tamas; Stephens, Sean A.; Adams, Lexor; Bonneville, Alain; Kuprat, Andrew P.; Fernandez, Carlos A.


    Cost-effective yet safe creation of high-permeability reservoirs within deep bedrock is the primary challenge for the viability of enhanced geothermal systems (EGS) and unconventional oil/gas recovery. Although fracturing fluids are commonly used for oil/gas, standard fracturing methods are not developed or proven for EGS temperatures and pressures. Furthermore, the environmental impacts of currently used fracturing methods 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 enable EGS feasibility and lessen environmental impact of reservoir stimulation, an environmentally benign, CO2-activated, rheoreversible fracturing fluid that enhances permeability through fracturing (at significantly lower effective stress than standard fracturing fluids) due to in situ volume expansion and gel formation is investigated herein. The chemical mechanism, stability, phase-change behavior, and rheology for a novel polyallylamine (PAA)-CO2 fracturing fluid was characterized at EGS temperatures and pressures. Hydrogel is formed upon reaction with CO2 and this process is reversible (via CO2 depressurization or solubilizing with a mild acid) allowing removal from the formation and recycling, decreasing environmental impact. Rock obtained from the Coso geothermal field was fractured in laboratory experiments under various EGS temperatures and pressures with comparison to standard fracturing fluids, and the fractures were characterized with imaging, permeability measurement, and flow modeling. This novel fracturing fluid and process may vastly reduce water usage and the environmental impact of fracturing practices and effectively make EGS production and unconventional oil/gas exploitation cost-effective and cleaner.

  4. Hydraulic properties of fracture networks; Analyse des proprietes hydrauliques des reseaux de fractures: discussion des modeles d'ecoulement compatibles avec les principales proprietes geometriques

    Dreuzy, J.R. de


    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)

  5. Optimization and Field Application of Hydraulic Fracturing Techniques in Deep Shale Reservoirs%深层页岩压裂工艺优化与现场试验

    王海涛; 蒋廷学; 卞晓冰; 段华


    Hydraulic fracturing of deep shale reveals that high injection pressure ,low fracture conduc‐tivity ,limited stimulated reservoir volume ,and unsatisfactory primary production are mainly due to deep burial ,variable lithology and high in‐situ stresses .Based on the comprehensive evaluation of geological characteristics and fracturing potential of deep shale reservoirs ,technical difficulties in volumetric stimula‐tion were discussed and relevant countermeasures were proposed .Then ,a fracturing optimization method for deep shales was proposed ,and it combined a numerical simulation of the gas reservoir ,a calculation of induced stress and fracturing simulation .Fracturing segment/cluster ,perforation and stimulation treat‐ment parameters were analyzed .Taking Well Dingye 2HF as an example ,the implementation and control of deep shale fracturing techniques were discussed ,and the responses of stimulation pressure in field appli‐cation were identified .Through stage‐by‐stage optimization and fine adjustment of parameters in aspects of pad volume ,fracture initiation by gel ,and initial sand and fluid ratio .Finally ,a composite fracturing treatment procedure was formed ,i .e .pre acid + moderate viscosity gel + slick water + low viscosity gel+ moderate viscosity gel .The fracturing of deep shales has been improved successfully through the appli‐cation of the proposed procedure .In field application of Well Dingye 2HF ,12 stages of fracturing stimula‐tion were completed with initial gas production of 10 .5 × 104 m3/d after the treatment .This procedure will provide technical reference for hydraulic fracturing in similar deep shale gas reservoirs in the future .%深层页岩埋藏深、岩性差异大、地应力高,压裂改造时存在施工压力高、裂缝导流能力低、改造体积偏小、压后初产效果差等问题。在分析深层页岩地质特征参数和综合评价可压性的基础上,分析了体积改造面临的技术难

  6. N80-1油管在水力压裂作业过程中开裂原因分析%Cause analysis of N80-1 tubing fracture during hydraulic fracturing operation

    蔡亚西; 赵映辉; 陈先富; 刘涛; 孙建安


    N80-1油管在进行油层水力压裂作业过程中发生脆性开裂,采用断口宏观分析、断口微观分析、金相检验等方法,对其开裂原因进行了系统的分析。结果表明,失效油管理化性能均符合API SPEC 5 CT—2011标准规定值。该油管内壁存在一条深0.2~0.8 mm的缺陷是导致该油管在压裂过程中发生开裂的主要原因。经对失效油管实物以及金相组织形态观察,初步认定缺陷为芯棒划伤。另外,N80-1油管的断裂韧性KIC值较低亦加速该油管发生脆性开裂。改选用断裂韧性KIC值高的油管进行压裂作业将会降低压裂过程中油管发生脆性开裂的概率。%Brittle fracture occurs to N80-1 tubing during hydraulic fracturing operation at oil reservoir . Adopting the methods of macro analysis on fracture , micro analysis on fracture , metallographic test , etc, systematic analysis on the reasons to fracture was performed .The test results showed that properties of the failure tubing conform to API SPEC 5CT-2011.The results indicated that the primary reason of the fracture was the scratch of 0.2-0.8 mm existed in the inner wall of tubing , which happened due to mandrel .In addition, low fracture toughness K IC of N80-1 tubing also enhanced the brittle fracture to this tubing .When the tubing with higher fracture toughness KIC was selected , it would reduce the probability of brittle fracture to tubing during fracturing process .

  7. Numerical Investigation on Stress Shadowing in Fluid Injection-Induced Fracture Propagation in Naturally Fractured Geothermal Reservoirs

    Yoon, Jeoung Seok; Zimmermann, Günter; Zang, Arno


    In low permeability shale reservoirs, multi-stage hydraulic fracturing is largely used to increase the productivity by enlarging the stimulated rock volume. Hydraulic fracture created alters the stress field around it, and affects the subsequent fractures by the change of the stress field, in particular, mostly increased minimum principal stress at the area of subsequent fracturing. This is called stress shadow which accumulates as the fracturing stages advance from toe to heel. Hydraulic fractures generated in such altered stress field are shorter and compact with orientation deviating significantly from the far-field maximum horizontal stress orientation. This paper presents 2D discrete element-based numerical modeling of multi-stage hydraulic fracturing in a naturally fractured reservoir and investigates stress shadowing. The stress shadowing is tested with two different injection scenarios: constant and cyclic rate injections. The results show that cyclic injection tends to lower the effect of stress shadow as well as mitigates the magnitude of the induced seismicity. Another modeling case is presented to show how the stress shadow can be utilized to optimize a hydraulic fracture network in application to Groß Schönebeck geothermal reservoir, rather than being mitigated. The modeling demonstrated that the stress shadow is successfully utilized for optimizing the geothermal heat exchanger by altering the initial in situ stress field from highly anisotropic to less or even to isotropic.

  8. Adverse Reproductive and Developmental Health Outcomes Following Prenatal Exposure to a Hydraulic Fracturing Chemical Mixture in Female C57Bl/6 Mice.

    Kassotis, Christopher D; Bromfield, John J; Klemp, Kara C; Meng, Chun-Xia; Wolfe, Andrew; Zoeller, R Thomas; Balise, Victoria D; Isiguzo, Chiamaka J; Tillitt, Donald E; Nagel, Susan C


    Unconventional oil and gas operations using hydraulic fracturing can contaminate surface and groundwater with endocrine-disrupting chemicals. We have previously shown that 23 of 24 commonly used hydraulic fracturing chemicals can activate or inhibit the estrogen, androgen, glucocorticoid, progesterone, and/or thyroid receptors in a human endometrial cancer cell reporter gene assay and that mixtures can behave synergistically, additively, or antagonistically on these receptors. In the current study, pregnant female C57Bl/6 dams were exposed to a mixture of 23 commonly used unconventional oil and gas chemicals at approximately 3, 30, 300, and 3000 μg/kg·d, flutamide at 50 mg/kg·d, or a 0.2% ethanol control vehicle via their drinking water from gestational day 11 through birth. This prenatal exposure to oil and gas operation chemicals suppressed pituitary hormone concentrations across experimental groups (prolactin, LH, FSH, and others), increased body weights, altered uterine and ovary weights, increased heart weights and collagen deposition, disrupted folliculogenesis, and other adverse health effects. This work suggests potential adverse developmental and reproductive health outcomes in humans and animals exposed to these oil and gas operation chemicals, with adverse outcomes observed even in the lowest dose group tested, equivalent to concentrations reported in drinking water sources. These endpoints suggest potential impacts on fertility, as previously observed in the male siblings, which require careful assessment in future studies.