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Sample records for reservoirs requiring fractures

  1. FRACTURED PETROLEUM RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Abbas Firoozabadi

    1999-06-11

    The four chapters that are described in this report cover a variety of subjects that not only give insight into the understanding of multiphase flow in fractured porous media, but they provide also major contribution towards the understanding of flow processes with in-situ phase formation. In the following, a summary of all the chapters will be provided. Chapter I addresses issues related to water injection in water-wet fractured porous media. There are two parts in this chapter. Part I covers extensive set of measurements for water injection in water-wet fractured porous media. Both single matrix block and multiple matrix blocks tests are covered. There are two major findings from these experiments: (1) co-current imbibition can be more efficient than counter-current imbibition due to lower residual oil saturation and higher oil mobility, and (2) tight fractured porous media can be more efficient than a permeable porous media when subjected to water injection. These findings are directly related to the type of tests one can perform in the laboratory and to decide on the fate of water injection in fractured reservoirs. Part II of Chapter I presents modeling of water injection in water-wet fractured media by modifying the Buckley-Leverett Theory. A major element of the new model is the multiplication of the transfer flux by the fractured saturation with a power of 1/2. This simple model can account for both co-current and counter-current imbibition and computationally it is very efficient. It can be orders of magnitude faster than a conventional dual-porosity model. Part II also presents the results of water injection tests in very tight rocks of some 0.01 md permeability. Oil recovery from water imbibition tests from such at tight rock can be as high as 25 percent. Chapter II discusses solution gas-drive for cold production from heavy-oil reservoirs. The impetus for this work is the study of new gas phase formation from in-situ process which can be significantly

  2. Fractured Petroleum Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Firoozabadi, Dr. Abbas

    2000-01-18

    In this report the results of experiments of water injection in fractured porous media comprising a number of water-wet matrix blocks are reported for the first time. The blocks experience an advancing fracture-water level (FWL). Immersion-type experiments are performed for comparison; the dominant recovery mechanism changed from co-current to counter-current imbibition when the boundary conditions changed from advancing FWL to immersion-type. Single block experiments of co-current and counter-current imbibition was performed and co-current imbibition leads to more efficient recovery was found.

  3. A reservoir simulation approach for modeling of naturally fractured reservoirs

    Directory of Open Access Journals (Sweden)

    H. Mohammadi

    2012-12-01

    Full Text Available In this investigation, the Warren and Root model proposed for the simulation of naturally fractured reservoir was improved. A reservoir simulation approach was used to develop a 2D model of a synthetic oil reservoir. Main rock properties of each gridblock were defined for two different types of gridblocks called matrix and fracture gridblocks. These two gridblocks were different in porosity and permeability values which were higher for fracture gridblocks compared to the matrix gridblocks. This model was solved using the implicit finite difference method. Results showed an improvement in the Warren and Root model especially in region 2 of the semilog plot of pressure drop versus time, which indicated a linear transition zone with no inflection point as predicted by other investigators. Effects of fracture spacing, fracture permeability, fracture porosity, matrix permeability and matrix porosity on the behavior of a typical naturally fractured reservoir were also presented.

  4. Fracture characterization in a deep geothermal reservoir

    Science.gov (United States)

    Rühaak, Wolfram; Hehn, Vera; Hassanzadegan, Alireza; Tischner, Torsten

    2017-04-01

    At the geothermal research drilling Horstberg in North West Germany studies for the characterization of a vertical fracture are performed. The fracture was created by a massive hydraulic stimulation in 2003 in approx. 3700 m depth within rocks of the middle Buntsandstein. The fracture surface is in the order of 100,000 m2, depending on the flow rate at which water is injected. Besides hydraulic characterization, multiple tracer tests are planned. At the depth of interest the reservoir temperature is around 150 °C, pressure is around 600 bar (60 MPa) and due to salinity the water density is around 1200 kg/m3. Knowledge of tracer stability and behavior at these reservoir conditions is limited. Additionally, the planned tracer tests will be performed within one single borehole. In a closed cycle water is injected into the inner pipe of the well (tubing), which is separated by a permanent packer from the outer pipe (annulus). The water is produced back from the annulus approximately 150 m above the injection point. Thus, the circulation of thermal water between two sandstone layers via an artificial fracture can be achieved. Tests will be carried out with different flow rates and accordingly with different pressures, resulting in different fracture areas. Due to this test setup tracer signals will be stacked and will remain for a longer time in the fracture - which is the reason why different tracers are required. For an optimal characterization both conservative and reactive tracers will be used and different injection methods (continuous, instantaneous and pulsed) will be applied. For a proper setup of the tracer test numerical modelling studies are performed in advance. The relevant thermal, hydraulic and chemical processes (mainly adsorption and degredation) are coupled, resulting in a THC model; additionally the dependence of fracture aperture and area on fluid pressure has to be considered. Instead of applying a mechanically coupled model (THMC) a simplified

  5. Discrete fracture modeling of multiphase flow and hydrocarbon production in fractured shale or low permeability reservoirs

    Science.gov (United States)

    Hao, Y.; Settgast, R. R.; Fu, P.; Tompson, A. F. B.; Morris, J.; Ryerson, F. J.

    2016-12-01

    It has long been recognized that multiphase flow and transport in fractured porous media is very important for various subsurface applications. Hydrocarbon fluid flow and production from hydraulically fractured shale reservoirs is an important and complicated example of multiphase flow in fractured formations. The combination of horizontal drilling and hydraulic fracturing is able to create extensive fracture networks in low permeability shale rocks, leading to increased formation permeability and enhanced hydrocarbon production. However, unconventional wells experience a much faster production decline than conventional hydrocarbon recovery. Maintaining sustainable and economically viable shale gas/oil production requires additional wells and re-fracturing. Excessive fracturing fluid loss during hydraulic fracturing operations may also drive up operation costs and raise potential environmental concerns. Understanding and modeling processes that contribute to decreasing productivity and fracturing fluid loss represent a critical component for unconventional hydrocarbon recovery analysis. Towards this effort we develop a discrete fracture model (DFM) in GEOS (LLNL multi-physics computational code) to simulate multiphase flow and transfer in hydraulically fractured reservoirs. The DFM model is able to explicitly account for both individual fractures and their surrounding rocks, therefore allowing for an accurate prediction of impacts of fracture-matrix interactions on hydrocarbon production. We apply the DFM model to simulate three-phase (water, oil, and gas) flow behaviors in fractured shale rocks as a result of different hydraulic stimulation scenarios. Numerical results show that multiphase flow behaviors at the fracture-matrix interface play a major role in controlling both hydrocarbon production and fracturing fluid recovery rates. The DFM model developed in this study will be coupled with the existing hydro-fracture model to provide a fully integrated

  6. Discrete Fracture Network Characterization of Fractured Shale Reservoirs with Implications to Hydraulic Fracturing Optimization

    Science.gov (United States)

    Jin, G.

    2016-12-01

    Shales are important petroleum source rocks and reservoir seals. Recent developments in hydraulic fracturing technology have facilitated high gas production rates from shale and have had a strong impact on the U.S. gas supply and markets. Modeling of effective permeability for fractured shale reservoirs has been challenging because the presence of a fracture network significantly alters the reservoir hydrologic properties. Due to the frequent occurrence of fracture networks, it is of vital importance to characterize fracture networks and to investigate how these networks can be used to optimize the hydraulic fracturing. We have conducted basic research on 3-D fracture permeability characterization and compartmentization analyses for fractured shale formations, which takes the advantages of the discrete fracture networks (DFN). The DFN modeling is a stochastic modeling approach using the probabilistic density functions of fractures. Three common scenarios of DFN models have been studied for fracture permeability mapping using our previously proposed techniques. In DFN models with moderately to highly concentrated fractures, there exists a representative element volume (REV) for fracture permeability characterization, which indicates that the fractured reservoirs can be treated as anisotropic homogeneous media. Hydraulic fracturing will be most effective if the orientation of the hydraulic fracture is perpendicular to the mean direction of the fractures. A DFN model with randomized fracture orientations, on the other hand, lacks an REV for fracture characterization. Therefore, a fracture permeability tensor has to be computed from each element. Modeling of fracture interconnectivity indicates that there exists no preferred direction for hydraulic fracturing to be most effective oweing to the interconnected pathways of the fracture network. 3-D fracture permeability mapping has been applied to the Devonian Chattanooga Shale in Alabama and the results suggest that an

  7. Numerical simulation of hydraulic fracture propagation in heterogeneous unconventional reservoir

    Science.gov (United States)

    Liu, Chunting; Li, Mingzhong; Hao, Lihua; Hu, Hang

    2017-10-01

    The distribution of the unconventional reservoir fracture network is influenced by many factors. For the natural fracture undeveloped reservoir, the reservoir heterogeneity, construction factors (fracturing fluid flow rate, fluid viscosity, perforation clusters spacing), horizontal stress difference and stress different coefficient are the main factors that affect the fracture propagation. In the study, first, calculate the reservoir physics mechanics parameters that affect the fracture propagation on the base of the logging date from one actual horizontal well. Set the formation parameters according to the calculation that used to simulate the reservoir heterogeneity. Then, using damage mechanics method, the 2D fracture propagation model with seepage-stress-damage coupling of multi-fracture tight sand reservoir was established. Study the influences of different fracturing ways (open whole fracturing and oriented perforation fracturing) and the position of the perforation clusters to the fracture propagation for heterogeneity reservoir. Analyze the effects of flow rate, fracturing fluid viscosity, perforation clusters spacing, horizontal stress difference and stress different coefficient to fracture morphology for the heterogeneity reservoir and contrast with the homogeneous reservoir. The simulation results show that: the fracture morphology is more complexity formed by oriented perforation crack than open whole crack; For natural fracture undeveloped reservoir, as the flow rate or the fracturing fluid viscosity increases within a certain range, the fracture network tends to be more complexity and the effect is more obvious to heterogeneous reservoir than homogeneous reservoir; As the perforation clusters spacing decreases, the interaction of each fracture will increase, it tends to form more complexity fracture network but with short major fracture; If the horizontal stress difference and stress different coefficient is large (The stress different coefficient >0

  8. A New Method for Fracturing Wells Reservoir Evaluation in Fractured Gas Reservoir

    Directory of Open Access Journals (Sweden)

    Jianchun Guo

    2014-01-01

    Full Text Available Natural fracture is a geological phenomenon widely distributed in tight formation, and fractured gas reservoir stimulation effect mainly depends on the communication of natural fractures. Therefore it is necessary to carry out the evaluation of this reservoir and to find out the optimal natural fractures development wells. By analyzing the interactions and nonlinear relationships of the parameters, it establishes three-level index system of reservoir evaluation and proposes a new method for gas well reservoir evaluation model in fractured gas reservoir on the basis of fuzzy logic theory and multilevel gray correlation. For this method, the Gaussian membership functions to quantify the degree of every factor in the decision-making system and the multilevel gray relation to determine the weight of each parameter on stimulation effect. Finally through fuzzy arithmetic operator between multilevel weights and fuzzy evaluation matrix, score, rank, the reservoir quality, and predicted production will be gotten. Result of this new method shows that the evaluation of the production coincidence rate reaches 80%, which provides a new way for fractured gas reservoir evaluation.

  9. A simplified approach to well test analysis of naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Aguilera, R. [Servipetrol Ltd., Calgary, AB (Canada)

    2004-07-01

    This paper presents a simplified equation for drawdown and well test analysis of naturally fractured reservoirs. It can also be used for conventional single porosity reservoirs. The proposed technique allows approximate solutions to determine parameters such as fracture, permeability, wellbore storage, skin, storativity ratio, interporosity flow coefficient, fracture spacing, number of fractures intercepted by the wellbore and the amount of secondary mineralization within fractures. The results are in reasonable agreement with more rigorous methods published in the literature which require specialized software. The proposed method was illustrated with actual data from fractured reservoirs. 13 refs., 2 tabs., 4 figs.

  10. Development of Reservoir Characterization Techniques and Production Models for Exploiting Naturally Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Wiggins, Michael L.; Brown, Raymon L.; Civan, Frauk; Hughes, Richard G.

    2001-08-15

    Research continues on characterizing and modeling the behavior of naturally fractured reservoir systems. Work has progressed on developing techniques for estimating fracture properties from seismic and well log data, developing naturally fractured wellbore models, and developing a model to characterize the transfer of fluid from the matrix to the fracture system for use in the naturally fractured reservoir simulator.

  11. Development of Reservoir Characterization Techniques and Production Models for Exploiting Naturally Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Wiggins, M.L.; Evans, R.D.; Brown, R.L.; Gupta, A.

    2001-03-28

    This report focuses on integrating geoscience and engineering data to develop a consistent characterization of the naturally fractured reservoirs. During this reporting period, effort was focused on relating seismic data to reservoir properties of naturally fractured reservoirs, scaling well log data to generate interwell descriptors of these reservoirs, enhancing and debugging a naturally fractured reservoir simulator, and developing a horizontal wellbore model for use in the simulator.

  12. A review on hydraulic fracturing of unconventional reservoir

    OpenAIRE

    Quanshu Li; Huilin Xing; Jianjun Liu; Xiangchon Liu

    2015-01-01

    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 u...

  13. Reactive Tracers for Characterizing Fractured Geothermal Reservoirs

    Science.gov (United States)

    Hawkins, Adam J.

    Multi-component tracer tests were conducted at a 10 x 10 m well field located in the Altona Flat Rocks of northern New York. Temperature advancement between two wells separated by 14 m was monitored throughout the well field during progressive heating of the reservoir over 6 d. Multiple approaches to predicting heat transport were applied to field data and compared to temperature rise recorded during reservoir heat-up. Tracer analysis incorporated both an analytical one-dimensional model and a two-dimensional numerical model for non-uniform fractures experiencing "flow-channeling." Modeling efforts demonstrated that estimating heat transfer surface area using a combined inert/adsorbing tracer (cesium-iodide) could provide accurate forecasting of premature thermal breakthrough. In addition, thermally degrading tracer tests were used to monitor inter-well temperature during progressive reservoir heating. Inert tracers alone were, in general, inadequate in forecasting thermal performance. In fact, moment analysis shows that, mathematically, thermal breakthrough is independent of parameters that primarily influence inert tracers. The most accurate prediction of thermal breakthrough using inert tracer alone was produced by treating hydrodynamic dispersion as a truly Fickian process with known and accurate mathematical models. Under this assumption, inert tracer data was matched by solving an inverse problem for non-uniform fracture aperture. Early arrival of the thermal front was predicted at the production, but was less accurate than using a combined inert/adsorbing tracer test. The spatial distribution of fluid flow paths in the plane of the fracture were identified using computational models, Fiber-Optic Distributed Temperature Sensing (FO-DTS), and Ground Penetrating Radar (GPR) imaging of saline tracer flow paths in the target fracture. Without exception, fluid flow was found to be concentrated in a roughly 1 m wide flow channel directly between the two wells. The

  14. Naturally fractured tight gas reservoir detection optimization

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-06-01

    Building upon the partitioning of the Greater Green River Basin (GGRB) that was conducted last quarter, the goal of the work this quarter has been to conclude evaluation of the Stratos well and the prototypical Green River Deep partition, and perform the fill resource evaluation of the Upper Cretaceous tight gas play, with the goal of defining target areas of enhanced natural fracturing. The work plan for the quarter of November 1-December 31, 1998 comprised four tasks: (1) Evaluation of the Green River Deep partition and the Stratos well and examination of potential opportunity for expanding the use of E and P technology to low permeability, naturally fractured gas reservoirs, (2) Gas field studies, and (3) Resource analysis of the balance of the partitions.

  15. Theoretical Analysis of the Mechanism of Fracture Network Propagation with Stimulated Reservoir Volume (SRV) Fracturing in Tight Oil Reservoirs.

    Science.gov (United States)

    Su, Yuliang; Ren, Long; Meng, Fankun; Xu, Chen; Wang, Wendong

    2015-01-01

    Stimulated reservoir volume (SRV) fracturing in tight oil reservoirs often induces complex fracture-network growth, which has a fundamentally different formation mechanism from traditional planar bi-winged fracturing. To reveal the mechanism of fracture network propagation, this paper employs a modified displacement discontinuity method (DDM), mechanical mechanism analysis and initiation and propagation criteria for the theoretical model of fracture network propagation and its derivation. A reasonable solution of the theoretical model for a tight oil reservoir is obtained and verified by a numerical discrete method. Through theoretical calculation and computer programming, the variation rules of formation stress fields, hydraulic fracture propagation patterns (FPP) and branch fracture propagation angles and pressures are analyzed. The results show that during the process of fracture propagation, the initial orientation of the principal stress deflects, and the stress fields at the fracture tips change dramatically in the region surrounding the fracture. Whether the ideal fracture network can be produced depends on the geological conditions and on the engineering treatments. This study has both theoretical significance and practical application value by contributing to a better understanding of fracture network propagation mechanisms in unconventional oil/gas reservoirs and to the improvement of the science and design efficiency of reservoir fracturing.

  16. Theoretical Analysis of the Mechanism of Fracture Network Propagation with Stimulated Reservoir Volume (SRV Fracturing in Tight Oil Reservoirs.

    Directory of Open Access Journals (Sweden)

    Yuliang Su

    Full Text Available Stimulated reservoir volume (SRV fracturing in tight oil reservoirs often induces complex fracture-network growth, which has a fundamentally different formation mechanism from traditional planar bi-winged fracturing. To reveal the mechanism of fracture network propagation, this paper employs a modified displacement discontinuity method (DDM, mechanical mechanism analysis and initiation and propagation criteria for the theoretical model of fracture network propagation and its derivation. A reasonable solution of the theoretical model for a tight oil reservoir is obtained and verified by a numerical discrete method. Through theoretical calculation and computer programming, the variation rules of formation stress fields, hydraulic fracture propagation patterns (FPP and branch fracture propagation angles and pressures are analyzed. The results show that during the process of fracture propagation, the initial orientation of the principal stress deflects, and the stress fields at the fracture tips change dramatically in the region surrounding the fracture. Whether the ideal fracture network can be produced depends on the geological conditions and on the engineering treatments. This study has both theoretical significance and practical application value by contributing to a better understanding of fracture network propagation mechanisms in unconventional oil/gas reservoirs and to the improvement of the science and design efficiency of reservoir fracturing.

  17. Data assimilation method for fractured reservoirs using mimetic finite differences and ensemble Kalman filter

    KAUST Repository

    Ping, Jing

    2017-05-19

    Optimal management of subsurface processes requires the characterization of the uncertainty in reservoir description and reservoir performance prediction. For fractured reservoirs, the location and orientation of fractures are crucial for predicting production characteristics. With the help of accurate and comprehensive knowledge of fracture distributions, early water/CO 2 breakthrough can be prevented and sweep efficiency can be improved. However, since the rock property fields are highly non-Gaussian in this case, it is a challenge to estimate fracture distributions by conventional history matching approaches. In this work, a method that combines vector-based level-set parameterization technique and ensemble Kalman filter (EnKF) for estimating fracture distributions is presented. Performing the necessary forward modeling is particularly challenging. In addition to the large number of forward models needed, each model is used for sampling of randomly located fractures. Conventional mesh generation for such systems would be time consuming if possible at all. For these reasons, we rely on a novel polyhedral mesh method using the mimetic finite difference (MFD) method. A discrete fracture model is adopted that maintains the full geometry of the fracture network. By using a cut-cell paradigm, a computational mesh for the matrix can be generated quickly and reliably. In this research, we apply this workflow on 2D two-phase fractured reservoirs. The combination of MFD approach, level-set parameterization, and EnKF provides an effective solution to address the challenges in the history matching problem of highly non-Gaussian fractured reservoirs.

  18. DEVELOPMENT OF RESERVOIR CHARACTERIZATION TECHNIQUES AND PRODUCTION MODELS FOR EXPLOITING NATURALLY FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Michael L. Wiggins; Raymon L. Brown; Faruk Civan; Richard G. Hughes

    2002-12-31

    For many years, geoscientists and engineers have undertaken research to characterize naturally fractured reservoirs. Geoscientists have focused on understanding the process of fracturing and the subsequent measurement and description of fracture characteristics. Engineers have concentrated on the fluid flow behavior in the fracture-porous media system and the development of models to predict the hydrocarbon production from these complex systems. This research attempts to integrate these two complementary views to develop a quantitative reservoir characterization methodology and flow performance model for naturally fractured reservoirs. The research has focused on estimating naturally fractured reservoir properties from seismic data, predicting fracture characteristics from well logs, and developing a naturally fractured reservoir simulator. It is important to develop techniques that can be applied to estimate the important parameters in predicting the performance of naturally fractured reservoirs. This project proposes a method to relate seismic properties to the elastic compliance and permeability of the reservoir based upon a sugar cube model. In addition, methods are presented to use conventional well logs to estimate localized fracture information for reservoir characterization purposes. The ability to estimate fracture information from conventional well logs is very important in older wells where data are often limited. Finally, a desktop naturally fractured reservoir simulator has been developed for the purpose of predicting the performance of these complex reservoirs. The simulator incorporates vertical and horizontal wellbore models, methods to handle matrix to fracture fluid transfer, and fracture permeability tensors. This research project has developed methods to characterize and study the performance of naturally fractured reservoirs that integrate geoscience and engineering data. This is an important step in developing exploitation strategies for

  19. Naturally fractured tight gas reservoir detection optimization

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-30

    The work plan for October 1, 1997 to September 30, 1998 consisted of investigation of a number of topical areas. These topical areas were reported in four quarterly status reports, which were submitted to DOE earlier. These topical areas are reviewed in this volume. The topical areas covered during the year were: (1) Development of preliminary tests of a production method for determining areas of natural fracturing. Advanced Resources has demonstrated that such a relationship exists in the southern Piceance basin tight gas play. Natural fracture clusters are genetically related to stress concentrations (also called stress perturbations) associated with local deformation such a faulting. The mechanical explanation of this phenomenon is that deformation generally initiates at regions where the local stress field is elevated beyond the regional. (2) Regional structural and geologic analysis of the Greater Green River Basin (GGRB). Application of techniques developed and demonstrated during earlier phases of the project for sweet-spot delineation were demonstrated in a relatively new and underexplored play: tight gas from continuous-typeUpper Cretaceous reservoirs of the Greater Green River Basin (GGRB). The effort included data acquisition/processing, base map generation, geophysical and remote sensing analysis and the integration of these data and analyses. (3) Examination of the Table Rock field area in the northern Washakie Basin of the Greater Green River Basin. This effort was performed in support of Union Pacific Resources- and DOE-planned horizontal drilling efforts. The effort comprised acquisition of necessary seismic data and depth-conversion, mapping of major fault geometry, and analysis of displacement vectors, and the development of the natural fracture prediction. (4) Greater Green River Basin Partitioning. Building on fundamental fracture characterization work and prior work performed under this contract, namely structural analysis using satellite and

  20. A review on hydraulic fracturing of unconventional reservoir

    Directory of Open Access Journals (Sweden)

    Quanshu Li

    2015-03-01

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

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

    Science.gov (United States)

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

    2010-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad Ghassemi

    2003-06-30

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

  3. New Heat Flow Models in Fractured Geothermal Reservoirs - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Reis, John

    2001-03-31

    This study developed new analytical models for predicting the temperature distribution within a geothermal reservoir following reinjection of water having a temperature different from that of the reservoir. The study consisted of two parts: developing new analytical models for the heat conduction rate into multi-dimensional, parallelepiped matrix blocks and developing new analytical models for the advance of the thermal front through the geothermal reservoir. In the first part of the study, a number of semi-empirical models for the multi-dimensional heat conduction were developed to overcome the limitations to the exact solutions. The exact solution based on a similarity solution to the heat diffusion equation is the best model for the early-time period, but fails when thermal conduction fronts from opposing sides of the matrix block merge. The exact solution based on an infinite series solution was found not to be useful because it required tens of thousands of terms to be include d for accuracy. The best overall model for the entire conduction time was a semi-empirical model based on an exponential conduction rate. In the second part of the study, the early-time period exact solution based on similarity methods and the semi-empirical exponential model were used to develop new analytical models for the location of the thermal front within the reservoir during injection. These equations were based on an energy balance on the water in the fractured network. These convective models allowed for both dual and triple porosity reservoirs, i.e., one or two independent matrix domains. A method for incorporating measured fracture spacing distributions into these convective models was developed. It was found that there were only minor differences in the predicted areal extent of the heated zone between the dual and triple porosity models. Because of its simplicity, the dual porosity model is recommended. These new models can be used for preliminary reservoir studies

  4. Numerical modeling of shear stimulation in naturally fractured geothermal reservoirs

    OpenAIRE

    Ucar, Eren

    2018-01-01

    Shear-dilation-based hydraulic stimulations are conducted to create enhanced geothermal systems (EGS) from low permeable geothermal reservoirs, which are initially not amenable to energy production. Reservoir stimulations are done by injecting low-pressurized fluid into the naturally fractured formations. The injection aims to activate critically stressed fractures by decreasing frictional strength and ultimately cause a shear failure. The shear failure leads to a permanent ...

  5. Geomechanical production optimization in faulted and fractured reservoirs

    NARCIS (Netherlands)

    Heege, J.H. ter; Pizzocolo, F.; Osinga, S.; Veer, E.F. van der

    2016-01-01

    Faults and fractures in hydrocarbon reservoirs are key to some major production issues including (1) varying productivity of different well sections due to intersection of preferential flow paths with the wellbore, (2) varying hydrocarbon column heights in different reservoir compartments due to

  6. Quantifying Fracture Heterogeneity in Different Domains of Folded Carbonate Rocks to Improve Fractured Reservoir Analog Fluid Flow Models

    NARCIS (Netherlands)

    Bisdom, K.; Bertotti, G.; Gauthier, B.D.M.; Hardebol, N.J.

    2013-01-01

    Fluid flow in carbonate reservoirs is largely controlled by multiscale fracture networks. Significant variations of fracture network porosity and permeability are caused by the 3D heterogeneity of the fracture network characteristics, such as intensity, orientation and size. Characterizing fracture

  7. RESEARCH PROGRAM ON FRACTURED PETROLEUM RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Abbas Firoozabadi

    2002-04-12

    Numerical simulation of water injection in discrete fractured media with capillary pressure is a challenge. Dual-porosity models in view of their strength and simplicity can be mainly used for sugar-cube representation of fractured media. In such a representation, the transfer function between the fracture and the matrix block can be readily calculated for water-wet media. For a mixed-wet system, the evaluation of the transfer function becomes complicated due to the effect of gravity. In this work, they use a discrete-fracture model in which the fractures are discretized as one dimensional entities to account for fracture thickness by an integral form of the flow equations. This simple step greatly improves the numerical solution. Then the discrete-fracture model is implemented using a Galerkin finite element method. The robustness and the accuracy of the approach are shown through several examples. First they consider a single fracture in a rock matrix and compare the results of the discrete-fracture model with a single-porosity model. Then, they use the discrete-fracture model in more complex configurations. Numerical simulations are carried out in water-wet media as well as in mixed-wet media to study the effect of matrix and fracture capillary pressures.

  8. An analytical thermohydraulic model for discretely fractured geothermal reservoirs

    Science.gov (United States)

    Fox, Don B.; Koch, Donald L.; Tester, Jefferson W.

    2016-09-01

    In discretely fractured reservoirs such as those found in Enhanced/Engineered Geothermal Systems (EGS), knowledge of the fracture network is important in understanding the thermal hydraulics, i.e., how the fluid flows and the resulting temporal evolution of the subsurface temperature. The purpose of this study was to develop an analytical model of the fluid flow and heat transport in a discretely fractured network that can be used for a wide range of modeling applications and serve as an alternative analysis tool to more computationally intensive numerical codes. Given the connectivity and structure of a fracture network, the flow in the system was solved using a linear system of algebraic equations for the pressure at the nodes of the network. With the flow determined, the temperature in the fracture was solved by coupling convective heat transport in the fracture with one-dimensional heat conduction perpendicular to the fracture, employing the Green's function derived solution for a single discrete fracture. The predicted temperatures along the fracture surfaces from the analytical solution were compared to numerical simulations using the TOUGH2 reservoir code. Through two case studies, we showed the capabilities of the analytical model and explored the effect of uncertainty in the fracture apertures and network structure on thermal performance. While both sources of uncertainty independently produce large variations in production temperature, uncertainty in the network structure, whenever present, had a predominant influence on thermal performance.

  9. Physical Aspects in Upscaling of Fractured Reservoirs and Improved Oil Recovery Prediction

    NARCIS (Netherlands)

    Salimi, H.

    2010-01-01

    This thesis is concerned with upscaled models for waterflooded naturally fractured reservoirs (NFRs). Naturally fractured petroleum reservoirs provide over 20% of the world’s oil reserves and production. From the fluid-flow point of view, a fractured reservoir is defined as a reservoir in which a

  10. Three-Dimensional Modeling of Fracture Clusters in Geothermal Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Ghassemi, Ahmad [Univ. of Oklahoma, Norman, OK (United States)

    2017-08-11

    The objective of this is to develop a 3-D numerical model for simulating mode I, II, and III (tensile, shear, and out-of-plane) propagation of multiple fractures and fracture clusters to accurately predict geothermal reservoir stimulation using the virtual multi-dimensional internal bond (VMIB). Effective development of enhanced geothermal systems can significantly benefit from improved modeling of hydraulic fracturing. In geothermal reservoirs, where the temperature can reach or exceed 350oC, thermal and poro-mechanical processes play an important role in fracture initiation and propagation. In this project hydraulic fracturing of hot subsurface rock mass will be numerically modeled by extending the virtual multiple internal bond theory and implementing it in a finite element code, WARP3D, a three-dimensional finite element code for solid mechanics. The new constitutive model along with the poro-thermoelastic computational algorithms will allow modeling the initiation and propagation of clusters of fractures, and extension of pre-existing fractures. The work will enable the industry to realistically model stimulation of geothermal reservoirs. The project addresses the Geothermal Technologies Office objective of accurately predicting geothermal reservoir stimulation (GTO technology priority item). The project goal will be attained by: (i) development of the VMIB method for application to 3D analysis of fracture clusters; (ii) development of poro- and thermoelastic material sub-routines for use in 3D finite element code WARP3D; (iii) implementation of VMIB and the new material routines in WARP3D to enable simulation of clusters of fractures while accounting for the effects of the pore pressure, thermal stress and inelastic deformation; (iv) simulation of 3D fracture propagation and coalescence and formation of clusters, and comparison with laboratory compression tests; and (v) application of the model to interpretation of injection experiments (planned by our

  11. 49 CFR 393.50 - Reservoirs required.

    Science.gov (United States)

    2010-10-01

    ... depressing the brake pedal or treadle valve to the limit of its travel. (c) Safeguarding of air and vacuum... NECESSARY FOR SAFE OPERATION Brakes § 393.50 Reservoirs required. (a) Reservoir capacity for air-braked... driver to make a full service brake application with the engine stopped without depleting the air...

  12. Electrical characteristics of rocks in fractured and caved reservoirs

    Science.gov (United States)

    Tang, Tianzhi; Lu, Tao; Zhang, Haining; Jiang, Liming; Liu, Tangyan; Meng, He; Wang, Feifei

    2017-12-01

    The conductive paths formed by fractures and cave in complex reservoirs differ from those formed by pores and throats in clastic rocks. In this paper, a new formation model based on fractured and caved reservoirs is established, and the electrical characteristics of rocks are analyzed with different pore structures using resistance law to understand their effects on rock resistivity. The ratio of fracture width to cave radius (C e value) and fracture dip are employed to depict pore structure in this model. Our research shows that the electrical characteristics of rocks in fractured and caved reservoirs are strongly affected by pore structure and porous fluid distribution. Although the rock electrical properties associated with simple pore structure agree well with Archie formulae, the relationships between F and φ or between I and S w , in more complicated pore structures, are nonlinear in double logarithmic coordinates. The parameters in Archie formulae are not constant and they depend on porosity and fluid saturation. Our calculations suggest that the inclined fracture may lead to resistivity anisotropy in the formation. The bigger dip the inclining fracture has, the more anisotropy the formation resistivity has. All of these studies own practical sense for the evaluation of oil saturation using resistivity logging data.

  13. Effective Local-Global Upscaling of Fractured Reservoirs under Discrete Fractured Discretization

    Directory of Open Access Journals (Sweden)

    Junchao Li

    2015-09-01

    Full Text Available The subsurface flow in fractured reservoirs is strongly affected by the distribution of fracture networks. Discrete fracture models, which represent all fractures individually by unstructured grid systems, are thus developed and act as a more accurate way for fractured reservoir simulation. However, it is usually not realistic to directly apply discrete fracture models to simulate field scale models for efficiency reasons. There is a need for upscaling techniques to coarsen the high resolution fracture descriptions to sizes that can be accommodated by reservoir simulators. In this paper, we extended the adaptive local-global upscaling technique to construct a transmissibility-based dual-porosity dual-permeability model from discrete fracture characterizations. An underlying unstructured fine-scale grid is firstly generated as a base grid. A global coarse-scale simulation is performed to provide boundary conditions for local regions and local upscaling procedures are carried out in every local region for transmissibility calculations. Iterations are performed until the consistency between the global and local properties is achieved. The procedure is applied to provide dual-porosity dual-permeability (DPDK parameters including coarse-scale matrix-matrix, fracture-fracture and matrix-fracture flux transmissibilities. The methodology is applied to several cases. The simulation results demonstrate the accuracy, efficiency and robustness of the proposed method.

  14. Transient pressure analysis of a volume fracturing well in fractured tight oil reservoirs

    Science.gov (United States)

    Lu, Cheng; Wang, Jiahang; Zhang, Cong; Cheng, Minhua; Wang, Xiaodong; Dong, Wenxiu; Zhou, Yingfang

    2017-12-01

    This paper presents a semi-analytical model to simulate transient pressure curves for a vertical well with a reconstructed fracture network in fractured tight oil reservoirs. In the proposed model, the reservoir is a composite system and contains two regions. The inner region is described as a formation with a finite conductivity hydraulic fracture network and the flow in the fracture is assumed to be linear, while the outer region is modeled using the classical Warren–Root model where radial flow is applied. The transient pressure curves of a vertical well in the proposed reservoir model are calculated semi-analytically using the Laplace transform and Stehfest numerical inversion. As shown in the type curves, the flow is divided into several regimes: (a) linear flow in artificial main fractures; (b) coupled boundary flow; (c) early linear flow in a fractured formation; (d) mid radial flow in the semi-fractures of the formation; (e) mid radial flow or pseudo steady flow; (f) mid cross-flow; (g) closed boundary flow. Based on our newly proposed model, the effects of some sensitive parameters, such as elastic storativity ratio, cross-flow coefficient, fracture conductivity and skin factor, on the type curves were also analyzed extensively. The simulated type curves show that for a vertical fractured well in a tight reservoir, the elastic storativity ratios and crossflow coefficients affect the time and the degree of crossflow respectively. The pressure loss increases with an increase in the fracture conductivity. To a certain extent, the effect of the fracture conductivity is more obvious than that of the half length of the fracture on improving the production effect. With an increase in the wellbore storage coefficient, the fluid compressibility is so large that it might cover the early stage fracturing characteristics. Linear or bilinear flow may not be recognized, and the pressure and pressure derivative gradually shift to the right. With an increase in the skin

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

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  16. Naturally fractured tight gas reservoir detection optimization. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-11-19

    This DOE-funded research into seismic detection of natural fractures is one of six projects within the DOE`s Detection and Analysis of Naturally Fractured Gas Reservoirs Program, a multidisciplinary research initiative to develop technology for prediction, detection, and mapping of naturally fractured gas reservoirs. The demonstration of successful seismic techniques to locate subsurface zones of high fracture density and to guide drilling orientation for enhanced fracture permeability will enable better returns on investments in the development of the vast gas reserves held in tight formations beneath the Rocky Mountains. The seismic techniques used in this project were designed to capture the azimuthal anisotropy within the seismic response. This seismic anisotropy is the result of the symmetry in the rock fabric created by aligned fractures and/or unequal horizontal stresses. These results may be compared and related to other lines of evidence to provide cross-validation. The authors undertook investigations along the following lines: Characterization of the seismic anisotropy in three-dimensional, P-wave seismic data; Characterization of the seismic anisotropy in a nine-component (P- and S-sources, three-component receivers) vertical seismic profile; Characterization of the seismic anisotropy in three-dimensional, P-to-S converted wave seismic data (P-wave source, three-component receivers); and Description of geological and reservoir-engineering data that corroborate the anisotropy: natural fractures observed at the target level and at the surface, estimation of the maximum horizontal stress in situ, and examination of the flow characteristics of the reservoir.

  17. Characterization of reservoir fractures using conventional geophysical logging

    Directory of Open Access Journals (Sweden)

    Paitoon Laongsakul

    2011-04-01

    Full Text Available In hydrocarbon exploration fractures play an important role as possible pathways for the hydrocarbon flow and bythis enhancing the overall formation’s permeability. Advanced logging methods for fracture analysis, like the boreholeacoustic televiewer and Formation Microscanner (FMS are available, but these are additional and expensive tools. However,open and with water or hydrocarbon filled fractures are also sensitive to electrical and other conventional logging methods.For this study conventional logging data (electric, seismic, etc were available plus additional fracture information from FMS.Taking into account the borehole environment the results show that the micro-spherically focused log indicates fractures byshowing low resistivity spikes opposite open fractures, and high resistivity spikes opposite sealed ones. Compressional andshear wave velocities are reduced when passing trough the fracture zone, which are assumed to be more or less perpendicularto borehole axis. The photoelectric absorption curve exhibit a very sharp peak in front of a fracture filled with bariteloaded mud cake. The density log shows low density spikes that are not seen by the neutron log, usually where fractures,large vugs, or caverns exist. Borehole breakouts can cause a similar effect on the logging response than fractures, but fracturesare often present when this occurs. The fracture index calculation by using threshold and input weight was calculatedand there was in general a good agreement with the fracture data from FMS especially in fracture zones, which mainlycontribute to the hydraulic system of the reservoir. Finally, the overall results from this study using one well are promising,however further research in the combination of different tools for fracture identification is recommended as well as the useof core for further validation.

  18. A New Model to Predict Productivity of Multiple-Fractured Horizontal Well in Naturally Fractured Reservoirs

    Directory of Open Access Journals (Sweden)

    Junchao Wang

    2015-01-01

    Full Text Available In order to predict productivity of multiple-fractured horizontal well in fractured reservoir, flow models of reservoir and hydraulic fractures based on the volumetric source idealization are developed. The models are solved by utilizing Laplace transformation and orthogonal transformation, and flow rate of the well is calculated by coupling the two models. Compared to traditional point source functions, volumetric source function has many advantages in properties of function and programming calculation. The productivity predicting model is verified via an analytical ternary-porosity model. Moreover, a practical example of fractured horizontal well is studied to analyze the productivity and its influent factors. The result shows that flow rate of each fracture is different and inner fracture contributes least to productivity. Meanwhile, there are optimizing ranges for number, length, and conductivity of hydraulic fractures. In low-permeability reservoir, increasing surface area in contact with reservoir by increasing number and length of hydraulic fractures is the most effective method to improve the productivity.

  19. Fractured reservoir discrete feature network technologies. Final report, March 7, 1996 to September 30, 1998

    Energy Technology Data Exchange (ETDEWEB)

    Dershowitz, William S.; Einstein, Herbert H.; LaPoint, Paul R.; Eiben, Thorsten; Wadleigh, Eugene; Ivanova, Violeta

    1998-12-01

    This report summarizes research conducted for the Fractured Reservoir Discrete Feature Network Technologies Project. The five areas studied are development of hierarchical fracture models; fractured reservoir compartmentalization, block size, and tributary volume analysis; development and demonstration of fractured reservoir discrete feature data analysis tools; development of tools for data integration and reservoir simulation through application of discrete feature network technologies for tertiary oil production; quantitative evaluation of the economic value of this analysis approach.

  20. Rate Transient Analysis for Multistage Fractured Horizontal Well in Tight Oil Reservoirs considering Stimulated Reservoir Volume

    Directory of Open Access Journals (Sweden)

    Ruizhong Jiang

    2014-01-01

    Full Text Available A mathematical model of multistage fractured horizontal well (MsFHW considering stimulated reservoir volume (SRV was presented for tight oil reservoirs. Both inner and outer regions were assumed as single porosity media but had different formation parameters. Laplace transformation method, point source function integration method, superposition principle, Stehfest numerical algorithm, and Duhamel’s theorem were used comprehensively to obtain the semianalytical solution. Different flow regimes were divided based on pressure transient analysis (PTA curves. According to rate transient analysis (RTA, the effects of related parameters such as SRV radius, storativity ratio, mobility ratio, fracture number, fracture half-length, and fracture spacing were analyzed. The presented model and obtained results in this paper enrich the performance analysis models of MsFHW considering SRV.

  1. Advanced Hydraulic Fracturing Technology for Unconventional Tight Gas Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Holditch; A. Daniel Hill; D. Zhu

    2007-06-19

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

  2. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Seright, Randall S.; Liang, Jenn-Tai; Schrader, Richard; Hagstrom II, John; Liu, Jin; Wavrik, Kathryn

    1999-09-27

    This report describes work performed during the first year of the project, ''Using Chemicals to Optimize Conformance Control in Fractured Reservoirs.'' This research project has three objectives. The first objective is to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective is to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective is to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consists of three tasks, each of which addresses one of the above objectives. Our work is directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

  4. Modeling of non-equilibrium effects in solvent-enhanced spontaneous imbibition in fractured reservoirs

    NARCIS (Netherlands)

    Chahardowli, M.; Bruining, J.

    2013-01-01

    In fractured reservoirs, much of the oil is stored in low permeable matrix blocks that are surrounded by a high permeability fracture network. Therefore, production from fractured reservoir depends on the transfer between fracture and matrix, which is critically dependent on their interaction.

  5. Mineral Reactions in Shale Gas Reservoirs: Barite Scale Formation from Reusing Produced Water As Hydraulic Fracturing Fluid.

    Science.gov (United States)

    Paukert Vankeuren, Amelia N; Hakala, J Alexandra; Jarvis, Karl; Moore, Johnathan E

    2017-08-15

    Hydraulic fracturing for gas production is now ubiquitous in shale plays, but relatively little is known about shale-hydraulic fracturing fluid (HFF) reactions within the reservoir. To investigate reactions during the shut-in period of hydraulic fracturing, experiments were conducted flowing different HFFs through fractured Marcellus shale cores at reservoir temperature and pressure (66 °C, 20 MPa) for one week. Results indicate HFFs with hydrochloric acid cause substantial dissolution of carbonate minerals, as expected, increasing effective fracture volume (fracture volume + near-fracture matrix porosity) by 56-65%. HFFs with reused produced water composition cause precipitation of secondary minerals, particularly barite, decreasing effective fracture volume by 1-3%. Barite precipitation occurs despite the presence of antiscalants in experiments with and without shale contact and is driven in part by addition of dissolved sulfate from the decomposition of persulfate breakers in HFF at reservoir conditions. The overall effect of mineral changes on the reservoir has yet to be quantified, but the significant amount of barite scale formed by HFFs with reused produced water composition could reduce effective fracture volume. Further study is required to extrapolate experimental results to reservoir-scale and to explore the effect that mineral changes from HFF interaction with shale might have on gas production.

  6. Predicting the natural state of fractured carbonate reservoirs: An Andector Field, West Texas test of a 3-D RTM simulator

    Energy Technology Data Exchange (ETDEWEB)

    Tuncay, K.; Romer, S.; Ortoleva, P. [Indiana Univ., Bloomington, IN (United States); Hoak, T. [Kestrel Geoscience, Littleton, CO (United States); Sundberg, K. [Phillips Petroleum Co., Bartlesville, OK (United States)

    1998-12-31

    The power of the reaction, transport, mechanical (RTM) modeling approach is that it directly uses the laws of geochemistry and geophysics to extrapolate fracture and other characteristics from the borehole or surface to the reservoir interior. The objectives of this facet of the project were to refine and test the viability of the basin/reservoir forward modeling approach to address fractured reservoir in E and P problems. The study attempts to resolve the following issues: role of fracturing and timing on present day location and characteristics; clarifying the roles and interplay of flexure dynamics, changing rock rheological properties, fluid pressuring and tectonic/thermal histories on present day reservoir location and characteristics; and test the integrated RTM modeling/geological data approach on a carbonate reservoir. Sedimentary, thermal and tectonic data from Andector Field, West Texas, were used as input to the RTM basin/reservoir simulator to predict its preproduction state. The results were compared with data from producing reservoirs to test the RTM modeling approach. The effects of production on the state of the field are discussed in a companion report. The authors draw the following conclusions: RTM modeling is an important new tool in fractured reservoir E and P analysis; the strong coupling of RTM processes and the geometric and tensorial complexity of fluid flow and stresses require the type of fully coupled, 3-D RTM model for fracture analysis as pioneered in this project; flexure analysis cannot predict key aspects of fractured reservoir location and characteristics; fracture history over the lifetime of a basin is required to understand the timing of petroleum expulsion and migration and the retention properties of putative reservoirs.

  7. Modeling the Risk of Commercial Failure for Hydraulic Fracturing Projects Due to Reservoir Heterogeneity

    Directory of Open Access Journals (Sweden)

    Hadi Parvizi

    2018-01-01

    Full Text Available Hydraulic fracturing technologies play a major role in the global energy supply and affect oil pricing. The current oil price fluctuations within 40 to 55 USD per barrel have caused diminished economical margins for hydraulic fracturing projects. Hence, successful decision making the for execution of hydraulic fracturing projects requires a higher level of integration of technical, commercial, and uncertainty analyses. However, the complexity of hydraulic fracturing modeling, and the sensitivity and the effects of uncertainty of reservoir heterogeneity on well performance renders the integration of such studies rather impractical. The impact of reservoir heterogeneity on hydraulic fracturing performance has been quantified by the introduction of Heterogeneity Impact Factor (HIF and formulas have been developed to forecast well performance using HIF. These advances provide a platform for introducing a practical approach for introducing the Risk of Commercial Failure (RCF due to reservoir heterogeneity in hydraulic fracturing projects. This paper defines such a parameter and the methodology to calculate it in a time-efficient manner. The proposed approach has been exercised on a real project in which a RCF of 20% is computed. The analysis also covers the sensitivity on Capital Expenditure (CAPEX, Operational Expenditure (OPEX, gas price, HIF and discount rate.

  8. An Efficient Upscaling Procedure Based on Stokes-Brinkman Model and Discrete Fracture Network Method for Naturally Fractured Carbonate Karst Reservoirs

    KAUST Repository

    Qin, Guan

    2010-01-01

    Naturally-fractured carbonate karst reservoirs are characterized by various-sized solution caves that are connected via fracture networks at multiple scales. These complex geologic features can not be fully resolved in reservoir simulations due to the underlying uncertainty in geologic models and the large computational resource requirement. They also bring in multiple flow physics which adds to the modeling difficulties. It is thus necessary to develop a method to accurately represent the effect of caves, fractures and their interconnectivities in coarse-scale simulation models. In this paper, we present a procedure based on our previously proposed Stokes-Brinkman model (SPE 125593) and the discrete fracture network method for accurate and efficient upscaling of naturally fractured carbonate karst reservoirs.

  9. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Seright, Randall S.

    2000-09-20

    This research project has three objectives. The first objective is to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective is to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective is to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consists of three tasks, each of which addresses one of the above objectives. This work is directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

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

    Directory of Open Access Journals (Sweden)

    Zhao Jinzhou

    2014-10-01

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

  11. Introduction to the appropriate-stimulation degree of hydraulic fracture networks in shale gas reservoirs

    Directory of Open Access Journals (Sweden)

    Yuzhang Liu

    2018-02-01

    Full Text Available Due to the limitation of actual shale gas reservoir conditions and fracturing technologies, artificial fracture networks are different greatly even in the same or similar stimulated reservoir volume. Deviations and even faults occur in evaluation and cognition if only the stimulated reservoir volume (SRV is used to characterize and evaluate the effect of stimulation. In this paper, the spatial distribution of artificial fractures and natural fractures and the internal pressure state and degree of reserve recovery of stimulated shale gas reservoirs were studied by means of artificial fracture propagation numerical simulation and production numerical simulation. And three concepts were proposed, i.e., shale gas fracture network, ideal fracture network and appropriate-stimulation degree of fracture network. The study results indicate that, at the end of reservoir development, target zones can be classified into three types (i.e., relatively appropriate stimulation zone, transitional stimulation zone, and uncompleted stimulation zone according to the recovery degree and production time of stimulated reservoirs; and that the final morphologic parameter of fracture networks and the reservoir characteristic are two main factors affecting the appropriate-stimulation degree of fracture networks. As for a specific gas reservoir, the orientation, length, conduction, height and spatial location of its fracture network are the main factors influencing its appropriate-stimulation degree if the well trajectory is set. The proposal of the theory on the appropriate-stimulation degree of hydraulic fracture networks in shale gas reservoir enriches the theoretical system of shale reservoir stimulation technology, and it can be used as the reference for characterizing the fracture systems in other unconventional reservoirs, such as tight oil and gas reservoirs. Keywords: Shale gas, Reservoir stimulation, Ideal fracture network, Appropriate-stimulation degree of

  12. Feasibility study on application of volume acid fracturing technology to tight gas carbonate reservoir development

    Directory of Open Access Journals (Sweden)

    Nianyin Li

    2015-09-01

    Full Text Available How to effectively develop tight-gas carbonate reservoir and achieve high recovery is always a problem for the oil and gas industry. To solve this problem, domestic petroleum engineers use the combination of the successful experiences of North American shale gas pools development by stimulated reservoir volume (SRV fracturing with the research achievements of Chinese tight gas development by acid fracturing to propose volume acid fracturing technology for fractured tight-gas carbonate reservoir, which has achieved a good stimulation effect in the pilot tests. To determine what reservoir conditions are suitable to carry out volume acid fracturing, this paper firstly introduces volume acid fracturing technology by giving the stimulation mechanism and technical ideas, and initially analyzes the feasibility by the comparison of reservoir characteristics of shale gas with tight-gas carbonate. Then, this paper analyzes the validity and limitation of the volume acid fracturing technology via the analyses of control conditions for volume acid fracturing in reservoir fracturing performance, natural fracture, horizontal principal stress difference, orientation of in-situ stress and natural fracture, and gives the solution for the limitation. The study results show that the volume acid fracturing process can be used to greatly improve the flow environment of tight-gas carbonate reservoir and increase production; the incremental or stimulation response is closely related with reservoir fracturing performance, the degree of development of natural fracture, the small intersection angle between hydraulic fracture and natural fracture, the large horizontal principal stress difference is easy to form a narrow fracture zone, and it is disadvantageous to create fracture network, but the degradable fiber diversion technology may largely weaken the disadvantage. The practices indicate that the application of volume acid fracturing process to the tight-gas carbonate

  13. Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

    Energy Technology Data Exchange (ETDEWEB)

    Groshong, R.H.; Pashin, J.C.; McIntyre, M.R. [University of Alabama, Tuscaloosa, AL (United States). Dept. of Geological Science

    2009-09-15

    Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same sigma(1) direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend.

  14. Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

    Science.gov (United States)

    Groshong, Richard H., Jr.; Pashin, Jack C.; McIntyre, Marcella R.

    2009-09-01

    Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same σ1 direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend.

  15. Shape factor for dual-permeability fractured reservoir simulation : Effect of non-uniform flow in 2D fracture network

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2016-01-01

    The flow properties of naturally fractured reservoirs are dominated by flow through the fractures. In a previous study we showed that even a well-connected fracture network behaves like a much sparser network when the aperture distribution is broad enough: i.e., most fractures can be eliminated

  16. An Embedded 3D Fracture Modeling Approach for Simulating Fracture-Dominated Fluid Flow and Heat Transfer in Geothermal Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Henry [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wang, Cong [Colorado School of Mines; Winterfeld, Philip [Colorado School of Mines; Wu, Yu-Shu [Colorado School of Mines

    2018-02-14

    An efficient modeling approach is described for incorporating arbitrary 3D, discrete fractures, such as hydraulic fractures or faults, into modeling fracture-dominated fluid flow and heat transfer in fractured geothermal reservoirs. This technique allows 3D discrete fractures to be discretized independently from surrounding rock volume and inserted explicitly into a primary fracture/matrix grid, generated without including 3D discrete fractures in prior. An effective computational algorithm is developed to discretize these 3D discrete fractures and construct local connections between 3D fractures and fracture/matrix grid blocks of representing the surrounding rock volume. The constructed gridding information on 3D fractures is then added to the primary grid. This embedded fracture modeling approach can be directly implemented into a developed geothermal reservoir simulator via the integral finite difference (IFD) method or with TOUGH2 technology This embedded fracture modeling approach is very promising and computationally efficient to handle realistic 3D discrete fractures with complicated geometries, connections, and spatial distributions. Compared with other fracture modeling approaches, it avoids cumbersome 3D unstructured, local refining procedures, and increases computational efficiency by simplifying Jacobian matrix size and sparsity, while keeps sufficient accuracy. Several numeral simulations are present to demonstrate the utility and robustness of the proposed technique. Our numerical experiments show that this approach captures all the key patterns about fluid flow and heat transfer dominated by fractures in these cases. Thus, this approach is readily available to simulation of fractured geothermal reservoirs with both artificial and natural fractures.

  17. On-line Optimization-Based Simulators for Fractured and Non-fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Milind D. Deo

    2005-08-31

    Oil field development is a multi-million dollar business. Reservoir simulation is often used to guide the field management and development process. Reservoir characterization and geologic modeling tools have become increasingly sophisticated. As a result the geologic models produced are complex. Most reservoirs are fractured to a certain extent. The new geologic characterization methods are making it possible to map features such as faults and fractures, field-wide. Significant progress has been made in being able to predict properties of the faults and of the fractured zones. Traditionally, finite difference methods have been employed in discretizing the domains created by geologic means. For complex geometries, finite-element methods of discretization may be more suitable. Since reservoir simulation is a mature science, some of the advances in numerical methods (linear, nonlinear solvers and parallel computing) have not been fully realized in the implementation of most of the simulators. The purpose of this project was to address some of these issues. {sm_bullet} One of the goals of this project was to develop a series of finite-element simulators to handle problems of complex geometry, including systems containing faults and fractures. {sm_bullet} The idea was to incorporate the most modern computing tools; use of modular object-oriented computer languages, the most sophisticated linear and nonlinear solvers, parallel computing methods and good visualization tools. {sm_bullet} One of the tasks of the project was also to demonstrate the construction of fractures and faults in a reservoir using the available data and to assign properties to these features. {sm_bullet} Once the reservoir model is in place, it is desirable to find the operating conditions, which would provide the best reservoir performance. This can be accomplished by utilization optimization tools and coupling them with reservoir simulation. Optimization-based reservoir simulation was one of the

  18. Productivity model for gas reservoirs with open-hole multi-fracturing horizontal wells and optimization of hydraulic fracture parameters

    Directory of Open Access Journals (Sweden)

    Jianqiang Xue

    2017-12-01

    Full Text Available Multi-fractured horizontal wells are commonly employed to improve the productivity of low and ultra-low permeability gas reservoirs. However, conventional productivity models for open-hole multi-fractured horizontal wells do not consider the interferences between hydraulic fractures and the open-hole segments, resulting in significant errors in calculation results. In this article, a novel productivity prediction model for gas reservoirs with open-hole multi-fractured horizontal wells was proposed based on complex potential theories, potential superimposition, and numerical analysis. Herein, an open-hole segment between two adjacent fractures was regarded as an equivalent fracture, which was discretized as in cases of artificial fractures. The proposed model was then applied to investigate the effects of various parameters, such as the angle between the fracture and horizontal shaft, fracture quantity, fracture length, diversion capacity of fractures, horizontal well length, and inter-fracture distance, on the productivity of low permeability gas reservoirs with multi-fractured horizontal wells. Simulation results revealed that the quantity, length, and distribution of fractures had significant effects on the productivity of low permeability gas reservoirs while the effects of the diversion capacity of fractures and the angle between the fracture and horizontal shaft were negligible. Additionally, a U-shaped distribution of fracture lengths was preferential as the quantity of fractures at shaft ends was twice that in the middle area. Keywords: Low permeability gas reservoir, Multi-fractured horizontal well, Productivity prediction, Open-hole completion, Unsteady-state flow, Fracture parameters optimization

  19. Simulation studies to evaluate the effect of fracture closure on the performance of fractured reservoirs; Final report

    Energy Technology Data Exchange (ETDEWEB)

    Howrie, I.; Dauben, D.

    1994-03-01

    A three-year research program to evaluate the effect of fracture closure on the recovery of oil and gas from naturally fractured reservoirs has been completed. The overall objectives of the study were to: (1) evaluate the reservoir conditions for which fracture closure is significant, and (2) evaluate innovative fluid injection techniques capable of maintaining pressure within the reservoir. The evaluations of reservoir performance were made by a modern dual porosity simulator, TETRAD. This simulator treats both porosity and permeability as functions of pore pressure. The Austin Chalk in the Pearsall Field in of South Texas was selected as the prototype fractured reservoir for this work. During the first year, simulations of vertical and horizontal well performance were made assuming that fracture permeability was insensitive to pressure change. Sensitivity runs indicated that the simulator was predicting the effects of critical reservoir parameters in a logical and consistent manner. The results confirmed that horizontal wells could increase both rate of oil recovery and total oil recovery from naturally fractured reservoirs. In the second year, the performance of the same vertical and horizontal wells was reevaluated with fracture permeability treated as a function of reservoir pressure. To investigate sensitivity to in situ stress, differing loading conditions were assumed. Simulated natural depletions confirm that pressure sensitive fractures degrade well performance. The severity of degradation worsens when the initial reservoir pressure approaches the average stress condition of the reservoir, such as occurs in over pressured reservoirs. Simulations with water injection indicate that degradation of permeability can be counteracted when reservoir pressure is maintained and oil recovery can be increased when reservoir properties are favorable.

  20. Fracture detection, mapping, and analysis of naturally fractured gas reservoirs using seismic technology. Final report, November 1995

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-10-01

    Many basins in the Rocky Mountains contain naturally fractured gas reservoirs. Production from these reservoirs is controlled primarily by the shape, orientation and concentration of the natural fractures. The detection of gas filled fractures prior to drilling can, therefore, greatly benefit the field development of the reservoirs. The objective of this project was to test and verify specific seismic methods to detect and characterize fractures in a naturally fractured reservoir. The Upper Green River tight gas reservoir in the Uinta Basin, Northeast Utah was chosen for the project as a suitable reservoir to test the seismic technologies. Knowledge of the structural and stratigraphic geologic setting, the fracture azimuths, and estimates of the local in-situ stress field, were used to guide the acquisition and processing of approximately ten miles of nine-component seismic reflection data and a nine-component Vertical Seismic Profile (VSP). Three sources (compressional P-wave, inline shear S-wave, and cross-line, shear S-wave) were each recorded by 3-component (3C) geophones, to yield a nine-component data set. Evidence of fractures from cores, borehole image logs, outcrop studies, and production data, were integrated with the geophysical data to develop an understanding of how the seismic data relate to the fracture network, individual well production, and ultimately the preferred flow direction in the reservoir. The multi-disciplinary approach employed in this project is viewed as essential to the overall reservoir characterization, due to the interdependency of the above factors.

  1. FRACTURED RESERVOIR E&P IN ROCKY MOUNTAIN BASINS: A 3-D RTM MODELING APPROACH

    Energy Technology Data Exchange (ETDEWEB)

    P. Ortoleva; J. Comer; A. Park; D. Payne; W. Sibo; K. Tuncay

    2001-11-26

    Key natural gas reserves in Rocky Mountain and other U.S. basins are in reservoirs with economic producibility due to natural fractures. In this project, we evaluate a unique technology for predicting fractured reservoir location and characteristics ahead of drilling based on a 3-D basin/field simulator, Basin RTM. Recommendations are made for making Basin RTM a key element of a practical E&P strategy. A myriad of reaction, transport, and mechanical (RTM) processes underlie the creation, cementation and preservation of fractured reservoirs. These processes are often so strongly coupled that they cannot be understood individually. Furthermore, sedimentary nonuniformity, overall tectonics and basement heat flux histories make a basin a fundamentally 3-D object. Basin RTM is the only 3-D, comprehensive, fully coupled RTM basin simulator available for the exploration of fractured reservoirs. Results of Basin RTM simulations are presented, that demonstrate its capabilities and limitations. Furthermore, it is shown how Basin RTM is a basis for a revolutionary automated methodology for simultaneously using a range of remote and other basin datasets to locate reservoirs and to assess risk. Characteristics predicted by our model include reserves and composition, matrix and fracture permeability, reservoir rock strength, porosity, in situ stress and the statistics of fracture aperture, length and orientation. Our model integrates its input data (overall sedimentation, tectonic and basement heat flux histories) via the laws of physics and chemistry that describe the RTM processes to predict reservoir location and characteristics. Basin RTM uses 3-D, finite element solutions of the equations of rock mechanics, organic and inorganic diagenesis and multi-phase hydrology to make its predictions. As our model predicts reservoir characteristics, it can be used to optimize production approaches (e.g., assess the stability of horizontal wells or vulnerability of fractures to

  2. Natural-Fracture Reactivation in Shale Gas Reservoir and Resulting Microseismicity

    NARCIS (Netherlands)

    Shahid, A.S.A.; Wassing, B.B.T.; Fokker, P.A.; Verga, F.

    2015-01-01

    A geomechanical and fluid-flow coupled model was developed to simulate natural-fracture-network reactivation during hydraulicfracturing treatments in shale gas reservoirs. The fractures were modelled using the continuum approach in a commercial finitedifference code, labeled the "softening

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

    Science.gov (United States)

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

    2018-01-01

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

  4. Modelling of fractured reservoirs. Case of multi-scale media; Modelisation des reservoirs fractures. Cas des milieux multi-echelles

    Energy Technology Data Exchange (ETDEWEB)

    Henn, N.

    2000-12-13

    Some of the most productive oil and gas reservoirs are found in formations crossed by multi-scale fractures/faults. Among them, conductive faults may closely control reservoir performance. However, their modelling encounters numerical and physical difficulties linked with (a) the necessity to keep an explicit representation of faults through small-size grid blocks, (b) the modelling of multiphase flow exchanges between the fault and the neighbouring medium. In this thesis, we propose a physically-representative and numerically efficient modelling approach in order to incorporate sub-vertical conductive faults in single and dual-porosity simulators. To validate our approach and demonstrate its efficiency, simulation results of multiphase displacements in representative field sector models are presented. (author)

  5. On the evaluation of steam assisted gravity drainage in naturally fractured oil reservoirs

    Directory of Open Access Journals (Sweden)

    Seyed Morteza Tohidi Hosseini

    2017-06-01

    Full Text Available Steam Assisted Gravity Drainage (SAGD as a successful enhanced oil recovery (EOR process has been applied to extract heavy and extra heavy oils. Huge amount of global heavy oil resources exists in carbonate reservoirs which are mostly naturally fractured reservoirs. Unlike clastic reservoirs, few studies were carried out to determine the performance of SAGD in carbonate reservoirs. Even though SAGD is a highly promising technique, several uncertainties and unanswered questions still exist and they should be clarified for expansion of SAGD methods to world wide applications especially in naturally fractured reservoirs. In this communication, the effects of some operational and reservoir parameters on SAGD processes were investigated in a naturally fractured reservoir with oil wet rock using CMG-STARS thermal simulator. The purpose of this study was to investigate the role of fracture properties including fracture orientation, fracture spacing and fracture permeability on the SAGD performance in naturally fractured reservoirs. Moreover, one operational parameter was also studied; one new well configuration, staggered well pair was evaluated. Results indicated that fracture orientation influences steam expansion and oil production from the horizontal well pairs. It was also found that horizontal fractures have unfavorable effects on oil production, while vertical fractures increase the production rate for the horizontal well. Moreover, an increase in fracture spacing results in more oil production, because in higher fracture spacing model, steam will have more time to diffuse into matrices and heat up the entire reservoir. Furthermore, an increase in fracture permeability results in process enhancement and ultimate recovery improvement. Besides, diagonal change in the location of injection wells (staggered model increases the recovery efficiency in long-term production plan.

  6. Modeling flow in naturally fractured reservoirs : effect of fracture aperture distribution on dominant sub-network for flow

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2017-01-01

    Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture

  7. New boundary conditions for oil reservoirs with fracture

    Science.gov (United States)

    Andriyanova, Elena; Astafev, Vladimir

    2017-06-01

    Based on the fact that most of oil fields are on the late stage of field development, it becomes necessary to produce hard-to-extract oil, which can be obtained only by use of enhance oil recovery methods. For example many low permeable or shale formations can be developed only with application of massive hydraulic fracturing technique. In addition, modern geophysical researches show that mostly oil bearing formations are complicated with tectonic faults of different shape and permeability. These discontinuities exert essential influence on the field development process and on the well performance. For the modeling of fluid flow in the reservoir with some area of different permeability, we should determine the boundary conditions. In this article for the first time the boundary conditions for the problem of fluid filtration in the reservoir with some discontinuity are considered. This discontinuity represents thin but long area, which can be hydraulic fracturing of tectonic fault. The obtained boundary condition equations allow us to take into account pressure difference above and below the section and different values of permeability.

  8. Fractured reservoir discrete feature network technologies. Annual report, March 7, 1996--February 28, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Dershowitz, W.S.; La Pointe, P.R.; Einstein, H.H.; Ivanova, V.

    1998-01-01

    This report describes progress on the project, {open_quotes}Fractured Reservoir Discrete Feature Network Technologies{close_quotes} during the period March 7, 1996 to February 28, 1997. The report presents summaries of technology development for the following research areas: (1) development of hierarchical fracture models, (2) fractured reservoir compartmentalization and tributary volume, (3) fractured reservoir data analysis, and (4) integration of fractured reservoir data and production technologies. In addition, the report provides information on project status, publications submitted, data collection activities, and technology transfer through the world wide web (WWW). Research on hierarchical fracture models included geological, mathematical, and computer code development. The project built a foundation of quantitative, geological and geometrical information about the regional geology of the Permian Basin, including detailed information on the lithology, stratigraphy, and fracturing of Permian rocks in the project study area (Tracts 17 and 49 in the Yates field). Based on the accumulated knowledge of regional and local geology, project team members started the interpretation of fracture genesis mechanisms and the conceptual modeling of the fracture system in the study area. Research on fractured reservoir compartmentalization included basic research, technology development, and application of compartmentalized reservoir analyses for the project study site. Procedures were developed to analyze compartmentalization, tributary drainage volume, and reservoir matrix block size. These algorithms were implemented as a Windows 95 compartmentalization code, FraCluster.

  9. Analysis of multi-factor coupling effect on hydraulic fracture network in shale reservoirs

    Directory of Open Access Journals (Sweden)

    Yuzhang Liu

    2015-03-01

    Full Text Available Based on the research results of lab triaxial hydraulic fracturing simulation experiments, field fracturing practice, and theory analysis, the factors affecting the growth of hydraulic fracture network in shale reservoirs, including brittleness, difference of horizontal stress, distribution and mechanical characteristics of natural fractures, fluid viscosity and fracturing parameters, etc are analyzed in this study. The results show that the growth of fracture network in shale reservoirs is affected by geological factors and engineering factors jointly. From the perspective of reservoir geological factors, the higher the rock brittleness, the more developed the natural fractures, and the poorer the natural fracture consolidation, the more likely hydraulic fracture network will be formed. From the perspective of fracturing engineering factors, lower fluid viscosity and larger fracturing scale will be more helpful to the formation of extensive fracture network. On the basis of the analysis of single factors, a multi-factor coupling index has been established to characterize the growth degree of hydraulic fracture network and evaluate the complexity of hydraulic fractures after the fracturing of shale reservoirs.

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

    Energy Technology Data Exchange (ETDEWEB)

    David S. Schechter

    2005-04-27

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

  11. Performance Analysis of Fractured Wells with Stimulated Reservoir Volume in Coal Seam Reservoirs

    Directory of Open Access Journals (Sweden)

    Yu-long Zhao

    2016-01-01

    Full Text Available CoalBed Methane (CBM, as one kind of unconventional gas, is an important energy resource, attracting industry interest in research and development. Using the Langmuir adsorption isotherm, Fick’s law in the matrix and Darcy flow in cleat fractures, and treating the Stimulated Reservoir Volume (SRV induced by hydraulic fracturing as a radial composite model, the continuous linear source function with constant production is derived by the methods of the Laplace transform and Duhamel theory. Based on the linear source function, semi-analytical solutions are obtained for a fractured vertical well producing at a constant production rate or constant bottom-hole pressure. With the help of the Stehfest numerical algorithm and computer programing, the well test and rate decline type curves are obtained, and the key flow regimes of fractured CBM wells are: wellbore storage, linear flow in SRV region, diffusion flow and later pseudo-radial flow. Finally, we analyze the effect of various parameters, such as the Langmuir volume, radius and permeability in the SRV region, on the production performance. The research results concluded in this paper have significant importance in terms of the development, well test interpretations and production performance analysis of unconventional gas.

  12. Stress-Induced Fracturing of Reservoir Rocks: Acoustic Monitoring and μCT Image Analysis

    Science.gov (United States)

    Pradhan, Srutarshi; Stroisz, Anna M.; Fjær, Erling; Stenebråten, Jørn F.; Lund, Hans K.; Sønstebø, Eyvind F.

    2015-11-01

    Stress-induced fracturing in reservoir rocks is an important issue for the petroleum industry. While productivity can be enhanced by a controlled fracturing operation, it can trigger borehole instability problems by reactivating existing fractures/faults in a reservoir. However, safe fracturing can improve the quality of operations during CO2 storage, geothermal installation and gas production at and from the reservoir rocks. Therefore, understanding the fracturing behavior of different types of reservoir rocks is a basic need for planning field operations toward these activities. In our study, stress-induced fracturing of rock samples has been monitored by acoustic emission (AE) and post-experiment computer tomography (CT) scans. We have used hollow cylinder cores of sandstones and chalks, which are representatives of reservoir rocks. The fracture-triggering stress has been measured for different rocks and compared with theoretical estimates. The population of AE events shows the location of main fracture arms which is in a good agreement with post-test CT image analysis, and the fracture patterns inside the samples are visualized through 3D image reconstructions. The amplitudes and energies of acoustic events clearly indicate initiation and propagation of the main fractures. Time evolution of the radial strain measured in the fracturing tests will later be compared to model predictions of fracture size.

  13. Statistical analysis of surface lineaments and fractures for characterizing naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Genliang; George, S.A.; Lindsey, R.P.

    1997-08-01

    Thirty-six sets of surface lineaments and fractures mapped from satellite images and/or aerial photos from parts of the Mid-continent and Colorado Plateau regions were collected, digitized, and statistically analyzed in order to obtain the probability distribution functions of natural fractures for characterizing naturally fractured reservoirs. The orientations and lengths of the surface linear features were calculated using the digitized coordinates of the two end points of each individual linear feature. The spacing data of the surface linear features within an individual set were, obtained using a new analytical sampling technique. Statistical analyses were then performed to find the best-fit probability distribution functions for the orientation, length, and spacing of each data set. Twenty-five hypothesized probability distribution functions were used to fit each data set. A chi-square goodness-of-fit test was used to rank the significance of each fit. A distribution which provides the lowest chi-square goodness-of-fit value was considered the best-fit distribution. The orientations of surface linear features were best-fitted by triangular, normal, or logistic distributions; the lengths were best-fitted by PearsonVI, PearsonV, lognormal2, or extreme-value distributions; and the spacing data were best-fitted by lognormal2, PearsonVI, or lognormal distributions. These probability functions can be used to stochastically characterize naturally fractured reservoirs.

  14. Structural analysis of a fractured basement reservoir, central Yemen

    Science.gov (United States)

    Veeningen, Resi; Rice, Hugh; Schneider, Dave; Grasemann, Bernhard; Decker, Kurt

    2013-04-01

    The Pan-African Arabian-Nubian Shield (ANS), within which Yemen lies, formed as a result of Neoproterozoic collisional events between c. 870-550 Ma. Several subsequent phases of extension occurred, from the Mesozoic (due to the breakup of Gondwana) to the Recent (forming the Gulf of Aden and the Red Sea). These resulted in the formation of numerous horst- and-graben structures and the development of fractured basement reservoirs in the southeast part of the ANS. Two drill cores from the Mesozoic Marib-Shabwa Basin, central Yemen, penetrated the upper part of the Pan-African basement. The cores show both a lithological and structural inhomogeneity, with variations in extension-related deformation structures such as dilatational breccias, open fractures and closed veins. At least three deformation events have been recognized: D1) Ductile to brittle NW-SE directed faulting during cooling of a granitic pluton. U-Pb zircon ages revealed an upper age limit for granite emplacement at 627±3.5 Ma. As these structures show evidence for ductile deformation, this event must have occurred during the Ediacaran, shortly after intrusion, since Rb/Sr and (U-Th)/He analyses show that subsequent re-heating of the basement did not take place. D2) The development of shallow dipping, NNE-SSW striking extensional faults that formed during the Upper Jurassic, simultaneously with the formation of the Marib-Shabwa Basin. These fractures are regularly cross-cut by D3. D3) Steeply dipping NNE-SSW to ENE-WSW veins that are consistent with the orientation of the opening of the Gulf of Aden. These faults are the youngest structures recognized. The formation of ductile to brittle faults in the granite (D1) resulted in a hydrothermally altered zone ca. 30 cm wide replacing (mainly) plagioclase with predominantly chlorite, as well as kaolinite and heavy element minerals such as pyrite. The alteration- induced porosity has an average value of 20%, indicating that the altered zone is potentially a

  15. Multi-zone coupling productivity of horizontal well fracturing with complex fracture networks in shale gas reservoirs

    Directory of Open Access Journals (Sweden)

    Weiyao Zhu

    2018-02-01

    Full Text Available In this paper, a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro pores–complex fracture networks–wellbore during the development of shale reservoirs by means of horizontal well fracturing. First, hydraulic fractures were induced by means of Brazilian splitting tests. Second, the forms of the hydraulic fractures inside the rock samples were observed by means of X-ray CT scanning to measure the opening of hydraulic fractures. Third, based on the multi-scale unified flowing model, morphological description of fractures and gas flowing mechanism in the matrix–complex fracture network–wellbore, the productivity equation of single-stage horizontal well fracturing which includes diffusion, slipping and desorption was established. And fourthly, a productivity prediction model of horizontal well multi-stage fracturing in the shale reservoir was established considering the interference between the multi-stage fracturing zones and the pressure drop in the horizontal wellbore. The following results were obtained. First, hydraulic fractures are in the form of a complex network. Second, the measured opening of hydraulic fractures is in the range of 4.25–453 μm, averaging 112 μm. Third, shale gas flowing in different shapes of fracture networks follows different nonlinear flowing laws. Forth, as the fracture density in the strongly stimulated zones rises and the distribution range of the hydraulic fractures in strongly/weakly stimulated zones enlarges, gas production increases gradually. As the interference occurs in the flowing zones of fracture networks between fractured sections, the increasing amplitude of gas production rates decreases. Fifth, when the length of a simulated horizontal well is 1500 m and the half length of a fracture network in the strongly stimulated zone is 100 m, the productivity effect of stage 10 fracturing is the

  16. Reservoir Characterization and Flow Simulation for CO 2-EOR in the Tensleep Formation Using Discrete Fracture Networks, Teapot Dome, Wyoming

    Science.gov (United States)

    Kavousi Ghahfarokhi, Payam

    The Tensleep oil reservoir at Teapot Dome, Wyoming, USA, is a naturally fractured tight sandstone reservoir that has been considered for carbon-dioxide enhanced oil recovery (CO2-EOR) and sequestration. CO2-EOR analysis requires a thorough understanding of the Tensleep fracture network. Wireline image logs from the field suggest that the reservoir fracture network is dominated by early formed structural hinge oblique fractures with interconnectivity enhanced by hinge parallel and hinge perpendicular fracture sets. Available post stack 3D seismic data are used to generate a seismic fracture intensity attribute for the reservoir fracture network. The resulting seismic fracture intensity is qualitatively correlated to the field production history. Wells located on hinge-oblique discontinuities are more productive than other wells in the field. We use Oda's method to upscale the fracture permeabilities in the discrete fracture network for use in a dual porosity fluid flow simulator. We analytically show that Oda's method is sensitive to the grid orientation relative to fracture set strike. Results show that the calculated permeability tensors have maximum geometric mean for the non-zero permeability components (kxx,kyy,kzz,kxy) when the dominant fracture set cuts diagonally through the grid cell at 45° relative to the grid cell principal directions (i,j). The geometric mean of the permeability tensor components falls to a minimum when the dominant fracture set is parallel to either grid wall (i or j principal directions). The latter case has off-diagonal permeability terms close to zero. We oriented the Tensleep reservoir grid to N72°W to minimize the off-diagonal permeability terms. The seismic fracture intensity attribute is then used to generate a realization of the reservoir fracture network. Subsequently, fracture properties are upscaled to the reservoir grid scale for a fully compositional flow simulation. We implemented a PVT analysis using CO2 swelling test

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

    Directory of Open Access Journals (Sweden)

    REZA MASOOMI

    2017-01-01

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

  18. Formation Damage due to Drilling and Fracturing Fluids and Its Solution for Tight Naturally Fractured Sandstone Reservoirs

    Directory of Open Access Journals (Sweden)

    Tianbo Liang

    2017-01-01

    Full Text Available Drilling and fracturing fluids can interact with reservoir rock and cause formation damage that impedes hydrocarbon production. Tight sandstone reservoir with well-developed natural fractures has a complex pore structure where pores and pore throats have a wide range of diameters; formation damage in such type of reservoir can be complicated and severe. Reservoir rock samples with a wide range of fracture widths are tested through a multistep coreflood platform, where formation damage caused by the drilling and/or fracturing fluid is quantitatively evaluated and systematically studied. To further mitigate this damage, an acidic treating fluid is screened and evaluated using the same coreflood platform. Experimental results indicate that the drilling fluid causes the major damage, and the chosen treating fluid can enhance rock permeability both effectively and efficiently at least at the room temperature with the overburden pressure.

  19. Fractured reservoir history matching improved based on artificial intelligent

    Directory of Open Access Journals (Sweden)

    Sayyed Hadi Riazi

    2016-12-01

    Full Text Available In this paper, a new robust approach based on Least Square Support Vector Machine (LSSVM as a proxy model is used for an automatic fractured reservoir history matching. The proxy model is made to model the history match objective function (mismatch values based on the history data of the field. This model is then used to minimize the objective function through Particle Swarm Optimization (PSO and Imperialist Competitive Algorithm (ICA. In automatic history matching, sensitive analysis is often performed on full simulation model. In this work, to get new range of the uncertain parameters (matching parameters in which the objective function has a minimum value, sensitivity analysis is also performed on the proxy model. By applying the modified ranges to the optimization methods, optimization of the objective function will be faster and outputs of the optimization methods (matching parameters are produced in less time and with high precision. This procedure leads to matching of history of the field in which a set of reservoir parameters is used. The final sets of parameters are then applied for the full simulation model to validate the technique. The obtained results show that the present procedure in this work is effective for history matching process due to its robust dependability and fast convergence speed. Due to high speed and need for small data sets, LSSVM is the best tool to build a proxy model. Also the comparison of PSO and ICA shows that PSO is less time-consuming and more effective.

  20. Integrated detection of fractures and caves in carbonate fractured-vuggy reservoirs based on seismic data and well data

    Science.gov (United States)

    Cao, Zhanning; Li, Xiangyang; Sun, Shaohan; Liu, Qun; Deng, Guangxiao

    2018-04-01

    Aiming at the prediction of carbonate fractured-vuggy reservoirs, we put forward an integrated approach based on seismic and well data. We divide a carbonate fracture-cave system into four scales for study: micro-scale fracture, meso-scale fracture, macro-scale fracture and cave. Firstly, we analyze anisotropic attributes of prestack azimuth gathers based on multi-scale rock physics forward modeling. We select the frequency attenuation gradient attribute to calculate azimuth anisotropy intensity, and we constrain the result with Formation MicroScanner image data and trial production data to predict the distribution of both micro-scale and meso-scale fracture sets. Then, poststack seismic attributes, variance, curvature and ant algorithms are used to predict the distribution of macro-scale fractures. We also constrain the results with trial production data for accuracy. Next, the distribution of caves is predicted by the amplitude corresponding to the instantaneous peak frequency of the seismic imaging data. Finally, the meso-scale fracture sets, macro-scale fractures and caves are combined to obtain an integrated result. This integrated approach is applied to a real field in Tarim Basin in western China for the prediction of fracture-cave reservoirs. The results indicate that this approach can well explain the spatial distribution of carbonate reservoirs. It can solve the problem of non-uniqueness and improve fracture prediction accuracy.

  1. Incorporating Scale-Dependent Fracture Stiffness for Improved Reservoir Performance Prediction

    Science.gov (United States)

    Crawford, B. R.; Tsenn, M. C.; Homburg, J. M.; Stehle, R. C.; Freysteinson, J. A.; Reese, W. C.

    2017-12-01

    We present a novel technique for predicting dynamic fracture network response to production-driven changes in effective stress, with the potential for optimizing depletion planning and improving recovery prediction in stress-sensitive naturally fractured reservoirs. A key component of the method involves laboratory geomechanics testing of single fractures in order to develop a unique scaling relationship between fracture normal stiffness and initial mechanical aperture. Details of the workflow are as follows: tensile, opening mode fractures are created in a variety of low matrix permeability rocks with initial, unstressed apertures in the micrometer to millimeter range, as determined from image analyses of X-ray CT scans; subsequent hydrostatic compression of these fractured samples with synchronous radial strain and flow measurement indicates that both mechanical and hydraulic aperture reduction varies linearly with the natural logarithm of effective normal stress; these stress-sensitive single-fracture laboratory observations are then upscaled to networks with fracture populations displaying frequency-length and length-aperture scaling laws commonly exhibited by natural fracture arrays; functional relationships between reservoir pressure reduction and fracture network porosity, compressibility and directional permeabilities as generated by such discrete fracture network modeling are then exported to the reservoir simulator for improved naturally fractured reservoir performance prediction.

  2. Using outcrop data for geological well test modelling in fractured reservoirs

    NARCIS (Netherlands)

    Aljuboori, F.; Corbett, P.; Bisdom, K.; Bertotti, G.; Geiger, S.

    2015-01-01

    Outcrop fracture data sets can now be acquired with ever more accuracy using drone technology augmented by field observations. These models can be used to form realistic, deterministic models of fractured reservoirs. Fractured well test models are traditionally seen to be finite or infinite

  3. Seismic signatures of the Lodgepole fractured reservoir in Utah-Wyoming overthrust belt

    Energy Technology Data Exchange (ETDEWEB)

    Parra, J.; Collier, H.; Angstman, B.

    1997-08-01

    In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based upon the effects of such conditions on the propagation of acoustic and seismic waves in the rock. We present the feasibility of using seismic measurement techniques to map the fracture zones between wells spaced 2400 ft at depths of about 1000 ft. For this purpose we constructed computer models (which include azimuthal anisotropy) using Lodgepole reservoir parameters to predict seismic signatures recorded at the borehole scale, crosswell scale, and 3 D seismic scale. We have integrated well logs with existing 2D surfaces seismic to produce petrophysical and geological cross sections to determine the reservoir parameters and geometry for the computer models. In particular, the model responses are used to evaluate if surface seismic and crosswell seismic measurements can capture the anisotropy due to vertical fractures. Preliminary results suggested that seismic waves transmitted between two wells will propagate in carbonate fracture reservoirs, and the signal can be received above the noise level at the distance of 2400 ft. In addition, the large velocities contrast between the main fracture zone and the underlying unfractured Boundary Ridge Member, suggested that borehole reflection imaging may be appropriate to map and fracture zone thickness variation and fracture distributions in the reservoir.

  4. Using microstructure observations to quantify fracture properties and improve reservoir simulations. Final report, September 1998

    Energy Technology Data Exchange (ETDEWEB)

    Laubach, S.E.; Marrett, R.; Rossen, W.; Olson, J.; Lake, L.; Ortega, O.; Gu, Y.; Reed, R.

    1999-01-01

    The research for this project provides new technology to understand and successfully characterize, predict, and simulate reservoir-scale fractures. Such fractures have worldwide importance because of their influence on successful extraction of resources. The scope of this project includes creation and testing of new methods to measure, interpret, and simulate reservoir fractures that overcome the challenge of inadequate sampling. The key to these methods is the use of microstructures as guides to the attributes of the large fractures that control reservoir behavior. One accomplishment of the project research is a demonstration that these microstructures can be reliably and inexpensively sampled. Specific goals of this project were to: create and test new methods of measuring attributes of reservoir-scale fractures, particularly as fluid conduits, and test the methods on samples from reservoirs; extrapolate structural attributes to the reservoir scale through rigorous mathematical techniques and help build accurate and useful 3-D models of the interwell region; and design new ways to incorporate geological and geophysical information into reservoir simulation and verify the accuracy by comparison with production data. New analytical methods developed in the project are leading to a more realistic characterization of fractured reservoir rocks. Testing diagnostic and predictive approaches was an integral part of the research, and several tests were successfully completed.

  5. Enhanced oil recovery in naturally fractured reservoirs in mexico, technical challenge

    Energy Technology Data Exchange (ETDEWEB)

    Garcia H, Francisco; Meza P, Edgar; Moran O, Oscar [PEMEX - Petroleos Mexicanos, Mexico D.F. (Mexico)

    2008-07-01

    Unlike single porosity reservoirs, naturally fractured reservoirs have several problems to implant any additional recovery processes (secondary or enhanced) due to a great amount of oil is trapped in the matrix and the injected fluids bypass matrix through fractures because of they have a greater capacity to allow flow. So far there, there is not a complete knowledge of improved recovery processes that can be applied to naturally fractured reservoirs, there are some laboratory tests, tests pilot in fields and very few projects in execution. All this make an opportunity area to develop more investigation. Taking into account the previous limitations is possible to begin to evaluate several processes for naturally fractured reservoirs as: gas injection, chemical treatments and thermal processes, but a common process to all of them is gravity drainage which implies new considerations in operation to extract hydrocarbons of the fractured reservoirs. There are many challenges to implant additional recovery processes in naturally fractured reservoirs and we mentioned in this work, moreover we show Mexican experience in EOR processes in Naturally Fractured Reservoirs, too. (author)

  6. Production performance laws of vertical wells by volume fracturing in CBM reservoirs

    Directory of Open Access Journals (Sweden)

    Liehui Zhang

    2017-05-01

    Full Text Available Volume fracturing technology has been widely applied in the development of coalbed methane (CBM reservoirs. As for the stimulated reservoir volume (SRV created by volume fracturing, the seepage laws of fluids are described more accurately and rationally in the rectangular composite model than in the traditional radial composite model. However, the rectangular composite model considering SRV cannot be solved using the analytical or semi-analytical function method, and its solution from the linear flow model has larger errors. In view of this, SRV areas of CBM reservoirs were described by means of dual-medium model in this paper. The complex CBM migration mechanisms were investigated comprehensively, including adsorption, desorption, diffusion and seepage. A well testing model for rectangular composite fracturing wells in CBM reservoirs based on unsteady-state diffusion was built and solved using the boundary element method combined with Laplace transformation, Stehfest numerical inversion and computer programming technology. Thus, production performance laws of CBM reservoirs were clarified. The flow regimes of typical well testing curves were divided and the effects on change laws of production performance from the boundary size of gas reservoirs, permeability of volume fractured areas, adsorption gas content, reservoir permeability and SRV size were analyzed. Eventually, CBM reservoirs after the volume fracturing stimulation were described more accurately and rationally. This study provides a theoretical basis for a better understanding of the CBM migration laws and an approach to evaluating and developing CBM reservoirs efficiently and rationally.

  7. Results of high resolution seismic imaging experiments for defining permeable pathways in fractured gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Majer, E.L.; Peterson, J.E.; Daley, T. [and others

    1997-10-01

    As part of its Department of Energy (DOE) Industry cooperative program in oil and gas, Berkeley Lab has an ongoing effort in cooperation with Industry partners to develop equipment, field techniques, and interpretational methods to further the practice of characterizing fractured heterogeneous reservoirs. The goal of this work is to demonstrate the combined use of state-of-the-art technology in fluid flow modeling and geophysical imaging into an interdisciplinary approach for predicting the behavior of heterogeneous fractured gas reservoirs. The efforts in this program have mainly focused on using seismic methods linked with geologic and reservoir engineering analysis for the detection and characterization of fracture systems in tight gas formations, i.e., where and how to detect the fractures, what are the characteristics of the fractures, and how the fractures interact with the natural stresses, lithology, and their effect on reservoir performance. The project has also integrated advanced reservoir engineering methods for analyzing flow in fractured systems such that reservoir management strategies can be optimized. The work at Berkeley Lab focuses on integrating high resolution seismic imaging, (VSP, crosswell, and single well imaging), geologic information and well test data to invert for flow paths in fractured systems.

  8. Experimental analysis of multiple factors on hydraulic fracturing in coalbed methane reservoirs.

    Science.gov (United States)

    Zhang, Fan; Ma, Geng; Liu, Xiao; Tao, Yunqi; Feng, Dan; Li, Rui

    2018-01-01

    Hydraulic fracturing can improve the permeability of coalbed methane (CBM) reservoirs effectively, which is of great significance to the commercial production of CBM. However, the efficiency of hydraulic fracturing is affected by multiple factors. The mechanism of fracture initiation, morphology and propagation in CBM reservoirs is not clear and need to be further explored. Hydraulic fracturing experiment is an accurate tool to explore these mechanisms. The quantity of experimental coal rock is large and processing method is complex, so specimen made of similar materials was applied to replace coal rock. The true triaxial hydraulic fracturing experimental apparatus, 3D scanning device for coal rock section were applied to carry out hydraulic fracturing experiment. The results show that the initiation pressure is inversely proportional to the horizontal stress difference (Δσ) and positively related to fracturing fluid injection rate. When vertical stress (σv) is constant, the initiation pressure and fracture width decrease with the increasing of Δσ. Natural fractures can be connected by main fracture when propagates perpendicular to the direction of minimum horizontal stress (σh), then secondary fractures and fracture network form in CBM reservoirs. When two stresses of crustal stress are close and far different from the third one, the fracture morphology and propagation become complex. Influenced by perforations and filtration of fracturing fluid in specimen, fracturing fluid flows to downward easily after comparing horizontal well fracturing with vertical well fracturing. Fracture width increases with the decreasing of elastic modulus, the intensity of fracture is positively related with the elastic modulus of coal rock. The research results can provide theoretical basis and technical support for the efficient development of CBM.

  9. 3-D RESERVOIR AND STOCHASTIC FRACTURE NETWORK MODELING FOR ENHANCED OIL RECOVERY, CIRCLE RIDGE PHOSPHORIA/TENSLEEP RESERVOIR, WIND RIVER RESERVATION, ARAPAHO AND SHOSHONE TRIBES, WYOMING

    Energy Technology Data Exchange (ETDEWEB)

    Paul La Pointe; Jan Hermanson; Robert Parney; Thorsten Eiben; Mike Dunleavy; Ken Steele; John Whitney; Darrell Eubanks; Roger Straub

    2002-11-18

    This report describes the results made in fulfillment of contract DE-FG26-00BC15190, ''3-D Reservoir and Stochastic Fracture Network Modeling for Enhanced Oil Recovery, Circle Ridge Phosphoria/Tensleep Reservoir, Wind River Reservation, Arapaho and Shoshone Tribes, Wyoming''. The goal of this project is to improve the recovery of oil from the Tensleep and Phosphoria Formations in Circle Ridge Oilfield, located on the Wind River Reservation in Wyoming, through an innovative integration of matrix characterization, structural reconstruction, and the characterization of the fracturing in the reservoir through the use of discrete fracture network models. Fields in which natural fractures dominate reservoir permeability, such as the Circle Ridge Field, often experience sub-optimal recovery when recovery processes are designed and implemented that do not take advantage of the fracture systems. For example, a conventional waterflood in a main structural block of the Field was implemented and later suspended due to unattractive results. It is estimated that somewhere less than 20% of the OOIP in the Circle Ridge Field have been recovered after more than 50 years' production. Marathon Oil Company identified the Circle Ridge Field as an attractive candidate for several advanced IOR processes that explicitly take advantage of the natural fracture system. These processes require knowledge of the distribution of matrix porosity, permeability and oil saturations; and understanding of where fracturing is likely to be well-developed or poorly developed; how the fracturing may compartmentalize the reservoir; and how smaller, relatively untested subthrust fault blocks may be connected to the main overthrust block. For this reason, the project focused on improving knowledge of the matrix properties, the fault block architecture and to develop a model that could be used to predict fracture intensity, orientation and fluid flow/connectivity properties. Knowledge

  10. Numerical simulation of the environmental impact of hydraulic fracturing of tight/shale gas reservoirs on near-surface groundwater: Background, base cases, shallow reservoirs, short-term gas, and water transport.

    Science.gov (United States)

    Reagan, Matthew T; Moridis, George J; Keen, Noel D; Johnson, Jeffrey N

    2015-04-01

    Hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques, such as hydraulic fracturing, has grown explosively over the last decade. However, concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers, thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids. This study investigates, by numerical simulation, gas and water transport between a shallow tight-gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations, if such a connecting pathway has been created. We focus on two general failure scenarios: (1) communication between the reservoir and aquifer via a connecting fracture or fault and (2) communication via a deteriorated, preexisting nearby well. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure, and not producing may increase the potential for release. We also find that hydrostatic tight-gas reservoirs are unlikely to act as a continuing source of migrating gas, as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination. Such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes. Short-term leakage fractured reservoirs requires high-permeability pathways Production strategy affects the likelihood and magnitude of gas release Gas release is likely short-term, without additional driving forces.

  11. Characterization of fractured reservoirs joint inversion of seismic and production data

    Energy Technology Data Exchange (ETDEWEB)

    Shahraini, Ali

    2011-03-15

    Significant amounts of oil and gas reserves are trapped in fractured reservoirs. A proper characterization of fractured reservoirs can contribute to better reservoir management, including optimum well placement, planning of enhanced oil recovery (EOR) methods, well completion and so on. Characterization of fractured (and faulted) reservoirs has been a challenging and complicated task due to the high degree of heterogeneity and anisotropy that exists in this kind of reservoirs. In this thesis I look at the problem of fractured reservoir characterization as an inverse problem, and try to estimate the uncertain fracture parameters by joint inversion (or history matching) of seismic and production data. Updating a reservoir model to behave as closely as possible to the real reservoir is called history matching, which generally has a non-unique solution. History matching is a time consuming problem. Using both production and seismic data can help to narrow the solution space. This work aims to propose and develop work flows and methodologies for improved characterization of fractured reservoirs. It is based on an integrated approach using both seismic and production data in the characterization process. The fluid flow- seismic wave system for fractured reservoir characterization consists of a reservoir simulator coupled to consistent rock physics models and forward seismic modeling tools. A consistent (computationally inexpensive) rock physics model is used to calculate the effective permeability and stiffness tensors of fractured porous media from a limited number of uncertain fracture parameters. Based on the calculated effective permeability tensors, the reservoir simulator calculates production data such as well oil production, well bottom hole pressure, well water cut, saturation and pressure for all grid blocks at specific time steps. Similarly, using the effective stiffness tensors (calculated from saturation maps and assumed fracture parameters), seismic

  12. Productivity Analysis of Volume Fractured Vertical Well Model in Tight Oil Reservoirs

    Directory of Open Access Journals (Sweden)

    Jiahang Wang

    2017-01-01

    Full Text Available This paper presents a semianalytical model to simulate the productivity of a volume fractured vertical well in tight oil reservoirs. In the proposed model, the reservoir is a composite system which contains two regions. The inner region is described as formation with finite conductivity hydraulic fracture network and the flow in fracture is assumed to be linear, while the outer region is simulated by the classical Warren-Root model where radial flow is applied. The transient rate is calculated, and flow patterns and characteristic flowing periods caused by volume fractured vertical well are analyzed. Combining the calculated results with actual production data at the decline stage shows a good fitting performance. Finally, the effects of some sensitive parameters on the type curves are also analyzed extensively. The results demonstrate that the effect of fracture length is more obvious than that of fracture conductivity on improving production in tight oil reservoirs. When the length and conductivity of main fracture are constant, the contribution of stimulated reservoir volume (SRV to the cumulative oil production is not obvious. When the SRV is constant, the length of fracture should also be increased so as to improve the fracture penetration and well production.

  13. Production decline type curves analysis of a finite conductivity fractured well in coalbed methane reservoirs

    Science.gov (United States)

    Wei, Mingqiang; Wen, Ming; Duan, Yonggang; Fang, Quantang; Ren, Keyi

    2017-04-01

    Production decline type curves analysis is one of the robust methods used to analyze transport flow behaviors and to evaluate reservoir properties, original gas in place, etc. Although advanced production decline analysis methods for several well types in conventional reservoirs are widely used, there are few models of production decline type curves for a fractured well in coalbed methane (CBM) reservoirs. In this work, a novel pseudo state diffusion and convection model is firstly developed to describe CBM transport in matrix systems. Subsequently, based on the Langmuir adsorption isotherm, pseudo state diffusion and convection in matrix systems and Darcy flow in cleat systems, the production model of a CBM well with a finite conductivity fracture is derived and solved by Laplace transform. Advanced production decline type curves of a fractured well in CBM reservoirs are plotted through the Stehfest numerical inversion algorithm and computer programming. Six flow regimes, including linear flow regime, early radial flow in cleat systems, interporosity flow regime, late pseudo radial flow regime, transient regime and boundary dominated flow regime, are recognized. Finally, the effect of relevant parameters, including the storage coefficient of gas in cleat systems, the transfer coefficient from a matrix system to the cleat system, the modified coefficient of permeability, dimensionless fracture conductivity and dimensionless reservoir drainage radius, are analyzed on type curves. This paper does not only enrich the production decline type curves model of CBM reservoirs, but also expands our understanding of fractured well transport behaviors in CBM reservoirs and guides to analyze the well's production performance.

  14. Fractured reservoirs - Indication from the EGS at Soultz

    Science.gov (United States)

    Schill, E.; Kümmritz, J.; Geiermann, J.

    2009-04-01

    The Soultz geothermal site is located in the Upper Rhine Graben, which is part of Cenozoic European Rift Structure. Local heat flow maxima of up to 150 mW m2 in the Upper Rhine valley originate from a strong convectional heat transport mainly in the granitic basement (e.g. Bächler, 2003). Such systems may be exploited using Enchanced Geothermal System (EGS) technology. By definition these systems are characterised by natural permeability, which is improved using stimulation techniques. In the case of the Soultz reservoir natural permeability of about up to 3x10-14 m2 was inferred from the temperature distribution (Kohl et al., 2000). High permeability is often related to active faulting (Gudmundsson et al., 2001). Seismic activity and GPS measurements indicate active faulting in the entire Upper Rhine Graben (Bonjer, 1997, Tesauro et al., 2006, Cardozo et al., 2005). The granitic basement at Soultz underwent multi-phase tectonic deformation including the Hercynian and Alpine phases. The main faults in the sedimentary cover of Soultz strike N20°E, i.e. they follow the Rhenish direction. At depth a horst structure is present and the top basement is at 1400 m. Within the horst seismic sections reveal faults mainly dipping to the W. In the five deep wells at Soultz 39 fracture zones have been determined on three different scales (Dezayes and Genter, 2008). In the granite the major direction is about N160°E to N-S with steep dipping to the East and West. With depth the strike of the main sets is consistent, the dip orientation, however, changes. Between 1420 to 2700 m TVD, the main fracture set dips to the East. In the sections between 2700 and 4800 m two conjugate sets reveal fractures dipping to the East and to the West and at reservoir depth between 4800 m and 5000 m the westward dipping set is dominant (Valley, 2007; Dezayes and Genter, 2008). New magnetotelluric (MT) data, as well as inversion of gravity and MT data may be used for estimating relative porosity

  15. Design philosophy and practice of asymmetrical 3D fracturing and random fracturing: A case study of tight sand gas reservoirs in western Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Jianchun Guo

    2015-03-01

    Full Text Available At present two technical models are commonly taken in tight gas reservoir stimulation: conventional massive fracturing and SRV fracturing, but how to select a suitable fracturing model suitable for reservoir characteristics is still a question waiting to be answered. In this paper, based on the analysis of geological characteristics and seepage mechanism of tight gas and shale gas reservoirs, the differences between stimulation philosophy of tight gas reservoirs and shale reservoirs are elucidated, and the concept that a suitable stimulation model should be selected based on reservoir geological characteristics and seepage mechanism aiming at maximally improving the seepage capability of a reservoir. Based on this concept, two fracturing design methods were proposed for two tight gas reservoirs in western Sichuan Basin: asymmetrical 3D fracturing design (A3DF for the middle-shallow Upper Jurassic Penglaizhen Fm stacked reservoirs in which the hydraulic fractures can well match the sand spatial distribution and seepage capability of the reservoirs; SRV fracturing design which can increase fracture randomness in the sandstone and shale laminated reservoirs for the 5th Member of middle-deep Upper Triassic Xujiahe Fm. Compared with that by conventional fracturing, the average production of horizontal wells fractured by A3DF increased by 41%, indicating that A3DF is appropriate for gas reservoir development in the Penglaizhen Fm; meanwhile, the average production per well of the 5th Member of the Xujiahe Fm was 2.25 × 104 m3/d after SRV fracturing, showing that the SRV fracturing is a robust technical means for the development of this reservoir.

  16. Double-Porosity Models for a Fissured Groundwater Reservoir With Fracture Skin

    Science.gov (United States)

    Moench, Allen F.

    1984-07-01

    Theories of flow to a well in a double-porosity groundwater reservoir are modified to incorporate effects of a thin layer of low-permeability material or fracture skin that may be present at fracture-block interfaces as a result of mineral deposition or alteration. The commonly used theory for flow in double- porosity formations that is based upon the assumption of pseudo-steady state block-to-fissure flow is shown to be a special case of the theory presented in this paper. The latter is based on the assumption of transient block-to-fissure flow with fracture skin. Under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock, it may be assumed to impede the interchange of fluid between the fissures and blocks. Resistance to flow at fracture-block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks. This provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo-steady state flow model. Coupled boundary value problems for flow to a well discharging at a constant rate were solved in the Laplace domain. Both slab-shaped and sphere-shaped blocks were considered, as were effects of well bore storage and well bore skin. Results obtained by numerical inversion were used to construct dimensionless-type curves that were applied to well test data, for a pumped well and for an observation well, from the fractured volcanic rock terrane of the Nevada Test Site.

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

    Directory of Open Access Journals (Sweden)

    Cong Wang

    2015-06-01

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

  18. Modeling of wettability alteration during spontaneous imbibition of mutually soluble solvents in mixed wet fractured reservoirs

    NARCIS (Netherlands)

    Chahardowli, M.; Bruining, J.

    2014-01-01

    Mutually-soluble solvents can enhance oil recovery both in mixed-wet fractured reservoirs. When a partially waterwet matrix is surrounded by an immiscible wetting phase in the fracture, spontaneous imbibition is the most important production mechanism. Initially, the solvent moves with the imbibing

  19. CHARACTERIZATION OF IN-SITU STRESS AND PERMEABILITY IN FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; Nafi Toksoz

    2006-03-16

    Using a 3-D finite difference method with a rotated-staggered-grid (RSG) scheme we generated synthetic seismograms for a reservoir model consisting of three horizontal layers with the middle layer containing parallel, equally spaced fractures. By separating and analyzing the backscattered signals in the FK domain, we can obtain an estimate of the fracture spacing. The fracture spacing is estimated by taking one-half of the reciprocal of the dominant wavenumber of the backscattered energy in data acquired normal to the fractures. FK analysis for fracture spacing estimation was successfully applied to these model results, with particular focus on PS converted waves. The method was then tested on data from the Emilio Field. The estimated fracture spacing from the dominant wavenumber values in time windows at and below the reservoir level is 25-40m. A second approach for fracture spacing estimation is based on the observation that interference of forward and backscattered energy from fractures introduces notches in the frequency spectra of the scattered wavefield for data acquired normal to the fracture strike. The frequency of these notches is related to the spacing of the fractures. This Spectral Notch Method was also applied to the Emilio data, with the resulting range of fracture spacing estimates being 25-50m throughout the field. The dominant spacing fracture spacing estimate is about 30-40 m, which is very similar to the estimates obtained from the FK method.

  20. Fracture Evolution Following a Hydraulic Stimulation within an EGS Reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Mella, Michael [Univ. of Utah, Salt Lake City, UT (United States). Energy and Geoscience Inst.

    2016-08-31

    The objective of this project was to develop and demonstrate an approach for tracking the evolution of circulation immediately following a hydraulic stimulation in an EGS reservoir. Series of high-resolution tracer tests using conservative and thermally reactive tracers were designed at recently created EGS reservoirs in order to track changes in fluid flow parameters such as reservoir pore volume, flow capacity, and effective reservoir temperature over time. Data obtained from the project would be available for the calibration of reservoir models that could serve to predict EGS performance following a hydraulic stimulation.

  1. Implications of heterogeneous fracture distribution on reservoir quality; an analogue from the Torridon Group sandstone, Moine Thrust Belt, NW Scotland

    Science.gov (United States)

    Watkins, Hannah; Healy, David; Bond, Clare E.; Butler, Robert W. H.

    2018-03-01

    Understanding fracture network variation is fundamental in characterising fractured reservoirs. Simple relationships between fractures, stress and strain are commonly assumed in fold-thrust structures, inferring relatively homogeneous fracture patterns. In reality fractures are more complex, commonly appearing as heterogeneous networks at outcrop. We use the Achnashellach Culmination (NW Scotland) as an outcrop analogue to a folded tight sandstone reservoir in a thrust belt. We present fracture data is collected from four fold-thrust structures to determine how fracture connectivity, orientation, permeability anisotropy and fill vary at different structural positions. We use a 3D model of the field area, constructed using field observations and bedding data, and geomechanically restored using Move software, to determine how factors such as fold curvature and strain influence fracture variation. Fracture patterns in the Torridon Group are consistent and predictable in high strain forelimbs, however in low strain backlimbs fracture patterns are inconsistent. Heterogeneities in fracture connectivity and orientation in low strain regions do not correspond to fluctuations in strain or fold curvature. We infer that where strain is low, other factors such as lithology have a greater control on fracture formation. Despite unpredictable fracture attributes in low strain regions, fractured reservoir quality would be highest here because fractures in high strain forelimbs are infilled with quartz. Heterogeneities in fracture attribute data on fold backlimbs mean that fractured reservoir quality and reservoir potential is difficult to predict.

  2. Fracture-network analysis of the Latemar Platform (northern Italy): integrating outcrop studies to constrain the hydraulic properties of fractures in reservoir models

    NARCIS (Netherlands)

    Boro, H.; Rosero, E.; Bertotti, G.V.

    2014-01-01

    Fractures in subsurface reservoirs are known to have significant impacts on reservoir productivity. Quantifying their importance, however, is challenged by limited subsurface observations, and intense computations for modelling and upscaling. In this paper, we present a workflow to construct and

  3. Production forecasting and economic evaluation of horizontal wells completed in natural fractured reservoirs

    International Nuclear Information System (INIS)

    Evans, R. D.

    1996-01-01

    A technique for optimizing recovery of hydrocarbons from naturally fractured reservoirs using horizontal well technology was proposed. The technique combines inflow performance analysis, production forecasting and economic considerations, and is based on material balance analysis and linear approximations of reservoir fluid properties as functions of reservoir pressure. An economic evaluation model accounting for the time value of cash flow, interest and inflation rates, is part of the package. Examples of using the technique have been demonstrated. The method is also applied to a gas well producing from a horizontal wellbore intersecting discrete natural fractures. 11 refs., 2 tabs,. 10 figs

  4. SCREENING METHODS FOR SELECTION OF SURFACTANT FORMULATIONS FOR IOR FROM FRACTURED CARBONATE RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    William A. Goddard III; Yongchun Tang; Patrick Shuler; Mario Blanco; Yongfu Wu; Seung Soon Jang

    2005-07-01

    This topical report presents details of the laboratory work performed to complete Task 1 of this project; developing rapid screening methods to assess surfactant performance for IOR (Improved Oil Recovery) from fractured carbonate reservoirs. The desired outcome is to identify surfactant formulations that increase the rate and amount of aqueous phase imbibition into oil-rich, oil-wet carbonate reservoir rock. Changing the wettability from oil-wet to water-wet is one key to enhancing this water-phase imbibition process that in turn recovers additional oil from the matrix portion of a carbonate reservoir. The common laboratory test to evaluate candidate surfactant formulations is to measure directly the aqueous imbibition rate and oil recovery from small outcrop or reservoir cores, but this procedure typically requires several weeks. Two methods are presented here for the rapid screening of candidate surfactant formulations for their potential IOR performance in carbonate reservoirs. One promising surfactant screening protocol is based on the ability of a surfactant solution to remove aged crude oil that coats a clear calcite crystal (Iceland Spar). Good surfactant candidate solutions remove the most oil the quickest from the chips, plus change the apparent contact angle of the remaining oil droplets on the surface that thereby indicate increased water-wetting. The other fast surfactant screening method is based on the flotation behavior of powdered calcite in water. In this test protocol, first the calcite power is pre-treated to make the surface oil-wet. The next step is to add the pre-treated powder to a test tube and add a candidate aqueous surfactant formulation; the greater the percentage of the calcite that now sinks to the bottom rather than floats, the more effective the surfactant is in changing the solids to become now preferentially water-wet. Results from the screening test generally are consistent with surfactant performance reported in the literature.

  5. A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Qian Li

    2017-09-01

    Full Text Available Hydraulic fracturing is used widely to stimulate coalbed methane production in coal mines. However, some factors associated with conventional hydraulic fracturing, such as the simple morphology of the fractures it generates and inhomogeneous stress relief, limit its scope of application in coal mines. These problems mean that gas extraction efficiency is low. Conventional fracturing may leave hidden pockets of gas, which will be safety hazards for subsequent coal mining operations. Based on a new drilling technique applicable to drilling boreholes in coal seams, this paper proposes a tree-type fracturing technique for stimulating reservoir volumes. Tree-type fracturing simulation experiments using a large-scale triaxial testing apparatus were conducted in the laboratory. In contrast to the single hole drilled for conventional hydraulic fracturing, the tree-type sub-boreholes induce radial and tangential fractures that form complex fracture networks. These fracture networks can eliminate the “blank area” that may host dangerous gas pockets. Gas seepage in tree-type fractures was analyzed, and gas seepage tests after tree-type fracturing showed that permeability was greatly enhanced. The equipment developed for tree-type fracturing was tested in the Fengchun underground coal mine in China. After implementing tree-type fracturing, the gas extraction rate was around 2.3 times greater than that for traditional fracturing, and the extraction rate remained high for a long time during a 30-day test. This shortened the gas drainage time and improved gas extraction efficiency.

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

    OpenAIRE

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

    2015-01-01

    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 ...

  7. Seismic Wave Attenuation in Fractured Reservoir: Application on Abu Dhabi Oil Fields.

    Science.gov (United States)

    Bouchaala, F.; Ali, M.; Matsushima, J.

    2016-12-01

    There is a close link between fractures network and fluids circulation so information about nature and geometry of fractures in the reservoir zone is benificial for the petroleum industry. However the immaturity of the methodology and the complication of fractures network in some reservoirs like those of Abu Dhabi oil fields, make getting such information challenging. Since several studies showed the close link between physical properties of the subsurface and seismic wave attenuation (eg. Müller et al. 2010), we use this parameter in this study to assess its potentiality on fractures detection and characterization, even though its use is not common for reservoir characterization and even less for fractures characterization. To get an accurate attenuation profiles, we use a robust methods recently developed to estimate accurately attenuation from Vertical Seismic Profiling (VSP) (Matsushima et al. 2016) and sonic waveforms (Suziki and Matsushima 2013) in the reservoir zones. The data were acquired from many wells located in offshore and onshore oil fields of Abu Dhabi region. The subsurface of this region is mainly composed of carbonate rocks, such media are known to be highly heterogeneous. Scattering and intrinsic attenuation profiles were compared to interpreted fractures by using Formation Micro-imager (FMI). The comparison shows a correlation between these two parameters and fractures characteristic, such as their density and dipping. We also performed Alford rotation on dipole data to estimate the attenuation from fast and slow shear waveforms. The anisotropy is proportional to the dispersion of the points plotted from the ratio between the intrinsic attenuation of fast and slow shear over the depth, from the line (Qslow /Qfast=1), which corresponds to the isotropic case. We noticed that the zones with low fractures density display less dispersion than those of high density. Even though our results show potentiality of the attenuation for fractured

  8. Well test simulation through Discrete Fracture Network modelling in a fractured carbonate reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Casciano, C.; Ruvo, L.; Volpi, B.; Masserano, F.

    2004-07-01

    A Discrete Fracture Network (DFN) model was used to simulate the results of a production test carried out in a well drilled in a tight, fractured carbonate reservoir. Several static DFN models, depicting different geological scenarios, were built based on data from well logs, core analyses, PLT surveys and structural geology studies. Each of these models underwent a validation procedure, consisting of the simulation of the production test. The comparison between the simulated results and the actual data identified the scenarios whose results most closely matched the actual well behaviour. In order to compensate for the lack of geological data, an iterative loop was performed between the static model and the dynamic simulation. Constraints-added flow simulations provided new information for use in modifying the DFN model, resulting in a step-by-step updating of the static model itself. Finally, a geologically sound model accurately matching the results of the production test was obtained. The final DFN model was used to calculate the equivalent petrophysical parameters that were transferred to the corresponding region of the full field dual-porosity fluid flow model. (author)

  9. CHARACTERIZATION OF IN-SITU STRESS AND PERMEABILITY IN FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; M. Nafi Toksoz

    2005-02-04

    Numerical modeling and field data tests are presented on the Transfer Function/Scattering Index Method for estimating fracture orientation and density in subsurface reservoirs from the ''coda'' or scattered energy in the seismic trace. Azimuthal stacks indicate that scattered energy is enhanced along the fracture strike direction. A transfer function method is used to more effectively indicate fracture orientation. The transfer function method, which involves a comparison of the seismic signature above and below a reservoir interval, effectively eliminates overburden effects and acquisition imprints in the analysis. The transfer function signature is simplified into a scattering index attribute value that gives fracture orientation and spatial variations of the fracture density within a field. The method is applied to two field data sets, a 3-D Ocean Bottom Cable (OBC) seismic data set from an offshore fractured carbonate reservoir in the Adriatic Sea and a 3-D seismic data set from an onshore fractured carbonate field in the Middle East. Scattering index values are computed in both fields at the reservoir level, and the results are compared to borehole breakout data and Formation MicroImager (FMI) logs in nearby wells. In both cases the scattering index results are in very good agreement with the well data. Field data tests and well validation will continue. In the area of technology transfer, we have made presentations of our results to industry groups at MIT technical review meetings, international technical conferences, industry workshops, and numerous exploration and production company visits.

  10. Fracture network growth for prediction of fracture characteristics and connectivity in tight reservoir rocks

    NARCIS (Netherlands)

    Barnhoorn, A.; Cox, S.F.

    2012-01-01

    Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by

  11. Model of mechanical representation of the formation of natural fractures inside a petroleum reservoir; Modele de representation mecanique de la formation des fractures naturelles d'un reservoir petrolier

    Energy Technology Data Exchange (ETDEWEB)

    Picard, D.

    2005-09-15

    The optimisation of the oil production requires a better characterisation of naturally fractured reservoirs. We consider and analyse two spatial distributions. One with systematic joints is arranged in an homogeneous way; joint spacing is linked to individual bedding thickness with propagation frequently interrupted by stratigraphic interfaces (single layer jointing). The second, so-called fracture swarms, consists in fractures clustering, where stratigraphic interfaces seem to play a minor role. The analysis is based on the singularity theory and matched asymptotic expansions method with a fine scale for local perturbations and a global one for general trends. We examine the conditions of fracture propagation that are determined herein using simultaneously two fracture criteria an energy and a stress condition. We consider two modes of loading. Usually, the joint (crack opening mode) and fracture swarm growths are explained by a first order phenomenon involving effective traction orthogonal to fracture plane. Although commonly used, this hypothesis seems unrealistic in many circumstances and may conflict with geological observations. Then, we try to describe fracture growth as a second order phenomena resulting from crack parallel compression. As far as propagation across layer interfaces is concerned, the effect of loading and geometry has been summarised in maps of fracture mechanisms, describing areas of 'step-over', 'straight through propagation' and 'crack arrest'. Fracture criteria, relative size of heterogeneities, contrast of mechanical properties between bed and layer are parameters of the problem. For fracture swarms, we present a discussion bringing out what is reasonable as a loading to justify their morphology. In particular, horizontal effective tension is unable to explain neighbouring joints. Simultaneous propagation of parallel near cracks is explained by finite width cracks growing under the influence of vertical

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

    Energy Technology Data Exchange (ETDEWEB)

    David S. Schechter

    2003-10-01

    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.

  13. Dual permeability modeling of flow in a fractured geothermal reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.D.; Allman, D.W.

    1986-01-01

    A three dimensional fracture system synthesis and flow simulation has been developed to correlate drawdown characteristics measured in a geothermal well and to provide the basis for an analysis of tracer tests. A new dual permeability approach was developed which incorporates simulations at two levels to better represent a discrete fracture system within computer limitations. The first incorporates a discrete simulation of the largest fractures in the system plus distributed or representative element stimulation of the smaller fractures. The second determines the representative element properties by discrete simulation of the smaller fractures. The fracture system was synthesized from acoustic televiewer data on the orientation and separation of three distinct fracture sets, together with additional data from the literature. Lognormal and exponential distributions of fracture spacing and radius were studied with the exponential distribution providing more reasonable results. Hydraulic apertures were estimated as a function of distance from the model boundary to a constant head boundary. Mean values of 6.7, 101 and 46 ..mu..m were chosen as the most representative values for the three fracture sets. Recommendations are given for the additional fracture characterization needed to reduce the uncertainties in the model. 20 refs., 6 figs.

  14. Rationale for finding and exploiting fractured reservoirs, based on the MWX/SHCT-Piceance basin experience

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, J.C.; Warpinski, N.R.; Teufel, L.W.

    1993-08-01

    The deliverability of a reservoir depends primarily on its permeability, which, in many reservoirs, is controlled by a combination of natural fractures and the in situ stresses. Therefore it is important to be able to predict which parts of a basin are most likely to contain naturally fractured strata, what the characteristics of those fractures might be, and what the most likely in situ stresses are at a given location. This paper presents a set of geologic criteria that can be superimposed onto factors, such as levels of maturation and porosity development, in order to predict whether fractures are present once the likelihood of petroleum presence and reservoir development have been determined. Stress causes fracturing, but stresses are not permanent. A natural-fracture permeability pathway opened by one system of stresses may be held open by those stresses, or narrowed or even closed by changes of the stress to an oblique or normal orientation. The origin of stresses and stress anisotropies in a basin, the potential for stress to create natural fractures, and the causes of stress reorientation are examined in this paper. The appendices to this paper present specific techniques for exploiting and characterizing natural fractures, for measuring the present-day in situ stresses, and for reconstructing a computerized stress history for a basin.

  15. Reviving Abandoned Reservoirs with High-Pressure Air Injection: Application in a Fractured and Karsted Dolomite Reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Robert Loucks; Stephen C. Ruppel; Dembla Dhiraj; Julia Gale; Jon Holder; Jeff Kane; Jon Olson; John A. Jackson; Katherine G. Jackson

    2006-09-30

    Engineering (both at The University of Texas at Austin) to define the controls on fluid flow in the reservoir as a basis for developing a reservoir model. The successful development of HPAI technology has tremendous potential for increasing the flow of oil from deep carbonate reservoirs in the Permian Basin, a target resource that can be conservatively estimated at more than 1.5 billion barrels. Successful implementation in the field chosen for demonstration, for example, could result in the recovery of more than 34 million barrels of oil that will not otherwise be produced. Geological and petrophysical analysis of available data at Barnhart field reveals the following important observations: (1) the Barnhart Ellenburger reservoir is similar to most other Ellenburger reservoirs in terms of depositional facies, diagenesis, and petrophysical attributes; (2) the reservoir is characterized by low to moderate matrix porosity much like most other Ellenburger reservoirs in the Permian Basin; (3) karst processes (cave formation, infill, and collapse) have substantially altered stratigraphic architecture and reservoir properties; (4) porosity and permeability increase with depth and may be associated with the degree of karst-related diagenesis; (5) tectonic fractures overprint the reservoir, improving overall connectivity; (6) oil-saturation profiles show that the oil-water contact (OWC) is as much as 125 ft lower than previous estimations; (7) production history and trends suggest that this reservoir is very similar to other solution-gas-drive reservoirs in the Permian Basin; and (8) reservoir simulation study showed that the Barnhart reservoir is a good candidate for HPAI and that application of horizontal-well technology can improve ultimate resource recovery from the reservoir.

  16. 10 CFR Appendix G to Part 50 - Fracture Toughness Requirements

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Fracture Toughness Requirements G Appendix G to Part 50..., App. G Appendix G to Part 50—Fracture Toughness Requirements I. Introduction and scope. II. Definitions. III. Fracture toughness tests. IV. Fracture toughness requirements. I. Introduction and Scope...

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

    Directory of Open Access Journals (Sweden)

    Wei Yu

    2013-01-01

    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.

  18. A new method of well test analysis in naturally fractured reservoirs based on elliptical flow

    Energy Technology Data Exchange (ETDEWEB)

    Igbokoyi, A.O.; Tiab, D. [Oklahoma Univ., Norman, OK (United States)

    2008-07-01

    Well testing analysis in naturally fractured reservoirs is usually based on the radial flow model. However, this model is only applicable to purely homogeneous system and long time solution and cannot provide complete formation analysis in a reservoir that exhibits anisotropy. This paper presented a new method of estimating permeability anisotropy in naturally fractured reservoirs. Maximum and minimum permeability were obtained in one well test. The paper discussed the mathematical formulation for the study which used Warren and Root's matrix pseudo-steady state model. The paper presented the assumptions for this model which included an isotropic homogeneous or anisotropic homogeneous formation; a slightly compressible fluid with single phase flow in both the matrix and fracture; initial reservoir pressure; two-dimensional flow; and laminar flow which obeys Darcy's law. The paper also discussed the computation of wellbore pressure and interpretation methods for both early linear flow and the long time radial flow regimes. Anisotropy was also outlined as the purpose of the study was to use an elliptical flow model in quantifying the permeability anisotropy of the reservoir. The type curve model was also explained to demonstrate the validity of the method of quantifying the permeability anisotropy with a known problem. Last, the paper explained the direct method with several example. It was concluded that the elliptical flow model is the most appropriate method of analyzing pressure transient data in naturally fractured reservoirs. 22 refs., 5 tabs., 15 figs., 3 appendices.

  19. MULTI-ATTRIBUTE SEISMIC/ROCK PHYSICS APPROACH TO CHARACTERIZING FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Gary Mavko

    2000-10-01

    This project consists of three key interrelated Phases, each focusing on the central issue of imaging and quantifying fractured reservoirs, through improved integration of the principles of rock physics, geology, and seismic wave propagation. This report summarizes the results of Phase I of the project. The key to successful development of low permeability reservoirs lies in reliably characterizing fractures. Fractures play a crucial role in controlling almost all of the fluid transport in tight reservoirs. Current seismic methods to characterize fractures depend on various anisotropic wave propagation signatures that can arise from aligned fractures. We are pursuing an integrated study that relates to high-resolution seismic images of natural fractures to the rock parameters that control the storage and mobility of fluids. Our goal is to go beyond the current state-of-the art to develop and demonstrate next generation methodologies for detecting and quantitatively characterizing fracture zones using seismic measurements. Our study incorporates 3 key elements: (1) Theoretical rock physics studies of the anisotropic viscoelastic signatures of fractured rocks, including up scaling analysis and rock-fluid interactions to define the factors relating fractures in the lab and in the field. (2) Modeling of optimal seismic attributes, including offset and azimuth dependence of travel time, amplitude, impedance and spectral signatures of anisotropic fractured rocks. We will quantify the information content of combinations of seismic attributes, and the impact of multi-attribute analyses in reducing uncertainty in fracture interpretations. (3) Integration and interpretation of seismic, well log, and laboratory data, incorporating field geologic fracture characterization and the theoretical results of items 1 and 2 above. The focal point for this project is the demonstration of these methodologies in the Marathon Oil Company Yates Field in West Texas.

  20. An Efficient Upscaling Process Based on a Unified Fine-scale Multi-Physics Model for Flow Simulation in Naturally Fracture Carbonate Karst Reservoirs

    KAUST Repository

    Bi, Linfeng

    2009-01-01

    The main challenges in modeling fluid flow through naturally-fractured carbonate karst reservoirs are how to address various flow physics in complex geological architectures due to the presence of vugs and caves which are connected via fracture networks at multiple scales. In this paper, we present a unified multi-physics model that adapts to the complex flow regime through naturally-fractured carbonate karst reservoirs. This approach generalizes Stokes-Brinkman model (Popov et al. 2007). The fracture networks provide the essential connection between the caves in carbonate karst reservoirs. It is thus very important to resolve the flow in fracture network and the interaction between fractures and caves to better understand the complex flow behavior. The idea is to use Stokes-Brinkman model to represent flow through rock matrix, void caves as well as intermediate flows in very high permeability regions and to use an idea similar to discrete fracture network model to represent flow in fracture network. Consequently, various numerical solution strategies can be efficiently applied to greatly improve the computational efficiency in flow simulations. We have applied this unified multi-physics model as a fine-scale flow solver in scale-up computations. Both local and global scale-up are considered. It is found that global scale-up has much more accurate than local scale-up. Global scale-up requires the solution of global flow problems on fine grid, which generally is computationally expensive. The proposed model has the ability to deal with large number of fractures and caves, which facilitate the application of Stokes-Brinkman model in global scale-up computation. The proposed model flexibly adapts to the different flow physics in naturally-fractured carbonate karst reservoirs in a simple and effective way. It certainly extends modeling and predicting capability in efficient development of this important type of reservoir.

  1. Effective Stress Approximation using Geomechanical Formulation of Fracturing Technology (GFFT) in Petroleum Reservoirs

    Science.gov (United States)

    Haghi, A.; Asef, M.; Kharrat, R.

    2010-12-01

    Recently, rock mechanics and geophysics contribution in petroleum industry has been significantly increased. Wellbore stability analysis in horizontal wells, sand production problem while extracting hydrocarbon from sandstone reservoirs, land subsidence due to production induced reservoir compaction, reservoir management, casing shearing are samples of these contributions. In this context, determination of the magnitude and orientation of the in-situ stresses is an essential parameter. This paper is presenting new method to estimate the magnitude of in-situ stresses based on fracturing technology data. Accordingly, kirsch equations for the circular cavities and fracturing technology models in permeable formations have been used to develop an innovative Geomechanical Formulation (GFFT). GFFT introduces a direct reasonable relation between the reservoir stresses and the breakdown pressure of fracture, while the concept of effective stress was employed. Thus, this complex formula contains functions of some rock mechanic parameters such as poison ratio, Biot’s coefficient, Young’s modulus, rock tensile strength, depth of reservoir and breakdown/reservoir pressure difference. Hence, this approach yields a direct method to estimate maximum and minimum effective/insitu stresses in an oil field and improves minimum in-situ stress estimation compared to previous studies. In case of hydraulic fracturing; a new stress analysis method is developed based on well known Darcy equations for fluid flow in porous media which improves in-situ stress estimation using reservoir parameters such as permeability, and injection flow rate. The accuracy of the method would be verified using reservoir data of a case history. The concepts discussed in this research would eventually suggest an alternative methodology with sufficient accuracy to derive in-situ stresses in hydrocarbon reservoirs, while no extra experimental work is accomplished for this purpose.

  2. Evaluation on the effectiveness of natural fractures in Changxing Fm reef-flat facies reservoirs, Yuanba area, Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Xiangyuan Zhao

    2017-07-01

    Full Text Available Study on the effectiveness of fractures is of great significance for understanding reservoir types and properties, identifying reservoir seepage mechanisms and delineating the reasonable development technologies and policies. In this paper, the Changxing reef-flat facies reservoirs in the Yuanba area, Sichuan Basin, was taken as an example. After the characteristics of natural fractures were evaluated, the effectiveness of different types of fractures was investigated by using core, thin section, imaging logging and production performance data. Then, the main geological factors that influence fracture effectiveness were analyzed, and the development significance of effective fractures was illustrated. The following results are obtained. (1 Structural fractures and diagenetic fractures are mainly developed in Changxing Fm carbonate reservoirs in Yuanba area. Structural fractures include shear fractures and extensional fractures, and diagenetic fractures include dissolution fractures, structural-dissolution fractures and pressure-solution fractures. (2 High-angle structural fractures are the most effective, followed by horizontal fractures and then oblique fractures, and pressure-solution fractures are the least effective. (3 Among structural fractures, those of NW–SE and nearly E–W oriented are more effective than those of the NE–SW oriented. (4 The earlier the fractures are formed, the more likely they are to be filled with calcite or dolomite and become invalid. (5 The fractures which are formed before or during the oil and gas charging tend to be filled with organic matters and become invalid. The late fractures which are formed after oil and gas charging are mostly effective and their contribution to the reservoir is the greatest. (6 The fractures nearly parallel to the maximum principal stress direction of current ground stress present good effectiveness with large opening. It is concluded that the opening and filling features of

  3. Experiments and Simulations of Fluid Flow in Heterogeneous Reservoir Models - Emphasis on Impacts from Crossbeds and Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Boerresen, Knut Arne

    1996-12-31

    Hydrocarbon recovery from subsurface reservoirs has become increasingly dependent on advanced recovery techniques that require improved understanding of the physics of fluid flow within and across geological units including small-scale heterogeneities and fractures. In this thesis, impacts from heterogeneities on local fluid flow are studied experimentally by means of imaging techniques to visualize fluid flow in two dimensions during flooding of larger reservoir models. Part 1 reflects the multi-disciplinary collaboration, by briefly introducing the relevant geology, the literature on experiments on fluid flow in bedded structures, and outlining the applied numerical simulator and imaging techniques applied to visualize fluid flow. The second part contains a synopsis of displacement experiments in naturally laminated sandstones and in crossbed laboratory models, and of the impact from incipient shear fractures on oil recovery. The detailed results obtained from the experiments and simulations are described in six papers, all included. 215 refs., 108 figs., 16 tabs.

  4. Identification and characterisation of individual Fractures in 3D fracture-network of shale reservoir rocks from microtomography

    Science.gov (United States)

    Qi, C.; Liu, J.

    2017-12-01

    between the fractal dimension and temperature/pressure. This study is a first trial of the characterization of individual cracks in 3D network. It lays a foundation for future research on the prediction of large-scale fractures in tight reservoirs.

  5. Characterization of In-Situ Stress and Permeability in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; M. Nafi Toksoz

    2006-06-30

    Fracture orientation and spacing are important parameters in reservoir development. This project resulted in the development and testing of a new method for estimating fracture orientation and two new methods for estimating fracture spacing from seismic data. The methods developed were successfully applied to field data from fractured carbonate reservoirs. Specific results include: the development a new method for estimating fracture orientation from scattered energy in seismic data; the development of two new methods for estimating fracture spacing from scattered energy in seismic data; the successful testing of these methods on numerical model data and field data from two fractured carbonate reservoirs; and the validation of fracture orientation results with borehole data from the two fields. Researchers developed a new method for determining the reflection and scattering characteristics of seismic energy from subsurface fractured formations. The method is based upon observations made from 3D finite difference modeling of the reflected and scattered seismic energy over discrete systems of vertical fractures. Regularly spaced, discrete vertical fractures impart a ringing coda type signature to seismic energy that is transmitted through or reflected off of them. This signature varies in amplitude and coherence as a function of several parameters including: (1) the difference in angle between the orientation of the fractures and the acquisition direction, (2) the fracture spacing, (3) the wavelength of the illuminating seismic energy, and (4) the compliance, or stiffness, of the fractures. This coda energy is the most coherent when the acquisition direction is parallel to the strike of the fractures. It has the largest amplitude when the seismic wavelengths are tuned to the fracture spacing, and when the fractures have low stiffness. The method uses surface seismic reflection traces to derive a transfer function that quantifies the change in the apparent source

  6. Study on fracture identification of shale reservoir based on electrical imaging logging

    Science.gov (United States)

    Yu, Zhou; Lai, Fuqiang; Xu, Lei; Liu, Lin; Yu, Tong; Chen, Junyu; Zhu, Yuantong

    2017-05-01

    In recent years, shale gas exploration has made important development, access to a major breakthrough, in which the study of mud shale fractures is extremely important. The development of fractures has an important role in the development of gas reservoirs. Based on the core observation and the analysis of laboratory flakes and laboratory materials, this paper divides the lithology of the shale reservoirs of the XX well in Zhanhua Depression. Based on the response of the mudstone fractures in the logging curve, the fracture development and logging Response to the relationship between the conventional logging and electrical imaging logging to identify the fractures in the work, the final completion of the type of fractures in the area to determine and quantify the calculation of fractures. It is concluded that the fracture type of the study area is high and the microstructures are developed from the analysis of the XX wells in Zhanhua Depression. The shape of the fractures can be clearly seen by imaging logging technology to determine its type.

  7. A Fully Three Dimensional Semianalytical Model for Shale Gas Reservoirs with Hydraulic Fractures

    Directory of Open Access Journals (Sweden)

    Yuwei Li

    2018-02-01

    Full Text Available Two challenges exist for modeling gas transport in shale. One is the existence of complex gas transport mechanisms, and the other is the impact of hydraulic fracture networks. In this study, a truly three dimensional semianalytical model was developed for shale gas reservoirs with hydraulic fractures of various shapes. Using the instantaneous point source solution, the pressure are solved for a bounded reservoir with fully 3D, partially penetrated hydraulic fractures of different strike angles and dip angles. The fractures could have various shapes such as rectangles, disks and ellipses. The shale gas diffusion equations considers complex transport mechanism such as gas slippage and gas diffusion. This semianalytical model is verified with a commercial software and an analytical method for single fully penetrated rectangle fracture, and the production results of shale gas are consistent. The impacts of fracture height and strike angles are investigated by five systematically constructed models. The comparison shows that the production increases proportionally with the fracture height, and decreases with the increase of strike angles. The method proposed in this study could also be applied in well testing to analyze the reservoir properties and used to forecast the production for tight oil and conventional resources.

  8. Double-beam Stacking to Infer Seismic Properties of Fractured Reservoirs

    Science.gov (United States)

    Zheng, Y.; Fang, X.; Fehler, M.; Burns, D.

    2011-12-01

    The Earth is constantly deforming, thereby creating stress field, which may generate fractures when the material fails. Fracture spacing, orientation and compliance are key parameters we want to infer about a fractured reservoir that may contain oil and gas. Fractures can be modeled as inclusions with contrasting material properties and they can also be characterized by Schoenberg's linear slip boundary condition, which garnered experimental support from laboratories in 1980s and 90s. In both models, fractures scatter seismic waves. We adopt the linear slip boundary condition as a working hypothesis for the fracture model. The more compliant the fracture is, the better the permeability is and the stronger the scattering is. When the wavelength λ is large compared to the fracture spacing D, e.g. λ >10D, one can use the effective medium theory which treats the fractured reservoir as a homogeneous but anisotropic medium. In this case, the common-midpoint stacks should vary with the azimuth. However, when the wavelength is comparable to the fracture spacing, seismic scattering theory is needed and we have developed a theory for using 3D beam interference to infer scattering properties of a fractured reservoir using reflected seismic P data. For the sake of simplicity, we use Gaussian beams. The method involves interference of two beams, one from the source region and the other emanating from the receivers. Each beam is formed by first windowing the scattered data in space and time and then performing the f-k filtering. The interference pattern depends on frequency, the incident angle, the reflection angle, and the azimuth. We try to interpret the interference pattern using local Born scattering in the target region. This interpretation is motivated by the observation that full-wave finite difference simulation of waves propagating through a set of vertical fractures using Schoenberg's linear-slip boundary condition and fracture compliances consistent with those

  9. The subsurface impact of hydraulic fracturing in shales- Perspectives from the well and reservoir

    Science.gov (United States)

    ter Heege, Jan; Coles, Rhys

    2017-04-01

    It has been identified that the main risks of subsurface shale gas operations in the U.S.A. and Canada are associated with (1) drilling and well integrity, (2) hydraulic fracturing, and (3) induced seismicity. Although it is unlikely that hydraulic fracturing operations result in direct pathways of enhanced migration between stimulated fracture disturbed rock volume and shallow aquifers, operations may jeopardize well integrity or induce seismicity. From the well perspective, it is often assumed that fluid injection leads to the initiation of tensile (mode I) fractures at different perforation intervals along the horizontal sections of shale gas wells if pore pressure exceeds the minimum principal stress. From the reservoir perspective, rise in pore pressure resulting from fluid injection may lead to initiation of tensile fractures, reactivation of shear (mode II) fractures if the criterion for failure in shear is exceeded, or combinations of different fracturing modes. In this study, we compare tensile fracturing simulations using conventional well-based models with shear fracturing simulations using a fractured shale model with characteristic fault populations. In the fractured shale model, stimulated permeability is described by an analytical model that incorporates populations of reactivated faults and that combines 3D permeability tensors for layered shale matrix, damage zone and fault core. Well-based models applied to wells crosscutting the Posidonia Shale Formation are compared to generic fractured shale models, and fractured shale models are compared to micro-seismic data from the Marcellus Shale. Focus is on comparing the spatial distribution of permeability, stimulated reservoir volume and seismicity, and on differences in fracture initiation pressure and fracture orientation for tensile and shear fracturing end-members. It is shown that incorporation of fault populations (for example resulting from analysis of 3D seismics or outcrops) in hydraulic

  10. Permeable fracture zones in the hard rocks of the geothermal reservoir at Rittershoffen, France

    Science.gov (United States)

    Vidal, J.; Genter, A.; Chopin, F.

    2017-07-01

    Fluid circulation in zones of fractures are a key challenge to exploit deep geothermal heat from natural reservoir. At Rittershoffen (Upper Rhine Graben, France), two geothermal boreholes, GRT-1 and GRT-2, were drilled in 2012 and 2014, respectively. They targeted the local Rittershoffen normal fault, which strikes N-S and dips westward. In this study, major natural fractures were observed in the open holes of both wells from acoustic image logs correlated with other standard geophysical logs (gamma ray, neutron porosity, and caliper). Their permeability was evaluated at the borehole scale from temperature logs, mud losses, and gas surveys. One originally permeable (OP) fracture zone was observed in the granite of GRT-1. In GRT-2, four OP fracture zones were observed in the granite and two in sandstones. In GRT-2, fracture zones are composed by several fluid pathways that could explain the higher natural permeability than in GRT-1. All OP fractures are associated with positive temperature anomaly, interpreted as circulation of hot geothermal water through the permeable fracture, or negative one, interpreted as the cooling of a porous, altered and fractured zone around the permeable fracture after drilling operations. Permeability of natural fracture oriented N170° seems to be intimately linked to the secondary mineral deposits resulting from paleocirculations. The geometrical fracture model along the wellbore suggests that the inclined trajectory of GRT-2 increases the connection between the borehole and the nearly vertical fracture network associated to the local fault. A good characterization of zones of fractures in a targeted natural reservoir allows an optimal exploitation of geothermal resource.

  11. Carbon dioxide sequestration induced mineral precipitation healing of fractured reservoir seals

    Science.gov (United States)

    Welch, N.; Crawshaw, J.

    2017-12-01

    Initial experiments and the thermodynaic basis for carbon dioxide sequestration induced mineral precipitation healing of fractures through reservoir seals will be presented. The basis of this work is the potential exists for the dissolution of reservoir host rock formation carbonate minerals in the acidified injection front of CO2 during sequestration or EOR. This enriched brine and the bulk CO2 phase will then flow through the reservoir until contact with the reservoir seal. At this point any fractures present in the reservoir seal will be the preferential flow path for the bulk CO2 phase as well as the acidified brine front. These fractures would currently be filled with non-acidified brine saturated in seal formation brine. When the acidifeid brine from the host formation and the cap rock brine mix there is the potential for minerals to fall out of solution, and for these precipitated minerals to decrease or entirely cut off the fluid flow through the fractures present in a reservoir seal. Initial equilibrium simulations performed using the PHREEQC1 database drived from the PHREEQE2 database are used to show the favorable conditions under which this mineral precipitation can occurs. Bench scale fluid mixing experiments were then performed to determine the kinetics of the mineral precipitation process, and determine the progress of future experiemnts involving fluid flow within fractured anhydrite reservoir seal samples. 1Parkhurst, D.L., and Appelo, C.A.J., 2013, Description of input and examples for PHREEQC version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Techniques and Methods, book 6, chap. A43, 497 p., available only at https://pubs.usgs.gov/tm/06/a43/. 2Parkhurst, David L., Donald C. Thorstenson, and L. Niel Plummer. PHREEQE: a computer program for geochemical calculations. No. 80-96. US Geological Survey, Water Resources Division,, 1980.

  12. Production decline type curves analysis of a finite conductivity fractured well in coalbed methane reservoirs

    Directory of Open Access Journals (Sweden)

    Wei Mingqiang

    2017-04-01

    Full Text Available Production decline type curves analysis is one of the robust methods used to analyze transport flow behaviors and to evaluate reservoir properties, original gas in place, etc. Although advanced production decline analysis methods for several well types in conventional reservoirs are widely used, there are few models of production decline type curves for a fractured well in coalbed methane (CBM reservoirs. In this work, a novel pseudo state diffusion and convection model is firstly developed to describe CBM transport in matrix systems. Subsequently, based on the Langmuir adsorption isotherm, pseudo state diffusion and convection in matrix systems and Darcy flow in cleat systems, the production model of a CBM well with a finite conductivity fracture is derived and solved by Laplace transform. Advanced production decline type curves of a fractured well in CBM reservoirs are plotted through the Stehfest numerical inversion algorithm and computer programming. Six flow regimes, including linear flow regime, early radial flow in cleat systems, interporosity flow regime, late pseudo radial flow regime, transient regime and boundary dominated flow regime, are recognized. Finally, the effect of relevant parameters, including the storage coefficient of gas in cleat systems, the transfer coefficient from a matrix system to the cleat system, the modified coefficient of permeability, dimensionless fracture conductivity and dimensionless reservoir drainage radius, are analyzed on type curves. This paper does not only enrich the production decline type curves model of CBM reservoirs, but also expands our understanding of fractured well transport behaviors in CBM reservoirs and guides to analyze the well's production performance.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-09-15

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

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

    International Nuclear Information System (INIS)

    Henk, A.; Fischer, K.

    2014-09-01

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

  15. Impact of Petrophysical Properties on Hydraulic Fracturing and Development in Tight Volcanic Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Yinghao Shen

    2017-01-01

    Full Text Available The volcanic reservoir is an important kind of unconventional reservoir. The aqueous phase trapping (APT appears because of fracturing fluids filtration. However, APT can be autoremoved for some wells after certain shut-in time. But there is significant distinction for different reservoirs. Experiments were performed to study the petrophysical properties of a volcanic reservoir and the spontaneous imbibition is monitored by nuclear magnetic resonance (NMR and pulse-decay permeability. Results showed that natural cracks appear in the samples as well as high irreducible water saturation. There is a quick decrease of rock permeability once the rock contacts water. The pores filled during spontaneous imbibition are mainly the nanopores from NMR spectra. Full understanding of the mineralogical effect and sample heterogeneity benefits the selection of segments to fracturing. The fast flow-back scheme is applicable in this reservoir to minimize the damage. Because lots of water imbibed into the nanopores, the main flow channels become larger, which are beneficial to the permeability recovery after flow-back of hydraulic fracturing. This is helpful in understanding the APT autoremoval after certain shut-in time. Also, Keeping the appropriate production differential pressure is very important in achieving the long term efficient development of volcanic gas reservoirs.

  16. Naturally fractured tight gas reservoir detection optimization. Quarterly report, January 1, 1997--March 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This document contains the quarterly report dated January 1-March 31, 1997 for the Naturally Fractured Tight Gas Reservoir Detection Optimization project. Topics covered in this report include AVOA modeling using paraxial ray tracing, AVOA modeling for gas- and water-filled fractures, 3-D and 3-C processing, and technology transfer material. Several presentations from a Geophysical Applications Workshop workbook, workshop schedule, and list of workshop attendees are also included.

  17. Seismic fracture detection of shale gas reservoir in Longmaxi formation, Sichuan Basin, China

    Science.gov (United States)

    Lu, Yujia; Cao, Junxing; Jiang, Xudong

    2017-11-01

    In the shale reservoirs, fractures play an important role, which not only provide space for the oil and gas, but also offer favorable petroleum migration channel. Therefore, it is of great significance to study the fractures characteristics in shale reservoirs for the exploration and development of shale gas. In this paper, four analysis technologies involving coherence, curvature attribute, structural stress field simulation and pre-stack P-wave azimuthal anisotropy have been applied to predict the fractures distribution in the Longmaxi formation, Silurian, southeast of Sichuan Basin, China. By using the coherence and curvature attribute, we got the spatial distribution characteristics of fractures in the study area. Structural stress field simulation can help us obtain distribution characteristics of structural fractures. And using the azimuth P-wave fracture detection technology, we got the characteristics about the fracture orientation and density of this region. Application results show that there are NW and NE fractures in the study block, which is basically consistent with the result of log interpretation. The results also provide reliable geological basis for shale gas sweet spots prediction.

  18. CHARACTERIZATION OF IN-SITU STRESS AND PERMEABILITY IN FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; M. Nafi Toksoz

    2004-07-19

    Expanded details and additional results are presented on two methods for estimating fracture orientation and density in subsurface reservoirs from scattered seismic wavefield signals. In the first, fracture density is estimated from the wavenumber spectra of the integrated amplitudes of the scattered waves as a function of offset in pre-stack data. Spectral peaks correctly identified the 50m, 35m, and 25m fracture spacings from numerical model data using a 40Hz source wavelet. The second method, referred to as the Transfer Function-Scattering Index Method, is based upon observations from 3D finite difference modeling that regularly spaced, discrete vertical fractures impart a ringing coda-type signature to any seismic energy that is transmitted through or reflected off of them. This coda energy is greatest when the acquisition direction is parallel to the fractures, the seismic wavelengths are tuned to the fracture spacing, and when the fractures have low stiffness. The method uses surface seismic reflection traces to derive a transfer function, which quantifies the change in an apparent source wavelet propagating through a fractured interval. The transfer function for an interval with low scattering will be more spike-like and temporally compact. The transfer function for an interval with high scattering will ring and be less temporally compact. A Scattering Index is developed based on a time lag weighting of the transfer function. When a 3D survey is acquired with a full range of azimuths, the Scattering Index allows the identification of subsurface areas with high fracturing and the orientation (or strike) of those fractures. The method was calibrated with model data and then applied to field data from a fractured reservoir giving results that agree with known field measurements. As an aid to understanding the scattered wavefield seen in finite difference models, a series of simple point scatterers was used to create synthetic seismic shot records collected over

  19. Porosity, permeability and 3D fracture network characterisation of dolomite reservoir rock samples.

    Science.gov (United States)

    Voorn, Maarten; Exner, Ulrike; Barnhoorn, Auke; Baud, Patrick; Reuschlé, Thierry

    2015-03-01

    With fractured rocks making up an important part of hydrocarbon reservoirs worldwide, detailed analysis of fractures and fracture networks is essential. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) however suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this paper, we therefore explore the use of an additional method - non-destructive 3D X-ray micro-Computed Tomography (μCT) - to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. We process the 3D μCT data in this study by a Hessian-based fracture filtering routine and can successfully extract porosity, fracture aperture, fracture density and fracture orientations - in bulk as well as locally. Additionally, thin sections made from selected plug samples provide 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) towards more realistic reservoir conditions. This study shows that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that although there are limitations, several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these and

  20. Porosity, permeability and 3D fracture network characterisation of dolomite reservoir rock samples

    Science.gov (United States)

    Voorn, Maarten; Exner, Ulrike; Barnhoorn, Auke; Baud, Patrick; Reuschlé, Thierry

    2015-01-01

    With fractured rocks making up an important part of hydrocarbon reservoirs worldwide, detailed analysis of fractures and fracture networks is essential. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) however suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this paper, we therefore explore the use of an additional method – non-destructive 3D X-ray micro-Computed Tomography (μCT) – to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. We process the 3D μCT data in this study by a Hessian-based fracture filtering routine and can successfully extract porosity, fracture aperture, fracture density and fracture orientations – in bulk as well as locally. Additionally, thin sections made from selected plug samples provide 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) towards more realistic reservoir conditions. This study shows that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that although there are limitations, several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these

  1. Advancing New 3D Seismic Interpretation Methods for Exploration and Development of Fractured Tight Gas Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    James Reeves

    2005-01-31

    In a study funded by the U.S. Department of Energy and GeoSpectrum, Inc., new P-wave 3D seismic interpretation methods to characterize fractured gas reservoirs are developed. A data driven exploratory approach is used to determine empirical relationships for reservoir properties. Fractures are predicted using seismic lineament mapping through a series of horizon and time slices in the reservoir zone. A seismic lineament is a linear feature seen in a slice through the seismic volume that has negligible vertical offset. We interpret that in regions of high seismic lineament density there is a greater likelihood of fractured reservoir. Seismic AVO attributes are developed to map brittle reservoir rock (low clay) and gas content. Brittle rocks are interpreted to be more fractured when seismic lineaments are present. The most important attribute developed in this study is the gas sensitive phase gradient (a new AVO attribute), as reservoir fractures may provide a plumbing system for both water and gas. Success is obtained when economic gas and oil discoveries are found. In a gas field previously plagued with poor drilling results, four new wells were spotted using the new methodology and recently drilled. The wells have estimated best of 12-months production indicators of 2106, 1652, 941, and 227 MCFGPD. The latter well was drilled in a region of swarming seismic lineaments but has poor gas sensitive phase gradient (AVO) and clay volume attributes. GeoSpectrum advised the unit operators that this location did not appear to have significant Lower Dakota gas before the well was drilled. The other three wells are considered good wells in this part of the basin and among the best wells in the area. These new drilling results have nearly doubled the gas production and the value of the field. The interpretation method is ready for commercialization and gas exploration and development. The new technology is adaptable to conventional lower cost 3D seismic surveys.

  2. The impact of azimuthal anisotropy on seismic AVO and petrophysical response in a fractured Wabamun gas reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Rex, B.; Goodway, B.; Martin, C.; Uswak, G. [EnCana Corp., Calgary, AB (Canada)

    2003-07-01

    A reliable method for determining fracture density and orientation is needed to properly evaluate fractured carbonate reservoirs. This paper examines the potential of using the azimuthal information contained in seismic amplitude versus offset (AVO) analysis at a gas well drilled in the Resthaven prospect in the Smokey sub-basin of north-west Alberta. A low angle fault is present in Wabamun limestone, and near vertical fractures create strong anisotropic horizontal transverse isotropy (HTI) intervals in the footwall of the thrust. The AVO method was used to define the extent of the HTI interval. A method was proposed to map the boundary of the fractured reservoir. The study also examined the potential for LMR analysis which is commonly used in isotropic environments. Applying LMR to the Resthaven prospect required some reevaluation of local relationships between LMR and the in-situ HTI environment. LMR was shown to be a powerful tool if the interpreter understands the limitations of the model on which it is based. 6 refs., 13 figs.

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

    OpenAIRE

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2018-01-01

    Development of unconventional shale gas reservoirs (SGRs) has been boosted by the advancements in two key technologies: horizontal drilling and multi-stage hydraulic fracturing. A large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in SGRs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the SGRs with MsFHW is influenced by both reservoir conditions and hyd...

  4. A Mathematical Pressure Transient Analysis Model for Multiple Fractured Horizontal Wells in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Yan Zeng

    2018-01-01

    Full Text Available Multistage fractured horizontal wells (MFHWs have become the main technology for shale gas exploration. However, the existing models have neglected the percolation mechanism in nanopores of organic matter and failed to consider the differences among the reservoir properties in different areas. On that account, in this study, a modified apparent permeability model was proposed describing gas flow in shale gas reservoirs by integrating bulk gas flow in nanopores and gas desorption from nanopores. The apparent permeability was introduced into the macroseepage model to establish a dynamic pressure analysis model for MFHWs dual-porosity formations. The Laplace transformation and the regular perturbation method were used to obtain an analytical solution. The influences of fracture half-length, fracture permeability, Langmuir volume, matrix radius, matrix permeability, and induced fracture permeability on pressure and production were discussed. Results show that fracture half-length, fracture permeability, and induced fracture permeability exert a significant influence on production. A larger Langmuir volume results in a smaller pressure and pressure derivative. An increase in matrix permeability increases the production rate. Besides, this model fits the actual field data relatively well. It has a reliable theoretical foundation and can preferably describe the dynamic changes of pressure in the exploration process.

  5. Fracture properties from tight reservoir outcrop analogues with application to geothermal exploration

    Science.gov (United States)

    Philipp, Sonja L.; Reyer, Dorothea; Afsar, Filiz; Bauer, Johanna F.; Meier, Silke; Reinecker, John

    2015-04-01

    In geothermal reservoirs, similar to other tight reservoirs, fluid flow may be intensely affected by fracture systems, in particular those associated with fault zones. When active (slipping) the fault core, that is, the inner part of a fault zone, which commonly consists of breccia or gouge, can suddenly develop high permeability. Fault cores of inactive fault zones, however, may have low permeabilities and even act as flow barriers. In the outer part of a fault zone, the damage zone, permeability depends mainly on the fracture properties, that is, the geometry (orientation, aperture, density, connectivity, etc.) of the fault-associated fracture system. Mineral vein networks in damage zones of deeply eroded fault zones in palaeogeothermal fields demonstrate their permeability. In geothermal exploration, particularly for hydrothermal reservoirs, the orientation of fault zones in relation to the current stress field as well as their internal structure, in particular the properties of the associated fracture system, must be known as accurately as possible for wellpath planning and reservoir engineering. Here we present results of detailed field studies and numerical models of fault zones and associated fracture systems in palaeogeo¬thermal fields and host rocks for geothermal reservoirs from various stratigraphies, lithologies and tectonic settings: (1) 74 fault zones in three coastal sections of Upper Triassic and Lower Jurassic age (mudstones and limestone-marl alternations) in the Bristol Channel Basin, UK. (2) 58 fault zones in 22 outcrops from Upper Carboniferous to Upper Cretaceous in the Northwest German Basin (siliciclastic, carbonate and volcanic rocks); and (3) 16 fault zones in 9 outcrops in Lower Permian to Middle Triassic (mainly sandstone and limestone) in the Upper Rhine Graben shoulders. Whereas (1) represent palaeogeothermal fields with mineral veins, (2) and (3) are outcrop analogues of reservoir horizons from geothermal exploration. In the study

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

    Science.gov (United States)

    Pecher, Radek

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

  7. Studies of fracture network geometry of reservoir outcrop analogues from terrestrial lidar data: attempts to quantify spatial variations of fracture characteristics

    Science.gov (United States)

    Vsemirnova, E. A.; Jones, R. R.; McCaffrey, K. J. W.

    2012-04-01

    We describe studies analysing terrestrial lidar datasets of fracture systems from a range of reservoir analogues in clastic and carbonate lithologies that represent geological analogues of offshore hydrocarbon reservoirs for the UK continental shelf. As fracture networks (observed here from centimetre to kilometre scale) can significantly affect the permeability of a fractured reservoir, the definition of fracture network geometry at various scales has become an important goal of structural analysis. The main aim of the study has been to extend the investigation of fracture networks in order to quantify spatial variations in fracture parameters in a variety of lithologies. The datasets were pre-processed using RiSCAN PRO software, and then re-sampled and filtered to derive characteristics which are traditionally measured from outcrops, including size distributions, fracture spacing and clustering statistics. This type of analysis can significantly reduce the uncertainty associated with some field fracture network measurements. The digitised fracture networks datasets are then used to investigate various aspects of spatial heterogeneity. A series of fracture maps (joints and faults) were generated at different scales, and fracture trends were studied to test scale dependency of fracture orientations. Multiscale trend analysis was then applied to describe the trend structure of the fracture networks.

  8. Analytical modeling of coupled flow and geomechanics for vertical fractured well in tight gas reservoirs

    Directory of Open Access Journals (Sweden)

    Wang Ruifei

    2017-12-01

    Full Text Available The mathematical model of coupled flow and geomechanics for a vertical fractured well in tight gas reservoirs was established. The analytical modeling of unidirectional flow and radial flow was achieved by Laplace transforms and integral transforms. The results show that uncoupled flow would lead to an overestimate in performance of a vertical fractured well, especially in the later stage. The production rate decreases with elastic modulus because porosity and permeability decrease accordingly. Drawdown pressure should be optimized to lower the impact of coupled flow and geomechanics as a result of permeability decreasing. Production rate increases with fracture half-length significantly in the initial stage and becomes stable gradually. This study could provide a theoretical basis for effective development of tight gas reservoirs.

  9. Analytical modeling of coupled flow and geomechanics for vertical fractured well in tight gas reservoirs

    Science.gov (United States)

    Wang, Ruifei; Gao, Xuhua; Song, Hongqing; Shang, Xinchun

    2017-12-01

    The mathematical model of coupled flow and geomechanics for a vertical fractured well in tight gas reservoirs was established. The analytical modeling of unidirectional flow and radial flow was achieved by Laplace transforms and integral transforms. The results show that uncoupled flow would lead to an overestimate in performance of a vertical fractured well, especially in the later stage. The production rate decreases with elastic modulus because porosity and permeability decrease accordingly. Drawdown pressure should be optimized to lower the impact of coupled flow and geomechanics as a result of permeability decreasing. Production rate increases with fracture half-length significantly in the initial stage and becomes stable gradually. This study could provide a theoretical basis for effective development of tight gas reservoirs.

  10. A multi-scale case study of natural fracture systems in outcrops and boreholes with applications to reservoir modelling

    NARCIS (Netherlands)

    Taal-van Koppen, J.K.J.

    2008-01-01

    Fractured reservoirs are notoriously difficult to characterize because the resolution of seismic data is too low to detect fractures whereas borehole data is detailed but sparse. Therefore, outcrops can be of great support in gaining knowledge of the three-dimensional geometry of fracture networks,

  11. Research program on fractured petroleum reservoirs. Final report, January 1, 1996--December 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Firoozabadi, A.

    1997-05-01

    Multiphase flow in fractured porous media is a complex problem. While the study of single phase flow in a fractured or a layered medium can be pursued by some kind of averaging process, there is no meaning to averaging two-phase flow when capillarity is an active force. For a two-layer system comprised of high and low permeable layers, the performance of gas-oil gravity can be less efficient than the homogeneous low permeable medium. On the other hand, heterogeneity may enhance water imbibition due to capillarity. Due to the above and various other complexities, current tools for predicting the performance of fractured hydrocarbon reservoirs are not reliable. Based on the research work carried out at the Reservoir Engineering Research Institute, and some other Institutions, a good deal of progress has been made in recent years. But still we are a long way from good predictive reservoir models. In this final report, we summarize some of our achievements in the understanding of multiphase flow in fractured media. Since some of the features of two-phase flow in fractured and layered many are similar due to the capillary forces, the work includes progress in both types of media. There are some basic issues of flow in both fractured and unfractured media that are currently unresolved. These issues include: (1) new phase formation such as the formation of liquid phase in gas condensate reservoirs, and gas phase formation in solution gas drive process and (2) composition variation due to thermal convection and diffusion processes. In the following, a brief summary of our findings in the last three years during the course of the project is presented.

  12. 3-D Reservoir and Stochastic Fracture Network Modeling for Enhanced Oil Recovery, Circle Ridge Phosphoria/Tensleep Reservoir, and River Reservation, Arapaho and Shoshone Tribes, Wyoming

    Energy Technology Data Exchange (ETDEWEB)

    La Pointe; Paul; Parney, Robert; Eiben, Thorsten; Dunleavy, Mike; Whitney, John

    2002-09-09

    The goal of this project is to improve the recovery of oil from the Circle Ridge Oilfield, located on the Wind River Reservation in Wyoming, through an innovative integration of matrix characterization, structural reconstruction, and the characterization of the fracturing in the reservoir through the use of discrete fracture network models.

  13. Radar Mapping of Fractures and Fluids in Hydrocarbon Reservoirs

    Science.gov (United States)

    Stolarczyk, L. G.; Wattley, G. G.; Caffey, T. W.

    2001-05-01

    A stepped-frequency radar has been developed for mapping of fractures and fluids within 20 meters of the wellbore. The operating range has been achieved by using a radiating magnetic dipole operating in the low- and medium-frequency bands. Jim Wait has shown that the electromagnetic (EM) wave impedance in an electrically conductive media is largely imaginary, enabling energy to be stored in the near field instead of dissipated, as in the case for an electric dipole. This fact, combined with the low attenuation rate of a low-frequency band EM wave, enables radiation to penetrate deeply into the geology surrounding the wellbore. The radiation pattern features a vertical electric field for optimum electric current induction into vertical fractures. Current is also induced in sedimentary rock creating secondary waves that propagate back to the wellbore. The radiation pattern is electrically driven in azimuth around the wellbore. The receiving antenna is located in the null field of the radiating antenna so that the primary wave is below the thermal noise of the receiver input. By stepping the frequency through the low- and medium-frequency bands, the depth of investigation is varied, and enables electrical conductivity profiling away from the wellbore. Interpretation software has been developed for reconstructive imaging in dipping sedimentary layers. Because electrical conductivity can be related to oil/water saturation, both fractures and fluids can be mapped. Modeling suggests that swarms of fractures can be imaged and fluid type determined. This information will be useful in smart fracking and sealing. Conductivity tomography images will indicate bed dip, oil/water saturation, and map fluids. This paper will provide an overview of the technology development program.

  14. Fatigue hydraulic fracturing by cyclic reservoir treatment enhances permeability and reduces induced seismicity

    Science.gov (United States)

    Zang, Arno; Yoon, Jeoung Seok; Stephansson, Ove; Heidbach, Oliver

    2013-11-01

    The occurrence of induced seismic events during hydraulic fracturing of reservoirs to enhance permeability is an unavoidable process. Due to the increased public concern with respect to the risks imposed by induced seismicity, however, the development of a soft stimulation method is needed creating higher permeability with less induced seismicity. We use a discrete element model of naturally fractured rock with pore fluid flow algorithm in order to analyse two scenarios of high-pressure fluid injection (hydraulic fracturing) at depth and associated induced seismicity. The ratio of pumped-in energy to released seismic energy is in agreement with field data. Our results suggest that cyclic reservoir treatment is a safer alternative to conventional hydraulic fracture stimulation as both, the total number of induced events as well as the occurrence of larger magnitude events are lowered. This work is motivated by results of laboratory triaxial indenter tests on granite rock samples where continuous loading leads to a wide fracture process zone while cyclic treatment with frequent starting and stopping of loading fatigues the rock, resulting in smaller damage volume and more persistent fracture growth.

  15. Simulation of petroleum recovery in naturally fractured reservoirs: physical process representation

    Energy Technology Data Exchange (ETDEWEB)

    Paiva, Hernani P.; Miranda Filho, Daniel N. de [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Schiozer, Denis J. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

    2012-07-01

    The naturally fractured reservoir recovery normally involves risk especially in intermediate to oil wet systems because of the simulations poor efficiency results under waterflood displacement. Double-porosity models are generally used in fractured reservoir simulation and have been implemented in the major commercial reservoir simulators. The physical processes acting in petroleum recovery are represented in double-porosity models by matrix-fracture transfer functions, therefore commercial simulators have their own implementations, and as a result different kinetics and final recoveries are attained. In this work, a double porosity simulator was built with Kazemi et al. (1976), Sabathier et al. (1998) and Lu et al. (2008) transfer function implementations and their recovery results have been compared using waterflood displacement in oil-wet or intermediate-wet systems. The results of transfer function comparisons have showed recovery improvements in oil-wet or intermediate-wet systems under different physical processes combination, particularly in fully discontinuous porous medium when concurrent imbibition takes place, coherent with Firoozabadi (2000) experimental results. Furthermore, the implemented transfer functions, related to a double-porosity model, have been compared to double-porosity commercial simulator model, as well a discrete fracture model with refined grid, showing differences between them. Waterflood can be an effective recovery method even in fully discontinuous media for oil-wet or intermediate-wet systems where concurrent imbibition takes place with high enough pressure gradients across the matrix blocks. (author)

  16. Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Gary Mavko

    2004-11-30

    Most current seismic methods to seismically characterize fractures in tight reservoirs depend on a few anisotropic wave propagation signatures that can arise from aligned fractures. While seismic anisotropy can be a powerful fracture diagnostic, a number of situations can lessen its usefulness or introduce interpretation ambiguities. Fortunately, laboratory and theoretical work in rock physics indicates that a much broader spectrum of fracture seismic signatures can occur, including a decrease in P- and S-wave velocities, a change in Poisson's ratio, an increase in velocity dispersion and wave attenuation, as well as well as indirect images of structural features that can control fracture occurrence. The goal of this project was to demonstrate a practical interpretation and integration strategy for detecting and characterizing natural fractures in rocks. The approach was to exploit as many sources of information as possible, and to use the principles of rock physics as the link among seismic, geologic, and log data. Since no single seismic attribute is a reliable fracture indicator in all situations, the focus was to develop a quantitative scheme for integrating the diverse sources of information. The integrated study incorporated three key elements: The first element was establishing prior constraints on fracture occurrence, based on laboratory data, previous field observations, and geologic patterns of fracturing. The geologic aspects include analysis of the stratigraphic, structural, and tectonic environments of the field sites. Field observations and geomechanical analysis indicates that fractures tend to occur in the more brittle facies, for example, in tight sands and carbonates. In contrast, strain in shale is more likely to be accommodated by ductile flow. Hence, prior knowledge of bed thickness and facies architecture, calibrated to outcrops, are powerful constraints on the interpreted fracture distribution. Another important constraint is that

  17. Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Horne, Roland N.; Li, Kewen; Alaskar, Mohammed; Ames, Morgan; Co, Carla; Juliusson, Egill; Magnusdottir, Lilja

    2012-06-30

    This report highlights the work that was done to characterize fractured geothermal reservoirs using production data. That includes methods that were developed to infer characteristic functions from production data and models that were designed to optimize reinjection scheduling into geothermal reservoirs, based on these characteristic functions. The characterization method provides a robust way of interpreting tracer and flow rate data from fractured reservoirs. The flow-rate data are used to infer the interwell connectivity, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods were developed to estimate the tracer kernels for situations where data is collected at variable flow-rate or variable injected concentration conditions. The characteristic functions can be used to calibrate thermal transport models, which can in turn be used to predict the productivity of geothermal systems. This predictive model can be used to optimize injection scheduling in a geothermal reservoir, as is illustrated in this report.

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

    Science.gov (United States)

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

    2017-04-01

    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.

  19. Optimisation of decision making under uncertainty throughout field lifetime: A fractured reservoir example

    Science.gov (United States)

    Arnold, Dan; Demyanov, Vasily; Christie, Mike; Bakay, Alexander; Gopa, Konstantin

    2016-10-01

    Assessing the change in uncertainty in reservoir production forecasts over field lifetime is rarely undertaken because of the complexity of joining together the individual workflows. This becomes particularly important in complex fields such as naturally fractured reservoirs. The impact of this problem has been identified in previous and many solutions have been proposed but never implemented on complex reservoir problems due to the computational cost of quantifying uncertainty and optimising the reservoir development, specifically knowing how many and what kind of simulations to run. This paper demonstrates a workflow that propagates uncertainty throughout field lifetime, and into the decision making process by a combination of a metric-based approach, multi-objective optimisation and Bayesian estimation of uncertainty. The workflow propagates uncertainty estimates from appraisal into initial development optimisation, then updates uncertainty through history matching and finally propagates it into late-life optimisation. The combination of techniques applied, namely the metric approach and multi-objective optimisation, help evaluate development options under uncertainty. This was achieved with a significantly reduced number of flow simulations, such that the combined workflow is computationally feasible to run for a real-field problem. This workflow is applied to two synthetic naturally fractured reservoir (NFR) case studies in appraisal, field development, history matching and mid-life EOR stages. The first is a simple sector model, while the second is a more complex full field example based on a real life analogue. This study infers geological uncertainty from an ensemble of models that are based on the carbonate Brazilian outcrop which are propagated through the field lifetime, before and after the start of production, with the inclusion of production data significantly collapsing the spread of P10-P90 in reservoir forecasts. The workflow links uncertainty

  20. Optimizing Fracture Treatments in a Mississippian "Chat" Reservoir, South-Central Kansas

    Energy Technology Data Exchange (ETDEWEB)

    K. David Newell; Saibal Bhattacharya; Alan Byrnes; W. Lynn Watney; Willard Guy

    2005-10-01

    This project is a collaboration of Woolsey Petroleum Corporation (a small independent operator) and the Kansas Geological Survey. The project will investigate geologic and engineering factors critical for designing hydraulic fracture treatments in Mississippian ''chat'' reservoirs. Mississippian reservoirs, including the chat, account for 159 million m3 (1 billion barrels) of the cumulative oil produced in Kansas. Mississippian reservoirs presently represent {approx}40% of the state's 5.6*106m3 (35 million barrels) annual production. Although geographically widespread, the ''chat'' is a heterogeneous reservoir composed of chert, cherty dolomite, and argillaceous limestone. Fractured chert with micro-moldic porosity is the best reservoir in this 18- to 30-m-thick (60- to 100-ft) unit. The chat will be cored in an infill well in the Medicine Lodge North field (417,638 m3 [2,626,858 bbls] oil; 217,811,000 m3 [7,692,010 mcf] gas cumulative production; discovered 1954). The core and modern wireline logs will provide geological and petrophysical data for designing a fracture treatment. Optimum hydraulic fracturing design is poorly defined in the chat, with poor correlation of treatment size to production increase. To establish new geologic and petrophysical guidelines for these treatments, data from core petrophysics, wireline logs, and oil-field maps will be input to a fracture-treatment simulation program. Parameters will be established for optimal size of the treatment and geologic characteristics of the predicted fracturing. The fracturing will be performed and subsequent wellsite tests will ascertain the results for comparison to predictions. A reservoir simulation program will then predict the rate and volumetric increase in production. Comparison of the predicted increase in production with that of reality, and the hypothetical fracturing behavior of the reservoir with that of its actual behavior, will serve as tests of

  1. Modeling Wettability Alteration using Chemical EOR Processes in Naturally Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Mojdeh Delshad; Gary A. Pope; Kamy Sepehrnoori

    2007-09-30

    The objective of our search is to develop a mechanistic simulation tool by adapting UTCHEM to model the wettability alteration in both conventional and naturally fractured reservoirs. This will be a unique simulator that can model surfactant floods in naturally fractured reservoir with coupling of wettability effects on relative permeabilities, capillary pressure, and capillary desaturation curves. The capability of wettability alteration will help us and others to better understand and predict the oil recovery mechanisms as a function of wettability in naturally fractured reservoirs. The lack of a reliable simulator for wettability alteration means that either the concept that has already been proven to be effective in the laboratory scale may never be applied commercially to increase oil production or the process must be tested in the field by trial and error and at large expense in time and money. The objective of Task 1 is to perform a literature survey to compile published data on relative permeability, capillary pressure, dispersion, interfacial tension, and capillary desaturation curve as a function of wettability to aid in the development of petrophysical property models as a function of wettability. The new models and correlations will be tested against published data. The models will then be implemented in the compositional chemical flooding reservoir simulator, UTCHEM. The objective of Task 2 is to understand the mechanisms and develop a correlation for the degree of wettability alteration based on published data. The objective of Task 3 is to validate the models and implementation against published data and to perform 3-D field-scale simulations to evaluate the impact of uncertainties in the fracture and matrix properties on surfactant alkaline and hot water floods.

  2. Parallel, Multigrid Finite Element Simulator for Fractured/Faulted and Other Complex Reservoirs based on Common Component Architecture (CCA)

    Energy Technology Data Exchange (ETDEWEB)

    Milind Deo; Chung-Kan Huang; Huabing Wang

    2008-08-31

    Black-oil, compositional and thermal simulators have been developed to address different physical processes in reservoir simulation. A number of different types of discretization methods have also been proposed to address issues related to representing the complex reservoir geometry. These methods are more significant for fractured reservoirs where the geometry can be particularly challenging. In this project, a general modular framework for reservoir simulation was developed, wherein the physical models were efficiently decoupled from the discretization methods. This made it possible to couple any discretization method with different physical models. Oil characterization methods are becoming increasingly sophisticated, and it is possible to construct geologically constrained models of faulted/fractured reservoirs. Discrete Fracture Network (DFN) simulation provides the option of performing multiphase calculations on spatially explicit, geologically feasible fracture sets. Multiphase DFN simulations of and sensitivity studies on a wide variety of fracture networks created using fracture creation/simulation programs was undertaken in the first part of this project. This involved creating interfaces to seamlessly convert the fracture characterization information into simulator input, grid the complex geometry, perform the simulations, and analyze and visualize results. Benchmarking and comparison with conventional simulators was also a component of this work. After demonstration of the fact that multiphase simulations can be carried out on complex fracture networks, quantitative effects of the heterogeneity of fracture properties were evaluated. Reservoirs are populated with fractures of several different scales and properties. A multiscale fracture modeling study was undertaken and the effects of heterogeneity and storage on water displacement dynamics in fractured basements were investigated. In gravity-dominated systems, more oil could be recovered at a given pore

  3. Exploring a carbonate reef reservoir - nuclear magnetic resonance and computed microtomography confronted with narrow channel and fracture porosity

    Science.gov (United States)

    Fheed, Adam; Krzyżak, Artur; Świerczewska, Anna

    2018-04-01

    The complexity of hydrocarbon reservoirs, comprising numerous moulds, vugs, fractures and channel porosity, requires a specific set of methods to be used in order to obtain plausible petrophysical information. Both computed microtomography (μCT) and nuclear magnetic resonance (NMR) are nowadays commonly utilized in pore space investigation. The principal aim of this paper is to propose an alternative, quick and easily executable approach, enabling a thorough understanding of the complicated interiors of the carbonate hydrocarbon reservoir rocks. Highly porous and fractured Zechstein bioclastic packstones from the Brońsko Reef, located in West Poland were studied. Having examined 20 thin sections coming from two different well bores, 10 corresponding core samples were subjected to both μCT and NMR experiments. After a preliminary μCT-based image analysis, 9.4 [T] high-field zero echo time (ZTE) imaging, using a very short repetition time (RT) of 2 [μs] was conducted. Taking into consideration the risk of internal gradients' generation, the reliability of ZTE was verified by 0.6 [T] Single Point Imaging (SPI), during which such a phenomenon is much less probable. Both narrow channels and fractures of different apertures appeared to be common within the studied rocks. Their detailed description was therefore undertaken based on an additional tool - the spatially-resolved 0.05 [T] T2 profiling. According to the obtained results, ZTE seems to be especially suitable for studying porous and fractured carbonate rocks, as little disturbance to the signal appears. This can be confirmed by the SPI, indicating the negligible impact of the internal gradients on the registered ZTE images. Both NMR imaging and μCT allowed for locating the most porous intervals including well-developed mouldic porosity, as well as the contrasting impermeable structures, such as the stylolites and anhydrite veins. The 3D low-field profiling, in turn, showed the fracture aperture variations

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

    Directory of Open Access Journals (Sweden)

    He Zhang

    2015-01-01

    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.

  5. Testing of fractured carbonate oil and gas reservoirs in Western Latvia

    Energy Technology Data Exchange (ETDEWEB)

    Bakhtin, V.V.; Sliznikov, N.I.; Chechetkin, S.I.

    1970-01-01

    A description is given of fractured carbonate reservoirs in Upper and Middle Ordovician, which have high oil saturation, but do not produce at commercial rates. Low production rates were basically caused by low porosity (4 to 6%) and an integranular permeability of less than 0.1 md. The oil is present in the secondary porosity while oil flow is through a system of microfractures. Low productivity also is caused by use of too dense drilling fuid whose clay reduces formation permeability. A new well completion procedure is suggested, in which the formation is perforated by a sand jet and hydraulically fractured by acid. The acid should be 6% in concentration and should contain 0.1% surfactant DME-15. The cost of fracturing can be reduced by using locally available sand.

  6. Outcrop-based reservoir modeling of a naturally fractured siliciclastic CO 2 sequestration site, Svalbard, Arctic Norway

    NARCIS (Netherlands)

    Senger, K.; Ogata, K.; Tveranger, J.; Braathen, A.; Olaussen, S.

    2013-01-01

    We present a geological model of an unconventional siliciclastic reservoir projected for CO2 sequestration near Longyearbyen, Svalbard. The reservoir is characterized by a substantial sub-hydrostatic pressure regime, very low matrix porosity and -permeability values, extensive natural fracturing and

  7. Outcrop-based reservoir modeling of a naturally fractured siliciclastic CO2 sequestration site, Svalbard, Arctic Norway

    NARCIS (Netherlands)

    Senger, K.; Ogata, K.; Tveranger, J.; Braathen, A.; Olaussen, S.

    2013-01-01

    We present a geological model of an unconventional siliciclastic reservoir projected for CO2 sequestration near Longyearbyen, Svalbard. The reservoir is characterized by a substantial sub-hydrostatic pressure regime, very low matrix porosity and -permeability values, extensive natural fracturing and

  8. CHARACTERIZATION OF IN-SITU STRESS AND PERMEABILITY IN FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; M. Nafi Toksoz

    2005-08-01

    During the past six months we have adapted our 3-D elastic, anisotropic finite difference code by implementing the rotated staggered grid (RSG) method to more accurately represent large contrasts of elastic moduli between the fractures and surrounding formation, and applying the perfectly matched layer (PML) absorbing boundary condition to minimize boundary reflections. Two approaches for estimating fracture spacing from scattered seismic energy were developed. The first relates notches in the amplitude spectra of the scattered wavefield to the dominant fracture spacing that caused the scattering. The second uses conventional FK filtering to isolate the backscattered signals and then recovers an estimate of the fracture spacing from the dominant wavelength of those signals. Both methods were tested on synthetic data and then applied to the Emilio field data. The spectral notch method estimated the Emilio fracture spacing to be about 30 to 40 m, while the FK method found fracture spacing of about 48 to 53 m. We continue to work on two field data sets from fractured carbonate reservoirs provided by our industry sponsors--the offshore Emilio Field data (provided by ENIAGIP), and an onshore reservoir from the Middle East (provided by Shell). Calibration data in the form of well logs and previous fracture studies are available for both data sets. In previous reports we showed the spatial distribution fractures in the Emilio Field based on our calculated scattering index values. To improve these results we performed a map migration of all the scattering indices. The results of this migration process show a very strong correlation between the spatial distribution and orientation of our estimated fracture distribution and the fault system in the field. We observe that the scattering index clusters tend to congregate around the fault zones, particularly near multiple faults and at fault tips. We have also processed a swath of data from the second data set (the onshore

  9. Advanced Reservoir Characterization and Evaluation of C02 Gravity Drainage in the Naturally Fractured Sprayberry Trend Area

    Energy Technology Data Exchange (ETDEWEB)

    David S. Schechter

    1998-04-30

    The objective is to assess the economic feasibility of CO2 flooding of the naturally fractured Straberry Trend Area in west Texas. Research is being conducted in the extensive characterization of the reservoirs, the experimental studies of crude oil/brine/rock (COBR) interaction in the reservoirs, the analytical and numerical simulation of Spraberry reservoirs, and the experimental investigations on CO2 gravity drainage in Spraberry whole cores.

  10. AN INTEGRATED APPROACH TO CHARACTERIZING BYPASSED OIL IN HETEROGENEOUS AND FRACTURED RESERVOIRS USING PARTITIONING TRACERS

    Energy Technology Data Exchange (ETDEWEB)

    Akhil Datta-Gupta

    2003-08-01

    We explore the use of efficient streamline-based simulation approaches for modeling partitioning interwell tracer tests in hydrocarbon reservoirs. Specifically, we utilize the unique features of streamline models to develop an efficient approach for interpretation and history matching of field tracer response. A critical aspect here is the underdetermined and highly ill-posed nature of the associated inverse problems. We have adopted an integrated approach whereby we combine data from multiple sources to minimize the uncertainty and non-uniqueness in the interpreted results. For partitioning interwell tracer tests, these are primarily the distribution of reservoir permeability and oil saturation distribution. A novel approach to multiscale data integration using Markov Random Fields (MRF) has been developed to integrate static data sources from the reservoir such as core, well log and 3-D seismic data. We have also explored the use of a finite difference reservoir simulator, UTCHEM, for field-scale design and optimization of partitioning interwell tracer tests. The finite-difference model allows us to include detailed physics associated with reactive tracer transport, particularly those related with transverse and cross-streamline mechanisms. We have investigated the potential use of downhole tracer samplers and also the use of natural tracers for the design of partitioning tracer tests. Finally, the behavior of partitioning tracer tests in fractured reservoirs is investigated using a dual-porosity finite-difference model.

  11. Simulation of commercial scale CO2 injection into a fracture reservoir

    Science.gov (United States)

    Li, Y.; Li, S.; Zhang, Y.

    2011-12-01

    Geologic Carbon Sequestration is a proposed means to reduce atmospheric concentration of carbon dioxide (CO2). At Teapot Dome, Wyoming, CO2 will be injected into the Tensleep Formation, a depleted oil reservoir characterized with significant heterogeneity including facies, faults, and fractures. We've collected geological and engineering characterization data of the entire Teapot Dome field, including core data, well logs, seismic data, and production records. All data were screened for accuracy, before subsets of the data are used to build a geologic reservoir model. A formation structural model is created first by interpreting faults and stratigraphy from 3D seismic data. Formation MicroImager logs are analyzed for fracture characteristics to generate in-situ fracture intensity at wells, which is subsequently interpolated throughout the model with kriging. Based on the intensity and a set of geometric fracture parameters (constrained by outcrop and core measurements), a 3D stochastic Discrete Fracture Network (DFN) is created. One realization of the DFN is upscaled to a dual-porosity simulation model using a variant of the Oda's method. This method upscales the fracture network to an effective grid-block fracture permeability. To account for fluid transfer from matrix to fracture, a sigma factor is computed using average fracture spacings within the grid block. Matrix porosity is populated in the model by kriging interpolation of well-log-derived values. With the dual-porosity model, CO2 is injected near the crest of the dome (the proposed location) at a rate of 2.6 Mt/year for 50 years, with an injection bottomhole pressure set at 160% hydrostatic pressure. Boundary of the model is open except along one bounding fault assumed sealed. Results of the simulation suggest that provided that fluid pressure buildup is not an issue (simulated pressure buildup near the fault is minor), the Tensleep Formation at Teapot Dome can sustain commercial-scale injection over time

  12. Improving Geologic and Engineering Models of Midcontinent Fracture and Karst-Modified Reservoirs Using New 3-D Seismic Attributes

    Energy Technology Data Exchange (ETDEWEB)

    Susan Nissen; Saibal Bhattacharya; W. Lynn Watney; John Doveton

    2009-03-31

    Our project goal was to develop innovative seismic-based workflows for the incremental recovery of oil from karst-modified reservoirs within the onshore continental United States. Specific project objectives were: (1) to calibrate new multi-trace seismic attributes (volumetric curvature, in particular) for improved imaging of karst-modified reservoirs, (2) to develop attribute-based, cost-effective workflows to better characterize karst-modified carbonate reservoirs and fracture systems, and (3) to improve accuracy and predictiveness of resulting geomodels and reservoir simulations. In order to develop our workflows and validate our techniques, we conducted integrated studies of five karst-modified reservoirs in west Texas, Colorado, and Kansas. Our studies show that 3-D seismic volumetric curvature attributes have the ability to re-veal previously unknown features or provide enhanced visibility of karst and fracture features compared with other seismic analysis methods. Using these attributes, we recognize collapse features, solution-enlarged fractures, and geomorphologies that appear to be related to mature, cockpit landscapes. In four of our reservoir studies, volumetric curvature attributes appear to delineate reservoir compartment boundaries that impact production. The presence of these compartment boundaries was corroborated by reservoir simulations in two of the study areas. Based on our study results, we conclude that volumetric curvature attributes are valuable tools for mapping compartment boundaries in fracture- and karst-modified reservoirs, and we propose a best practices workflow for incorporating these attributes into reservoir characterization. When properly calibrated with geological and production data, these attributes can be used to predict the locations and sizes of undrained reservoir compartments. Technology transfer of our project work has been accomplished through presentations at professional society meetings, peer-reviewed publications

  13. A new method in predicting productivity of multi-stage fractured horizontal well in tight gas reservoirs

    Directory of Open Access Journals (Sweden)

    Yunsheng Wei

    2016-10-01

    Full Text Available The generally accomplished technique for horizontal wells in tight gas reservoirs is by multi-stage hydraulic fracturing, not to mention, the flow characteristics of a horizontal well with multiple transverse fractures are very intricate. Conventional methods, well as an evaluation unit, are difficult to accurately predict production capacity of each fracture and productivity differences between wells with a different number of fractures. Thus, a single fracture sets the minimum evaluation unit, matrix, fractures, and lateral wellbore model that are then combined integrally to approximate horizontal well with multiple transverse hydraulic fractures in tight gas reservoirs. This paper presents a new semi-analytical methodology for predicting the production capacity of a horizontal well with multiple transverse hydraulic fractures in tight gas reservoirs. Firstly, a mathematical flow model used as a medium, which is disturbed by finite conductivity vertical fractures and rectangular shaped boundaries, is established and explained by the Fourier integral transform. Then the idea of a single stage fracture analysis is incorporated to establish linear flow model within a single fracture with a variable rate. The Fredholm integral numerical solution is applicable for the fracture conductivity function. Finally, the pipe flow model along the lateral wellbore is adapted to couple multi-stages fracture mathematical models, and the equation group of predicting productivity of a multi-stage fractured horizontal well. The whole flow process from the matrix to bottom-hole and production interference between adjacent fractures is also established. Meanwhile, the corresponding iterative algorithm of the equations is given. In this case analysis, the productions of each well and fracture are calculated under the different bottom-hole flowing pressure, and this method also contributes to obtaining the distribution of pressure drop and production for every

  14. A Novel Integrated Approach to Modelling of Depletion-Induced Change in Full Permeability Tensor of Naturally Fractured Reservoirs

    Directory of Open Access Journals (Sweden)

    Zahra Izadi

    2014-12-01

    Full Text Available More than half of all hydrocarbon reservoirs are Naturally Fractured Reservoirs (NFRs, in which production forecasting is a complicated function of fluid flow in a fracture-matrix system. Modelling of fluid flow in NFRs is challenging due to formation heterogeneity and anisotropy. Stress sensitivity and depletion effect on already-complex reservoir permeability add to the sophistication. Horizontal permeability anisotropy and stress sensitivity are often ignored or inaccurately taken into account when simulating fluid flow in NFRs. The aim of this paper is to present an integrated approach for evaluating the dynamic and true anisotropic nature of permeability in naturally fractured reservoirs. Among other features, this approach considers the effect of reservoir depletion on reservoir permeability tensor, allowing more realistic production forecasts. In this approach the NFR is discretized into grids for which an analytical model yields full permeability tensors. Then, fluid flow is modelled using the finite-element method to obtain pore-pressure distribution within the reservoir. Next, another analytical model evaluates the change in the aperture of individual fractures as a function of effective stress and rock mechanical properties. The permeability tensor of each grid is then updated based on the apertures obtained for the current time step. The integrated model proceeds according to the next prescribed time increments.

  15. Investigation of water/gas coning in natural fractured hydrocarbon reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Shadizadeh, S.R. [University of Petroleum Industry (Iran, Islamic Republic of); Ghorbani, D. [National Iranian Oil Co. (Iran, Islamic Republic of)

    2001-06-01

    A study was conducted in which actual field data from two different naturally fractured reservoir in south western Iran was used to study the mechanism of coning. Coning is generally associated with production from oil reservoirs with overlying gas or underlying water or from a gas reservoir with underlying water. Water/gas coning is a major concern in terms of productivity, increased water disposal and environmental effects. Coning can be avoided if the well is produced below its critical rate which is the maximum water-free or gas-free production rates. The study showed that water/gas coning is caused by an imbalance between the gravitational and viscous forces around the completion interval, leading to lower revenues and increased operating costs. In this study, allowable critical flow rate was calculated using conservative models such as the open tank model and Birk's model with zero angle of vertical fracture. It was concluded that coning is also affected by other pressure drawdown related to some other mechanism resulting in premature water and gas production. 14 refs., 8 figs.

  16. Designing cyclic pressure pulsing in naturally fractured reservoirs using an inverse looking recurrent neural network

    Science.gov (United States)

    Artun, E.; Ertekin, T.; Watson, R.; Miller, B.

    2012-01-01

    In this paper, an inverse looking approach is presented to efficiently design cyclic pressure pulsing (huff 'n' puff) with N 2 and CO 2, which is an effective improved oil recovery method in naturally fractured reservoirs. A numerical flow simulation model with compositional, dual-porosity formulation is constructed. The model characteristics are from the Big Andy Field, which is a depleted, naturally fractured oil reservoir in Kentucky. A set of cyclic pulsing design scenarios is created and run using this model. These scenarios and corresponding performance indicators are fed into the recurrent neural network for training. In order to capture the cyclic, time-dependent behavior of the process, recurrent neural networks are used to develop proxy models that can mimic the reservoir simulation model in an inverse looking manner. Two separate inverse looking proxy models for N 2 and CO 2 injections are constructed to predict the corresponding design scenarios, given a set of desired performance characteristics. Predictive capabilities of developed proxy models are evaluated by comparing simulation outputs with neural-network outputs. It is observed that networks are able to accurately predict the design parameters, such as the injection rate and the duration of injection, soaking and production periods.

  17. Major factors controlling fracture development in the Middle Permian Lucaogou Formation tight oil reservoir, Junggar Basin, NW China

    Science.gov (United States)

    Zhang, Chen; Zhu, Deyu; Luo, Qun; Liu, Luofu; Liu, Dongdong; Yan, Lin; Zhang, Yunzhao

    2017-09-01

    Natural fractures in seven wells from the Middle Permian Lucaogou Formation in the Junggar Basin were evaluated in light of regional structural evolution, tight reservoir geochemistry (including TOC and mineral composition), carbon and oxygen isotopes of calcite-filled fractures, and acoustic emission (AE). Factors controlling the development of natural fractures were analyzed using qualitative and/or semi-quantitative techniques, with results showing that tectonic factors are the primary control on fracture development in the Middle Permian Lucaogou Formation of the Junggar Basin. Analyses of calcite, dolomite, and TOC show positive correlations with the number of fractures, while deltaic lithofacies appear to be the most favorable for fracture development. Mineral content was found to be a major control on tectonic fracture development, while TOC content and sedimentary facies mainly control bedding fractures. Carbon and oxygen isotopes vary greatly in calcite-filled fractures (δ13C ranges from 0.87‰ to 7.98‰, while δ18O ranges from -12.63‰ to -5.65‰), indicating that fracture development increases with intensified tectonic activity or enhanced diagenetic alteration. By analyzing the cross-cutting relationships of fractures in core, as well as four Kaiser Effect points in the acoustic emission curve, we observed four stages of tectonic fracture development. First-stage fractures are extensional, and were generated in the late Triassic, with calcite fracture fills formed between 36.51 °C and 56.89 °C. Second-stage fractures are shear fractures caused by extrusion stress from the southwest to the northeast, generated by the rapid uplift of the Tianshan in the Middle and Late Jurassic; calcite fracture fills formed between 62.91 °C and 69.88 °C. Third-stage fractures are NNW-trending shear fractures that resulted from north-south extrusion and thrusting in a foreland depression along the front of the Early Cretaceous Bogda Mountains. Calcite fracture

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

    Science.gov (United States)

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

    2016-12-01

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

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

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-11-01

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

  20. Characterization of fractures in a carbonate reservoir using walkaway VSP reverse time migration

    Science.gov (United States)

    Takam Takougang, E. M.; Bouzidi, Y.

    2017-12-01

    We present a case study of fracture characterization in a carbonate reservoir from an Abu Dhabi oil field, using reverse time migration of walkaway VSP data. The data were acquired offshore, in a deviated borehole, with an angle of deviation varying between 0 and 24 degree from the vertical direction. The line had a total length of 9 km with the receivers in the borehole located half-way down. Reverse time migration of the up-going wavefield was used to form a high resolution seismic image for interpretation. The reverse time migration scheme was based on a high-order finite-difference solution to the two-way acoustic wave equation. The seismic depth images of the subsurface were formed by the correlation of the forward propagation and the backward propagation of the acoustic wavefields. The velocity model for reverse time migration was derived by full waveform tomography, using the frequencies 4 to 50 Hz. Fractures were extracted from the seismic image using a workflow based on advance seismic attributes (deep steered attribute, similarity attribute) and the Hough's transform. After filtering the data to minimize any frequency related noise, dip-steered sections that contain seismic dips were computed. Similarity attribute were obtained using the previously computed deep steered attribute, and enabled us to extract features such as subtle faults and fractures. The Hough transform was then used to characterize the linear features (fractures and faults) from the similarity attribute. Based on the rose diagram of the orientation of fractures, it appears that the azimuth of the most characteristic strike direction is approximately 5 degree i.e. roughly north-south while that of the second most characteristic strike direction is approximately 20 degree. A few lines are strongly separated from the previous strike directions and are characterize with an azimuth of approximately 95 degree i.e. almost perpendicular. This implies that the development of fractures in the

  1. Oil recovery enhancement from fractured, low permeability reservoirs. Annual report 1990--1991, Part 1

    Energy Technology Data Exchange (ETDEWEB)

    Poston, S.W.

    1991-12-31

    Joint funding by the Department of Energy and the State of Texas has Permitted a three year, multi-disciplinary investigation to enhance oil recovery from a dual porosity, fractured, low matrix permeability oil reservoir to be initiated. The Austin Chalk producing horizon trending thru the median of Texas has been identified as the candidate for analysis. Ultimate primary recovery of oil from the Austin Chalk is very low because of two major technological problems. The commercial oil producing rate is based on the wellbore encountering a significant number of natural fractures. The prediction of the location and frequency of natural fractures at any particular region in the subsurface is problematical at this time, unless extensive and expensive seismic work is conducted. A major portion of the oil remains in the low permeability matrix blocks after depletion because there are no methods currently available to the industry to mobilize this bypassed oil. The following multi-faceted study is aimed to develop new methods to increase oil and gas recovery from the Austin Chalk producing trend. These methods may involve new geological and geophysical interpretation methods, improved ways to study production decline curves or the application of a new enhanced oil recovery technique. The efforts for the second year may be summarized as one of coalescing the initial concepts developed during the initial phase to more in depth analyses. Accomplishments are predicting natural fractures; relating recovery to well-log signatures; development of the EOR imbibition process; mathematical modeling; and field test.

  2. Can introduction of hydraulic fracturing fluids induce biogenic methanogenesis in the shale reservoirs?

    Science.gov (United States)

    Sharma, S.; Wilson, T.; Wrighton, K. C.; Borton, M.; O'Banion, B.

    2017-12-01

    The hydraulic fracturing fluids (HFF) injected into the shale formation are composed primarily of water, proppant and some chemical additives ( 0.5- 2% by volume). The additives contain a lot of organic and inorganic compounds like ammonium sulfate, guar gum, boric acid, hydrochloric acid, citric acid, potassium carbonate, glutaraldehyde, ethylene glycols which serve as friction reducers, gelling agents, crosslinkers, biocides, corrosion/scale inhibitors, etc. The water and additives introduced into the formation ensue a variety of microbiogechmical reactions in the reservoir. For this study produced, water and gas samples were collected from several old and new Marcellus wells in SE Pennsylvania and NE West Virginia to better understand these microbe-water-rock interactions. The carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the produced fluids and CO2 in produced gas (δ13CCO2) are highly enriched with values > +10‰ and +14 ‰ V-PDB respectively. The injected hydraulic fracturing fluid had low δ13CDIC values of < -8‰ V-PDB. The high carbon isotope values in produced fluids and gas possibly indicate 1) dissolution of 13C enriched carbonates in the host rock of reservoir, cement or drilling muds or 2) biogenic methanogenesis in the reservoir. The carbon signatures of carbonates in and around the landing zone and all possible sources of carbon put downhole were analyzed for their 13C signatures. The cement and silica sand had no detectable carbon in them. The drilling mud and carbonate veins had δ13C values of -1.8 and < 2.0 ‰ V-PDB respectively. Therefore, the high δ13CDIC signatures in produced water are possibly due to the microbial utilization of lighter carbon (12C) by microbes or methanogenic bacteria in the reservoir. It is possible that introduction of C containing nutrients like guar, methanol, methylamines, etc. stimulates certain methanogen species in the reservoir to produce biogenic methane. Genomic analysis reveals

  3. Pressure Transient Analysis and Flux Distribution for Multistage Fractured Horizontal Wells in Triple-Porosity Reservoir Media with Consideration of Stress-Sensitivity Effect

    Directory of Open Access Journals (Sweden)

    Jingjing Guo

    2015-01-01

    Full Text Available Triple-porosity model is usually adopted to describe reservoirs with multiscaled pore spaces, including matrix pores, natural fractures, and vugs. Multiple fractures created by hydraulic fracturing can effectively improve the connectivity between existing natural fractures and thus increase well deliverability. However, little work has been done on pressure transient behavior of multistage fractured horizontal wells in triple-porosity reservoirs. Based on source/sink function method, this paper presents a triple-porosity model to investigate the transient pressure dynamics and flux distribution for multistage fractured horizontal wells in fractured-vuggy reservoirs with consideration of stress-dependent natural fracture permeability. The model is semianalytically solved by discretizing hydraulic fractures and Pedrosa’s transformation, perturbation theory, and integration transformation method. Type curves of transient pressure dynamics are generated, and flux distribution among hydraulic fractures for a fractured horizontal well with constant production rate is also discussed. Parametric study shows that major influential parameters on transient pressure responses are parameters pertinent to reservoir properties, interporosity mass transfer, and hydraulic fractures. Analysis of flux distribution indicates that flux density gradually increases from the horizontal wellbore to fracture tips, and the flux contribution of outermost fractures is higher than that of inner fractures. The model can also be extended to optimize hydraulic fracture parameters.

  4. Fractured Reservoir Simulation: a Challenging and Rewarding Issue Simulation des réservoirs fracturés : un défi et un enjeu

    Directory of Open Access Journals (Sweden)

    Bourbiaux B.

    2010-03-01

    Full Text Available The recent years have seen a growing awareness of the role played by fractures in petroleum reservoirs production and recovery. Hence, much effort was devoted to the diagnosis of fracture presence and impact on production. However, turning that diagnosis into field development decisions goes through reservoir simulation. This paper addresses some of the specificities of fractured reservoirs that make that their simulation is both challenging and rewarding. Indeed, the integration of fractures into a flow simulation model is not straightforward because of the existing gap between the geological fault/fracture network and the fingerprint of that network on often-complex recovery mechanisms. Considering that fractures may impede or enhance production, fractured reservoir simulation may be seen as a technical challenge with potentially-high reward. This paper underlines that specific framework as an introduction to two technical articles dedicated to dual-porosity reservoir simulation. Although it constitutes another major aspect of any fractured reservoir study, the geological characterization of fractures is not discussed herein, but only evoked because of more and more integration of static and dynamic aspects. Au cours des années récentes, la prise de conscience du rôle des fractures sur la production et la récupération des champs est devenue de plus en plus forte au sein de la communauté pétrolière. Aussi beaucoup d’efforts ont-ils été consacrés à la détection des fractures et à l’analyse de leur impact sur la production. Toutefois, la prise en considération de ces observations dans les choix de développement des champs passe par la simulation de réservoir. Cet article traite des spécificités propres aux réservoirs fracturés et qui font de leur simulation à la fois un défi et un enjeu. En effet, l’intégration des fractures dans un modèle de simulation des écoulements n’est pas immédiate en raison du difficile

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

    Directory of Open Access Journals (Sweden)

    Chaohua Guo

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

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

    Science.gov (United States)

    Guo, Chaohua; Wei, Mingzhen; Liu, Hong

    2018-01-01

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

  7. A modeling and numerical algorithm for thermoporomechanics in multiple porosity media for naturally fractured reservoirs

    Science.gov (United States)

    Kim, J.; Sonnenthal, E. L.; Rutqvist, J.

    2011-12-01

    Rigorous modeling of coupling between fluid, heat, and geomechanics (thermo-poro-mechanics), in fractured porous media is one of the important and difficult topics in geothermal reservoir simulation, because the physics are highly nonlinear and strongly coupled. Coupled fluid/heat flow and geomechanics are investigated using the multiple interacting continua (MINC) method as applied to naturally fractured media. In this study, we generalize constitutive relations for the isothermal elastic dual porosity model proposed by Berryman (2002) to those for the non-isothermal elastic/elastoplastic multiple porosity model, and derive the coupling coefficients of coupled fluid/heat flow and geomechanics and constraints of the coefficients. When the off-diagonal terms of the total compressibility matrix for the flow problem are zero, the upscaled drained bulk modulus for geomechanics becomes the harmonic average of drained bulk moduli of the multiple continua. In this case, the drained elastic/elastoplastic moduli for mechanics are determined by a combination of the drained moduli and volume fractions in multiple porosity materials. We also determine a relation between local strains of all multiple porosity materials in a gridblock and the global strain of the gridblock, from which we can track local and global elastic/plastic variables. For elastoplasticity, the return mapping is performed for all multiple porosity materials in the gridblock. For numerical implementation, we employ and extend the fixed-stress sequential method of the single porosity model to coupled fluid/heat flow and geomechanics in multiple porosity systems, because it provides numerical stability and high accuracy. This sequential scheme can be easily implemented by using a porosity function and its corresponding porosity correction, making use of the existing robust flow and geomechanics simulators. We implemented the proposed modeling and numerical algorithm to the reaction transport simulator

  8. CHARACTERIZATION OF IN-SITU STRESS AND PERMEABILITY IN FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Daniel R. Burns; M. Nafi Toksoz

    2002-12-31

    We have extended a three-dimensional finite difference elastic wave propagation model previously developed at the Massachusetts Institute of Technology (MIT) Earth Resources Laboratory (ERL) for modeling and analyzing the effect of fractures on seismic waves. The code has been translated into C language and parallelized [using message passing interface (MPI)] to allow for larger models to be run on Linux PC computer clusters. We have also obtained another 3-D code from Lawrence Berkeley Laboratory, which we will use for verification of our ERL code results and also to run discrete fracture models. Testing of both codes is underway. We are working on a new finite difference model of borehole wave propagation for stressed formations. This code includes coordinate stretching to provide stable, variable grid sizes that will allow us to model the thin fluid annulus layers in borehole problems, especially for acoustic logging while drilling (LWD) applications. We are also extending our analysis routines for the inversion of flexural wave dispersion measurements for in situ stress estimates. Initial results on synthetic and limited field data are promising for a method to invert cross dipole data for the rotation angle and stress state simultaneously. A meeting is being scheduled between MIT and Shell Oil Company scientists to look at data from a fractured carbonate reservoir that may be made available to the project. The Focus/Disco seismic processing system from Paradigm Geophysical has been installed at ERL for field data analysis and as a platform for new analysis modules. We have begun to evaluate the flow properties of discrete fracture distributions through a simple 2D numerical model. Initial results illustrate how fluid flow pathways are very sensitive to variations in the geometry and apertures of fracture network.

  9. The pore-fracture system properties of coalbed methane reservoirs in the Panguan Syncline, Guizhou, China

    Directory of Open Access Journals (Sweden)

    Song Li

    2012-11-01

    Full Text Available The Panguan Syncline contains abundant coal resources, which may be a potential source of coalbed methane. In order to evaluate the coalbed methane production potential in this area, we investigated the pore-fracture system of coalbed methane reservoirs, and analyzed the gas sorption and seepage capacities by using various analytical methods, including scanning electron microscopy (SEM, optical microscopy, mercury-injection test, low-temperature N2 isotherm adsorption/desorption analyses, low-field nuclear magnetic resonance and methane isothermal adsorption measurements. The results show that the samples of the coal reservoirs in the Panguan Syncline have moderate gas sorption capacity. However, the coals in the study area have favorable seepage capacities, and are conductive for the coalbed methane production. The physical properties of the coalbed methane reservoirs in the Panguan Syncline are generally controlled by coal metamorphism: the low rank coal usually has low methane sorption capacity and its pore and microfractures are poorly developed; while the medium rank coal has better methane sorption capacity, and its seepage pores and microfractures are well developed, which are sufficient for the coalbed methane’s gathering and exploration. Therefore, the medium rank coals in the Panguan Syncline are the most prospective targets for the coalbed methane exploration and production.

  10. The Influence of Fold and Fracture Development on Reservoir Behavior of the Lisburne Group of Northern Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, Wesley K.; Hanks, Catherine L.; Whalen, Michael T.; Jensen1, Jerry; Shackleton, J. Ryan; Jadamec, Margarete A.; McGee, Michelle M.; Karpov1, Alexandre V.

    2001-07-23

    The Carboniferous Lisburne Group is a major carbonate reservoir unit in northern Alaska. The lisburne is detachment folded where it is exposed throughout the northeastern Brooks Range, but is relatively underformed in areas of current production in the subsurface of the North Slope. The objectives of this study are to develop a better understanding of four major aspects of the Lisburne: (1) The geometry and kinematics of detachment folds and their truncation by thrust faults, (2) The influence of folding on fracture patterns, (3) The influence of deformation on fluid flow, and (4) Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics.

  11. A feasibility study on the expected seismic AVA signatures of deep fractured geothermal reservoirs in an intrusive basement

    International Nuclear Information System (INIS)

    Aleardi, Mattia; Mazzotti, Alfredo

    2014-01-01

    The deep geothermal reservoirs in the Larderello-Travale field (southern Tuscany) are found in intensively fractured portions of intrusive/metamorphic rocks. Therefore, the geothermal exploration has been in search of possible fracture signatures that could be retrieved from the analysis of geophysical data. In the present work we assess the feasibility of finding seismic markers in the pre-stack domain which may pinpoint fractured levels. Thanks to the availability of data from boreholes that ENEL GreenPower drilled in the deep intrusive basement of this geothermal field, we derived the expected amplitude versus angle (AVA) responses of the vapour reservoirs found in some intensely, but very localized, fractured volumes within the massive rocks. The information we have available limit us to build 1D elastic and isotropic models only and thus anisotropy effects related to the presence of fractures cannot be properly modelled. We analysed the velocities and the density logs pertaining to three wells which reached five deep fractured zones in the basement. The AVA response of the fractured intervals is modelled downscaling the log data to seismic scale and comparing the analytical AVA response (computed with the Aki and Richards approximation) and the AVA extracted from a synthetic common mid point (calculated making use of a reflectivity algorithm). The results show that the amplitude of the reflections from the fractured level is characterized by negative values at vertical incidence and by decreasing absolute amplitudes with the increase of the source to receiver offset. This contrasts with many observations from hydrocarbon exploration in clastic reservoirs where gas-sand reflections often exhibit negative amplitudes at short offsets but increasing absolute amplitudes for increasing source to receiver offsets. Thereby, some common AVA attributes considered in silicoclastic lithologies would lead to erroneous fracture localization. For this reason we propose a

  12. Using Biosurfactants Produced from Agriculture Process Waste Streams to Improve Oil Recovery in Fractured Carbonate Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Johnson; Mehdi Salehi; Karl Eisert; Sandra Fox

    2009-01-07

    This report describes the progress of our research during the first 30 months (10/01/2004 to 03/31/2007) of the original three-year project cycle. The project was terminated early due to DOE budget cuts. This was a joint project between the Tertiary Oil Recovery Project (TORP) at the University of Kansas and the Idaho National Laboratory (INL). The objective was to evaluate the use of low-cost biosurfactants produced from agriculture process waste streams to improve oil recovery in fractured carbonate reservoirs through wettability mediation. Biosurfactant for this project was produced using Bacillus subtilis 21332 and purified potato starch as the growth medium. The INL team produced the biosurfactant and characterized it as surfactin. INL supplied surfactin as required for the tests at KU as well as providing other microbiological services. Interfacial tension (IFT) between Soltrol 130 and both potential benchmark chemical surfactants and crude surfactin was measured over a range of concentrations. The performance of the crude surfactin preparation in reducing IFT was greater than any of the synthetic compounds throughout the concentration range studied but at low concentrations, sodium laureth sulfate (SLS) was closest to the surfactin, and was used as the benchmark in subsequent studies. Core characterization was carried out using both traditional flooding techniques to find porosity and permeability; and NMR/MRI to image cores and identify pore architecture and degree of heterogeneity. A cleaning regime was identified and developed to remove organic materials from cores and crushed carbonate rock. This allowed cores to be fully characterized and returned to a reproducible wettability state when coupled with a crude-oil aging regime. Rapid wettability assessments for crushed matrix material were developed, and used to inform slower Amott wettability tests. Initial static absorption experiments exposed limitations in the use of HPLC and TOC to determine

  13. The Influence of Fold and Fracture Development on Reservoir Behavior of the Lisburne Group of Northern Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, W.K.; Hanks, C.L.; Whalen, M.T.; Jensen, J.; Atkinson, P.K.; Brinton, J.S.

    2001-01-09

    The objectives of this study were to develop a better understanding of four major aspects of the Lisburne: (1) The geometry and kinematics of detachment folds and their truncation by thrust faults, (2) The influence of folding and lithostratigraphy on fracture patterns, (3) Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics, and (4) The influence of lithostratigraphy and deformation on fluid flow.

  14. Advanced Reservoir Characterization and Evaluation of CO2 Gravity Drainage in the Naturally Fractured Spraberry Trend Area, Class III

    Energy Technology Data Exchange (ETDEWEB)

    Knight, Bill; Schechter, David S.

    2002-07-26

    The goal of this project was to assess the economic feasibility of CO2 flooding the naturally fractured Spraberry Trend Area in west Texas. This objective was accomplished through research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interactions in the reservoirs, (3) reservoir performance analysis, and (4) experimental investigations on CO2 gravity drainage in Spraberry whole cores. This provides results of the final year of the six-year project for each of the four areas.

  15. Advanced Reservoir Characterization and Evaluation of CO{sub 2} Gravity Drainage in the Naturally Fractured Spraberry Trend Area

    Energy Technology Data Exchange (ETDEWEB)

    Schechter, D.S.

    1999-02-03

    The overall goal of this project is to assess the economic feasibility of CO{sub 2} flooding the naturally fractured Spraberry Trend Area in West Texas. This objective is being accomplished by conducting research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interactions in the reservoirs, (3) reservoir performance analysis, and, (4) experimental investigations on CO2 gravity drainage in Spraberry whole cores. This report provides results of the third year of the five-year project for each of the four areas including a status report of field activities leading up to injection of CO2.

  16. An Analysis for the Influences of Fracture Network System on Multi-Stage Fractured Horizontal Well Productivity in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Deliang Zhang

    2018-02-01

    Full Text Available This paper presents two representative models to analyze the flow dynamic of multi-scale porous medium in hydraulic fractured horizontal shale gas wells. In this work, considering the characteristic mechanisms (multi-scale porous space, desorption and diffusion, flow equations in shale are established. After that, two representative models (discrete fracture model and dual-porosity model are tailored to our issues. Solved by the control-volume finite element method (CVFEM, influences of fracture network system on productivity in shale reservoirs are analyzed in detail. Based on the analysis, the effects can be summarized as follow: at the beginning of production, high conductivity fracture network means more free gas could be produced; at the later part of production, high conductive fracture network can form a large low pressure region, which can not only stimulate the desorption of adsorbed gas, but also reduce the flow resistance to the well. Finally, the sensitivities of characteristic parameters in shale are discussed.

  17. Capacity expansion analysis of UGSs rebuilt from low-permeability fractured gas reservoirs with CO2 as cushion gas

    Directory of Open Access Journals (Sweden)

    Yufei Tan

    2016-11-01

    Full Text Available The techniques of pressurized mining and hydraulic fracturing are often used to improve gas well productivity at the later development stage of low-permeability carbonate gas reservoirs, but reservoirs are watered out and a great number of micro fractures are produced. Therefore, one of the key factors for underground gas storages (UGS rebuilt from low-permeability fractured gas reservoirs with CO2 as the cushion gas is how to expand storage capacity effectively by injecting CO2 to displace water and to develop control strategies for the stable migration of gas–water interface. In this paper, a mathematical model was established to simulate the gas–water flow when CO2 was injected into dual porosity reservoirs to displace water. Then, the gas–water interface migration rules while CO2 was injected in the peripheral gas wells for water displacement were analyzed with one domestic UGS rebuilt from fractured gas reservoirs as the research object. And finally, discussion was made on how CO2 dissolution, bottom hole flowing pressure (BHFP, CO2 injection rate and micro fracture parameters affect the stability of gas–water interface in the process of storage capacity expansion. It is shown that the speed of capacity expansion reaches the maximum value at the fifth cycle and then decreases gradually when UGS capacity is expanded in the pattern of more injection and less withdrawal. Gas–water interface during UGS capacity expansion is made stable due to that the solubility of CO2 in water varies with the reservoir pressure. When the UGS capacity is expanded at constant BHFP and the flow rate, the expansion speed can be increased effectively by increasing the BHFP and the injection flow rate of gas wells in the central areas appropriately. In the reservoir areas with high permeability and fracture-matrix permeability ratio, the injection flow rate should be reduced properly to prevent gas–water interface fingering caused by a high-speed flow

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

    Science.gov (United States)

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

    2017-12-01

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

  19. ADVANCED CHARACTERIZATION OF FRACTURED RESERVOIRS IN CARBONATE ROCKS: THE MICHIGAN BASIN

    Energy Technology Data Exchange (ETDEWEB)

    James R. Wood; William B. Harrison

    2002-12-01

    The purpose of the study was to collect and analyze existing data on the Michigan Basin for fracture patterns on scales ranging form thin section to basin. The data acquisition phase has been successfully concluded with the compilation of several large digital databases containing nearly all the existing information on formation tops, lithology and hydrocarbon production over the entire Michigan Basin. These databases represent the cumulative result of over 80 years of drilling and exploration. Plotting and examination of these data show that contrary to most depictions, the Michigan Basin is in fact extensively faulted and fractured, particularly in the central portion of the basin. This is in contrast to most of the existing work on the Michigan Basin, which tends to show relatively simple structure with few or minor faults. It also appears that these fractures and faults control the Paleozoic sediment deposition, the subsequent hydrocarbon traps and very likely the regional dolomitization patterns. Recent work has revealed that a detailed fracture pattern exists in the interior of the Central Michigan Basin, which is related to the mid-continent gravity high. The inference is that early Precambrian, ({approx}1 Ga) rifting events presumed by many to account for the gravity anomaly subsequently controlled Paleozoic sedimentation and later hydrocarbon accumulation. There is a systematic relationship between the faults and a number of gas and oil reservoirs: major hydrocarbon accumulations consistently occur in small anticlines on the upthrown side of the faults. The main tools used in this study to map the fault/fracture patterns are detailed, close-interval (CI = 10 feet) contouring of the formation top picks accompanied by a new way of visualizing the data using a special color spectrum to bring out the third dimension. In addition, recent improvements in visualization and contouring software were instrumental in the study. Dolomitization is common in the

  20. Fracture systems and mesoscale structural patterns in the siliciclastic mesozoic reservoir-caprock succession of the longyearbyen CO2 lab project: Implications for geological CO2 sequestration in central spitsbergen, svalbard

    NARCIS (Netherlands)

    Ogata, Kei; Senger, Kim; Braathen, Alvar; Tveranger, Jan; Olaussen, Snorre

    2014-01-01

    In unconventional, naturally fractured reservoirs, networks of structural discontinuities largely control fluid flow. In this study, we mapped and analysed systematic fracture patterns within the Mesozoic succession of Central Spitsbergen to characterise the reservoir-caprock system explored for

  1. A Thermo-Hydro-Mechanical modeling of fracture opening and closing due heat extraction from geothermal reservoir

    Science.gov (United States)

    Nand Pandey, Sachchida; Chaudhuri, Abhijit; Kelkar, Sharad

    2015-04-01

    Increasing the carbon dioxide concentration in atmosphere become challenging task for the scientific community. To achieve the sustainable growth with minimum pollution in atmosphere requires the development of low carbon technology or switch towards renewable energy. Geothermal energy is one of the promising source of clean energy. Geothermal energy is also considered a sustainable, reliable and least-expensive. This study presents a numerical modeling of subsurface heat extraction from the reservoir. The combine flow, heat transfer and geo-mechanical problem are modeled using FEHM code, which was validated against existing field data, numerical code and commercial software. In FEHM the flow and heat transfer in reservoir are solved by control volume method while for mechanical deformation finite element technique is used. The 3-D computational domain (230m × 200m × 1000m) has single horizontal fault/fracture, which is located at 800 m depth from the ground surface. The fracture connects the injection and production wells. The distance between the wells is 100 m. A geothermal gradient 0.08 °C/m is considered. The temperatures at top and bottom boundaries are held fixed as 20 and 100 °C respectively. The zero heat and mass flux boundary conditions are imposed to all vertical side boundaries of the domain. The simulation results for 100 days suggests that the computational domain is sufficiently large as the temperature along the vertical boundaries are not affected by cold-water injection. To model the thermo-poro-elastic deformation, zero all three components of displacement are specified as zero at the bottom. The zero stress condition along all other boundaries allows the boundaries to move freely. The temperature and pressure dependent fluid properties such as density and viscosity with single phase flow in saturated medium is considered. We performed a series of thermo-hydro-mechanical (THM) simulations to show aperture alteration due to cold

  2. Fracture detection and mapping for geothermal reservoir definition: an assessment of current technology, research, and research needs

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, N.E.

    1984-11-01

    The detection and mapping of fractures and other zones of high permeability, whether natural or manmade, has been a subject of considerable economic and scientific interest to the pertroleum industry and to the geothermal community. Research related to fractured geothermal reservoirs has been conducted under several past DOE geothermal energy development programs. In this paper we review the present state of technology in fracture detection and mapping. We outline the major problems and limitations of the ''conventional'' techniques, and current research in new technologies. We also present research needs.

  3. Numerical simulation of electricity generation potential from fractured granite reservoir through vertical wells at Yangbajing geothermal field

    International Nuclear Information System (INIS)

    Zeng, Yu-chao; Zhan, Jie-min; Wu, Neng-you; Luo, Ying-ying; Cai, Wen-hao

    2016-01-01

    Yangbajing geothermal field is the first high-temperature hydrothermal convective geothermal system in China. Research and development of the deep fractured granite reservoir is of great importance for capacity expanding and sustaining of the ground power plant. The geological exploration found that there is a fractured granite heat reservoir at depth of 950–1350 m in well ZK4001 in the north of the geothermal field, with an average temperature of 248 °C and a pressure of 8.01–11.57 MPa. In this work, electricity generation potential and its dependent factors from this fractured granite reservoir by water circulating through vertical wells are numerically investigated. The results indicate that the vertical well system attains an electric power of 16.8–14.7 MW, a reservoir impedance of 0.29–0.46 MPa/(kg/s) and an energy efficiency of about 29.6–12.8 during an exploiting period of 50 years under reference conditions, showing good heat production performance. The main parameters affecting the electric power are water production rate and injection temperature. The main parameters affecting reservoir impedance are reservoir permeability, injection temperature and water production rate. The main parameters affecting the energy efficiency are reservoir permeability, injection temperature and water production rate. Higher reservoir permeability or more reasonable injection temperature or water production rate within certain ranges will be favorable for improving the electricity generation performance. - Highlights: • We established a numerical model of vertical well heat mining system. • Desirable electricity production performance can be obtained under suitable conditions. • The system attains an electric power of 16.8–14.7 MW with an efficiency of about 29.6–12.8. • Electric power mainly depends on water production rate and injection temperature. • Higher permeability within a certain range is favorable for electricity generation.

  4. Cavitation-based hydro-fracturing technique for geothermal reservoir stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John; Wang, Hong; Ren, Fei; Cox, Thomas S.

    2017-02-21

    A rotary shutter valve 500 is used for geothermal reservoir stimulation. The valve 500 includes a pressure chamber 520 for holding a working fluid (F) under pressure. A rotatable shutter 532 is turned with a powering device 544 to periodically align one or more windows 534 with one or more apertures 526 in a bulkhead 524. When aligned, the pressurized working fluid (F) flows through the bulkhead 524 and enters a pulse cavity 522, where it is discharged from the pulse cavity 522 as pressure waves 200. The pressure wave propagation 200 and eventual collapse of the bubbles 202 can be transmitted to a target rock surface 204 either in the form of a shock wave 206, or by micro jets 208, depending on the bubble-surface distance. Once cavitation at the rock face begins, fractures are initiated in the rock to create a network of micro-fissures for enhanced heat transfer.

  5. Simulation of Naturally Fractured Reservoirs. State of the Art Simulation des réservoirs naturellement fracturés. État de l’art

    Directory of Open Access Journals (Sweden)

    Lemonnier P.

    2010-04-01

    Full Text Available Naturally fractured reservoirs contain a significant amount of the world oil reserves. The production of this type of reservoirs constitutes a challenge for reservoir engineers. Use of reservoir simulators can help reservoir engineers in the understanding of the main physical mechanisms and in the choice of the best recovery process and its optimization. Significant progress has been made since the first publications on the dual-porosity concept in the sixties. This paper and the preceding one (Part 1 present the current techniques of modeling used in industrial simulators. The optimal way to predict matrix-fracture transfers at the simulator cell scale has no definite answer and various methods are implemented in industrial simulators. This paper focuses on the modeling of physical mechanisms driving flows and interactions/ exchanges within and between fracture and matrix media for a better understanding of proposed flow formula and simulation methods. Typical features of fractured reservoir numerical simulations are also described with an overview of the implementation of geomechanics effects, an application of uncertainty assessment methodology to a fractured gas reservoir and finally a presentation of a history matching methodology for fractured reservoirs. Les réservoirs naturellement fracturés contiennent une partie significative des réserves en huile mondiales. La production de ce type de réservoirs constitue un défi pour les ingénieurs de réservoir. L’utilisation des simulateurs de réservoir peut aider l’ingénieur de réservoir à mieux comprendre les principaux mécanismes physiques, à choisir le procédé de récupération le mieux adapté et à l’optimiser. Des progrès sensibles ont été réalisés depuis les premières publications sur le concept double-milieu dans les années soixante. Cet article et le précédent (Partie 1 présentent les techniques actuelles de modélisation utilisées dans les simulateurs

  6. Gas hydrate saturations estimated from pore-and fracture-filling gas hydrate reservoirs in the Qilian Mountain permafrost, China.

    Science.gov (United States)

    Xiao, Kun; Zou, Changchun; Lu, Zhenquan; Deng, Juzhi

    2017-11-24

    Accurate calculation of gas hydrate saturation is an important aspect of gas hydrate resource evaluation. The effective medium theory (EMT model), the velocity model based on two-phase medium theory (TPT model), and the two component laminated media model (TCLM model), are adopted to investigate the characteristics of acoustic velocity and gas hydrate saturation of pore- and fracture-filling reservoirs in the Qilian Mountain permafrost, China. The compressional wave (P-wave) velocity simulated by the EMT model is more consistent with actual log data than the TPT model in the pore-filling reservoir. The range of the gas hydrate saturation of the typical pore-filling reservoir in hole DKXX-13 is 13.0~85.0%, and the average value of the gas hydrate saturation is 61.9%, which is in accordance with the results by the standard Archie equation and actual core test. The P-wave phase velocity simulated by the TCLM model can be transformed directly into the P-wave transverse velocity in a fracture-filling reservoir. The range of the gas hydrate saturation of the typical fracture-filling reservoir in hole DKXX-19 is 14.1~89.9%, and the average value of the gas hydrate saturation is 69.4%, which is in accordance with actual core test results.

  7. Naturally fractured tight gas: Gas reservoir detection optimization. Quarterly report, January 1--March 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    Economically viable natural gas production from the low permeability Mesaverde Formation in the Piceance Basin, Colorado requires the presence of an intense set of open natural fractures. Establishing the regional presence and specific location of such natural fractures is the highest priority exploration goal in the Piceance and other western US tight, gas-centered basins. Recently, Advanced Resources International, Inc. (ARI) completed a field program at Rulison Field, Piceance Basin, to test and demonstrate the use of advanced seismic methods to locate and characterize natural fractures. This project began with a comprehensive review of the tectonic history, state of stress and fracture genesis of the basin. A high resolution aeromagnetic survey, interpreted satellite and SLAR imagery, and 400 line miles of 2-D seismic provided the foundation for the structural interpretation. The central feature of the program was the 4.5 square mile multi-azimuth 3-D seismic P-wave survey to locate natural fracture anomalies. The interpreted seismic attributes are being tested against a control data set of 27 wells. Additional wells are currently being drilled at Rulison, on close 40 acre spacings, to establish the productivity from the seismically observed fracture anomalies. A similar regional prospecting and seismic program is being considered for another part of the basin. The preliminary results indicate that detailed mapping of fault geometries and use of azimuthally defined seismic attributes exhibit close correlation with high productivity gas wells. The performance of the ten new wells, being drilled in the seismic grid in late 1996 and early 1997, will help demonstrate the reliability of this natural fracture detection and mapping technology.

  8. Coupling of two-phase flow in fractured-vuggy reservoir with filling medium

    Directory of Open Access Journals (Sweden)

    Xie Haojun

    2017-03-01

    Full Text Available Caves in fractured-vuggy reservoir usually contain lots of filling medium, so the two-phase flow in formations is the coupling of free flow and porous flow, and that usually leads to low oil recovery. Considering geological interpretation results, the physical filled cave models with different filling mediums are designed. Through physical experiment, the displacement mechanism between un-filled areas and the filling medium was studied. Based on the experiment model, we built a mathematical model of laminar two-phase coupling flow considering wettability of the porous media. The free fluid region was modeled using the Navier-Stokes and Cahn-Hilliard equations, and the two-phase flow in porous media used Darcy's theory. Extended BJS conditions were also applied at the coupling interface. The numerical simulation matched the experiment very well, so this numerical model can be used for two-phase flow in fracture-vuggy reservoir. In the simulations, fluid flow between inlet and outlet is free flow, so the pressure difference was relatively low compared with capillary pressure. In the process of water injection, the capillary resistance on the surface of oil-wet filling medium may hinder the oil-water gravity differentiation, leading to no fluid exchange on coupling interface and remaining oil in the filling medium. But for the water-wet filling medium, capillary force on the surface will coordinate with gravity. So it will lead to water imbibition and fluid exchange on the interface, high oil recovery will finally be reached at last.

  9. Some open issues in the analysis of the storage and migration properties of fractured carbonate reservoirs

    Science.gov (United States)

    Agosta, Fabrizio

    2017-04-01

    Underground CO2 storage in depleted hydrocarbon reservoirs may become a common practice in the future to lower the concentration of greenhouse gases in the atmosphere. Results from the first experiments conducted in carbonate rocks, for instance the Lacq integrated CCS Pilot site, SW France, are quite exciting. All monitored parameters, such as the CO2 concentration at well sites, well pressures, cap rock integrity and environmental indicators show the long-term integrity of this type of geological reservoirs. Other positive news arise from the OXY-CFB-300 Compostilla Project, NW Spain, where most of the injected CO2 dissolved into the formation brines, suggesting the long-term security of this method. However, in both cases, the CO2- rich fluids partially dissolved the carbonate minerals during their migration through the fractured reservoir, modifying the overall pore volume and pressure regimes. These results support the growing need for a better understanding of the mechanical behavior of carbonate rocks over geological time of scales. In fact, it is well known that carbonates exhibit a variety of deformation mechanisms depending upon many intrinsic factors such as composition, texture, connected pore volume, and nature of the primary heterogeneities. Commonly, tight carbonates are prone to opening-mode and/or pressure solution deformation. The interplay between these two mechanisms likely affects the petrophysical properties of the fault damage zones, which form potential sites for CO2 storage due to their high values of both connected porosity and permeability. On the contrary, cataclastic deformation produces fault rocks that often form localized fluid barriers for cross-fault fluid flow. Nowadays, questions on the conditions of sealing/leakage of carbonate fault rocks are still open. In particular, the relative role played by bulk crushing, chipping, cementation, and pressure solution on connected porosity of carbonate fault rocks during structural

  10. Requirement of system-reservoir bound states for entanglement protection

    Science.gov (United States)

    Behzadi, N.; Ahansaz, B.; Faizi, E.; Kasani, H.

    2018-03-01

    In this work, a genuine mechanism for entanglement protection of a two- qubit system interacting with a dissipative common reservoir is investigated. Based on generating a bound state for the system-reservoir, we show that stronger bound state in the energy spectrum can be created by adding another non-interacting qubits into the reservoir. It turns out that obtaining higher degrees of boundedness in the energy spectrum leads to a better protection of two-qubit entanglement against the dissipative noises. Also, it is figured out that the formation of bound state not only exclusively determines the long-time entanglement protection, irrespective to the Markovian and non-Markovian dynamics, but also performs the same task for reservoirs with different spectral densities.

  11. Simulation of counter-current imbibition in water-wet fractured reservoirs based on discrete-fracture model

    Directory of Open Access Journals (Sweden)

    Wang Yueying

    2017-08-01

    Full Text Available Isolated fractures usually exist in fractured media systems, where the capillary pressure in the fracture is lower than that of the matrix, causing the discrepancy in oil recoveries between fractured and non-fractured porous media. Experiments, analytical solutions and conventional simulation methods based on the continuum model approach are incompetent or insufficient in describing media containing isolated fractures. In this paper, the simulation of the counter-current imbibition in fractured media is based on the discrete-fracture model (DFM. The interlocking or arrangement of matrix and fracture system within the model resembles the traditional discrete fracture network model and the hybrid-mixed-finite-element method is employed to solve the associated equations. The Behbahani experimental data validates our simulation solution for consistency. The simulation results of the fractured media show that the isolated-fractures affect the imbibition in the matrix block. Moreover, the isolated fracture parameters such as fracture length and fracture location influence the trend of the recovery curves. Thus, the counter-current imbibition behavior of media with isolated fractures can be predicted using this method based on the discrete-fracture model.

  12. Fracture corridors as seal-bypass systems in siliciclastic reservoir-cap rock successions: Field-based insights from the Jurassic Entrada Formation (SE Utah, USA)

    NARCIS (Netherlands)

    Ogata, Kei; Senger, Kim; Braathen, Alvar; Tveranger, Jan

    2014-01-01

    Closely spaced, sub-parallel fracture networks contained within localized tabular zones that are fracture corridors may compromise top seal integrity and form pathways for vertical fluid flow between reservoirs at different stratigraphic levels. This geometry is exemplified by fracture corridors

  13. An Integrated Approach to Characterizing Bypassed Oil in Heterogeneous and Fractured Reservoirs Using Partitioning Tracers

    Energy Technology Data Exchange (ETDEWEB)

    Akhil Datta-Gupta

    2006-12-31

    We explore the use of efficient streamline-based simulation approaches for modeling partitioning interwell tracer tests in hydrocarbon reservoirs. Specifically, we utilize the unique features of streamline models to develop an efficient approach for interpretation and history matching of field tracer response. A critical aspect here is the underdetermined and highly ill-posed nature of the associated inverse problems. We have investigated the relative merits of the traditional history matching ('amplitude inversion') and a novel travel time inversion in terms of robustness of the method and convergence behavior of the solution. We show that the traditional amplitude inversion is orders of magnitude more non-linear and the solution here is likely to get trapped in local minimum, leading to inadequate history match. The proposed travel time inversion is shown to be extremely efficient and robust for practical field applications. The streamline approach is generalized to model water injection in naturally fractured reservoirs through the use of a dual media approach. The fractures and matrix are treated as separate continua that are connected through a transfer function, as in conventional finite difference simulators for modeling fractured systems. A detailed comparison with a commercial finite difference simulator shows very good agreement. Furthermore, an examination of the scaling behavior of the computation time indicates that the streamline approach is likely to result in significant savings for large-scale field applications. We also propose a novel approach to history matching finite-difference models that combines the advantage of the streamline models with the versatility of finite-difference simulation. In our approach, we utilize the streamline-derived sensitivities to facilitate history matching during finite-difference simulation. The use of finite-difference model allows us to account for detailed process physics and compressibility effects

  14. 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

    Science.gov (United States)

    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.

  15. The Force Required to Fracture Endodontically Roots Restored with ...

    African Journals Online (AJOL)

    2016-03-12

    Mar 12, 2016 ... Objective: To evaluate the effect of various materials as intra-orifice barriers on the force required fracture roots. Materials .... A total of 135 single-rooted, freshly extracted, noncarious human mandibular premolar teeth ... a two-bottle self-etch adhesive (Clearfil SE Bond,. Kuraray, Tokyo, Japan) was applied.

  16. The Force Required to Fracture Endodontically Roots Restored with ...

    African Journals Online (AJOL)

    While MTA groups did not increase the force required fracture the roots compared to the control groups, Biodentine increased significantly. Conclusions: Within the limitations of the present study, the use of nano‑hybrid composite, short fiber‑reinforced composite, bulk‑fill flowable composite, and glass ionomer cement as an ...

  17. Zonation of shale reservoir stimulation modes: a conceptual model based on hydraulic fracturing data from the Baltic Basin (Poland).

    Science.gov (United States)

    Jarosiński, Marek; Pachytel, Radomir

    2017-04-01

    Depending on the pressure distribution within Stimulated Reservoir Volume (SRV), a different modes of hydraulic fracturing or tectonic fracture reactivation are active. Hydraulic pressure-driven shortening or expansion of reservoir produces changes in stress field that results in decrease of differential stress either by increasing of horizontal stress minimum (Shmin) or/and by decreasing of horizontal stress maximum (SHmax). For further considerations we assume initial strike-slip stress regime which prevails in the Polish part of the Lower Paleozoic Baltic Basin (BB), as well as in majority of the USA shale basins. The data come from vertical and horizontal shale gas exploration wells drilled from one pad located in the middle of the BB. Structural survey of a long core interval combined with stress analysis based on microfrac tests and fracturing tests allow to reconstruct the initial structural and geomechanical state of reservoir. Further geomechanical evolution of the SRV depends on the hydraulic pressure bubble growth, which is in general unknown. However, the state of pressure can be determined close to the injection borehole and in the front of the SRV migrating in time. In our case, we are able to distinguish four stimulation zones characterized by increasingly diverse stimulation modes and successively closer to the borehole injection zone: (1) shear on preexisting fractures generates microseismic events that produce open fractures propped by their natural asperities being impenetrable for proppant grains; (2) above + initial hydraulic opening of natural fractures that are preferentially oriented to the Shmin, which favors microseismic events triggered by secondary shear on bedding planes and produces open spaces supported by natural fracture asperities and fine-grained proppant; (3) above + failure of primary hydraulic fractures, which increases extensional component of the microseismic events and opens space for coarse-grained proppant; (4) above

  18. Modeling Flow in Naturally Fractured Reservoirs : Effect of Fracture Aperture Distribution on Critical Sub-Network for Flow

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2014-01-01

    Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling the flow behavior of fractured formations. The effect of connectivity on flow properties is well documented. We focus here on the influence of fracture aperture distribution. We model a

  19. Palaeofluid evolution in a fractured basalt hosted reservoir in the Ulles-Ruzsa-Bordany area, southern sector of the Pannonian Basin

    Czech Academy of Sciences Publication Activity Database

    Szabó, B.; Schubert, F.; Toth, T.M.; Steinbach, Gabor

    2016-01-01

    Roč. 69, č. 3 (2016), s. 281-293 ISSN 1330-030X Institutional support: RVO:61388971 Keywords : fractured basalt reservoir * Pannonian Basin * zeolite minerals Subject RIV: EE - Microbiology, Virology Impact factor: 0.595, year: 2016

  20. A successful case study on development of a giant, highly fractured carbonate heavy-oil reservoir in Iran

    Energy Technology Data Exchange (ETDEWEB)

    Tabibi, M.; Mousavi Mirkalaei, S.M. [National Iranian Oil Co., Tehran (Iran, Islamic Republic of)

    2005-11-01

    Most Iranian heavy oil fields occur in carbonate reservoirs. Consequently, research from other types of reservoirs needs to be carefully tested and applied, as some in situ combustion methods can be dangerous and harmful to carbonate reservoirs. This paper presented results from a case study and planned pilot on an oil field with 3.6 billion barrels of oil in place. Pressure was 1408 psi at 1119 measured drilled depth. Details of previous studies in the field were presented, including a 3-D seismic and side view seismic location study. Details of a fracture study were also presented. A swabbing operation was conducted on a single well in order to identify rock and fluid properties. A progressing cavity pump (PCP) was planned for the well. Stimulation methods for enhanced oil recovery were reviewed, and included cold production such as gas lift or solvent treatment and thermal recovery such as steam injection and cyclic steam stimulation. It was estimated that the planned pilot study would last approximately 5 years. Results indicate that gas lifting methods are a suitable cold stimulation technique option for the carbonate reservoir. Challenges and technical considerations include a geological study; drilling operation; reservoir characterization and various techniques of production. Results gained from cores and surface studies have shown that the field was highly fractured, and that most of the fractures were vertical or sub-vertical. Results of the swabbing operation showed that the use of surface pumps would help to increase flow rate in continuous production.18 refs., 3 tabs., 6 figs.

  1. Mechanics and upscaling of heavy oil bitumen recovery by steam-over-solvent injection in fractured reservoirs method

    Energy Technology Data Exchange (ETDEWEB)

    Singh, R.; Babadagli, T. [Alberta Univ., Edmonton, AB (Canada)

    2011-01-15

    This paper discussed a numerical modelling scheme applied to the steam-over-solvent injection in fractured reservoirs (SOS-FR) method for a single-matrix block. After modelling the process at the core scale, sensitivity tests were performed to determine the optimal injection conditions for efficient oil recovery and solvent retrieval. The basic mechanisms and physics of the process were described along with the amount of injectant and the time required for recovering target oil for field-scale application. In the physics of the recovery mechanism, gravity was found to have a substantial effect on oil recovery when the matrix was exposed to solvent. Special attention was paid to the solvent retrieval rate and amount in the third cycle and the permeability reduction caused by asphaltene precipitation in the solvent injection phase; the latter factor was observed to be substantially critical for the process. An upscaling analysis yielded an encouraging straight-line relationship between the time value to reach ultimate recovery and the matrix size with a non-integer exponent less than 2. 21 refs., 1 tab., 15 figs.

  2. Advanced reservoir characterization and evaluation of CO2 gravity drainage in the naturally fractured Spraberry Trend Area. Annual report, September 1, 1996--August 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, P.

    1998-06-01

    The objective of the Spraberry CO{sub 2} pilot project is to determine the technical and economic feasibility of continuous CO{sub 2} injection in the naturally fractured reservoirs of the Spraberry Trend. In order to describe, understand, and model CO{sub 2} flooding in the naturally fractured Spraberry reservoirs, characterization of the fracture system is a must. Additional reservoir characterization was based on horizontal coring in the second year of the project. In addition to characterization of natural fractures, horizontal coring has confirmed a previously developed rock model for describing the Spraberry Trend shaly sands. A better method for identifying Spraberry pay zones has been verified. The authors have completed the reservoir characterization, which includes matrix description and detection (from core-log integration) and fracture characterization. This information is found in Section 1. The authors have completed extensive imbibition experiments that strongly indicate that the weakly water-wet behavior of the reservoir rock may be responsible for poor waterflood response observed in many Spraberry fields. The authors have also made significant progress in analytical and numerical simulation of performance in Spraberry reservoirs as seen in Section 3. They have completed several suites of CO{sub 2} gravity drainage in Spraberry and Berea whole cores at reservoir conditions and reported in Section 4. The results of these experiments have been useful in developing a model for free-fall gravity drainage and have validated the premise that CO{sub 2} will recover oil from tight, unconfined Spraberry matrix.

  3. A model for strong attenuation and dispersion of seismic P-waves in a partially saturated fractured reservoir

    Science.gov (United States)

    Brajanovski, Miroslav; Müller, Tobias M.; Parra, Jorge O.

    2010-08-01

    In this work we interpret the data showing unusually strong velocity dispersion of P-waves (up to 30%) and attenuation in a relatively narrow frequency range. The cross-hole and VSP data were measured in a reservoir, which is in the porous zone of the Silurian Kankakee Limestone Formation formed by vertical fractures within a porous matrix saturated by oil, and gas patches. Such a medium exhibits significant attenuation due to wave-induced fluid flow across the interfaces between different types of inclusions (fractures, fluid patches) and background. Other models of intrinsic attenuation (in particular squirt flow models) cannot explain the amount of observed dispersion when using realistic rock properties. In order to interpret data in a satisfactory way we develop a superposition model for fractured porous rocks accounting also for the patchy saturation effect.

  4. Fundamentals of Reservoir Surface Energy as Related to Surface Properties, Wettability, Capillary Action, and Oil Recovery from Fractured Reservoirs by Spontaneous Imbibition

    Energy Technology Data Exchange (ETDEWEB)

    Norman Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Zhengxin Tong; Evren Unsal; Siluni Wickramathilaka; Shaochang Wo; Peigui Yin

    2008-06-30

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  5. FUNDAMENTALS OF RESERVOIR SURFACE ENERGY AS RELATED TO SURFACE PROPERTIES, WETTABILITY, CAPILLARY ACTION, AND OIL RECOVERY FROM FRACTURED RESERVOIRS BY SPONTANEOUS IMBIBITION

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Peigui Yin; Shaochang Wo

    2004-10-01

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  6. Fundamentals of reservoir surface energy as related to surface properties, wettability, capillary action, and oil recovery from fractured reservoirs by spontaneous imbibition

    Energy Technology Data Exchange (ETDEWEB)

    Norman R. Morrow; Herbert Fischer; Yu Li; Geoffrey Mason; Douglas Ruth; Siddhartha Seth; Jason Zhengxin Tong; Peigui Yin; Shaochang Wo

    2006-06-08

    The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed

  7. 75 FR 72653 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-11-26

    ... RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal... Regulations (10 CFR) part 50, section 61a to provide alternate fracture toughness requirements for protection...

  8. Integrated reservoir characterization of a Posidonia Shale outcrop analogue: From serendipity to understanding

    NARCIS (Netherlands)

    Zijp, M.H.A.A.; Veen, J.H. ten; Verreussel, R.M.C.H.; Ventra, D.

    2014-01-01

    Shale gas reservoir stimulation procedures (e.g. hydraulic fracturing) require upfront prediction and planning that should be supported by a comprehensive reservoir characterization. Therefore, understanding shale depositional processes and associated vertical and lateral sedimentological

  9. Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

    Science.gov (United States)

    Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

    2017-12-01

    Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

  10. Numerical investigation and optimization of multiple fractures in tight gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Hou, M.Z. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE; Energie-Forschungszentrum Niedersachsen, Goslar (Germany); Zhou, L. [Energie-Forschungszentrum Niedersachsen, Goslar (Germany)

    2013-08-01

    The main objective of the project DGMK-680 in phase 2 was to investigate the influence of fractures on each other in a multi-fracture system including their space optimization by using the numerical program FLAC3D with our own developments, which treats all fractures in one 3D geometric model under 3D stress state with fully hydro-mechanical coupling effect. The case study was conducted on a horizontal wellbore at location A, which was stimulated hydraulically with a total of eight transverse fractures in summer 2009. Transverse multiple fractures were simulated using the modified continuum method. In the simulation all fractures were generated in one single model, comprising 22 different rock layers. Each layer was assumed to be homogeneous with regard to its rock and hydromechanical parameters. Thus the influence of the individual fractures on each other can be investigated. The simulation procedure applied, which is a consecutive execution ofa hydraulic and a mechanical computation, is the same for all fractures. The only differences are the primary in-situ stresses, the initial pore pressure, the injection parameters (location, rate, volume, duration), which lead to different patterns of fracture propagations. But there are still some common points, such as irregular patterns of the fracture front, which represents the heterogeneity of the model. All fractures (1 to 8) have their fracture average half-length between 70 m to 115 m, height between 93 m to 114 m and average width between 18 mm to 31 mm. The percentage difference of fracture height for individual fractures is obviously smaller than that of the fracture half-lengths, because the fracture barriers at bottom and top limit the fracture propagation in z-direction. Incomparison with the analytical simulator (FracPro) most results match well. Simulation of multiple fractures at location A, with the newly developed algorithms, shows that individual transverse multiple fractures at distances between 100

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

    Science.gov (United States)

    Zhou, Jing

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

  12. Fracture density determination using a novel hybrid computational scheme: a case study on an Iranian Marun oil field reservoir

    International Nuclear Information System (INIS)

    Nouri-Taleghani, Morteza; Mahmoudifar, Mehrzad; Shokrollahi, Amin; Tatar, Afshin; Karimi-Khaledi, Mina

    2015-01-01

    Most oil production all over the world is from carbonated reservoirs. Carbonate reservoirs are abundant in the Middle East, the Gulf of Mexico and in other major petroleum fields that are regarded as the main oil producers. Due to the nature of such reservoirs that are associated with low matrix permeability, the fracture is the key parameter that governs the fluid flow in porous media and consequently oil production. Conventional methods to determine the fracture density include utilizing core data and the image log family, which are both time consuming and costly processes. In addition, the cores are limited to certain intervals and there is no image log for the well drilled before the introduction of this tool. These limitations motivate petroleum engineers to try to find appropriate alternatives. Recently, intelligent systems on the basis of machine learning have been applied to various branches of science and engineering. The objective of this study is to develop a mathematical model to predict the fracture density using full set log data as inputs based on a combination of three intelligent systems namely, the radial basis function neural network, the multilayer perceptron neural network and the least square supported vector machine. The developed committee machine intelligent system (CMIS) is the weighted average of the individual results of each expert. Proper corresponding weights are determined using a genetic algorithm (GA). The other important feature of the proposed model is its generalization capability. The ability of this model to predict data that have not been introduced during the training stage is very good. (paper)

  13. Fracture corridors as seal-bypass systems in siliciclastic reservoir-cap rock successions: Field-based insights from the Jurassic Entrada Formation (SE Utah, USA)

    Science.gov (United States)

    Ogata, Kei; Senger, Kim; Braathen, Alvar; Tveranger, Jan

    2014-09-01

    Closely spaced, sub-parallel fracture networks contained within localized tabular zones that are fracture corridors may compromise top seal integrity and form pathways for vertical fluid flow between reservoirs at different stratigraphic levels. This geometry is exemplified by fracture corridors found in outcrops of the Jurassic Entrada Formation in Utah (USA). These fracture corridors exhibit discolored (bleached) zones, interpreted as evidence of ancient fracture-enhanced circulation of reducing fluids within an exhumed siliciclastic reservoir-cap rock succession. Extensive structural and stratigraphic mapping and logging provided fracture data for analysis with respect to their occurrence and relationships to larger faults and folds. Three types of fracture corridors, representing end-members of a continuum of possibly interrelated structures were identified: 1) fault damage zone including segment relays; 2) fault-tip process zone; and 3) fold-related crestal-zone fracture corridors. The three types exhibit intrinsic orientations and patterns, which in sum define a local- to regional network of inferred vertical and lateral, high-permeability conduits. The results from our analysis may provide improved basis for the evaluation of trap integrity and flow paths across the reservoir-cap rock interface, applicable to both CO2 storage operations and the hydrocarbon industry.

  14. Robot-Assisted Fracture Surgery: Surgical Requirements and System Design.

    Science.gov (United States)

    Georgilas, Ioannis; Dagnino, Giulio; Tarassoli, Payam; Atkins, Roger; Dogramadzi, Sanja

    2018-03-09

    The design of medical devices is a complex and crucial process to ensure patient safety. It has been shown that improperly designed devices lead to errors and associated accidents and costs. A key element for a successful design is incorporating the views of the primary and secondary stakeholders early in the development process. They provide insights into current practice and point out specific issues with the current processes and equipment in use. This work presents how information from a user-study conducted in the early stages of the RAFS (Robot Assisted Fracture Surgery) project informed the subsequent development and testing of the system. The user needs were captured using qualitative methods and converted to operational, functional, and non-functional requirements based on the methods derived from product design and development. This work presents how the requirements inform a new workflow for intra-articular joint fracture reduction using a robotic system. It is also shown how the various elements of the system are developed to explicitly address one or more of the requirements identified, and how intermediate verification tests are conducted to ensure conformity. Finally, a validation test in the form of a cadaveric trial confirms the ability of the designed system to satisfy the aims set by the original research question and the needs of the users.

  15. Accounting for geochemical alterations of caprock fracture permeability in basin-scale models of leakage from geologic CO2 reservoirs

    Science.gov (United States)

    Guo, B.; Fitts, J. P.; Dobossy, M.; Bielicki, J. M.; Peters, C. A.

    2012-12-01

    Climate mitigation, public acceptance and energy, markets demand that the potential CO2 leakage rates from geologic storage reservoirs are predicted to be low and are known to a high level of certainty. Current approaches to predict CO2 leakage rates assume constant permeability of leakage pathways (e.g., wellbores, faults, fractures). A reactive transport model was developed to account for geochemical alterations that result in permeability evolution of leakage pathways. The one-dimensional reactive transport model was coupled with the basin-scale Estimating Leakage Semi-Analytical (ELSA) model to simulate CO2 and brine leakage through vertical caprock pathways for different CO2 storage reservoir sites and injection scenarios within the Mt. Simon and St. Peter sandstone formations of the Michigan basin. Mineral dissolution in the numerical reactive transport model expands leakage pathways and increases permeability as a result of calcite dissolution by reactions driven by CO2-acidified brine. A geochemical model compared kinetic and equilibrium treatments of calcite dissolution within each grid block for each time step. For a single fracture, we investigated the effect of the reactions on leakage by performing sensitivity analyses of fracture geometry, CO2 concentration, calcite abundance, initial permeability, and pressure gradient. Assuming that calcite dissolution reaches equilibrium at each time step produces unrealistic scenarios of buffering and permeability evolution within fractures. Therefore, the reactive transport model with a kinetic treatment of calcite dissolution was coupled to the ELSA model and used to compare brine and CO2 leakage rates at a variety of potential geologic storage sites within the Michigan basin. The results are used to construct maps based on the susceptibility to geochemically driven increases in leakage rates. These maps should provide useful and easily communicated inputs into decision-making processes for siting geologic CO2

  16. Damage evaluation on oil-based drill-in fluids for ultra-deep fractured tight sandstone gas reservoirs

    Directory of Open Access Journals (Sweden)

    Jinzhi Zhu

    2017-07-01

    Full Text Available In order to explore the damage mechanisms and improve the method to evaluate and optimize the performance of formation damage control of oil-based drill-in fluids, this paper took an ultra-deep fractured tight gas reservoir in piedmont configuration, located in the Cretaceous Bashijiqike Fm of the Tarim Basin, as an example. First, evaluation experiments were conducted on the filtrate invasion, the dynamic damage of oil-based drill-in fluids and the loading capacity of filter cakes. Meanwhile, the evaluating methods were optimized for the formation damage control effect of oil-based drill-in fluids in laboratory: pre-processing drill-in fluids before grading analysis; using the dynamic damage method to simulate the damage process for evaluating the percentage of regained permeability; and evaluating the loading capacity of filter cakes. The experimental results show that (1 oil phase trapping damage and solid phase invasion are the main formation damage types; (2 the damage degree of filtrate is the strongest on the matrix; and (3 the dynamic damage degree of oil-based drill-in fluids reaches medium strong to strong on fractures and filter cakes show a good sealing capacity for the fractures less than 100 μm. In conclusion, the filter cakes' loading capacity should be first guaranteed, and both percentage of regained permeability and liquid trapping damage degree should be both considered in the oil-based drill-in fluids prepared for those ultra-deep fractured tight sandstone gas reservoirs.

  17. 75 FR 10410 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-03-08

    ... COMMISSION 10 CFR Part 50 RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against... (75 FR 13), that amends the NRC's regulations to provide alternate fracture toughness requirements for... adding Table 7 directly after Table 6 to read as follows: Sec. 50.61a Alternate fracture toughness...

  18. Pulse fracture simulation in shale rock reservoirs: DEM and FEM-DEM approaches

    Science.gov (United States)

    González, José Manuel; Zárate, Francisco; Oñate, Eugenio

    2017-11-01

    In this paper we analyze the capabilities of two numerical techniques based on DEM and FEM-DEM approaches for the simulation of fracture in shale rock caused by a pulse of pressure. We have studied the evolution of fracture in several fracture scenarios related to the initial stress state in the soil or the pressure pulse peak. Fracture length and type of failure have been taken as reference for validating the models. The results obtained show a good approximation to FEM results from the literature.

  19. Characterization of fracture reservoirs using static and dynamic data: From sonic and 3D seismic to permeability distribution. Annual report, March 1, 1996--February 28, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Parra, J.O.; Collier, H.A.; Owen, T.E. [and others

    1997-06-01

    In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. They also may connect the borehole to remote zones of better reservoir characteristics. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based on the effects of such conditions on the propagation of acoustic and seismic waves in the rock. The project is a study directed toward the evaluation of acoustic logging and 3D-seismic measurement techniques as well as fluid flow and transport methods for mapping permeability anisotropy and other petrophysical parameters for the understanding of the reservoir fracture systems and associated fluid dynamics. The principal application of these measurement techniques and methods is to identify and investigate the propagation characteristics of acoustic and seismic waves in the Twin Creek hydrocarbon reservoir owned by Union Pacific Resources (UPR) and to characterize the fracture permeability distribution using production data. This site is located in the overthrust area of Utah and Wyoming. UPR drilled six horizontal wells, and presently UPR has two rigs running with many established drill hole locations. In addition, there are numerous vertical wells that exist in the area as well as 3D seismic surveys. Each horizontal well contains full FMS logs and MWD logs, gamma logs, etc.

  20. The Influence of fold and fracture development on reservoir behavior of the Lisburne Group of northern Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Wesley K. Wallace; Catherine L. Hanks; Jerry Jensen: Michael T. Whalen; Paul Atkinson; Joseph Brinton; Thang Bui; Margarete Jadamec; Alexandre Karpov; John Lorenz; Michelle M. McGee; T.M. Parris; Ryan Shackleton

    2004-07-01

    The Carboniferous Lisburne Group is a major carbonate reservoir unit in northern Alaska. The Lisburne is folded and thrust faulted where it is exposed throughout the Brooks Range, but is relatively undeformed in areas of current production in the subsurface of the North Slope. The objectives of this study were to develop a better understanding of four major aspects of the Lisburne: (1) The geometry and kinematics of folds and their truncation by thrust faults. (2) The influence of folding on fracture patterns. (3) The influence of deformation on fluid flow. (4) Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics. Symmetrical detachment folds characterize the Lisburne in the northeastern Brooks Range. In contrast, Lisburne in the main axis of the Brooks Range is deformed into imbricate thrust sheets with asymmetrical hangingwall anticlines and footwall synclines. The Continental Divide thrust front separates these different structural styles in the Lisburne and also marks the southern boundary of the northeastern Brooks Range. Field studies were conducted for this project during 1999 to 2001 in various locations in the northeastern Brooks Range and in the vicinity of Porcupine Lake, immediately south of the Continental Divide thrust front. Results are summarized below for the four main subject areas of the study.

  1. THE INFLUENCE OF FOLD AND FRACTURE DEVELOPMENT ON RESERVOIR BEHAVIOR OF THE LISBURNE GROUP OF NORTHERN ALASKA

    Energy Technology Data Exchange (ETDEWEB)

    Wesley K. Wallace; Catherine L. Hanks; Michael T. Whalen; Jerry Jensen; Paul K. Atkinson; Joseph S. Brinton

    2000-05-01

    The Lisburne Group is a major carbonate reservoir unit in northern Alaska. The Lisburne is detachment folded where it is exposed throughout the northeastern Brooks Range, but is relatively undeformed in areas of current production in the subsurface of the North Slope. The objectives of this study are to develop a better understanding of four major aspects of the Lisburne: (1) The geometry and kinematics of detachment folds and their truncation by thrust faults. (2) The influence of folding and lithostratigraphy on fracture patterns. (3) Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics. (4) The influence of lithostratigraphy and deformation on fluid flow. The results of field work during the summer of 1999 offer some preliminary insights: The Lisburne Limestone displays a range of symmetrical detachment fold geometries throughout the northeastern Brooks Range. The variation in fold geometry suggests a generalized progression in fold geometry with increasing shortening: Straight-limbed, narrow-crested folds at low shortening, box folds at intermediate shortening, and folds with a large height-to-width ratio and thickened hinges at high shortening. This sequence is interpreted to represent a progressive change in the dominant shortening mechanism from flexural-slip at low shortening to bulk strain at higher shortening. Structural variations in bed thickness occur throughout this progression. Parasitic folding accommodates structural thickening at low shortening and is gradually succeeded by penetrative strain as shortening increases. The amount of structural thickening at low to intermediate shortening may be inversely related to the local amount of structural thickening of the Kayak Shale, the incompetent unit that underlies the Lisburne. The Lisburne Limestone displays a different structural style in the south, across the boundary between the northeastern Brooks Range and the main axis of the Brooks Range fold

  2. Reservoir fracture mapping using microearthquakes: Austin chalk, Giddings field, TX and 76 field, Clinton Co., KY

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, W.S.; Rutledge, J.T.; Gardner, T.L. [SPE, Richardson, TX (United States); Fairbanks, T.D.; Miller, M.E.; Schuessler, B.K. [Los Alamos National Lab., NM (United States)

    1996-11-01

    Patterns of microearthquakes detected downhole defined fracture orientation and extent in the Austin chalk, Giddings field, TX and the 76 field, Clinton Co., KY. We collected over 480 and 770 microearthquakes during hydraulic stimulation at two sites in the Austin chalk, and over 3200 during primary production in Clinton Co. Data were of high enough quality that 20%, 31% and 53% of the events could be located, respectively. Reflected waves constrained microearthquakes to the stimulated depths at the base of the Austin chalk. In plan view, microearthquakes defined elongate fracture zones extending from the stimulation wells parallel to the regional fracture trend. However, widths of the stimulated zones differed by a factor of five between the two Austin chalk sites, indicating a large difference in the population of ancillary fractures. Post-stimulation production was much higher from the wider zone. At Clinton Co., microearthquakes defined low-angle, reverse-fault fracture zones above and below a producing zone. Associations with depleted production intervals indicated the mapped fractures had been previously drained. Drilling showed that the fractures currently contain brine. The seismic behavior was consistent with poroelastic models that predicted slight increases in compressive stress above and below the drained volume.

  3. On the Versatility of Rheoreversible, Stimuli-responsive Hydraulic-Fracturing Fluids for Enhanced Geothermal Systems: Effect of Reservoir pH

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Carlos A.; Shao, Hongbo; Bonneville, Alain; Varga, Tamas; Zhong, Lirong

    2016-04-25

    Abstract The primary challenge for the feasibility of enhanced geothermal systems (EGS) is to cost-effectively create high-permeability reservoirs inside deep crystalline bedrock. 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. These authors recently reported an environmentally benign, CO2-activated, rheoreversible fracturing fluid that enhances permeability through fracturing due to in situ volume expansion and gel formation. The potential of this novel fracturing fluid is evaluated in this work towards its application at geothermal sites under different pH conditions. Laboratory-scale fracturing experiments using Coso Geothermal rock cores under different pH environments were performed followed by X-ray microtomography characterization. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable polyallylamine (PAA) consistently and reproducibly creates/propagates fracture networks through highly impermeable crystalline rock from Coso EGS sites at considerably lower effective stress as compared to conventional fracturing fluids. In addition, permeability was significantly enhanced in a wide range of formation-water pH values. This effective, and environmentally-friendly fracturing fluid technology represents a potential alternative to conventional fracturing fluids.

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

    Science.gov (United States)

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

  5. Why are brittleness and fracability not equivalent in designing hydraulic fracturing in tight shale gas reservoirs

    Directory of Open Access Journals (Sweden)

    Mao Bai

    2016-03-01

    With the objective review and sensible definition of brittleness used in the present petro-physical field to identify the desirable fracturing intervals, the paper presents the ambiguities of using the brittleness to define the formation fracability and points out that the formation brittleness can be unrelated to the formation fracability. As an alternative approach, the paper provides an effective method to define the most fracable formation intervals in designing the hydraulic fracturing in tight shale gas formations.

  6. Advanced reservoir characterization and evaluation of CO{sub 2} gravity drainage in the naturally fractured Spraberry Trend Area. Annual report, September 1, 1995--August 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Schechter, D.S.

    1997-12-01

    The overall goal of this project is to assess the economic feasibility of CO{sub 2} flooding in the naturally fractured Spraberry Trend Area in West Texas. This objective is being accomplished by conducting research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interaction in the reservoirs, (3) analytical and numerical simulation of Spraberry reservoirs, and, (4) experimental investigations on CO{sub 2} gravity drainage in Spraberry whole cores. This report provides results of the first year of the five-year project for each of the four areas.

  7. Controlling effect of fractures on gas accumulation and production within the tight sandstone: A case study on the Jurassic Dibei gas reservoir in the eastern part of the Kuqa foreland basin, China

    Directory of Open Access Journals (Sweden)

    Hui Lu

    2016-02-01

    Full Text Available Using Dibei tight sandstone gas reservoir in the eastern part of the Kuqa foreland basin as an example, this paper discusses tight sandstone reservoir fractures characterization, its effect on storage space and gas flow capacity, and its contribution to gas accumulation, enrichment and production in tight sandstone reservoir by using laser scanning confocal microscope (LSCM observation, mercury intrusion capillary pressure (MICP testing, and gas-water two-phase relative permeability testing. The statistics of laser scanning confocal microscopy observation showed that the microstructural fractures width in the Dibei gas reservoir was mainly 8–25 μm, and the associated micro-fractures width was mainly 4–10 μm. Additionally, the throat radius was mainly 1–4 μm. The fractures width was significantly wider than the throat radius that served as the main channel of in gas flow. In addition, it illustrated that the samples with developed fractures became easier for gas to flow under equal porosity condition, because of lower expulsion pressure, higher mercury injection saturation, and increased gas relative permeability based on the physical simulation experiment of gas charging into core samples with saturated water, mercury injection and gas-water two-phase permeability experiments. Furthermore, it had been concluded that the fractures control tight gas in the following aspects: (1 Fractures play a significant role in reservoir property improvement. The isolated pores were linked by the fractures to form connective reservoir spaces, and dissolution is prone to occur along the fractures forming new pores. The fractures with bigger width are reservoir space as well. (2 Fractures increased fluid flow capacity because it decreased the starting pressure gradient, and it increased gas effective permeability. Thus, fractures improved the gas injection efficiency as well as gas production. (3 Fractures that developed in different time and spatial

  8. Microfluidic Investigation of Oil Mobilization in Shale Fracture Networks at Reservoir Conditions

    Science.gov (United States)

    Porter, M. L.; Jimenez-Martinez, J.; Carey, J. W.; Viswanathan, H. S.

    2015-12-01

    Investigations of pore-scale fluid flow and transport phenomena using engineered micromodels has steadily increased in recent years. In these investigations fluid flow is restricted to two-dimensions allowing for real time visualization and quantification of complex flow and reactive transport behavior, which is difficult to obtain in other experimental systems. One drawback to these studies is the use of engineered materials that do not faithfully represent the rock properties (e.g., porosity, wettability, roughness, etc.) encountered in subsurface formations. In this work, we describe a unique high pressure (up to 1500 psi) and temperature (up to 80 °C) microfluidics experimental system in which we investigate fluid flow and transport in geo-material (e.g., shale, Portland cement, etc.) micromodels. The use of geo-material micromodels allows us to better represent fluid-rock interactions including wettability, chemical reactivity, and nano-scale porosity at conditions representative of natural subsurface environments. Here, we present experimental results in fracture systems with applications to hydrocarbon mobility in hydraulically fractured shale. Complex fracture network patterns are derived from 3D x-ray tomography images of actual fractures created in shale rock cores. We use both shale and glass micromodels, allowing for a detailed comparison between flow phenomena in the different materials. We discuss results from two-phase huff-and-puff experiments involving N2 and n-Decane, as well as three-phase displacement experiments involving supercritical CO2, brine, and n-Decane.

  9. Investigation of the Vapex process in high-pressure fractured heavy-oil reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Rostami, B.; Kharrat, R. [Society of Petroleum Engineers, Dubai (United Arab Emirates)]|[Petroleum Univ. of Technology, Tehran (Iran, Islamic Republic of); Azin, R. [Society of Petroleum Engineers, Dubai (United Arab Emirates)]|[Petroleum-Sharif Univ. of Technology, Tehran (Iran, Islamic Republic of)

    2005-11-01

    The vapour extraction process (VAPEX) was studied in a multiple block, dual porosity fractured system and compared with a conventional, non-fractured system under similar rock and fluid properties, bulk volume, pore volume, hydrocarbon volume, and injected pore volume of solvent and solvent injection rate. The effect of solvent injection rate on heavy oil recovery in the fractured system was also studied under two conditions. These conditions included a different injection rate at the same injection time, and a different injection rate with the same injected pore volume. This study used an equation of state (EOS)-based compositional simulator which was enhanced to include the effect of molecular diffusion and convective dispersion. It was found that in the fractured system, at the beginning stages of the VAPEX process, the oil chamber forms and shrinks in the center of each block. At the later stages of the VAPEX process, similar to the conventional system, solvent zones from all neighboring blocks combine and form an integrated solvent zone. 19 refs., 4 tabs. 14 figs., 1 appendix.

  10. Basic fracture toughness requirements for ferritic materials of nuclear class pressure retaining equipment in NPP

    International Nuclear Information System (INIS)

    Ning Dong; Yao Weida

    2005-01-01

    In this paper, theory basis on cold brittleness and anti-brittle fracture design of ferritic materials are introduced summarily and fracture toughness requirements for ferritic materials in ASME code for nuclear safety class pressure retaining equipment in NPP are summarized and evaluated. The results show that notch impact toughness requirements for materials relate to nuclear safety class of materials so as to ensure that brittle fracture of retaining pressure boundary in NPP can not occur. (authors)

  11. An Integrated Approach to Characterizing Bypassed Oil in Heterogeneous and Fractured Reservoirs Using Partitioning Tracers. Annual Report

    International Nuclear Information System (INIS)

    Akhil Datta-Gupta

    2006-01-01

    This report presents an efficient trajectory-based approach to integrate transient pressure data into high-resolution reservoir and aquifer models. The method involves alternating travel time and peak amplitude matching of pressure response using inverse modeling and is particularly well-suited for high resolution subsurface characterization using hydraulic tomography or pressure interference tests. Compared to travel time inversion only, our proposed approach results in a significantly improved match of the pressure response at the wells and also better estimates of subsurface properties. This is accomplished with very little increase in computational cost. Utilizing the concept of a ''diffusive'' time of flight derived from an asymptotic solution of the diffusivity equation, we develop analytical approaches to estimate the sensitivities for travel time and peak amplitude of pressure response to subsurface properties. The sensitivities are then used in an iterative least-squared minimization to match the pressure data. We illustrate our approach using synthetic and field examples. In the field application at a fractured limestone formation, the predominant fracture patterns emerging from the inversion are shown to be consistent with independent geophysical experiments and borehole data

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

    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

  13. 75 FR 5495 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-02-03

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION 10 CFR Part 50 RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against... (75 FR 13), that amends the NRC's regulations to provide alternate fracture toughness requirements for...

  14. Integrated seismic study of naturally fractured tight gas reservoirs. Final report, September 1991--January 1995

    Energy Technology Data Exchange (ETDEWEB)

    Mavko, G.; Nur, A.

    1995-01-01

    The approach in this project has been to integrate the principles of rock physics into a quantitative processing and interpretation scheme that exploits, where possible, the broader spectrum of fracture zone signatures: (1) anomalous compressional and shear wave velocity; (2) Q and velocity dispersion; (3) increased velocity anisotropy; (4) amplitude vs. offset (AVO) response, and (5) variations in frequency content. As part of this the authors have attempted to refine some of the theoretical rock physics tools that should be applied in any field study to link the observed seismic signatures to the physical/geologic description of the fractured rock. The project had 3 key elements: (1) rock physics studies of the anisotropic viscoelastic signatures of fractured rocks, (2) acquisition and processing of seismic reflection field data, and (3) interpretation of seismic and well log data. The study site is in a producing field operated by Amoco and Arco at the southern boundary of the Powder River basin in Wyoming. During the winter of 1992--1993 the authors collected about 50 km of 9-component reflection seismic data and obtained existing log data from several wells in the vicinity. The paper gives background information on laboratory studies, seismic field studies of fracture anisotropy, and the problem of upscaling from the laboratory to the field. It discusses fluid effects on seismic anisotropy and a method for predicting stress-induced seismic anisotropy. Then results from the field experiment are presented and discussed: regional geologic framework and site description; seismic data acquisition; shear wave data and validation; and P-wave data analysis. 106 refs., 52 figs.

  15. Surface analogue outcrops of deep fractured basement reservoirs in extensional geological settings. Examples within active rift system (Uganda) and proximal passive margin (Morocco).

    Science.gov (United States)

    Walter, Bastien; Géraud, Yves; Diraison, Marc

    2014-05-01

    The important role of extensive brittle faults and related structures in the development of reservoirs has already been demonstrated, notably in initially low-porosity rocks such as basement rocks. Large varieties of deep-seated resources (e.g. water, hydrocarbons, geothermal energy) are recognized in fractured basement reservoirs. Brittle faults and fracture networks can develop sufficient volumes to allow storage and transfer of large amounts of fluids. Development of hydraulic model with dual-porosity implies the structural and petrophysical characterization of the basement. Drain porosity is located within the larger fault zones, which are the main fluid transfer channels. The storage porosity corresponds both to the matrix porosity and to the volume produced by the different fractures networks (e.g. tectonic, primary), which affect the whole reservoir rocks. Multi-scale genetic and geometric relationships between these deformation features support different orders of structural domains in a reservoir, from several tens of kilometers to few tens of meters. In subsurface, 3D seismic data in basement can be sufficient to characterize the largest first order of structural domains and bounding fault zones (thickness, main orientation, internal architecture, …). However, lower order structural blocks and fracture networks are harder to define. The only available data are 1D borehole electric imaging and are used to characterize the lowest order. Analog outcrop studies of basement rocks fill up this resolution gap and help the understanding of brittle deformation, definition of reservoir geometries and acquirement of reservoir properties. These geological outcrop studies give information about structural blocks of second and third order, getting close to the field scale. This allows to understand relationships between brittle structures geometry and factors controlling their development, such as the structural inheritance or the lithology (e.g. schistosity, primary

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

    Directory of Open Access Journals (Sweden)

    Jian Zhou

    2016-09-01

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

  17. The Force Required to Fracture Endodontically Roots Restored with ...

    African Journals Online (AJOL)

    2016-03-12

    Mar 12, 2016 ... based materials, reduced cuspal deflection[7] and good marginal integrity[8] have been reported. Endodontically treated roots are more susceptible to fracture because of weakened structure. Endodontic treatment procedures, including access cavity preparation, root canal instrumentation, irrigation,.

  18. Sweet spot identification and smart development -An integrated reservoir characterization study of a posidonia shale of a posidonia shale outcrop analogue

    NARCIS (Netherlands)

    Veen, J.H. ten; Verreussel, R.M.C.H.; Ventra, D.; Zijp, M.H.A.A.

    2014-01-01

    Shale gas reservoir stimulation procedures (e.g. hydraulic fracturing) require upfront prediction and planning that should be supported by a comprehensive reservoir characterization. Therefore, understanding shale depositional processes and associated vertical and lateral sedimentological

  19. Risk Assessment of Carbon Sequestration into A Naturally Fractured Reservoir at Kevin Dome, Montana

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Minh [Univ. of Wyoming, Laramie, WY (United States); Onishi, Tsubasa [Texas A & M Univ., College Station, TX (United States); Carey, James William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Will, Bob [Schlumberger, Houston, TX (United States); Zaluski, Wade [Schlumberger, Houston, TX (United States); Bowen, David [Montana State Univ., Bozeman, MT (United States); DeVault, Brian [Vecta Oil and Gas, Dallas, TX (United States); Duguid, Andrew [Battelle Memorial Inst., Columbus, OH (United States); Spangler, Lee [Montana State Univ., Bozeman, MT (United States); Stauffer, Philip H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-12-22

    In this report, we describe risk assessment work done using the National Risk Assessment Partnership (NRAP) applied to CO2 storage at Kevin Dome, Montana. Geologic CO2 sequestration in saline aquifers poses certain risks including CO2/brine leakage through wells or non-sealing faults into groundwater or to the land surface. These risks are difficult to quantify due to data availability and uncertainty. One solution is to explore the consequences of these limitations by running large numbers of numerical simulations on the primary CO2 injection reservoir, shallow reservoirs/aquifers, faults, and wells to assess leakage risks and uncertainties. However, a large number of full-physics simulations is usually too computationally expensive. The NRAP integrated assessment model (NRAP-IAM) uses reduced order models (ROMs) developed from full-physics simulations to address this issue. A powerful stochastic framework allows NRAPIAM to explore complex interactions among many uncertain variables and evaluate the likely performance of potential sequestration sites.

  20. Numerical investigation of electricity generation potential from fractured granite reservoir by water circulating through three horizontal wells at Yangbajing geothermal field

    International Nuclear Information System (INIS)

    Zeng, Yuchao; Zhan, Jiemin; Wu, Nengyou; Luo, Yingying; Cai, Wenhao

    2016-01-01

    Highlights: • A numerical model of the 950–1350 m fractured granite reservoir through horizontal wells is established. • Desirable electricity production performance can be obtained under suitable conditions. • The system attains an electric power of 26.9–24.3 MW with an efficiency of about 50.10–22.39. • Electric power mainly depends on water production rate and injection temperature. • Higher permeability within a certain range is favorable for electricity generation. - Abstract: Deep geological exploration indicates that there is a high-temperature fractured granite reservoir at depth of 950–1350 m in well ZK4001 in the north of Yangbajing geothermal field, with an average temperature of 248 °C and a pressure within 8.01–11.57 MPa. In this work, we evaluated electricity generation potential from this fractured granite reservoir by water circulating through three horizontal wells, and analyzed main factors affecting the performance and efficiency through numerical simulation. The results show that in the reference case the system attains a production temperature of 248.0–235.7 °C, an electrical power of 26.9–24.3 MW, an injection pressure of 10.48–12.94 MPa, a reservoir impedance of 0.07–0.10 MPa/(kg/s), a pump power of 0.54–1.08 MW and an energy efficiency of 50.10–22.39 during a period of 20 years, displaying favorable production performance. Main factors affecting the production performance and efficiency are reservoir permeability, water production rate and injection temperature; within certain ranges increasing the reservoir permeability or adopting more reasonable water production rate or injection temperature will obviously improve the system production performance.

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

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    Predicting equivalent permeability in fractured reservoirs requires an understanding of the fracture network geometry and apertures. There are different methods for defining aperture, based on outcrop observations (power law scaling), fundamental mechanics (sublinear length-aperture scaling......), and experiments (Barton-Bandis conductive shearing). Each method predicts heterogeneous apertures, even along single fractures (i.e., intrafracture variations), but most fractured reservoir models imply constant apertures for single fractures. We compare the relative differences in aperture and permeability...

  2. The force required to fracture endodontically roots restored with ...

    African Journals Online (AJOL)

    ... was prepared, but not filled), filling using glass ionomer cement, nano‑hybrid composite resin, short fiber‑reinforced composite, bulk‑fill flowable composite, MTA Angelus, Micro Mega MTA or Biodentine. A fracture strength test was performed, and the data were analyzed using one‑way ANOVA and Tukey's post hoc tests.

  3. Nonlinear flow model of multiple fractured horizontal wells with stimulated reservoir volume including the quadratic gradient term

    Science.gov (United States)

    Ren, Junjie; Guo, Ping

    2017-11-01

    The real fluid flow in porous media is consistent with the mass conservation which can be described by the nonlinear governing equation including the quadratic gradient term (QGT). However, most of the flow models have been established by ignoring the QGT and little work has been conducted to incorporate the QGT into the flow model of the multiple fractured horizontal (MFH) well with stimulated reservoir volume (SRV). This paper first establishes a semi-analytical model of an MFH well with SRV including the QGT. Introducing the transformed pressure and flow-rate function, the nonlinear model of a point source in a composite system including the QGT is linearized. Then the Laplace transform, principle of superposition, numerical discrete method, Gaussian elimination method and Stehfest numerical inversion are employed to establish and solve the seepage model of the MFH well with SRV. Type curves are plotted and the effects of relevant parameters are analyzed. It is found that the nonlinear effect caused by the QGT can increase the flow capacity of fluid flow and influence the transient pressure positively. The relevant parameters not only have an effect on the type curve but also affect the error in the pressure calculated by the conventional linear model. The proposed model, which is consistent with the mass conservation, reflects the nonlinear process of the real fluid flow, and thus it can be used to obtain more accurate transient pressure of an MFH well with SRV.

  4. Aseismic Motions Drive a Sparse Seismicity During Fluid Injections Into a Fractured Zone in a Carbonate Reservoir

    Science.gov (United States)

    Duboeuf, Laure; De Barros, Louis; Cappa, Frédéric; Guglielmi, Yves; Deschamps, Anne; Seguy, Simon

    2017-10-01

    An increase in fluid pressure in faults can trigger seismicity and large aseismic motions. Understanding how fluid and faults interact is an essential goal for seismic hazard and reservoir monitoring, but this key relation remains unclear. We developed an in situ experiment of fluid injections at a 10 meter scale. Water was injected at high pressure in different geological structures inside a fault damaged zone, in limestone at 280 m depth in the Low Noise Underground Laboratory (France). Induced seismicity, as well as strains, pressure, and flow rate, was continuously monitored during the injections. Although nonreversible deformations related to fracture reactivations were observed for all injections, only a few tests generated seismicity. Events are characterized by a 0.5-to-4 kHz content and a small magnitude (approximately -3.5). They are located within 1.5 m accuracy between 1 and 12 m from the injections. Comparing strain measurements and seismicity shows that more than 96% of the deformation is aseismic. The seismic moment is also small compared to the one expected from the injected volume. Moreover, a dual seismic behavior is observed as (1) the spatiotemporal distribution of some cluster of events is clearly independent from the fluid diffusion (2) while a diffusion-type pattern can be observed for some others clusters. The seismicity might therefore appear as an indirect effect to the fluid pressure, driven by aseismic motion and related stress perturbation transferred through failure.

  5. Naturally fractured reservoirs: Optimized E and P strategies using a reaction-transport-mechanical simulator in an integrated approach. Annual report, 1996--1997

    Energy Technology Data Exchange (ETDEWEB)

    Hoak, T.; Jenkins, R. [Science Applications International Corp., McLean, VA (United States); Ortoleva, P.; Ozkan, G.; Shebl, M.; Sibo, W.; Tuncay, K. [Laboratory for Computational Geodynamics (United States); Sundberg, K. [Phillips Petroleum Company (United States)

    1998-07-01

    The methodology and results of this project are being tested using the Andector-Goldsmith Field in the Permian Basin, West Texas. The study area includes the Central Basin Platform and the Midland Basin. The Andector-Goldsmith Field lies at the juncture of these two zones in the greater West Texas Permian Basin. Although the modeling is being conducted in this area, the results have widespread applicability to other fractured carbonate and other reservoirs throughout the world.

  6. Modeling Multi-Reservoir Hydropower Systems in the Sierra Nevada with Environmental Requirements and Climate Warming

    Science.gov (United States)

    Rheinheimer, David Emmanuel

    Hydropower systems and other river regulation often harm instream ecosystems, partly by altering the natural flow and temperature regimes that ecosystems have historically depended on. These effects are compounded at regional scales. As hydropower and ecosystems are increasingly valued globally due to growing values for clean energy and native species as well as and new threats from climate warming, it is important to understand how climate warming might affect these systems, to identify tradeoffs between different water uses for different climate conditions, and to identify promising water management solutions. This research uses traditional simulation and optimization to explore these issues in California's upper west slope Sierra Nevada mountains. The Sierra Nevada provides most of the water for California's vast water supply system, supporting high-elevation hydropower generation, ecosystems, recreation, and some local municipal and agricultural water supply along the way. However, regional climate warming is expected to reduce snowmelt and shift runoff to earlier in the year, affecting all water uses. This dissertation begins by reviewing important literature related to the broader motivations of this study, including river regulation, freshwater conservation, and climate change. It then describes three substantial studies. First, a weekly time step water resources management model spanning the Feather River watershed in the north to the Kern River watershed in the south is developed. The model, which uses the Water Evaluation And Planning System (WEAP), includes reservoirs, run-of-river hydropower, variable head hydropower, water supply demand, and instream flow requirements. The model is applied with a runoff dataset that considers regional air temperature increases of 0, 2, 4 and 6 °C to represent historical, near-term, mid-term and far-term (end-of-century) warming. Most major hydropower turbine flows are simulated well. Reservoir storage is also

  7. Study on temperature distribution along wellbore of fracturing horizontal wells in oil reservoir

    Directory of Open Access Journals (Sweden)

    Junjun Cai

    2015-12-01

    Full Text Available The application of distributed temperature sensors (DTS to monitor producing zones of horizontal well through a real-time measurement of a temperature profile is becoming increasingly popular. Those parameters, such as flow rate along wellbore, well completion method, skin factor, are potentially related to the information from DTS. Based on mass-, momentum-, and energy-balance equations, this paper established a coupled model to study on temperature distribution along wellbore of fracturing horizontal wells by considering skin factor in order to predict wellbore temperature distribution and analyze the factors influencing the wellbore temperature profile. The models presented in this paper account for heat convective, fluid expansion, heat conduction, and viscous dissipative heating. Arriving temperature and wellbore temperature curves are plotted by computer iterative calculation. The non-perforated and perforated sections show different temperature distribution along wellbore. Through the study on the sensitivity analysis of skin factor and flow rate, we come to the conclusion that the higher skin factor generates larger temperature increase near the wellbore, besides, temperature along wellbore is related to both skin factors and flow rate. Temperature response type curves show that the larger skin factor we set, the less temperature augmenter from toe to heel could be. In addition, larger flow rate may generate higher wellbore temperature.

  8. Inversion of multicomponent seismic data and rock-physics intepretation for evaluating lithology, fracture and fluid distribution in heterogeneous anisotropic reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Ilya Tsvankin; Kenneth L. Larner

    2004-11-17

    Within the framework of this collaborative project with the Lawrence Livermore National Laboratory (LLNL) and Stanford University, the Colorado School of Mines (CSM) group developed and implemented a new efficient approach to the inversion and processing of multicomponent, multiazimuth seismic data in anisotropic media. To avoid serious difficulties in the processing of mode-converted (PS) waves, we devised a methodology for transforming recorded PP- and PS-wavefields into the corresponding SS-wave reflection data that can be processed by velocity-analysis algorithms designed for pure (unconverted) modes. It should be emphasized that this procedure does not require knowledge of the velocity model and can be applied to data from arbitrarily anisotropic, heterogeneous media. The azimuthally varying reflection moveouts of the PP-waves and constructed SS-waves are then combined in anisotropic stacking-velocity tomography to estimate the velocity field in the depth domain. As illustrated by the case studies discussed in the report, migration of the multicomponent data with the obtained anisotropic velocity model yields a crisp image of the reservoir that is vastly superior to that produced by conventional methods. The scope of this research essentially amounts to building the foundation of 3D multicomponent, anisotropic seismology. We have also worked with the LLNL and Stanford groups on relating the anisotropic parameters obtained from seismic data to stress, lithology, and fluid distribution using a generalized theoretical treatment of fractured, poroelastic rocks.

  9. Integrated interpretation of AE clusters and fracture system in Hijiori HDR artificial reservoir; Hijiori koon gantai jinko choryuso no AE cluster to kiretsu system ni kansuru togoteki kaishaku

    Energy Technology Data Exchange (ETDEWEB)

    Tezuka, K. [Japan Petroleum Exploration Corp., Tokyo (Japan); Niitsuma, H. [Tohoku University, Sendai (Japan)

    1997-05-27

    With regard to a fracture system in the Hijiori hot dry rock artificial reservoir, an attempt was made on an interpretation which integrates different data. Major factors that characterize development and performance of an artificial reservoir are composed of a fracture system in rocks, which acts as circulating water paths, a heat exchange face and a reservoir space. The system relates not only with crack density distribution, but also with cracks activated by water pressure fracturing, cracks generating acoustic emission (AE), and cracks working as major flow paths, all of which are characterized by having respective behaviors and roles. Characteristics are shown on AE cluster distribution, crack distribution, production zone and estimated stress fields. Mutual relationship among these elements was discussed based on the Coulomb`s theory. The most important paths are characterized by distribution of slippery cracks. Directions and appearance frequencies of the slippery cracks affect strongly directionality of the paths, which are governed by distribution of the cracks (weak face) and stress field. Among the slippery cracks, cracks that generate AE are cracks that release large energy when a slip occurs. Evaluation on slippery crack distribution is important. 7 refs., 8 figs.

  10. Advanced Reservoir Characterization and Evaluation of CO{sub 2} Gravity Drainage in the Naturally Fractured Spraberry Trend Area, Class III

    Energy Technology Data Exchange (ETDEWEB)

    Knight, Bill; Schechter, David S.

    2001-11-19

    The goal of this project was to assess the economic feasibility of CO{sub 2} flooding the naturally fractured Spraberry Trend Area in west Texas. This objective was accomplished through research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interactions in the reservoirs, (3) reservoir performance analysis, and (4) experimental investigations on CO{sub 2} gravity drainage in Spraberry whole cores. The four areas have been completed and reported in the previous annual reports. This report provides the results of the final year of the project including two SPE papers (SPE 71605 and SPE 71635) presented in the 2001 SPE Annual Meeting in New Orleans, two simulation works, analysis of logging observation wells (LOW) and progress of CO{sub 2} injection.

  11. Contribution to the tectonic characterization of fractured reservoirs, I: photo-elasticimetric modelling of the stress perturbations near faults and the associated fracture network: application to oil reserves, II mechanisms for the 3D joint organization in a natural reservoir analogue (flat-lying Devonian Old Red Sandstones of Caitness in North Scotland); Contribution a la caracterisation tectonique des reservoirs fractures, I: modelisation photoelecticimetrique des perturbations de contrainte au voisinage des failles et de la fracturation associee: application petroliere, II: mecanismes de developpement en 3D des diaclases dans un analogue de reservoir, le Devonien tabulaire du caithness (Ecosse)

    Energy Technology Data Exchange (ETDEWEB)

    Auzias, V.

    1995-10-27

    In order to understand joint network organisation in oil reservoirs, as a first step we have adapted to technique (the photo-elasticimetry) to study stress fields in 2D. This method allows to determine the principal stress trajectories near faults, as well as the associated joint network organisation. Natural joint networks perturbed near faults are modeled and the parameters that control stress perturbation are proposed. With the aim of extrapolating joint data from a well to the entire reservoir our modelling is based on both 3 D seismic data and local joint data. The second part of our research was dedicated to studying joint propagation mechanisms in a natural reservoir analogue (flat-lying Devonian Old Red Sandstones of Caitness in North Scotland). Several exposure observation at different scales and in 3D (horizontal and cliff sections) allow to reconstitute the fracturing geometry from centimeter to kilometer scale and to link these to the regional tectonic history. This study shows that it is possible to differentiate three types of joints major joints, `classic` joints and micro-joints, each with different vertical persistence. New concepts on the 3D joint organisation have been deduced from field quantitative data, which can be applied to reservoir fracture modeling. In particular the non-coexistence phenomenon in a single bed of two regional joint sets with close strikes. Some joint development mechanisms are discussed: interaction between joints and sedimentary interfaces, joint distribution near faults, origin of en echelon arrays associated with joints. (author) 142 refs.

  12. THE INFLUENCE OF FOLD AND FRACTURE DEVELOPMENT ON RESERVOIR BEHAVIOR OF THE LISBURNE GROUP OF NORTHERN ALASKA

    Energy Technology Data Exchange (ETDEWEB)

    Wesley K. Wallace; Catherine L. Hanks; Jerry Jensen; Michael T. Whalen

    2002-01-01

    The Carboniferous Lisburne Group is a major carbonate reservoir unit in northern Alaska. The Lisburne is detachment folded where it is exposed throughout the northeastern Brooks Range, but is relatively undeformed in areas of current production in the subsurface of the North Slope. The objectives of this study are to develop a better understanding of four major aspects of the Lisburne: (1) The geometry and kinematics of detachment folds and their truncation by thrust faults. (2) The influence of folding on fracture patterns. (3) The influence of deformation on fluid flow. (4) Lithostratigraphy and its influence on folding, faulting, fracturing, and reservoir characteristics. The Lisburne in the main axis of the Brooks Range is characteristically deformed into imbricate thrust sheets with asymmetrical hanging wall anticlines and footwall synclines. In contrast, the Lisburne in the northeastern Brooks Range is characterized by symmetrical detachment folds. The focus of our 2000 field studies was at the boundary between these structural styles in the vicinity of Porcupine Lake, in the Arctic National Wildlife Refuge. The northern edge of thrust-truncated folds in Lisburne is marked by a local range front that likely represents an eastward continuation of the central Brooks Range front. This is bounded to the north by a gently dipping panel of Lisburne with local asymmetrical folds. The leading edge of the flat panel is thrust over Permian to Cretaceous rocks in a synclinal depression. These younger rocks overlie symmetrically detachment-folded Lisburne, as is extensively exposed to the north. Six partial sections were measured in the Lisburne of the flat panel and local range front. The Lisburne here is about 700 m thick and is interpreted to consist primarily of the Wachsmuth and Alapah Limestones, with only a thin veneer of Wahoo Limestone. The Wachsmuth (200 m) is gradational between the underlying Missippian Kayak Shale and the overlying Mississippian Alapah, and

  13. Controlling effect of fractures on gas accumulation and production within the tight sandstone: A case study on the Jurassic Dibei gas reservoir in the eastern part of the Kuqa foreland basin, China

    OpenAIRE

    Lu, Hui; Lu, Xuesong; Fan, Junjia; Zhao, Mengjun; Wei, Hongxing; Zhang, Baoshou; Lu, Yuhong

    2016-01-01

    Using Dibei tight sandstone gas reservoir in the eastern part of the Kuqa foreland basin as an example, this paper discusses tight sandstone reservoir fractures characterization, its effect on storage space and gas flow capacity, and its contribution to gas accumulation, enrichment and production in tight sandstone reservoir by using laser scanning confocal microscope (LSCM) observation, mercury intrusion capillary pressure (MICP) testing, and gas-water two-phase relative permeability testing...

  14. Structural control on the deep hydrogeological and geothermal aquifers related to the fractured Campanian-Miocene reservoirs of north-eastern Tunisia foreland constrained by subsurface data

    Science.gov (United States)

    Khomsi, Sami; Echihi, Oussema; Slimani, Naji

    2012-03-01

    A set of different data including high resolution seismic sections, petroleum wire-logging well data, borehole piezometry, structural cross-sections and outcrop analysis allowed us to characterise the tectonic framework, and its relationships with the deep aquifers seated in Cretaceous-Miocene deep reservoirs. The structural framework, based on major structures, controls the occurrence of deep aquifers and sub-basin aquifer distributions. Five structural domains can be defined, having different morphostructural characteristics. The northernmost domain lying on the north-south axis and Zaghouan thrust system is a domain of recharge by underflow of the different subsurface reservoirs and aquifers from outcrops of highly fractured reservoirs. On the other hand, the morphostructural configuration controls the piezometry of underground flows in the Plio-Quaternary unconfined aquifer. In the subsurface the Late Cretaceous-Miocene reservoirs are widespread with high thicknesses in many places and high porosities and connectivities especially along major fault corridors and on the crestal parts of major anticlines. Among all reservoirs, the Oligo-Miocene, detritic series are widespread and present high cumulative thicknesses. Subsurface and fieldwork outline the occurrence of 10 fractured sandy reservoirs for these series with packages having high hydrodynamic and petrophysical characteristics. These series show low salinities (maximum 5 g/l) in the northern part of the study area and will constitute an important source of drinkable water for the next generations. A regional structural cross-section is presented, compiled from all the different data sets, allowing us to define the major characteristics of the hydrogeological-hydrogeothermal sub-basins. Eight hydrogeological provinces are defined from north-west to south-east. A major thermal anomaly is clearly identified in the south-eastern part of the study area in Sfax-Sidi Il Itayem. This anomaly is possibly related to

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

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    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...... 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...

  16. Characterization of fracture reservoirs using static and dynamic data: From sonic and 3D seismic to permeability distribution

    Energy Technology Data Exchange (ETDEWEB)

    Parra, J.O.; Hackett, C.L.; Brown, R.L.; Collier, H.A.; Datta-Gupta, A.

    1998-10-01

    To characterize the Buena Vista Hills field, the authors have implemented methods of modeling, processing and interpretation. The modeling methods are based on deterministic and stochastic solutions. Deterministic solutions were developed in Phase 1 and applied in Phase 2 to simulate acoustic responses of laminated reservoirs. Specifically, the simulations were aimed at implementing processing techniques to correct P-wave and S-wave velocity logs for scattering effects caused by thin layering. The authors are also including a summary of the theory and the processing steps of this new method for predicting intrinsic dispersion and attenuation in Section 2. Since the objective for correcting velocity scattering effects is to predict intrinsic dispersion from velocity data, they are presenting an application to illustrate how to relate permeability anisotropy with intrinsic dispersion. Also, the theoretical solution for calculating full waveform dipole sonic that was developed in Phase 1 was applied to simulate dipole responses at different azimuthal source orientations. The results will be used to interpret the effects of anisotropy associated with the presence of vertical fractures at Buena Vista Hills. The results of the integration of core, well logs, and geology of Buena Vista Hills is also given in Section 2. The results of this integration will be considered as the input model for the inversion technique for processing production data. Section 3 summarizes accomplishments. In Section 4 the authors present a summary of the technology transfer and promotion efforts associated with this project. In the last section, they address the work to be done in the next six months and future work by applying the processing, modeling and inversion techniques developed in Phases 1 and 2 of this project.

  17. Superficial Dorsal Vein Injury/Thrombosis Presenting as False Penile Fracture Requiring Dorsal Venous Ligation

    Directory of Open Access Journals (Sweden)

    Arash Rafiei, MD

    2014-12-01

    Conclusion: Early exploration of patients with suspected penile fracture provides excellent results with maintenance of erectile function. Also, in the setting of dorsal vein thrombosis, ligation preserves the integrity of the penile tissues and avoids unnecessary complications from conservative management. Rafiei A, Hakky TS, Martinez D, Parker J, and Carrion R. Superficial dorsal vein injury/thrombosis presenting as false penile fracture requiring dorsal venous ligation. Sex Med 2014;2:182–185.

  18. Initiation of Hydraulic Fractures in Natural Sandstones

    NARCIS (Netherlands)

    Lhomme, T.P.Y.

    2005-01-01

    Hydraulic fracturing is a stimulation technique commonly used for the enhancement of hydrocarbon reservoir recovery. Controlling the initiation of a hydraulic fracture from the open-hole section of a well without zone isolation requires an in-depth understanding of the factors which have a decisive

  19. Advanced reservoir characterization and evaluation of CO{sub 2} gravity drainage in the naturally fractured Spraberry Trend Area. Annual report, September 1, 1996--August 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Schechter, D.S.

    1998-07-01

    The overall goal of this project is to assess the economic feasibility of CO{sub 2} flooding the naturally fractured Spraberry Trend Area in West Texas. This objective is being accomplished by conducting research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interaction in the reservoirs, (3) reservoir performance analysis, and (4) experimental investigations on CO{sub 2} gravity drainage in Spraberry whole cores. This report provides results of the second year of the five-year project for each of the four areas. In the first area, the author has completed the reservoir characterization, which includes matrix description and detection (from core-log integration) and fracture characterization. This information is found in Section 1. In the second area, the author has completed extensive inhibition experiments that strongly indicate that the weakly water-wet behavior of the reservoir rock may be responsible for poor waterflood response observed in many Spraberry fields. In the third area, the author has made significant progress in analytical and numerical simulation of performance in Spraberry reservoirs as seen in Section 3. In the fourth area, the author has completed several suites of CO{sub 2} gravity drainage in Spraberry and Berea whole cores at reservoir conditions and reported in Section 4. The results of these experiments have been useful in developing a model for free-fall gravity drainage and have validated the premise that CO{sub 2} will recover oil from tight, unconfined Spraberry matrix. The final three years of this project involves implementation of the CO{sub 2} pilot. Up to twelve new wells are planned in the pilot area; water injection wells to contain the CO{sub 2}, three production wells to monitor performance of CO{sub 2}, CO{sub 2} injection wells including one horizontal injection well and logging observation wells to monitor CO{sub 2} flood fronts. Results of drilling

  20. Reservoir management

    International Nuclear Information System (INIS)

    Satter, A.; Varnon, J.E.; Hoang, M.T.

    1992-01-01

    A reservoir's life begins with exploration leading to discovery followed by delineation of the reservoir, development of the field, production by primary, secondary and tertiary means, and finally to abandonment. Sound reservoir management is the key to maximizing economic operation of the reservoir throughout its entire life. Technological advances and rapidly increasing computer power are providing tools to better manage reservoirs and are increasing the gap between good and neutral reservoir management. The modern reservoir management process involves goal setting, planning, implementing, monitoring, evaluating, and revising plans. Setting a reservoir management strategy requires knowledge of the reservoir, availability of technology, and knowledge of the business, political, and environmental climate. Formulating a comprehensive management plan involves depletion and development strategies, data acquisition and analyses, geological and numerical model studies, production and reserves forecasts, facilities requirements, economic optimization, and management approval. This paper provides management, engineers geologists, geophysicists, and field operations staff with a better understanding of the practical approach to reservoir management using a multidisciplinary, integrated team approach

  1. Study on Filtration and Damage Characteristics of Modified Dry CO2 Fracturing Fluid in Shale Gas Reservoir

    Science.gov (United States)

    Xu, Guixi; Wang, Shuzhong; Luo, Xiangrong; Jing, Zefeng

    2017-11-01

    The filtration and damage characteristics of modified dry CO2 fracturing fluid in the shale is studied in this paper. The results show that the modified dry CO2 fracturing fluid has good leak-off characteristics. Compared with liquid CO2, supercritical CO2 has a better permeation and diffusion capacity in the porous medium. The damage rate of the modified dry CO2 fracturing fluid to shale core is only between 0.63%~3.84% with obvious little damage. Under liquid conditions, the increase of temperature makes the fracturing fluid more harmful to shale formation.

  2. A geometrically based method for predicting stress-induced fracture aperture and flow in discrete fracture networks

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    Modeling of fluid flow in naturally fractured reservoirs is often done through modeling and upscaling of discrete fracture networks (DFNs). The two-dimensional fracture geometry required for DFNs is obtained from subsurface and outcropping analog data. However, these data provide little information...... networks, digitized from outcropping pavements. These networks cover a wide range of possible geometries and spatial distributions. The geometrically based method predicts the average hydraulic aperture and equivalent permeability of fractured porous media with error margins of less than 5%....

  3. A conversion of CO{sub 2}-ECBM related lab observations to reservoir requirements

    Energy Technology Data Exchange (ETDEWEB)

    Gensterblum, Y.; Merkel, A.; Busch, A. [RWTH Aachen Univ. (Germany). Inst. of Geology and Geochemistry of Petroleum and Coal; Krooss, B.M. [Shell Global Solutions International, Rijswijk (Netherlands)

    2013-08-01

    To predict a CBM production profile either during primary or secondary production, aspects like coal permeability and porosity, density, ash and moisture content, initial gas-in-place (GIP) (from canister desorption tests), gas sorption capacity from laboratory isotherms (to obtain gas saturations and desorption pressure), gas diffusivities, coal volumetrics (thickness and areal extent) need to be understood as a minimum requirement. When dealing with CO{sub 2}-ECBM selective adsorption, counter diffusion in the coal matrix, or coal shrinkage and swelling (from CH{sub 4} desorption and CO{sub 2} adsorption, respectively) and the influence of moisture need to be investigated in addition to the parameters above. During CO{sub 2}-ECBM processes, the areal distribution of the CO{sub 2} injected is accomplished by flow through the cleat network. When CO{sub 2} is entering the coal matrix by a combined sorption/diffusion process it will adsorb to the coal inner surface and at the same time replace part of the CH{sub 4}. This replacement occurs either by a reduction in the CH{sub 4} partial pressure or by a higher selective sorption of CO{sub 2} over CH{sub 4}. Because of a concentration gradient between CH{sub 4} in the matrix compared to the cleat system, CH{sub 4} diffuses from the coal matrix into the cleat system where, by pressure drawdown towards a production well, it can be produced. In this context this presentation summarizes gas (CO{sub 2}, CH{sub 4}) and water sorption on coal and specifically addresses the following topics: - CH{sub 4} saturation development in CBM reservoir with depth (thermodynamic considerations); - CO{sub 2}-ECBM 'sweet spot' identification; - CH{sub 4} and CO{sub 2} sorption capacity as a function depth and rank; - CO{sub 2} and CH{sub 4} sorption on natural coals and its dependence on coal specific parameters like coal rank, maceral composition or ash content (Busch and Gensterblum, 2011); - Water sorption on coal, its

  4. Ductile shear zones can induce hydraulically over-pressured fractures in deep hot-dry rock reservoirs: a new target for geothermal exploration?

    Science.gov (United States)

    Schrank, C. E.; Karrech, A.; Regenauer-Lieb, K.

    2014-12-01

    It is notoriously difficult to create and maintain permeability in deep hot-dry rock (HDR) geothermal reservoirs with engineering strategies. However, we predict that long-lived, slowly deforming HDR reservoirs likely contain hydraulically conductive, over-pressured fracture systems, provided that (a) the underlying lower crust and/or mantle are not entirely depleted of fluids and (b) the fracture system has not been drained into highly permeable overlying rocks. Such fracture systems could be targeted for the extraction of geothermal energy. Our prediction hinges on the notion that polycrystalline creep through matter transfer by a liquid phase (dissolution-precipitation creep) is a widespread mechanism for extracting fluids from the lower crust and mantle. Such processes - where creep cavities form during the slow, high-temperature deformation of crystalline solids, e.g., ceramics, metals, and rocks - entail the formation of (intergranular) fluid-assisted creep fractures. They constitute micron-scale voids formed along grain boundaries due to incompatibilities arising from diffusion or dislocation creep. Field and laboratory evidence suggest that the process leading to creep fractures may generate a dynamic permeability in the ductile crust, thus extracting fluids from this domain. We employed an elasto-visco-plastic material model that simulates creep fractures with continuum damage mechanics to model the slow contraction of high-heat-producing granites overlain by sedimentary rocks in 2D. The models suggest that deformation always leads to the initiation of a horizontal creep-damage front in the lower crust. This front propagates upwards towards the brittle-ductile transition (BDT) during protracted deformation where it collapses into highly damaged brittle-ductile shear zones. If the BDT is sufficiently shallow or finite strain sufficiently large, these shear zones trigger brittle faults emerging from their tips, which connect to the sub-horizontal damage

  5. Superficial dorsal vein injury/thrombosis presenting as false penile fracture requiring dorsal venous ligation.

    Science.gov (United States)

    Rafiei, Arash; Hakky, Tariq S; Martinez, Daniel; Parker, Justin; Carrion, Rafael

    2014-12-01

    Conditions mimicking penile fracture are extremely rare and have been seldom described. To describe a patient with false penile fracture who presented with superficial dorsal vein injury/thrombosis managed with ligation. A 33-year-old male presented with penile swelling and ecchymosis after intercourse. A penile ultrasound demonstrated a thrombosed superficial dorsal vein but also questionable fracture of the tunica albuginea. As the thrombus was expanding, he was emergently taken to the operating room for exploration and required only dorsal venous ligation. Postoperatively, patient's Sexual Health Inventory for Men score was 23, and he had no issues with erections or sexual intercourse. Early exploration of patients with suspected penile fracture provides excellent results with maintenance of erectile function. Also, in the setting of dorsal vein thrombosis, ligation preserves the integrity of the penile tissues and avoids unnecessary complications from conservative management. Rafiei A, Hakky TS, Martinez D, Parker J, and Carrion R. Superficial dorsal vein injury/thrombosis presenting as false penile fracture requiring dorsal venous ligation.

  6. Use of Cutting-Edge Horizontal and Underbalanced Drilling Technologies and Subsurface Seismic Techniques to Explore, Drill and Produce Reservoired Oil and Gas from the Fractured Monterey Below 10,000 ft in the Santa Maria Basin of California

    Energy Technology Data Exchange (ETDEWEB)

    George Witter; Robert Knoll; William Rehm; Thomas Williams

    2006-06-30

    This project was undertaken to demonstrate that oil and gas can be drilled and produced safely and economically from a fractured Monterey reservoir in the Santa Maria Basin of California by employing horizontal wellbores and underbalanced drilling technologies. Two vertical wells were previously drilled in this area with heavy mud and conventional completions; neither was commercially productive. A new well was drilled by the project team in 2004 with the objective of accessing an extended length of oil-bearing, high-resistivity Monterey shale via a horizontal wellbore, while implementing managed-pressure drilling (MPD) techniques to avoid formation damage. Initial project meetings were conducted in October 2003. The team confirmed that the demonstration well would be completed open-hole to minimize productivity impairment. Following an overview of the geologic setting and local field experience, critical aspects of the application were identified. At the pre-spud meeting in January 2004, the final well design was confirmed and the well programming/service company requirements assigned. Various design elements were reduced in scope due to significant budgetary constraints. Major alterations to the original plan included: (1) a VSP seismic survey was delayed to a later phase; (2) a new (larger) surface hole would be drilled rather than re-enter an existing well; (3) a 7-in. liner would be placed into the top of the Monterey target as quickly as possible to avoid problems with hole stability; (4) evaluation activities were reduced in scope; (5) geosteering observations for fracture access would be deduced from penetration rate, cuttings description and hydrocarbon in-flow; and (6) rather than use nitrogen, a novel air-injection MPD system was to be implemented. Drilling operations, delayed from the original schedule by capital constraints and lack of rig availability, were conducted from September 12 to November 11, 2004. The vertical and upper curved sections were

  7. Geomechanical Framework for Secure CO2 Storage in Fractured Reservoirs and Caprocks for Sedimentary Basins in theMidwest United States

    Energy Technology Data Exchange (ETDEWEB)

    Sminchak, Joel [Battelle, Columbus, OH (United States)

    2017-09-29

    This report presents final technical results for the project Geomechanical Framework for Secure CO2 Storage in Fractured Reservoirs and Caprocks for Sedimentary Basins in the Midwest United States (DE-FE0023330). The project was a three-year effort consisting of seven technical tasks focused on defining geomechanical factors for CO2 storage applications in deep saline rock formations in Ohio and the Midwest United States, because geomechancial issues have been identified as a significant risk factor for large-scale CO2 storage applications. A basin-scale stress-strain analysis was completed to describe the geomechanical setting for rock formations of Ordovician-Cambrian age in Ohio and adjacent areas of the Midwest United States in relation to geologic CO2 storage applications. The tectonic setting, stress orientation-magnitude, and geomechanical and petrophysical parameters for CO2 storage zones and caprocks in the region were cataloged. Ten geophysical image logs were analyzed for natural fractures, borehole breakouts, and drilling-induced fractures. The logs indicated mostly less than 10 fractures per 100 vertical feet in the borehole, with mostly N65E principal stress orientation through the section. Geophysical image logs and other logs were obtained for three wells located near the sites where specific models were developed for geomechanical simulations: Arches site in Boone County, Kentucky; Northern Appalachian Basin site in Chautauqua County, New York; and E-Central Appalachian Basin site in Tuscarawas County, Ohio. For these three wells, 9,700 feet of image logs were processed and interpreted to provide a systematic review of the distribution within each well of natural fractures, wellbore breakouts, faults, and drilling induced fractures. There were many borehole breakouts and drilling-induced tensile fractures but few natural fractures. Concentrated fractures were present at the Rome-basal sandstone

  8. Modeling brine-rock interactions in an enhanced geothermal systemdeep fractured reservoir at Soultz-Sous-Forets (France): a joint approachusing two geochemical codes: frachem and toughreact

    Energy Technology Data Exchange (ETDEWEB)

    Andre, Laurent; Spycher, Nicolas; Xu, Tianfu; Vuataz,Francois-D.; Pruess, Karsten.

    2006-12-31

    The modeling of coupled thermal, hydrological, and chemical (THC) processes in geothermal systems is complicated by reservoir conditions such as high temperatures, elevated pressures and sometimes the high salinity of the formation fluid. Coupled THC models have been developed and applied to the study of enhanced geothermal systems (EGS) to forecast the long-term evolution of reservoir properties and to determine how fluid circulation within a fractured reservoir can modify its rock properties. In this study, two simulators, FRACHEM and TOUGHREACT, specifically developed to investigate EGS, were applied to model the same geothermal reservoir and to forecast reservoir evolution using their respective thermodynamic and kinetic input data. First, we report the specifics of each of these two codes regarding the calculation of activity coefficients, equilibrium constants and mineral reaction rates. Comparisons of simulation results are then made for a Soultz-type geothermal fluid (ionic strength {approx}1.8 molal), with a recent (unreleased) version of TOUGHREACT using either an extended Debye-Hueckel or Pitzer model for calculating activity coefficients, and FRACHEM using the Pitzer model as well. Despite somewhat different calculation approaches and methodologies, we observe a reasonably good agreement for most of the investigated factors. Differences in the calculation schemes typically produce less difference in model outputs than differences in input thermodynamic and kinetic data, with model results being particularly sensitive to differences in ion-interaction parameters for activity coefficient models. Differences in input thermodynamic equilibrium constants, activity coefficients, and kinetics data yield differences in calculated pH and in predicted mineral precipitation behavior and reservoir-porosity evolution. When numerically cooling a Soultz-type geothermal fluid from 200 C (initially equilibrated with calcite at pH 4.9) to 20 C and suppressing mineral

  9. Advanced reservoir characterization and evaluation of CO{sub 2} gravity drainage in the naturally fractured Spraberry Trend Area. First annual technical progress report, September 1, 1995--August 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Schechter, D.S.

    1996-12-17

    The overall goal of this project is to assess the economic feasibility of CO{sub 2} flooding the naturally fractured Spraberry Trend Area in West Texas. This objective is being accomplished by conducting research in four areas: (1) extensive characterization of the reservoirs, (2) experimental studies of crude oil/brine/rock (COBR) interaction in the reservoirs, (3) analytical and numerical simulation of Spraberry reservoirs, and, (4) experimental investigations on CO{sub 2} gravity drainage in Spraberry whole cores. This report provides results of the first year of the five-year project for each of the four areas.

  10. Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Michael Grammer

    2006-09-30

    This topical report covers the year 2 of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). The characterization of select dolomite reservoirs has been the major focus of our efforts in Phase II/Year 2. Fields have been prioritized based upon the availability of rock data for interpretation of depositional environments, fracture density and distribution as well as thin section, geochemical, and petrophysical analyses. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in the 3 studied intervals (based upon initial fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. For the Niagaran (Silurian), a comprehensive high resolution sequence stratigraphic framework has been developed for a pinnacle reef in the northern reef trend where we had 100% core coverage throughout the reef section. Major findings to date are that facies types, when analyzed at a detailed level, have direct links to reservoir porosity and permeability in these dolomites. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point

  11. USE OF CUTTING-EDGE HORIZONTAL AND UNDERBALANCED DRILLING TECHNOLOGIES AND SUBSURFACE SEISMIC TECHNIQUES TO EXPLORE, DRILL AND PRODUCE RESERVOIRED OIL AND GAS FROM THE FRACTURED MONTEREY BELOW 10,000 FT IN THE SANTA MARIA BASIN OF CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    George Witter; Robert Knoll; William Rehm; Thomas Williams

    2005-02-01

    This project was undertaken to demonstrate that oil and gas can be drilled and produced safely and economically from a fractured Monterey reservoir in the Santa Maria Basin of California by employing horizontal wellbores and underbalanced drilling technologies. Two vertical wells were previously drilled in this area by Temblor Petroleum with heavy mud and conventional completions; neither was commercially productive. A new well was drilled by the project team in 2004 with the objective of accessing an extended length of oil-bearing, high-resistivity Monterey shale via a horizontal wellbore, while implementing managed-pressure drilling (MPD) techniques to avoid formation damage. Initial project meetings were conducted in October 2003. The team confirmed that the demonstration well would be completed open-hole to minimize productivity impairment. Following an overview of the geologic setting and local field experience, critical aspects of the application were identified. At the pre-spud meeting in January 2004, the final well design was confirmed and the well programming/service company requirements assigned. Various design elements were reduced in scope due to significant budgetary constraints. Major alterations to the original plan included: (1) a VSP seismic survey was delayed to a later phase; (2) a new (larger) surface hole would be drilled rather than re-enter an existing well; (3) a 7-in. liner would be placed into the top of the Monterey target as quickly as possible to avoid problems with hole stability; (4) evaluation activities were reduced in scope; (5) geosteering observations for fracture access would be deduced from penetration rate, cuttings description and hydrocarbon in-flow; and (6) rather than use nitrogen, a novel air-injection MPD system was to be implemented. Drilling operations, delayed from the original schedule by capital constraints and lack of rig availability, were conducted from September 12 to November 11, 2004. The vertical and upper

  12. Use of Cutting-Edge Horizontal and Underbalanced Drilling Technologies and Subsurface Seismic Techniques to Explore, Drill and Produce Reservoired Oil and Gas from the Fractured Monterey Below 10,000 ft in the Santa Maria Basin of California

    Energy Technology Data Exchange (ETDEWEB)

    George Witter; Robert Knoll; William Rehm; Thomas Williams

    2005-09-29

    This project was undertaken to demonstrate that oil and gas can be drilled and produced safely and economically from a fractured Monterey reservoir in the Santa Maria Basin of California by employing horizontal wellbores and underbalanced drilling technologies. Two vertical wells were previously drilled in this area with heavy mud and conventional completions; neither was commercially productive. A new well was drilled by the project team in 2004 with the objective of accessing an extended length of oil-bearing, high-resistivity Monterey shale via a horizontal wellbore, while implementing managed-pressure drilling (MPD) techniques to avoid formation damage. Initial project meetings were conducted in October 2003. The team confirmed that the demonstration well would be completed open-hole to minimize productivity impairment. Following an overview of the geologic setting and local field experience, critical aspects of the application were identified. At the pre-spud meeting in January 2004, the final well design was confirmed and the well programming/service company requirements assigned. Various design elements were reduced in scope due to significant budgetary constraints. Major alterations to the original plan included: (1) a VSP seismic survey was delayed to a later phase; (2) a new (larger) surface hole would be drilled rather than re-enter an existing well; (3) a 7-in. liner would be placed into the top of the Monterey target as quickly as possible to avoid problems with hole stability; (4) evaluation activities were reduced in scope; (5) geosteering observations for fracture access would be deduced from penetration rate, cuttings description and hydrocarbon in-flow; and (6) rather than use nitrogen, a novel air-injection MPD system was to be implemented. Drilling operations, delayed from the original schedule by capital constraints and lack of rig availability, were conducted from September 12 to November 11, 2004. The vertical and upper curved sections were

  13. A conversion of CO2-ECBM related lab observations to reservoir requirements

    Science.gov (United States)

    Gensterblum, Yves; Merkel, Alexej; Busch, Andreas; Krooß, Bernhard

    2013-04-01

    To predict a CBM production profile either during primary or secondary production, aspects like coal permeability and porosity, density, ash and moisture content, initial gas-in-place (GIP) (from canister desorption tests), gas sorption capacity from laboratory isotherms (to obtain gas saturations and desorption pressure), gas diffusivities, coal volumetrics (thickness and areal extent) need to be understood as a minimum requirement. When dealing with CO2-ECBM selective adsorption, counter diffusion in the coal matrix, or coal shrinkage and swelling (from CH4 desorption and CO2 adsorption, respectively) and the influence of moisture need to be investigated in addition to the parameters above. During CO2-ECBM processes, the areal distribution of the CO2 injected is accomplished by flow through the cleat network. When CO2 is entering the coal matrix by a combined sorption/diffusion process it will adsorb to the coal inner surface and at the same time replace part of the CH4. This replacement occurs either by a reduction in the CH4 partial pressure or by a higher selective sorption of CO2 over CH4. Because of a concentration gradient between CH4 in the matrix compared to the cleat system, CH4 diffuses from the coal matrix into the cleat system where, by pressure drawdown towards a production well, it can be produced. In this context this presentation summarizes gas (CO2, CH4) and water sorption on coal and specifically addresses the following topics: • CH4 and CO2 sorption capacity as a function depth and rank • CO2 and CH4 sorption on natural coals and its dependence on coal specific parameters like coal rank, maceral composition or ash content (Busch and Gensterblum, 2011). • Water sorption on coal, its dependence on coal properties such as rank and coal chemistry and gas sorption in the presence of water (Busch and Gensterblum, 2011). • Uncertainties in reservoir characterisation (Gensterblum et al., 2010; Gensterblum et al., 2009) • Sorption uptake

  14. A Comprehensive Study of Fracture Patterns and Densities in The Geysers Geothermal Reservoir Using Microearthquake Shear-Wave Splitting Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Peter E. Malin; Eylon Shalev; Min Lou; Silas M. Simiyu; Anastasia Stroujkova; Windy McCausland

    2004-02-24

    In this project we developed a method for using seismic S-wave data to map the patterns and densities of sub-surface fractures in the NW Geysers Geothermal Field/ (1) This project adds to both the general methods needed to characterize the geothermal production fractures that supply steam for power generation and to the specific knowledge of these in the Geysers area. (2)By locating zones of high fracture density it will be possible to reduce the cost of geothermal power development with the targeting of high production geothermal wells. (3) The results of the project having been transferred to both US based and international geothermal research and exploration agencies and concerns by several published papers and meeting presentations, and through the distribution of the data handling and other software codes we developed.

  15. Microseismic Monitoring of Stimulating Shale Gas Reservoir in SW China: 2. Spatial Clustering Controlled by the Preexisting Faults and Fractures

    Science.gov (United States)

    Chen, Haichao; Meng, Xiaobo; Niu, Fenglin; Tang, Youcai; Yin, Chen; Wu, Furong

    2018-02-01

    Microseismic monitoring is crucial to improving stimulation efficiency of hydraulic fracturing treatment, as well as to mitigating potential induced seismic hazard. We applied an improved matching and locating technique to the downhole microseismic data set during one treatment stage along a horizontal well within the Weiyuan shale gas play inside Sichuan Basin in SW China, resulting in 3,052 well-located microseismic events. We employed this expanded catalog to investigate the spatiotemporal evolution of the microseismicity in order to constrain migration of the injected fluids and the associated dynamic processes. The microseismicity is generally characterized by two distinctly different clusters, both of which are highly correlated with the injection activity spatially and temporarily. The distant and well-confined cluster (cluster A) is featured by relatively large-magnitude events, with 40 events of M -1 or greater, whereas the cluster in the immediate vicinity of the wellbore (cluster B) includes two apparent lineations of seismicity with a NE-SW trending, consistent with the predominant orientation of natural fractures. We calculated the b-value and D-value, an index of fracture complexity, and found significant differences between the two seismicity clusters. Particularly, the distant cluster showed an extremely low b-value ( 0.47) and D-value ( 1.35). We speculate that the distant cluster is triggered by reactivation of a preexisting critically stressed fault, whereas the two lineations are induced by shear failures of optimally oriented natural fractures associated with fluid diffusion. In both cases, the spatially clustered microseismicity related to hydraulic stimulation is strongly controlled by the preexisting faults and fractures.

  16. Analysis of pressure falloff tests of non-Newtonian power-law fluids in naturally-fractured bounded reservoirs

    Directory of Open Access Journals (Sweden)

    Omotayo Omosebi

    2015-12-01

    This article presents an analytic technique for interpreting pressure falloff tests of non-Newtonian Power-law fluids in wells that are located near boundaries in dual-porosity reservoirs. First, dimensionless pressure solutions are obtained and Stehfest inversion algorithm is used to develop new type curves. Subsequently, long-time analytic solutions are presented and interpretation procedure is proposed using direct synthesis. Two examples, including real field data from a heavy oil reservoir in Colombian eastern plains basin, are used to validate and demonstrate application of this technique. Results agree with conventional type-curve matching procedure. The approach proposed in this study avoids the use of type curves, which is prone to human errors. It provides a better alternative for direct estimation of formation and flow properties from falloff data.

  17. Fracture system influence on the reservoirs rock formation of Ordovician-Devonian carbonates in West Siberia tectonic depression

    OpenAIRE

    Koveshnikov, Aleksandr Evgenievich; Nesterova, A. C.; Dolgaya, Tatiana Fedorovna

    2016-01-01

    During the Paleozoic period from the beginning of the Cambrian to the end of the Carboniferous in the boundaries of the West Siberia tectonic depression there occurred the sea, where the carbonate platforms were formed by the limestones accumulation. All the area at the end of the Carboniferous period was turned to land. Resulting from Gertsynskaya folding in the times of Permian - Triassic the formed deposits were folded and denudated to a considerable extent. Besides, the reservoir rocks of...

  18. Natural fracture systems on planetary surfaces: Genetic classification and pattern randomness

    Science.gov (United States)

    Rossbacher, Lisa A.

    1987-01-01

    One method for classifying natural fracture systems is by fracture genesis. This approach involves the physics of the formation process, and it has been used most frequently in attempts to predict subsurface fractures and petroleum reservoir productivity. This classification system can also be applied to larger fracture systems on any planetary surface. One problem in applying this classification system to planetary surfaces is that it was developed for ralatively small-scale fractures that would influence porosity, particularly as observed in a core sample. Planetary studies also require consideration of large-scale fractures. Nevertheless, this system offers some valuable perspectives on fracture systems of any size.

  19. The effect of aspirin on blood loss and transfusion requirements in patients with femoral neck fractures.

    LENUS (Irish Health Repository)

    Manning, Brian J

    2012-02-03

    Although it is widely accepted that aspirin will increase the risk of intra- and post-operative bleeding, clinical studies have not consistently supported this assumption. We aimed to assess the effect of pre-operative aspirin on blood loss and transfusion requirements in patients undergoing emergency fixation of femoral neck fractures. A prospective case-control study was undertaken in patients presenting with femoral neck fractures. Parameters recorded included intra-operative blood loss, post-operative blood loss, transfusion requirements and peri-operative reduction in haemoglobin concentration. Of 89 patients presenting with femoral neck fractures 32 were on long-term aspirin therapy. Pre-operative aspirin ingestion did not significantly affect peri-operative blood loss, or change in haemoglobin concentration or haematocrit. However those patients taking aspirin pre-operatively had a significantly lower haemoglobin concentration and haematocrit and were more likely to be anaemic at presentation than those who were not receiving aspirin. Patients taking aspirin were also more likely to receive blood transfusion post-operatively.

  20. Fractured rock modeling in the National Waste Terminal Storage Program: a review of requirements and status

    Energy Technology Data Exchange (ETDEWEB)

    St. John, C.; Krug, A.; Key, S.; Monsees, J.

    1983-05-01

    Generalized computer codes capable of forming the basis for numerical models of fractured rock masses are being used within the NWTS program. Little additional development of these codes is considered justifiable, except in the area of representation of discrete fractures. On the other hand, model preparation requires definition of medium-specific constitutive descriptions and site characteristics and is therefore legitimately conducted by each of the media-oriented projects within the National Waste Terminal Storage program. However, it is essential that a uniform approach to the role of numerical modeling be adopted, including agreement upon the contribution of modeling to the design and licensing process and the need for, and means of, model qualification for particular purposes. This report discusses the role of numerical modeling, reviews the capabilities of several computer codes that are being used to support design or performance assessment, and proposes a framework for future numerical modeling activities within the NWTS program.

  1. Fractured rock modeling in the National Waste Terminal Storage Program: a review of requirements and status

    International Nuclear Information System (INIS)

    St John, C.; Krug, A.; Key, S.; Monsees, J.

    1983-05-01

    Generalized computer codes capable of forming the basis for numerical models of fractured rock masses are being used within the NWTS program. Little additional development of these codes is considered justifiable, except in the area of representation of discrete fractures. On the other hand, model preparation requires definition of medium-specific constitutive descriptions and site characteristics and is therefore legitimately conducted by each of the media-oriented projects within the National Waste Terminal Storage program. However, it is essential that a uniform approach to the role of numerical modeling be adopted, including agreement upon the contribution of modeling to the design and licensing process and the need for, and means of, model qualification for particular purposes. This report discusses the role of numerical modeling, reviews the capabilities of several computer codes that are being used to support design or performance assessment, and proposes a framework for future numerical modeling activities within the NWTS program

  2. The Influence of Hydraulic Fracturing on Carbon Storage Performance

    Science.gov (United States)

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

    2017-12-01

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

  3. Modelling fully-coupled Thermo-Hydro-Mechanical (THM) processes in fractured reservoirs using GOLEM: a massively parallel open-source simulator

    Science.gov (United States)

    Jacquey, Antoine; Cacace, Mauro

    2017-04-01

    Utilization of the underground for energy-related purposes have received increasing attention in the last decades as a source for carbon-free energy and for safe storage solutions. Understanding the key processes controlling fluid and heat flow around geological discontinuities such as faults and fractures as well as their mechanical behaviours is therefore of interest in order to design safe and sustainable reservoir operations. These processes occur in a naturally complex geological setting, comprising natural or engineered discrete heterogeneities as faults and fractures, span a relatively large spectrum of temporal and spatial scales and they interact in a highly non-linear fashion. In this regard, numerical simulators have become necessary in geological studies to model coupled processes and complex geological geometries. In this study, we present a new simulator GOLEM, using multiphysics coupling to characterize geological reservoirs. In particular, special attention is given to discrete geological features such as faults and fractures. GOLEM is based on the Multiphysics Object-Oriented Simulation Environment (MOOSE). The MOOSE framework provides a powerful and flexible platform to solve multiphysics problems implicitly and in a tightly coupled manner on unstructured meshes which is of interest for the considered non-linear context. Governing equations in 3D for fluid flow, heat transfer (conductive and advective), saline transport as well as deformation (elastic and plastic) have been implemented into the GOLEM application. Coupling between rock deformation and fluid and heat flow is considered using theories of poroelasticity and thermoelasticity. Furthermore, considering material properties such as density and viscosity and transport properties such as porosity as dependent on the state variables (based on the International Association for the Properties of Water and Steam models) increase the coupling complexity of the problem. The GOLEM application aims

  4. Estimating the Reactivation Potential of Pre-Existing Fractures in Subsurface Granitoids from Outcrop Analogues and in-Situ Stress Modeling: Implications for EGS Reservoir Stimulation with an Example from Thuringia (Central Germany)

    Science.gov (United States)

    Kasch, N.; Ustaszewski, K. M.; Siegburg, M.; Navabpour, P.; Hesse, G.

    2014-12-01

    The Mid-German Crystalline Rise (MGCR) in Thuringia (central Germany) is part of the European Variscan orogen and hosts large extents of Visean granites (c. 350 Ma), locally overlain by up to 3 km of Early Permian to Mid-Triassic volcanic and sedimentary rocks. A geothermal gradient of 36°C km-1 suggests that such subsurface granites form an economically viable hot dry rock reservoir at > 4 km depth. In order to assess the likelihood of reactivating any pre-existing fractures during hydraulic reservoir stimulation, slip and dilation tendency analyses (Morris et al. 1996) were carried out. For this purpose, we determined orientations of pre-existing fractures in 14 granite exposures along the southern border fault of an MGCR basement high. Additionally, the strike of 192 Permian magmatic dikes affecting the granite was considered. This analysis revealed a prevalence of NW-SE-striking fractures (mainly joints, extension veins, dikes and subordinately brittle faults) with a maximum at 030/70 (dip azimuth/dip). Borehole data and earthquake focal mechanisms reveal a maximum horizontal stress SHmax trending N150°E and a strike-slip regime. Effective in-situ stress magnitudes at 4.5 km depth, assuming hydrostatic conditions and frictional equilibrium along pre-existing fractures with a friction coefficient of 0.85 yielded 230 and 110 MPa for SHmax and Shmin, respectively. In this stress field, fractures with the prevailing orientations show a high tendency of becoming reactivated as dextral strike-slip faults if stimulated hydraulically. To ensure that a stimulation well creates fluid connectivity on a reservoir volume as large as possible rather than dissipating fluids along existing fractures, it should follow a trajectory at the highest possible angle to the orientation of prevailing fractures, i.e. subhorizontal and NE-SW-oriented. References: Morris, A., D. A. Ferrill, and D. B. Henderson (1996), Slip-tendency analysis and fault reactivation, Geology, 24, 275-278.

  5. AN ADVANCED FRACTURE CHARACTERIZATION AND WELL PATH NAVIGATION SYSTEM FOR EFFECTIVE RE-DEVELOPMENT AND ENHANCEMENT OF ULTIMATE RECOVERY FROM THE COMPLEX MONTEREY RESERVOIR OF SOUTH ELLWOOD FIELD, OFFSHORE CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    Steve Horner

    2004-04-29

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to 8,700,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful re-development and to optimize reservoir management, Venoco intends to investigate, map and characterize field fracture patterns and the reservoir conduit system. State of the art borehole imaging technologies including FMI, dipole sonic and cross-well seismic, interference tests and production logs will be employed to characterize fractures and micro faults. These data along with the existing database will be used for construction of a novel geologic model of the fracture network. Development of an innovative fracture network reservoir simulator is proposed to monitor and manage the aquifer's role in pressure maintenance and water production. The new fracture simulation model will be used for both planning optimal paths for new wells and improving ultimate recovery. In the second phase of this project, the model will be used for the design of a pilot program for downhole water re-injection into the aquifer simultaneously with oil production. Downhole water separation units attached to electric submersible pumps will be used to minimize surface fluid handling thereby improving recoveries per well and field economics while maintaining aquifer support. In cooperation with the DOE, results of the field studies as well as the new models developed and the fracture database will be shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the

  6. An Advanced Fracture Characterization and Well Path Navigation System for Effective Re-Development and Enhancement of Ultimate Recovery from the Complex Monterey Reservoir of South Ellwood Field, Offshore California

    Energy Technology Data Exchange (ETDEWEB)

    Horner, Steve; Ershaghi, Iraj

    2006-06-30

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to over 10,000,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful re-development and to optimize reservoir management, Venoco intended to investigate, map and characterize field fracture patterns and the reservoir conduit system. In the first phase of the project, state of the art borehole imaging technologies including FMI, dipole sonic, interference tests and production logs were employed to characterize fractures and micro faults. These data along with the existing database were used in the construction of a new geologic model of the fracture network. An innovative fracture network reservoir simulator was developed to better understand and manage the aquifer’s role in pressure maintenance and water production. In the second phase of this project, simulation models were used to plan the redevelopment of the field using high angle wells. Correct placement of the wells is critical to intersect the best-developed fracture zones and to avoid producing large volumes of water from the water leg. Particula r attention was paid to those areas of the field that have not been adequately developed with the existing producers. In cooperation with the DOE and the PTTC, the new data and the new fracture simulation model were shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the methodologies developed in this project. This report presents a summary of all technical work conducted during Budget Periods I

  7. AN ADVANCED FRACTURE CHARACTERIZATION AND WELL PATH NAVIGATION SYSTEM FOR EFFECTIVE RE-DEVELOPMENT AND ENHANCEMENT OF ULTIMATE RECOVERY FROM THE COMPLEX MONTEREY RESERVOIR OF SOUTH ELLWOOD FIELD, OFFSHORE CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    Steve Horner; Iraj Ershaghi

    2003-10-31

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to 8,700,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful re-development and to optimize reservoir management, Venoco intends to investigate, map and characterize field fracture patterns and the reservoir conduit system. State of the art borehole imaging technologies including FMI, dipole sonic and cross-well seismic, interference tests and production logs will be employed to characterize fractures and micro faults. These data along with the existing database will be used for construction of a novel geologic model of the fracture network. Development of an innovative fracture network reservoir simulator is proposed to monitor and manage the aquifer's role in pressure maintenance and water production. The new fracture simulation model will be used for both planning optimal paths for new wells and improving ultimate recovery. In the second phase of this project, the model will be used for the design of a pilot program for downhole water re-injection into the aquifer simultaneously with oil production. Downhole water separation units attached to electric submersible pumps will be used to minimize surface fluid handling thereby improving recoveries per well and field economics while maintaining aquifer support. In cooperation with the DOE, results of the field studies as well as the new models developed and the fracture database will be shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the

  8. AN ADVANCED FRACTURE CHARACTERIZATION AND WELL PATH NAVIGATION SYSTEM FOR EFFECTIVE RE-DEVELOPMENT AND ENHANCEMENT OF ULTIMATE RECOVERY FROM THE COMPLEX MONTEREY RESERVOIR OF SOUTH ELLWOOD FIELD, OFFSHORE CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    Steve Horner; Iraj Ershaghi

    2003-05-15

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to 8,700,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful re-development and to optimize reservoir management, Venoco intends to investigate, map and characterize field fracture patterns and the reservoir conduit system. State of the art borehole imaging technologies including FMI, dipole sonic and cross-well seismic, interference tests and production logs will be employed to characterize fractures and micro faults. These data along with the existing database will be used for construction of a novel geologic model of the fracture network. Development of an innovative fracture network reservoir simulator is proposed to monitor and manage the aquifer's role in pressure maintenance and water production. The new fracture simulation model will be used for both planning optimal paths for new wells and improving ultimate recovery. In the second phase of this project, the model will be used for the design of a pilot program for downhole water re-injection into the aquifer simultaneously with oil production. Downhole water separation units attached to electric submersible pumps will be used to minimize surface fluid handling thereby improving recoveries per well and field economics while maintaining aquifer support. In cooperation with the DOE, results of the field studies as well as the new models developed and the fracture database will be shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the

  9. AN ADVANCED FRACTURE CHARACTERIZATION AND WELL PATH NAVIGATION SYSTEM FOR EFFECTIVE RE-DEVELOPMENT AND ENHANCEMENT OF ULTIMATE RECOVERY FROM THE COMPLEX MONTEREY RESERVOIR OF SOUTH ELLWOOD FIELD, OFFSHORE CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    Steve Horner; Iraj Ershaghi

    2002-01-31

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to 8,700,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful re-development and to optimize reservoir management, Venoco intends to investigate, map and characterize field fracture patterns and the reservoir conduit system. State of the art borehole imaging technologies including FMI, dipole sonic and cross-well seismic, interference tests and production logs will be employed to characterize fractures and micro faults. These data along with the existing database will be used for construction of a novel geologic model of the fracture network. Development of an innovative fracture network reservoir simulator is proposed to monitor and manage the aquifer's role in pressure maintenance and water production. The new fracture simulation model will be used for both planning optimal paths for new wells and improving ultimate recovery. In the second phase of this project, the model will be used for the design of a pilot program for downhole water re-injection into the aquifer simultaneously with oil production. Downhole water separation units attached to electric submersible pumps will be used to minimize surface fluid handling thereby improving recoveries per well and field economics while maintaining aquifer support. In cooperation with the DOE, results of the field studies as well as the new models developed and the fracture database will be shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the

  10. AN ADVANCED FRACTURE CHARACTERIZATION AND WELL PATH NAVIGATION SYSTEM FOR EFFECTIVE RE-DEVELOPMENT AND ENHANCEMENT OF ULTIMATE RECOVERY FROM THE COMPLEX MONTEREY RESERVOIR OF SOUTH ELLWOOD FIELD, OFFSHORE CALIFORNIA

    Energy Technology Data Exchange (ETDEWEB)

    Steve Horner; Iraj Ershaghi

    2002-04-30

    Venoco Inc, intends to re-develop the Monterey Formation, a Class III basin reservoir, at South Ellwood Field, Offshore Santa Barbara, California. Well productivity in this field varies significantly. Cumulative Monterey production for individual wells has ranged from 260 STB to 8,700,000 STB. Productivity is primarily affected by how well the well path connects with the local fracture system and the degree of aquifer support. Cumulative oil recovery to date is a small percentage of the original oil in place. To embark upon successful redevelopment and to optimize reservoir management, Venoco intends to investigate, map and characterize field fracture patterns and the reservoir conduit system. State of the art borehole imaging technologies including FMI, dipole sonic and cross-well seismic, interference tests and production logs will be employed to characterize fractures and micro faults. These data along with the existing database will be used for construction of a novel geologic model of the fracture network. Development of an innovative fracture network reservoir simulator is proposed to monitor and manage the aquifer's role in pressure maintenance and water production. The new fracture simulation model will be used for both planning optimal paths for new wells and improving ultimate recovery. In the second phase of this project, the model will be used for the design of a pilot program for downhole water re-injection into the aquifer simultaneously with oil production. Downhole water separation units attached to electric submersible pumps will be used to minimize surface fluid handling thereby improving recoveries per well and field economics while maintaining aquifer support. In cooperation with the DOE, results of the field studies as well as the new models developed and the fracture database will be shared with other operators. Numerous fields producing from the Monterey and analogous fractured reservoirs both onshore and offshore will benefit from the

  11. A critical review of the data requirements for fluid flow models through fractured rock

    International Nuclear Information System (INIS)

    Priest, S.D.

    1986-01-01

    The report is a comprehensive critical review of the data requirements for ten models of fluid flow through fractured rock, developed in Europe and North America. The first part of the report contains a detailed review of rock discontinuities and how their important geometrical properties can be quantified. This is followed by a brief summary of the fundamental principles in the analysis of fluid flow through two-dimensional discontinuity networks and an explanation of a new approach to the incorporation of variability and uncertainty into geotechnical models. The report also contains a review of the geological and geotechnical properties of anhydrite and granite. Of the ten fluid flow models reviewed, only three offer a realistic fracture network model for which it is feasible to obtain the input data. Although some of the other models have some valuable or novel features, there is a tendency to concentrate on the simulation of contaminant transport processes, at the expense of providing a realistic fracture network model. Only two of the models reviewed, neither of them developed in Europe, have seriously addressed the problem of analysing fluid flow in three-dimensional networks. (author)

  12. Phase I (Year 1) Summary of Research--Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Michael Grammer

    2005-11-09

    This topical report covers the first 12 months of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). Phase I tasks, including Developing a Reservoir Catalog for selected dolomite reservoirs in the Michigan Basin, Characterization of Dolomite Reservoirs in Representative Fields and Technology Transfer have all been initiated and progress is consistent with our original scheduling. The development of a reservoir catalog for the 3 subject formations in the Michigan Basin has been a primary focus of our efforts during Phase I. As part of this effort, we currently have scanned some 13,000 wireline logs, and compiled in excess of 940 key references and 275 reprints that cover reservoir aspects of the 3 intervals in the Michigan Basin. A summary evaluation of the data in these publications is currently ongoing, with the Silurian Niagara Group being handled as a first priority. In addition, full production and reservoir parameter data bases obtained from available data sources have been developed for the 3 intervals in Excel and Microsoft Access data bases. We currently have an excess of 25 million cells of data for wells in the Basin. All Task 2 objectives are on time and on target for Phase I per our original proposal. Our mapping efforts to date, which have focused in large part on the Devonian Dundee Formation, have important implications for both new exploration plays and improved enhanced recovery methods in the Dundee ''play'' in Michigan--i.e. the interpreted fracture-related dolomitization control on the distribution of hydrocarbon reservoirs. In an exploration context, high-resolution structure mapping using quality-controlled well data should provide leads to convergence zones of fault/fracture

  13. Requirements for investigating the temperature-dependent fracture behavior of irradiated materials by indentation

    Energy Technology Data Exchange (ETDEWEB)

    Sacksteder, Irène, E-mail: irene.sacksteder@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, Eggenstein-Leopoldshafen (Germany); Hostettler, Simon [Synton-MDP Inc., Nidau (Switzerland); Charbonneau, Grégoire; Albinski, Bartlomiej; Schneider, Hans-Christian [Karlsruhe Institute of Technology, Institute for Applied Materials, Eggenstein-Leopoldshafen (Germany)

    2013-10-15

    Highlights: • A custom-made indenter is designed for indentations at high temperature. • The instrumented indentation technique at high temperature will be used to investigate temperature dependent fracture mechanisms in structural materials. • A finite-element based model has been validated with a view to predict crack initiation and propagation in Eurofer97 and tungsten-like materials. -- Abstract: The instrumented indentation technique is an interesting testing tool to examine temperature-dependent fracture mechanisms. It is planned to be used to generate cracks at defined temperatures in hard and brittle metallic materials. The present study describes the properties needed for the use of a new type of indenter operating at high temperature. The indenter was designed to meet mechanical and thermal requirements and other constraints relating to the operation of functional units of the indentation instrument. Additionally, a finite element model has been built with a view to predict indentation induced cracks in Eurofer97 and tungsten. The model has been validated both with the theory of Hertz and experimentally by comparison with indentation curves.

  14. Understanding the True Stimulated Reservoir Volume in Shale Reservoirs

    KAUST Repository

    Hussain, Maaruf

    2017-06-06

    Successful exploitation of shale reservoirs largely depends on the effectiveness of hydraulic fracturing stimulation program. Favorable results have been attributed to intersection and reactivation of pre-existing fractures by hydraulically-induced fractures that connect the wellbore to a larger fracture surface area within the reservoir rock volume. Thus, accurate estimation of the stimulated reservoir volume (SRV) becomes critical for the reservoir performance simulation and production analysis. Micro-seismic events (MS) have been commonly used as a proxy to map out the SRV geometry, which could be erroneous because not all MS events are related to hydraulic fracture propagation. The case studies discussed here utilized a fully 3-D simulation approach to estimate the SRV. The simulation approach presented in this paper takes into account the real-time changes in the reservoir\\'s geomechanics as a function of fluid pressures. It is consisted of four separate coupled modules: geomechanics, hydrodynamics, a geomechanical joint model for interfacial resolution, and an adaptive re-meshing. Reservoir stress condition, rock mechanical properties, and injected fluid pressure dictate how fracture elements could open or slide. Critical stress intensity factor was used as a fracture criterion governing the generation of new fractures or propagation of existing fractures and their directions. Our simulations were run on a Cray XC-40 HPC system. The studies outcomes proved the approach of using MS data as a proxy for SRV to be significantly flawed. Many of the observed stimulated natural fractures are stress related and very few that are closer to the injection field are connected. The situation is worsened in a highly laminated shale reservoir as the hydraulic fracture propagation is significantly hampered. High contrast in the in-situ stresses related strike-slip developed thereby shortens the extent of SRV. However, far field nature fractures that were not connected to

  15. Characterization and modelling of a naturally fractured reservoir-caprock unit targeted for CO2 storage in arctic Norway

    NARCIS (Netherlands)

    Senger, K.; Mulrooney, M.; Schaaf, N.; Tveranger, J.; Braathen, A.; Ogata, K.; Olaussen, S.

    2017-01-01

    Successfully storing CO2 underground requires a good understanding of the subsurface at the storage site, and its robust representation in geological models. Geological models, and related simulations, provide important quantitative information on critical parameters for the optimal utilisation of

  16. Wrist Fractures

    Science.gov (United States)

    ... a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Wrist Fractures Email to a friend * required fields From * To * DESCRIPTION A wrist fracture is a medical term for a broken wrist. The wrist is made up of eight ...

  17. Reservoir engineering and hydrogeology

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    Summaries are included which show advances in the following areas: fractured porous media, flow in single fractures or networks of fractures, hydrothermal flow, hydromechanical effects, hydrochemical processes, unsaturated-saturated systems, and multiphase multicomponent flows. The main thrust of these efforts is to understand the movement of mass and energy through rocks. This has involved treating fracture rock masses in which the flow phenomena within both the fractures and the matrix must be investigated. Studies also address the complex coupling between aspects of thermal, hydraulic, and mechanical processes associated with a nuclear waste repository in a fractured rock medium. In all these projects, both numerical modeling and simulation, as well as field studies, were employed. In the theoretical area, a basic understanding of multiphase flow, nonisothermal unsaturated behavior, and new numerical methods have been developed. The field work has involved reservoir testing, data analysis, and case histories at a number of geothermal projects

  18. Fracture toughness requirements of reactor vessel material in evaluation of the safety analysis report of nuclear power plants

    International Nuclear Information System (INIS)

    Widia Lastana Istanto

    2011-01-01

    Fracture toughness requirements of reactor vessel material that must be met by applicants for nuclear power plants construction permit has been investigated in this paper. The fracture toughness should be described in the Safety Analysis Reports (SARs) document that will be evaluated by the Nuclear Energy Regulatory Agency (BAPETEN). Because BAPETEN does not have a regulations or standards/codes regarding the material used for the reactor vessel, especially in the fracture toughness requirements, then the acceptance criteria that applied to evaluate the fracture toughness of reactor vessel material refers to the regulations/provisions from the countries that have been experienced in the operation of nuclear power plants, such as from the United States, Japan and Korea. Regulations and standards used are 10 CFR Part 50, ASME and ASTM. Fracture toughness of reactor vessel materials are evaluated to ensure compliance of the requirements and provisions of the Regulatory Body and the applicable standards, such as ASME or ASTM, in order to assure a reliability and integrity of the reactor vessels as well as providing an adequate safety margin during the operation, testing, maintenance, and postulated accident conditions over the reactor vessel lifetime. (author)

  19. Pore- and fracture-filling gas hydrate reservoirs in the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II Green Canyon 955 H well

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2012-01-01

    High-quality logging-while-drilling (LWD) downhole logs were acquired in seven wells drilled during the Gulf of MexicoGasHydrateJointIndustryProjectLegII in the spring of 2009. Well logs obtained in one of the wells, the GreenCanyon Block 955Hwell (GC955-H), indicate that a 27.4-m thick zone at the depth of 428 m below sea floor (mbsf; 1404 feet below sea floor (fbsf)) contains gashydrate within sand with average gashydrate saturations estimated at 60% from the compressional-wave (P-wave) velocity and 65% (locally more than 80%) from resistivity logs if the gashydrate is assumed to be uniformly distributed in this mostly sand-rich section. Similar analysis, however, of log data from a shallow clay-rich interval between 183 and 366 mbsf (600 and 1200 fbsf) yielded average gashydrate saturations of about 20% from the resistivity log (locally 50-60%) and negligible amounts of gashydrate from the P-wave velocity logs. Differences in saturations estimated between resistivity and P-wave velocities within the upper clay-rich interval are caused by the nature of the gashydrate occurrences. In the case of the shallow clay-rich interval, gashydrate fills vertical (or high angle) fractures in rather than fillingpore space in sands. In this study, isotropic and anisotropic resistivity and velocity models are used to analyze the occurrence of gashydrate within both the clay-rich and sand dominated gas-hydrate-bearing reservoirs in the GC955-Hwell.

  20. Well Test Analysis of Naturally Fractured Vuggy Reservoirs with an Analytical Triple Porosity – Double Permeability Model and a Global Optimization Method

    Directory of Open Access Journals (Sweden)

    Gómez Susana

    2014-07-01

    Full Text Available The aim of this work is to study the automatic characterization of Naturally Fractured Vuggy Reservoirs via well test analysis, using a triple porosity-dual permeability model. The inter-porosity flow parameters, the storativity ratios, as well as the permeability ratio, the wellbore storage effect, the skin and the total permeability will be identified as parameters of the model. In this work, we will perform the well test interpretation in Laplace space, using numerical algorithms to transfer the discrete real data given in fully dimensional time to Laplace space. The well test interpretation problem in Laplace space has been posed as a nonlinear least squares optimization problem with box constraints and a linear inequality constraint, which is usually solved using local Newton type methods with a trust region. However, local methods as the one used in our work called TRON or the well-known Levenberg-Marquardt method, are often not able to find an optimal solution with a good fit of the data. Also well test analysis with the triple porosity-double permeability model, like most inverse problems, can yield multiple solutions with good match to the data. To deal with these specific characteristics, we will use a global optimization algorithm called the Tunneling Method (TM. In the design of the algorithm, we take into account issues of the problem like the fact that the parameter estimation has to be done with high precision, the presence of noise in the measurements and the need to solve the problem computationally fast. We demonstrate that the use of the TM in this study, showed to be an efficient and robust alternative to solve the well test characterization, as several optimal solutions, with very good match to the data were obtained.

  1. Integrated Approach to Drilling Project in Unconventional Reservoir Using Reservoir Simulation

    Science.gov (United States)

    Stopa, Jerzy; Wiśniowski, Rafał; Wojnarowski, Paweł; Janiga, Damian; Skrzypaszek, Krzysztof

    2018-03-01

    Accumulation and flow mechanisms in unconventional reservoir are different compared to conventional. This requires a special approach of field management with drilling and stimulation treatments as major factor for further production. Integrated approach of unconventional reservoir production optimization assumes coupling drilling project with full scale reservoir simulation for determine best well placement, well length, fracturing treatment design and mid-length distance between wells. Full scale reservoir simulation model emulate a part of polish shale - gas field. The aim of this paper is to establish influence of technical factor for gas production from shale gas field. Due to low reservoir permeability, stimulation treatment should be direct towards maximizing the hydraulic contact. On the basis of production scenarios, 15 stages hydraulic fracturing allows boost gas production over 1.5 times compared to 8 stages. Due to the possible interference of the wells, it is necessary to determine the distance between the horizontal parts of the wells trajectories. In order to determine the distance between the wells allowing to maximize recovery factor of resources in the stimulated zone, a numerical algorithm based on a dynamic model was developed and implemented. Numerical testing and comparative study show that the most favourable arrangement assumes a minimum allowable distance between the wells. This is related to the volume ratio of the drainage zone to the total volume of the stimulated zone.

  2. Model to predict the flow of tracers in naturally fractured geothermal reservoirs; Modelo para predecir el flujo de trazadores en yacimientos geotermicos naturalmente fracturados

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez Sabag, Jetzabeth

    1988-02-01

    The proposed model has been developed to study the flow of tracers through naturally fractured geothermal reservoirs. The idealized system of the reservoir is made up of two regions: A movable region, where diffusion and convection mechanisms are present and a stagnant or immovable region where the diffusion and adsorption mechanisms are considered: in both regions the loss of mass by radioactive decay is considered. The solutions of the basic flow equations are in the Laplace space and for its numerical inversion the Stehfest algorithm was used. In spite of the numerical dispersion that these solutions involve, a well defined tendency to infer the system behavior under different flow conditions was found. It was found that, for practical purposes, the size of the matrix blocks does not have an influence on the concentration response, and the solution is reduced to the one presented by Tang and associates. Under these conditions, the system behavior can be described by two non-dimensional parameters: The Peclet number in fractures, P{sub e1}, and a parameter. The tracer response for the peak solution was also derived. An analytical solution limit was found for the case in which {alpha} tends to zero, which corresponds to the case of a homogenous system. It was verified that this limit solution is valid, for {alpha}<0.01. For the case of continuous injection, this solution is reduced to the one presented by Coasts and Smith. For the peak solution, it was found that the irruption time corresponding to the maximum concentration is directly related to the non-dimensional group. Therefore, it is possible to obtain the value of P{sub e1} for a given X{sub D}, or vice versa. A group of graphs of non-dimensional concentration in the fracture versus non-dimensional time, was developed. It was found that if P{sub e1} remains constant whereas {alpha} changes, the limit solution is the envelope of a family of curves in a graph of C{sub D} versus t{sub D}. In this figure P

  3. Large reservoirs: Chapter 17

    Science.gov (United States)

    Miranda, Leandro E.; Bettoli, Phillip William

    2010-01-01

    expressed effects, such as turbidity and water quality, zooplankton density and size composition, or fish growth rates and assemblage composition, are the upshot of large-scale factors operating outside reservoirs and not under the direct control of reservoir managers. Realistically, abiotic and biotic conditions in reservoirs are shaped by factors working inside and outside reservoirs, with the relative importance of external factors differing among reservoirs. With this perspective, large reservoirs are viewed from a habitat standpoint within the framework of a conceptual model in which individual reservoir characteristics are influenced by both local- and landscape-scale factors (Figure 17.1). In the sections that follow, how each element of this hierarchical model influences habitat and fish assemblages in reservoirs is considered. Important in-reservoir habitat issues and reservoirs as part of larger systems, where reservoir management requires looking for real solutions outside individual reservoirs are described.

  4. Etude fondamentale de l'imbibition dans un réservoir fissuré Basic Research on Inbibition in a Fractured Reservoir

    Directory of Open Access Journals (Sweden)

    Iffly R.

    2006-11-01

    efficiency in a fractured reservoir closely depends on the magnitude and rate of water imbibition within the matrix blocks. The effects of both block height and permeability on cil recovery as well as those of block boundary conditions (fractures may contain either water or oil, or may be tight have been determined through numerous laboratory experiments with actual rock and fluid samples from a field operated by Elf.

  5. Surface Roughness Effects on Fluid Transport Through a Natural Rock Fracture

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, D.M.; Ahmadi, Goodarz; Smith, D.H.

    2008-04-01

    Fluid flow through rock fractures can be orders of magnitude faster than through the adjacent low-permeability rock. Understanding how fluid moves through these pathways is important for the prediction of sequestered CO2 transport in geologic reservoirs. Reservoir-scale, discrete-fracture simulators use simplified models of flow through fractures to determine transport properties in complex fracture networks. A high level of approximation is required in these reservoir-scale simulations due to the number of fractures within the domain of interest and because of the limited amount of information that can be obtained from geophysical well-logs (Long et al. (1996)). For this study, flow simulations through a CT-scanned fracture were performed to evaluate different fluid transport parameters that are important in geological flow analysis. The ‘roughness’ of the fracture was varied to determine the effect of the bumpy fracture walls on the fluid flow. The permeability and effective aperture were determined for flow under a constant pressure head. The fracture roughness is shown to dramatically reduce the flow through the fracture, and various relations are described.

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

    Science.gov (United States)

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

    2018-02-01

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

  7. Rio Blanco massive hydraulic fracture

    Energy Technology Data Exchange (ETDEWEB)

    1973-01-01

    The Piceance Basin in Colorado contains an estimated 600 trillion cu ft of natural gas in place. Both the Rulison and Rio Blanco events have been detonated to determine the feasibility of nuclear fracturing to stimulate natural gas production in this basin. A demonstration program to test the relative effectiveness of massive hydraulic fracturing (MHF) to achieve natural gas production stimulation from the same gas reservoir is presented. Details are included on MHF design parameters, including surface and subsurface equipment, pumping requirements, evaluation of fracturing results, and all associated test programs; site characteristics and preparation; proposal for gas utilization program; environmental surveillance and comparative analysis of environmental aspects of MHF and nuclear stimulation; gas delivery estimates; project administration; and costs and scheduling.

  8. Reservoir management strategy for East Randolph Field, Randolph Township, Portage County, Ohio

    Energy Technology Data Exchange (ETDEWEB)

    Safley, L.E.; Salamy, S.P.; Young, M.A.; Fowler, M.L.; Wing, J.L.; Thomas, J.B.; Mills, J.; Wood, D.

    1998-07-01

    The primary objective of the Reservoir Management Field Demonstration Program is to demonstrate that multidisciplinary reservoir management teams using appropriate software and methodologies with efforts scaled to the size of the resource are a cost-effective method for: Increasing current profitability of field operations; Forestalling abandonment of the reservoir; and Improving long-term economic recovery for the company. The primary objective of the Reservoir Management Demonstration Project with Belden and Blake Corporation is to develop a comprehensive reservoir management strategy to improve the operational economics and optimize oil production from East Randolph field, Randolph Township, Portage County, Ohio. This strategy identifies the viable improved recovery process options and defines related operational and facility requirements. In addition, strategies are addressed for field operation problems, such as paraffin buildup, hydraulic fracture stimulation, pumping system optimization, and production treatment requirements, with the goal of reducing operating costs and improving oil recovery.

  9. Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

    Science.gov (United States)

    LBNL, in consultation with the EPA, expanded upon a previous study by injecting directly into a 3D representation of a hypothetical fault zone located in the geologic units between the shale-gas reservoir and the drinking water aquifer.

  10. Summary of Research through Phase II/Year 2 of Initially Approved 3 Phase/3 Year Project - Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Grammer

    2007-09-30

    This final scientific/technical report covers the first 2 years (Phases I and II of an originally planned 3 Year/3 Phase program). The project was focused on evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin. The characterization of select dolomite reservoirs was the major focus of our efforts in Phases I and II of the project. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault-related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in these 2 studied intervals (based upon fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. In the Niagaran (Silurian), there is a general trend of increasing dolomitization shelfward, with limestone predominant in more basinward positions. A major finding is that facies types, when analyzed at a detailed level, are directly related to reservoir porosity and permeability in these dolomites which increases the predictability of reservoir quality in these units. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point that the results should be exportable throughout the basin. Much of the data synthesis and modeling for the project was scheduled to be part of Year 3/Phase III, but the discontinuation of funding after Year 2 precluded those efforts

  11. 10 CFR 50.61 - Fracture toughness requirements for protection against pressurized thermal shock events.

    Science.gov (United States)

    2010-01-01

    ..., research results, and plant surveillance data, and may use probabilistic fracture mechanics techniques... analyses, submitted to demonstrate acceptable risk with RTPTS above the screening limit due to plant... obtained from the set of data used to establish the mean. If a generic mean value given in paragraph (c)(1...

  12. Évaluation de la fracturation des réservoirs par forages : comparaison entre les données de carottes et d'imagerie de paroi Assessment of Reservoir Fracturing from Boreholes : Comparison Between Core and Wall-Image Data

    Directory of Open Access Journals (Sweden)

    Genter A.

    2006-11-01

    étecter que les fractures ayant au moins cette épaisseur de colmatage. Dans les formations de Balazuc, 6 % des fractures sont détectées par le FMS, ce qui correspond exactement à la proportion de fractures dont la taille est supérieure à la résolution de l'outil. Malgré ces biais d'échantillonnage, les directions majeures de fracturation sont correctement détectées avec les deux techniques mises en oeuvre. Deep drilling was carried out of two sedimentary sequences considered as representative of reservoir formations; one at Soultz-sous-Forêts in Alsace and the other at Balazuc in the Ardèche, France. The natural fracturing in these predominantly sandstone sequences has been analysed both from the continuous cores collected during the drilling and from wall imagery obtained by acoustic (BHTV and electric (FMS methods. This core-imagery comparison shows, quite logically, that the core analysis gives more complete results than the interpretation of wall imagery. With the BHTV it was possible to characterize 50% of the fractures seen in the cores, as against only 6% using the FMS. In the Bundsandstein at Soultz the fractures that form clusters (i. e. very close to one another are not correctly recorded by the BHTV. This bias is even more significant with the FMS since it applies to the entire fracture distribution, regardless of the fracture spacing. This fracture-detection filtering that we find with the imagery techniques are even more evident where the fractures are filled (little physical contrast or small (below the detection threshold. The core-imagery comparison also shows that the horizontal resolution of the imaging tool is directly proportional to the number of fractures detected. The BHTV, which has a resolution of between 1 and 2 mm, does not detect fractures of this thickness or less, i. e. 45% of the population. This percentage is similar to the amount of fractures recognized by BHTV compared to that recorded in core. The FMS, with a much coarser

  13. FY 1995 report on verification of geothermal exploration technology. Development of fracture reservoir exploration technology (development of seismic exploration); 1995 nendo chinetsu tansa gijutsunado kensho chosa. Danretsugata choryuso tansaho kaihatsu (danseiha riyo tansaho kaihatsu) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    This report provides the development of new exploration technology using elastic waves, such as reflection seismic survey, VSP, and seismic tomography, for precisely characterizing subsurface fractures in geothermal reservoirs. In order to investigate and improve the effective data acquisition and analysis methods for detecting a fault type of fractures, an experiment of a seismic tomography method was conducted using wells drilled in the Ogiri geothermal field, Aira-gun, Kagoshima Prefecture. An experiment of propagation characteristics of piezo type underground seismic source in the volcanic field was also conducted as a trend survey of underground seismic sources. The fracture type in the model field was systematically analyzed by measuring the core samples obtained in the demonstration test field through remanence measurement, fluid inclusion measurement, and zircon measurement using test equipment, and by analyzing results obtained from cores and results of seismic tomography obtained from the wells. Based on these results, the effectiveness and practical application of exploration methods using elastic waves were investigated. 80 refs., 250 figs., 49 tabs.

  14. Analysis of the Influencing Factors on the Well Performance in Shale Gas Reservoir

    Directory of Open Access Journals (Sweden)

    Cheng Dai

    2017-01-01

    Full Text Available Due to the ultralow permeability of shale gas reservoirs, stimulating the reservoir formation by using hydraulic fracturing technique and horizontal well is required to create the pathway of gas flow so that the shale gas can be recovered in an economically viable manner. The hydraulic fractured formations can be divided into two regions, stimulated reservoir volume (SRV region and non-SRV region, and the produced shale gas may exist as free gas or adsorbed gas under the initial formation condition. Investigating the recovery factor of different types of shale gas in different region may assist us to make more reasonable development strategies. In this paper, we build a numerical simulation model, which has the ability to take the unique shale gas flow mechanisms into account, to quantitatively describe the gas production characteristics in each region based on the field data collected from a shale gas reservoir in Sichuan Basin in China. The contribution of the free gas and adsorbed gas to the total production is analyzed dynamically through the entire life of the shale gas production by adopting a component subdivision method. The effects of the key reservoir properties, such as shale matrix, secondary natural fracture network, and primary hydraulic fractures, on the recovery factor are also investigated.

  15. A Methodology for Calculating EGS Electricity Generation Potential Based on the Gringarten Model for Heat Extraction From Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Augustine, Chad

    2017-05-01

    Existing methodologies for estimating the electricity generation potential of Enhanced Geothermal Systems (EGS) assume thermal recovery factors of 5% or less, resulting in relatively low volumetric electricity generation potentials for EGS reservoirs. This study proposes and develops a methodology for calculating EGS electricity generation potential based on the Gringarten conceptual model and analytical solution for heat extraction from fractured rock. The electricity generation potential of a cubic kilometer of rock as a function of temperature is calculated assuming limits on the allowed produced water temperature decline and reservoir lifetime based on surface power plant constraints. The resulting estimates of EGS electricity generation potential can be one to nearly two-orders of magnitude larger than those from existing methodologies. The flow per unit fracture surface area from the Gringarten solution is found to be a key term in describing the conceptual reservoir behavior. The methodology can be applied to aid in the design of EGS reservoirs by giving minimum reservoir volume, fracture spacing, number of fractures, and flow requirements for a target reservoir power output. Limitations of the idealized model compared to actual reservoir performance and the implications on reservoir design are discussed.

  16. Requirements for a Stable Long-Term Result in Surgical Reduction of Vertebral Fragility Fractures.

    Science.gov (United States)

    Crespo-Sanjuán, Jesús; Ardura, Francisco; Hernández-Ramajo, Rubén; Noriega, David C

    2017-09-01

    Osteoporotic vertebral fractures are one of the major health problems in the world. Minimally invasive surgical treatment has great advantages compared with conservative treatment in treating these fractures, because it eliminates pain and functional disability. The percutaneous intravertebral expandable titanium device SpineJack (Vexim SA, Balma, France) is beneficial compared with other kyphoplasty devices, showing results that are maintained over time and a reduction in complications. However, controversy exists about the minimum amount of cement that should be used to achieve long-term restoration and which is essential to minimize complications. We reviewed publications studying the maintenance of long-term restoration using this percutaneous expandable titanium device in cadavers. In this study, we show the first long-term work with patients treated with percutaneous expandable titanium device, describing precise indications concerning the minimum amount of cement that should be used. Results were evaluated from a clinical study including 178 patient outcomes with long-term follow-up results performed by our team. The mean total quantity of cement injected was 4.4 mL (25% vertebral body filling). The leakage rate was 12.9%, and all of these occurrences were asymptomatic. The mean follow-up time was 77 months (60-96 months). All clinical scales improved significantly after the procedure. A recollapse of the treated vertebra was observed in 3 cases (1.6%), and the adjacent fracture rate was 2.2%. From the results of our study and review of the literature, cement equivalent to 25% of the vertebral body filling volume, when combined with the titanium expandable device, seems to be sufficient to prevent recollapse in osteoporotic and type A.3 fractures. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Approche numérique et quantitative de l'étude sur clichés aériens de la fracturation des réservoirs en roches fissurées Numerical and Quantitative Approach to Investigating Fracture Maps of Fissured Reservoirs from Airphotos

    Directory of Open Access Journals (Sweden)

    Razack M.

    2006-11-01

    Full Text Available Dans le cadre de la détermination de la structure des réservoirs en roches fissurées, une méthodologie de traitement numérique et quantitative de la fractu-ration relevée sur clichés aériens a été mise au point. La numérisation du relevé est obtenue par digitalisation sur un lecteur de courbes. Cette information est ensuite traitée à l'aide d'un algorithme (programme RAFRAC qui permet d'identifier numériquement la fracturation par un ensemble de para-mètres élémentaires (orientation, longueur , densité... à partir desquels il devient possible de procéder à une analyse approfondie du champ de fractures considéré. Un exemple d'application est présenté à propos de l'étude de la fracturation d'une zone à structure tabulaire (Causse du Larzac. Ces premiers résultats tendent à mettre en évidence une double nature mathématique de l'information analysée aléatoire d'une part, déterministe d'autre part. On montre également, à partir de la théorie desvariables régionalisées, que la fracturation suit une certaine logique dans sa répartition spatiale. Par ailleurs une organisation des familles de fractures a pu être mise en évidence, sur laquelle la structure géométrique du réservoir sous-jacent s'ajuste de façon très proche. As part of efforts ta determine the structure of reservoirs in fissured rocks, a numerical and quantitative processing methodology has been developed for mapping fractures with airphotos. The survey is digitized on a curve reader. This data is then processed by means of an algorithm (RAFRAC program sa as ta numerically identify fracturing by a set of elementary parameters (direction, length, density, etc. which con be used ta make an in-depth analysis of the fracture field being considered. A sample application is described having ta do with the surveying of the fracturing in a tabular structure (Causse plateau of Larzac. These initial results tend to reveol a dual mathematical nature

  18. APPLICATION OF INTEGRATED RESERVOIR MANAGEMENT AND RESERVOIR CHARACTERIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Jack Bergeron; Tom Blasingame; Louis Doublet; Mohan Kelkar; George Freeman; Jeff Callard; David Moore; David Davies; Richard Vessell; Brian Pregger; Bill Dixon; Bryce Bezant

    2000-03-01

    Reservoir performance and characterization are vital parameters during the development phase of a project. Infill drilling of wells on a uniform spacing, without regard to characterization does not optimize development because it fails to account for the complex nature of reservoir heterogeneities present in many low permeability reservoirs, especially carbonate reservoirs. These reservoirs are typically characterized by: (1) large, discontinuous pay intervals; (2) vertical and lateral changes in reservoir properties; (3) low reservoir energy; (4) high residual oil saturation; and (5) low recovery efficiency. The operational problems they encounter in these types of reservoirs include: (1) poor or inadequate completions and stimulations; (2) early water breakthrough; (3) poor reservoir sweep efficiency in contacting oil throughout the reservoir as well as in the nearby well regions; (4) channeling of injected fluids due to preferential fracturing caused by excessive injection rates; and (5) limited data availability and poor data quality. Infill drilling operations only need target areas of the reservoir which will be economically successful. If the most productive areas of a reservoir can be accurately identified by combining the results of geological, petrophysical, reservoir performance, and pressure transient analyses, then this ''integrated'' approach can be used to optimize reservoir performance during secondary and tertiary recovery operations without resorting to ''blanket'' infill drilling methods. New and emerging technologies such as geostatistical modeling, rock typing, and rigorous decline type curve analysis can be used to quantify reservoir quality and the degree of interwell communication. These results can then be used to develop a 3-D simulation model for prediction of infill locations. The application of reservoir surveillance techniques to identify additional reservoir ''pay'' zones

  19. Elbow Fractures

    Science.gov (United States)

    ... occur commonly in children and in the elderly. Nerve and/or artery injuries can be associated with these types of fractures and must be carefully evaluated by your doctor. These fractures usually require surgical repair with plates and/or screw, unless they are ...

  20. ADVANCED FRACTURING TECHNOLOGY FOR TIGHT GAS: AN EAST TEXAS FIELD DEMONSTRATION

    Energy Technology Data Exchange (ETDEWEB)

    Mukul M. Sharma

    2005-03-01

    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

  1. Cryogenic Fracturing: Laboratory Visualization Experiments and Numerical Simulations Using Peridynamics

    Science.gov (United States)

    Martin-Short, R.; Edmiston, J. K.

    2015-12-01

    Typical hydraulic fracturing operations involve the use of a large quantity of water, which can be problematic for several reasons including possible formation (permeability) damage, disposal of waste water, and the use of precious local water resource. An alternate reservoir permeability enhancing technology not requiring water is cryogenic fracturing. This method induces controlled fracturing of rock formations by thermal shock and has potentially important applications in the geothermal and hydrocarbon industries. In this process, cryogenic fluid—such as liquid nitrogen—is injected into the subsurface, causing fracturing due to thermal gradients. These fractures may improve the formation permeability relative to that achievable by hydraulic fracturing alone. We conducted combined laboratory visualization and numerical simulations studies of thermal-shock-induced fracture initiation and propagation resulting from liquid nitrogen injection in rock and analog materials. The experiment used transparent soda-lime glass cubes to facilitate real-time visualization of fracture growth and the fracture network geometry. In this contribution, we report the effect of overall temperature difference between cryogenic fluid and solid material on the produced fracture network, by pre-heating the glass cubes to several temperatures and injecting liquid nitrogen. Temperatures are monitored at several points by thermocouple and the fracture evolution is captured visually by camera. The experiment was modeled using a customized, thermoelastic, fracture-capable numerical simulation code based on peridynamics. The performance of the numerical code was validated by the results of the laboratory experiments, and then the code was used to study the different factors affecting a cryogenic fracturing operation, including the evolution of residual stresses and constitutive relationships for material failure. In complex rock such as shale, understanding the process of cryogenic

  2. PRODUCTIVITY OF FRACTURED HORIZONTAL WELLS

    Directory of Open Access Journals (Sweden)

    Stjepan Antolović

    2009-12-01

    Full Text Available The interest and performance of horizontal drilling and completions has increased during the last two decades. Horizontal wells are advantageous compared to vertical wells in thin reservoirs, reservoirs with favorable vertical permeability and reservoirs with water and gas coning problems. In many reservoirs, the ratio of horizontal permeability to the vertical permeability is substantially larger than one and often is close to 10. Thus, these reservoirs are very good candidates for hydraulic fracturing. By hydraulic fracturing one or more fractures are created, which can be longitudinal or orthogonal. By that, flow is altered and it mostly conducts horizontally through reservoir toward horizontal wellbore. With this altered flow, fluid is produced faster, with less pressure loss by fluid unit of produced fluid. Some of the existing mathematical models to determine the productivity of multifractured horizontal wells are presented in this work (the paper is published in Croatian.

  3. FRACOR-software toolbox for deterministic mapping of fracture corridors in oil fields on AutoCAD platform

    Science.gov (United States)

    Ozkaya, Sait I.

    2018-03-01

    Fracture corridors are interconnected large fractures in a narrow sub vertical tabular array, which usually traverse entire reservoir vertically and extended for several hundreds of meters laterally. Fracture corridors with their huge conductivities constitute an important element of many fractured reservoirs. Unlike small diffuse fractures, actual fracture corridors must be mapped deterministically for simulation or field development purposes. Fracture corridors can be identified and quantified definitely with borehole image logs and well testing. However, there are rarely sufficient image logs or well tests, and it is necessary to utilize various fracture corridor indicators with varying degrees of reliability. Integration of data from many different sources, in turn, requires a platform with powerful editing and layering capability. Available commercial reservoir characterization software packages, with layering and editing capabilities, can be cost intensive. CAD packages are far more affordable and may easily acquire the versatility and power of commercial software packages with addition of a small software toolbox. The objective of this communication is to present FRACOR, a software toolbox which enables deterministic 2D fracture corridor mapping and modeling on AutoCAD platform. The FRACOR toolbox is written in AutoLISPand contains several independent routines to import and integrate available fracture corridor data from an oil field, and export results as text files. The resulting fracture corridor maps consists mainly of fracture corridors with different confidence levels from combination of static and dynamic data and exclusion zones where no fracture corridor can exist. The exported text file of fracture corridors from FRACOR can be imported into an upscaling programs to generate fracture grid for dual porosity simulation or used for field development and well planning.

  4. A Rapid and Efficient Methodology to Convert Fractured Reservoir Images Into a Dual-Porosity Model Méthodologie rapide et efficace pour convertir les images de réservoir fracturé en modèle à double porosité

    Directory of Open Access Journals (Sweden)

    Bourbiaux B.

    2006-12-01

    Full Text Available Both characterization and dynamic simulation of naturally-fractured reservoirs have benefited from major advances in recent years. However, the reservoir engineer is still faced with the difficulty of parameterizing the dual-porosity model used to represent such reservoirs. In particular, the equivalent fracture permeabilities and the equivalent matrix block dimensions of such a model cannot be easily derived from observation of the complex images of natural fracture networks. This paper describes a novel and systematic methodology to compute these equivalent parameters. The results of its implementation with specially-designed software demonstrate its validity and efficiency in dealing with field situations. A tensor of equivalent fracture permeability is derived from single-phase steady-state flow computations on the actual fracture network using a 3D resistor network method and specific boundary conditions. The equivalent block dimensions in each layer are derived from the rapid identification of a geometrical function based on capillary imbibition. The methodology was validated against fine-grid reference simulations with a conventional reservoir simulator. Then, a complex outcrop image of a sandstone formation was processed for demonstration purposes. This innovative tool enables the reservoir engineer to build a dual-porosity model which best fits the hydraulic behavior of the actual fractured medium. La caractérisation et la simulation dynamique des réservoirs naturellement fracturés ont bénéficié d'avancées importantes ces dernières années. Toutefois, l'ingénieur réservoir reste confronté à la difficulté de paramétrer le modèle équivalent à double porosité utilisé pour représenter de tels réservoirs. En particulier, les perméabilités de fracture équivalentes et les dimensions du bloc matriciel équivalent ne peuvent pas être facilement déduites de l'observation des images complexes de réseaux naturels de

  5. Formation fracturing with foam

    Energy Technology Data Exchange (ETDEWEB)

    Blauer, R.E.; Kohlhaas, C.A.

    1974-01-01

    Over 60 wells have been treated with hydraulic fracturing techniques, with foam as the fracturing fluid. These foams contained as much as 95% gaseous phase; most treatments used foams with gas contents in the 65% to 85% range. Foam has several desirable properties for use as a fracturing fluid: high sand-carrying and sand-suspending capability, low fluid loss, low hydrostatic head, low pressure drops due to friction, quick fluid recovery, low formation damage, and no reduction of fracture conductivity due to fluid ingredients. Most applications of foam as a fracturing fluid have been in low permeability gas reservoirs. However, several oil reservoirs also have been successfully treated. Cost of the treatment is approx. the same or slightly less than a treatment with conventional fluids of comparable volume and rate. (25 refs.)

  6. Nose fracture

    Science.gov (United States)

    Fracture of the nose; Broken nose; Nasal fracture; Nasal bone fracture; Nasal septal fracture ... A fractured nose is the most common fracture of the face. It most ... occurs with other fractures of the face. Nose injuries and neck ...

  7. Are Geotehrmal Reservoirs Stressed Out?

    Science.gov (United States)

    Davatzes, N. C.; Laboso, R. C.; Layland-Bachmann, C. E.; Feigl, K. L.; Foxall, W.; Tabrez, A. R.; Mellors, R. J.; Templeton, D. C.; Akerley, J.

    2017-12-01

    Crustal permeability can be strongly influenced by developing connected networks of open fractures. However, the detailed evolution of a fracture network, its extent, and the persistence of fracture porosity are difficult to analyze. Even in fault-hosted geothermal systems, where heat is brought to the surface from depth along a fault, hydrothermal flow is heterogeneously distributed. This is presumably due to variations in fracture density, connectivity, and attitude, as well as variations in fracture permeability caused by sealing of fractures by precipitated cements or compaction. At the Brady Geothermal field in Nevada, we test the relationship between the modeled local stress state perturbed by dislocations representing fault slip or volume changes in the geothermal reservoir inferred from surface deformation measured by InSAR and the location of successful geothermal wells, hydrothermal activity, and seismicity. We postulate that permeability is favored in volumes that experience positive Coulomb stress changes and reduced compression, which together promote high densities of dilatant fractures. Conversely, permeability can be inhibited in locations where Coulomb stress is reduced, compression promotes compaction, or where the faults are poorly oriented in the stress field and consequently slip infrequently. Over geologic time scales spanning the development of the fault system, these local stress states are strongly influenced by the geometry of the fault network relative to the remote stress driving slip. At shorter time scales, changes in fluid pressure within the fracture network constituting the reservoir cause elastic dilations and contractions. We integrate: (1) direct observations of stress state and fractures in boreholes and the mapped geometry of the fault network; (2) evidence of permeability from surface hydrothermal features, production/injection wells and surface deformations related to pumping history; and (3) seismicity to test the

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

    Science.gov (United States)

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

    2016-10-13

    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'. © 2016 The Author(s).

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    2015-10-01

    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

  10. Production Decline Analysis for Two-Phase Flow in Multifractured Horizontal Well in Shale Gas Reservoirs

    OpenAIRE

    Xie, Wei-Yang; Li, Xiao-Ping; Zhang, Lie-Hui; Tan, Xiao-Hua; Wang, Jun-Chao; Wang, Hai-Tao

    2015-01-01

    After multistage fracturing, the flowback of fracturing fluid will cause two-phase flow through hydraulic fractures in shale gas reservoirs. With the consideration of two-phase flow and desorbed gas transient diffusion in shale gas reservoirs, a two-phase transient flow model of multistage fractured horizontal well in shale gas reservoirs was created. Accurate solution to this flow model is obtained by the use of source function theory, Laplace transform, three-dimensional eigenvalue method, ...

  11. Discrete fracture network modelling of Groß Schönebeck stimulation treatment

    Science.gov (United States)

    Urpi, L.; Zimmermann, G.; Blöcher, G.; van Wees, J. D. A. M.; Wassing, B.

    2012-04-01

    Microseismic events associated to geothermal reservoir are recorded before, during and after the establishment of an Enhanced Geothermal System (EGS). Differentiating recorded seismicity between natural and induced can be ambiguous, but reservoir response to stimulations treatment can be modelled and give useful insights in designing treatment. Our model reproduces the stimulation treatment done at Groß Schönebeck reservoir. The stimulation target was the volcanic layer of the Rotliegend formation at 4km depth. The treatment increased by a factor 22 the productivity index (volume of fluid produced per unit of time per drawdown) of the reservoir, while recorded seismicity was lower than expected (Bottom hole injection pressure was over the minimum stress, therefore we expect fracture opening due to both tensile and shearing opening. The interaction between a primary fracture initiating from the wellbore due to the injection and the secondary discrete fracture network (DFN) has been modelled with a hydraulic fracturing simulator. The DFN has been populated on the basis of available borehole data and lithological properties determined from rock sample analysis. Heat transfer has been computed since the temperature difference between injected fluid and reservoir rocks is over 100°C, inducing thermoelastic stresses around the the fractures. The model shows the importance of the natural fracture network, perturbing the reservoir state at distance in direction parallel to the minimum stress. Results are compared with commercial tensile and shear fracture models, which are compatible in term of predicting increased productivity of the well. We justify the absence of larger magnitude events after shut-in with the low natural seismicity and the high overpressure required to bring critically stressed faults to failure. We will calculate seismic rate, on a probabilistic approach basis, due to varying pore pressure and thermal stresses.

  12. On the application of artificial bee colony (ABC algorithm for optimization of well placements in fractured reservoirs; efficiency comparison with the particle swarm optimization (PSO methodology

    Directory of Open Access Journals (Sweden)

    Behzad Nozohour-leilabady

    2016-03-01

    Full Text Available The application of a recent optimization technique, the artificial bee colony (ABC, was investigated in the context of finding the optimal well locations. The ABC performance was compared with the corresponding results from the particle swarm optimization (PSO algorithm, under essentially similar conditions. Treatment of out-of-boundary solution vectors was accomplished via the Periodic boundary condition (PBC, which presumably accelerates convergence towards the global optimum. Stochastic searches were initiated from several random staring points, to minimize starting-point dependency in the established results. The optimizations were aimed at maximizing the Net Present Value (NPV objective function over the considered oilfield production durations. To deal with the issue of reservoir heterogeneity, random permeability was applied via normal/uniform distribution functions. In addition, the issue of increased number of optimization parameters was address, by considering scenarios with multiple injector and producer wells, and cases with deviated wells in a real reservoir model. The typical results prove ABC to excel PSO (in the cases studied after relatively short optimization cycles, indicating the great premise of ABC methodology to be used for well-optimization purposes.

  13. An Innovative Model to Estimate Fracture Extensions. | Adeniji ...

    African Journals Online (AJOL)

    Hydraulic fracturing is a Well intervention program, designed to create fracture(s) within a reservoir system and hopefully, extend the volumes of these fractures, to facilitate improved recovery of in-situ fluid(s). This paper presents mathematical equations in dimensionless forms, to rapidly estimate the fracture extension and ...

  14. Fracture-permeability development in organically-rich sediments through methane generation

    Science.gov (United States)

    Monroe, John Napier, Jr.

    The result of methane generation in low-permeability rock matrices is fracture-permeability development. Such expansion is the result of methane generation which, in turn, is the result of burial of organic matter under euxinic conditions. The fracture-permeability-development process has been demonstrated in the laboratory using a microwave oven to generate gas (water vapor) in well-indurated, low-permeability sedimentary rocks. The process has been quantified through modeling constrained by principles of chemistry and physics. The modeling process is applied to both shales and limestones and relates sediment expansion to sediment organic carbon content converted to methane. The model shows that the quantity of organic carbon required to be converted into methane for microfracture development is small compared to the amount commonly contained in hydrocarbon source rocks. A wide variety of fracture-producing mechanisms proposed to explain natural fracture development in hydrocarbon reservoirs is acknowledged. However, fracture permeability-development that appears to occur selectively in low-permeability, organically-rich sequences has received much less attention. Additionally, unabsolved anomalies that persist when current explanations are applied call attention to the need for alternative explanations. The fracture permeability, including the distribution and orientation of those fractures, which some reservoirs exhibit seem to defy explanation until now. A better understanding of fracture-permeability development and related aspects of petroleum maturation will remain illusive until the methane-generation fracture-permeability process, which until now has not been adequately quantified, is fully appreciated. Sediment expansion through methane generation in low-permeability rock matrices explains fracture-permeability development in many naturally-fractured hydrocarbon reservoirs including cleat permeability in coalbed methane reservoirs. Evidence is presented

  15. Application of zipper-fracturing of horizontal cluster wells in the Changning shale gas pilot zone, Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Bin Qian

    2015-03-01

    Full Text Available After several years of exploration practices in the Changning-Weiyuan national shale gas pilot zone, the industrial production has been achieved in a number of vertical and horizontal wells completed by SRV fracturing, and a series of independent shale gas reservoir stimulation technologies have come into being. Next, it is necessary to consider how to enhance the efficiency of fracturing by a factory-mode operation. This paper presents the deployment of Changning Well Pad A, the first cluster horizontal shale gas well group, and proposes the optimal design for the factory operation mode of this Pad according to the requirements of wellpad fracturing stimulation technologies and the mountainous landform in the Sichuan Basin. Accordingly, a zipper-fracturing mode was firstly adopted in the factory fracturing on wellpad. With the application of standardized field process, zipper operation, assembly line work, staggered placement of downhole fractures, and microseismic monitoring in real time, the speed of fracturing reached 3.16 stages a day on average, and the stimulated reservoir volume was maximized, which has fully revealed how the factory operation mode contributes to the large-scale SRV fracturing of horizontal shale gas cluster wells on wellpads in the aspect of speed and efficiency. Moreover, the fracturing process, operation mode, surface facilities and post-fracturing preliminary evaluation of the zipper-fracturing in the well group were examined comprehensively. It is concluded from the practice that the zipper-fracturing in the two wells enhanced the efficiency by 78% and stimulated reservoir volume by 50% compared with the single-well fracturing at the preliminary stage in this area.

  16. Multi-scale Fracture Patterns Associated with a Complex Anticline Structure: Insights from Field Outcrop Analogues of the Jebel Hafit Pericline, Al Ain-UAE

    Science.gov (United States)

    Kokkalas, S.; Jones, R. R.; Long, J. J.; Zampos, M.; Wilkinson, M. W.; Gilment, S.

    2017-12-01

    The formation of folds and their associated fracture patterns plays an important role in controlling the migration and concentration of fluids within the upper crust. Prediction of fracture patterns from various fold shapes and kinematics still remains poorly understood in terms of spatial and temporal distribution of fracture sets. Thus, a more detailed field-based multi scale approach is required to better constrain 3D models of fold-fracture relationships, which are critical for reservoir characterization studies. In order to generate reservoir-scale fracture models representative fracture properties across a wider range of scales are needed. For this reason we applied modern geospatial technologies, including terrestrial LiDAR, photogrammetry and satellite images in the asymmetric, east verging, four-way closure Jebel Hafit anticline, in the eastern part of the United Arab Emirates. The excellent surface outcrops allowed the rapid acquisition of extensive areas of fracture data from both limbs and fold hinge area of the anticline, even from large areas of steep exposure that are practically inaccessible on foot. The digital outcrops provide longer 1D transects, and 2D or 3D surface datasets and give more robust data, particularly for fracture heights, lengths, spacing, clustering, termination and connectivity. The fracture patterns across the folded structure are more complex than those predicted from conceptual models and geomechanical fracture modeling. Mechanical layering, pre-existing structures and sedimentation during fold growth seem to exert a critical influence in the development of fracture systems within Jebel Hafit anticline and directly affect fracture orientations, spacing/intensity, segmentation and connectivity. Seismic and borehole data provide additional constraints on the sub-surface fold geometry and existence of large-scale thrusting in the core of the anticline. The complexity of the relationship between fold geometry and fracture

  17. Reservoir and injection technology and Heat Extraction Project

    Energy Technology Data Exchange (ETDEWEB)

    Horne, R.N.; Ramey, H.H. Jr.; Miller, F.G.; Brigham, W.E.; Kruger, P.

    1989-12-31

    For the Stanford Geothermal Program in the fiscal year 1989, the task areas include predictive modeling of reservoir behavior and tracer test interpretation and testing. Major emphasis is in reservoir technology, reinjection technology, and heat extraction. Predictive modeling of reservoir behavior consists of a multi-pronged approach to well test analysis under a variety of conditions. The efforts have been directed to designing and analyzing well tests in (1) naturally fractured reservoirs; (2) fractured wells; (3) complex reservoir geometries; and, (4) gas reservoirs including inertial and other effects. The analytical solutions for naturally fractured reservoirs are determined using fracture size distribution. In the study of fractured wells, an elliptical coordinate system is used to obtain semi-analytical solutions to finite conductivity fractures. Effort has also been directed to the modeling and creation of a user friendly computer program for steam/gas reservoirs including wellbore storage, skin and non-Darcy flow effects. This work has a complementary effort on modeling high flow rate wells including inertial effects in the wellbore and fractures. In addition, work on gravity drainage systems is being continued.

  18. Fracture Mechanics

    International Nuclear Information System (INIS)

    Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

    1992-08-01

    This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

  19. Groundwater monitoring of hydraulic fracturing in California: Recommendations for permit-required monitoring

    Science.gov (United States)

    Esser, B. K.; Beller, H. R.; Carroll, S.; Cherry, J. A.; Jackson, R. B.; Jordan, P. D.; Madrid, V.; Morris, J.; Parker, B. L.; Stringfellow, W. T.; Varadharajan, C.; Vengosh, A.

    2015-12-01

    California recently passed legislation mandating dedicated groundwater quality monitoring for new well stimulation operations. The authors provided the State with expert advice on the design of such monitoring networks. Factors that must be considered in designing a new and unique groundwater monitoring program include: Program design: The design of a monitoring program is contingent on its purpose, which can range from detection of individual well leakage to demonstration of regional impact. The regulatory goals for permit-required monitoring conducted by operators on a well-by-well basis will differ from the scientific goals of a regional monitoring program conducted by the State. Vulnerability assessment: Identifying factors that increase the probability of transport of fluids from the hydrocarbon target zone to a protected groundwater zone enables the intensity of permit-required monitoring to be tiered by risk and also enables prioritization of regional monitoring of groundwater basins based on vulnerability. Risk factors include well integrity; proximity to existing wellbores and geologic features; wastewater disposal; vertical separation between the hydrocarbon and groundwater zones; and site-specific hydrogeology. Analyte choice: The choice of chemical analytes in a regulatory monitoring program is guided by the goals of detecting impact, assuring public safety, preventing resource degradation, and minimizing cost. Balancing these goals may be best served by tiered approach in which targeted analysis of specific chemical additives is triggered by significant changes in relevant but more easily analyzed constituents. Such an approach requires characterization of baseline conditions, especially in areas with long histories of oil and gas development. Monitoring technology: Monitoring a deep subsurface process or a long wellbore is more challenging than monitoring a surface industrial source. The requirement for monitoring multiple groundwater aquifers across

  20. Advanced fracture modeling in the Uinta Basin (Utah) for optimized primary and secondary recovery. Final report, September 1998

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-01

    The completed study focused on an area fracture-controlled highly unpredictable, fracture-controlled production near the Duchesne Fault Zone, Uinta Basin, in northeastern Utah. Production is seriously influenced by numerous high-angle faults and associated fractures--represented at the surface by a set of parallel, N80{degree}W-trending lineaments, and intricate fracture patterns in outcrop. Specific production is erratic and secondary recovery design is difficult because well-specific structural characterization and local fracture patterns are poorly understood. Furthermore, numerical models to simulate fluid flow in fractured reservoirs were either overly simplistic (did not adequately account for mechanical contrasts between matrix and fractures) or were extremely complex, requiring volumes of data typically not available to the operator. The contractors proposed implementing advanced geological, geomechanical and reservoir engineering methods to recognize and model the complex fracture networks exhibited at the surface and suggested in the shallow subsurface in the Duchesne Fault Zone. The intended methodology was to be developed in a data-limited environment, recognizing that operators in the basin will not have the financial resources or motivation to perform sophisticated and expensive reservoir engineering programs. User-friendly models for permeability, stress, and production using key geological and geophysical data, developed in this study can then be used to determine: economic placement of future operations, assessment of recoverable hydrocarbons, and forecasting of primary and secondary recovery.

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

    Directory of Open Access Journals (Sweden)

    O.V. Salimov

    2017-12-01

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

  2. A multi-scale experimental and simulation approach for fractured subsurface systems

    Science.gov (United States)

    Viswanathan, H. S.; Carey, J. W.; Frash, L.; Karra, S.; Hyman, J.; Kang, Q.; Rougier, E.; Srinivasan, G.

    2017-12-01

    Fractured systems play an important role in numerous subsurface applications including hydraulic fracturing, carbon sequestration, geothermal energy and underground nuclear test detection. Fractures that range in scale from microns to meters and their structure control the behavior of these systems which provide over 85% of our energy and 50% of US drinking water. Determining the key mechanisms in subsurface fractured 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 use microfluidic and triaxial core flood experiments required to reveal the fundamental dynamics of fracture-fluid interactions. In addition we have developed high fidelity fracture propagation and discrete fracture network flow models to simulate these fractured systems. We also have developed reduced order models of these fracture simulators in order to conduct uncertainty quantification for these systems. We demonstrate an integrated experimental/modeling approach that allows for a comprehensive characterization of fractured systems and develop models that can be used to optimize the reservoir operating conditions over a range of subsurface conditions.

  3. The role of reservoir characterization in the reservoir management process (as reflected in the Department of Energy`s reservoir management demonstration program)

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, M.L. [BDM-Petroleum Technologies, Bartlesville, OK (United States); Young, M.A.; Madden, M.P. [BDM-Oklahoma, Bartlesville, OK (United States)] [and others

    1997-08-01

    Optimum reservoir recovery and profitability result from guidance of reservoir practices provided by an effective reservoir management plan. Success in developing the best, most appropriate reservoir management plan requires knowledge and consideration of (1) the reservoir system including rocks, and rock-fluid interactions (i.e., a characterization of the reservoir) as well as wellbores and associated equipment and surface facilities; (2) the technologies available to describe, analyze, and exploit the reservoir; and (3) the business environment under which the plan will be developed and implemented. Reservoir characterization is the essential to gain needed knowledge of the reservoir for reservoir management plan building. Reservoir characterization efforts can be appropriately scaled by considering the reservoir management context under which the plan is being built. Reservoir management plans de-optimize with time as technology and the business environment change or as new reservoir information indicates the reservoir characterization models on which the current plan is based are inadequate. BDM-Oklahoma and the Department of Energy have implemented a program of reservoir management demonstrations to encourage operators with limited resources and experience to learn, implement, and disperse sound reservoir management techniques through cooperative research and development projects whose objectives are to develop reservoir management plans. In each of the three projects currently underway, careful attention to reservoir management context assures a reservoir characterization approach that is sufficient, but not in excess of what is necessary, to devise and implement an effective reservoir management plan.

  4. Improved efficiency of miscible CO{sub 2} floods and enhanced prospects for CO{sub 2} flooding heterogeneous reservoirs. Annual report, April 14, 1994--April 13, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Grigg, R.; Heller, J.; Schechter, D.

    1995-09-01

    The overall goal of this project is to improve the efficiency of miscible CO{sub 2} floods and enhance the prospects for flooding heterogeneous reservoirs. This objective is being accomplished by extending experimental research in three task areas: (1) foams for selective mobility control in heterogeneous reservoirs, (2) reduction of the amount of CO{sub 2} required in CO{sub 2} floods, and (3) miscible CO{sub 2} flooding in fractured reservoirs. This report provides results of the first year of the three-year project for each of the three task areas.

  5. Advances in photonic reservoir computing

    Science.gov (United States)

    Van der Sande, Guy; Brunner, Daniel; Soriano, Miguel C.

    2017-05-01

    We review a novel paradigm that has emerged in analogue neuromorphic optical computing. The goal is to implement a reservoir computer in optics, where information is encoded in the intensity and phase of the optical field. Reservoir computing is a bio-inspired approach especially suited for processing time-dependent information. The reservoir's complex and high-dimensional transient response to the input signal is capable of universal computation. The reservoir does not need to be trained, which makes it very well suited for optics. As such, much of the promise of photonic reservoirs lies in their minimal hardware requirements, a tremendous advantage over other hardware-intensive neural network models. We review the two main approaches to optical reservoir computing: networks implemented with multiple discrete optical nodes and the continuous system of a single nonlinear device coupled to delayed feedback.

  6. Ground-based hyperspectral imaging and terrestrial laser scanning for fracture characterization in the Mississippian Boone Formation

    Science.gov (United States)

    Sun, Lei; Khan, Shuhab D.; Sarmiento, Sergio; Lakshmikantha, M. R.; Zhou, Huawei

    2017-12-01

    Petroleum geoscientists have been using cores and well logs to study source rocks and reservoirs, however, the inherent discontinuous nature of these data cannot account for horizontal heterogeneities. Modern exploitation requires better understanding of important source rocks and reservoirs at outcrop scale. Remote sensing of outcrops is becoming a first order tool for reservoir analog studies including horizontal heterogeneities. This work used ground-based hyperspectral imaging, terrestrial laser scanning (TLS), and high-resolution photography to study a roadcut of the Boone Formation at Bella Vista, northwest Arkansas, and developed an outcrop model for reservoir analog analyses. The petroliferous Boone Formation consists of fossiliferous limestones interbedded with chert of early Mississippian age. We used remote sensing techniques to identify rock types and to collect 3D geometrical data. Mixture tuned matched filtering classification of hyperspectral data show that the outcrop is mostly limestones with interbedded chert nodules. 1315 fractures were classified according to their strata-bounding relationships, among these, larger fractures are dominantly striking in ENE - WSW directions. Fracture extraction data show that chert holds more fractures than limestones, and both vertical and horizontal heterogeneities exist in chert nodule distribution. Utilizing ground-based remote sensing, we have assembled a virtual outcrop model to extract mineral composition as well as fracture data from the model. We inferred anisotropy in vertical fracture permeability based on the dominancy of fracture orientations, the preferential distribution of fractures and distribution of chert nodules. These data are beneficial in reservoir analogs to study rock mechanics and fluid flow, and to improve well performances.

  7. Supracondylar Fracture

    Directory of Open Access Journals (Sweden)

    Jessica Andrusaitis

    2017-07-01

    posterior cortex and can be treated either surgically or with immobilization, and type III is completely displaced and requires orthopedic intervention and surgery.1,4 Due to the unstable nature of these type III fractures, rapid anatomic reduction is recommended followed by further orthopedic surgical stabilization.2 Orthopedic consultation should be obtained in the following scenarios: open fracture, neurovascular compromise, compartment syndrome, and a type II or III fracture.5

  8. Potosi Reservoir Modeling; History and Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Valerie; Leetaru, Hannes

    2014-09-30

    understand the extent of the Potosi. More specifically, the model could incorporate lateral changes or trends if deemed necessary to represent facies transition. - Currently there is no fracture gradient data available for the Potosi in the Decatur project area. The acquisition of the fracture pressure data could be considered to determine an appropriate maximum allowable bottomhole injection pressure. This would allow the evaluation of injectivity and the required number of wells in a more precise manner. - Special core analysis (SCAL) to determine the relative permeability and capillary pressure of the vugs and matrix could be considered to have a better estimation of the reservoir injectivity and plume extent. - Formation water sampling and analysis could be considered for the Potosi to estimate the water salinity and properties. A vertical flow performance evaluation could be considered for the succeeding task to determine the appropriate tubing size, the required injection tubing head pressure, and to investigate whether the corresponding well injection rate falls within the tubing erosional velocity limit. - A simulation using several injectors could also be considered to determine the required number of wells to achieve the injection target while taking into account the pressure interference.

  9. FRACTURING FLUID CHARACTERIZATION FACILITY

    Energy Technology Data Exchange (ETDEWEB)

    Subhash Shah

    2000-08-01

    Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids and slurries through hydraulically created fractures. During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled ''The High Pressure Simulator'' (HPS). The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of ''The Well Construction Technology Center'' (WCTC). This report documents the summary of the activities performed during 1992-2000 at the FFCF.

  10. Application of Reservoir Flow Simulation Integrated with Geomechanics in Unconventional Tight Play

    Science.gov (United States)

    Lin, Menglu; Chen, Shengnan; Mbia, Ernest; Chen, Zhangxing

    2018-01-01

    Multistage hydraulic fracturing techniques, combined with horizontal drilling, have enabled commercial production from the vast reserves of unconventional tight formations. During hydraulic fracturing, fracturing fluid and proppants are pumped into the reservoir matrix to create the hydraulic fractures. Understanding the propagation mechanism of hydraulic fractures is essential to estimate their properties, such as half-length. In addition, natural fractures are often present in tight formations, which might be activated during the fracturing process and contribute to the post-stimulation well production rates. In this study, reservoir simulation is integrated with rock geomechanics to predict the well post-stimulation productivities. Firstly, a reservoir geological model is built based on the field data collected from the Montney formation in the Western Canadian Sedimentary Basin. The hydraulic fracturing process is then simulated through an integrated approach of fracturing fluid injection, rock geomechanics, and tensile failure criteria. In such a process, the reservoir pore pressure increases with a continuous injection of the fracturing fluid and proppants, decreasing the effective stress exerted on the rock matrix accordingly as the overburden pressure remains constant. Once the effective stress drops to a threshold value, tensile failure of the reservoir rock occurs, creating hydraulic fractures in the formation. The early production history of the stimulated well is history-matched to validate the predicted fracture geometries (e.g., half-length) generated from the fracturing simulation process. The effects of the natural fracture properties and well bottom-hole pressures on well productivity are also studied. It has been found that nearly 40% of hydraulic fractures propagate in the beginning stage (the pad step) of the fracturing schedule. In addition, well post-stimulation productivity will increase significantly if the natural fractures are propped or

  11. Production Decline Analysis for Two-Phase Flow in Multifractured Horizontal Well in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Wei-Yang Xie

    2015-01-01

    Full Text Available After multistage fracturing, the flowback of fracturing fluid will cause two-phase flow through hydraulic fractures in shale gas reservoirs. With the consideration of two-phase flow and desorbed gas transient diffusion in shale gas reservoirs, a two-phase transient flow model of multistage fractured horizontal well in shale gas reservoirs was created. Accurate solution to this flow model is obtained by the use of source function theory, Laplace transform, three-dimensional eigenvalue method, and orthogonal transformation. According to the model’s solution, the bilogarithmic type curves of the two-phase model are illustrated, and the production decline performance under the effects of hydraulic fractures and shale gas reservoir properties are discussed. The result obtained in this paper has important significance to understand pressure response characteristics and production decline law of two-phase flow in shale gas reservoirs. Moreover, it provides the theoretical basis for exploiting this reservoir efficiently.

  12. Design and Implementation of Energized Fracture Treatment in Tight Gas Sands

    Energy Technology Data Exchange (ETDEWEB)

    Mukul Sharma; Kyle Friehauf

    2009-12-31

    Hydraulic fracturing is essential for producing gas and oil at an economic rate from low permeability sands. Most fracturing treatments use water and polymers with a gelling agent as a fracturing fluid. The water is held in the small pore spaces by capillary pressure and is not recovered when drawdown pressures are low. The un-recovered water leaves a water saturated zone around the fracture face that stops the flow of gas into the fracture. This is a particularly acute problem in low permeability formations where capillary pressures are high. Depletion (lower reservoir pressures) causes a limitation on the drawdown pressure that can be applied. A hydraulic fracturing process can be energized by the addition of a compressible, sometimes soluble, gas phase into the treatment fluid. When the well is produced, the energized fluid expands and gas comes out of solution. Energizing the fluid creates high gas saturation in the invaded zone, thereby facilitating gas flowback. A new compositional hydraulic fracturing model has been created (EFRAC). This is the first model to include changes in composition, temperature, and phase behavior of the fluid inside the fracture. An equation of state is used to evaluate the phase behavior of the fluid. These compositional effects are coupled with the fluid rheology, proppant transport, and mechanics of fracture growth to create a general model for fracture creation when energized fluids are used. In addition to the fracture propagation model, we have also introduced another new model for hydraulically fractured well productivity. This is the first and only model that takes into account both finite fracture conductivity and damage in the invaded zone in a simple analytical way. EFRAC was successfully used to simulate several fracture treatments in a gas field in South Texas. Based on production estimates, energized fluids may be required when drawdown pressures are smaller than the capillary forces in the formation. For this field

  13. Development of test practice requirements for a standard method on fracture toughness testing in the transition range

    International Nuclear Information System (INIS)

    McCabe, D.E.; Zerbst, U.; Heerens, J.

    1993-01-01

    This report covers the resolution of several issues that are relevant to the ductile to brittle transition range of structural steels. One of this issues was to compare a statistical-based weakest-link method to constraint data adjustment methods for modeling the specimen size effects on fracture toughness. Another was to explore the concept of a universal transition temperature curve shape (Master Curve). Data from a Materials Properties Council round robin activity were used to test the proposals empirically. The findings of this study are inclosed in an activity for the development of a draft standard test procedure ''Test Practice for Fracture Toughness in the Transition Range''. (orig.) [de

  14. Advances in photonic reservoir computing

    Directory of Open Access Journals (Sweden)

    Van der Sande Guy

    2017-05-01

    Full Text Available We review a novel paradigm that has emerged in analogue neuromorphic optical computing. The goal is to implement a reservoir computer in optics, where information is encoded in the intensity and phase of the optical field. Reservoir computing is a bio-inspired approach especially suited for processing time-dependent information. The reservoir’s complex and high-dimensional transient response to the input signal is capable of universal computation. The reservoir does not need to be trained, which makes it very well suited for optics. As such, much of the promise of photonic reservoirs lies in their minimal hardware requirements, a tremendous advantage over other hardware-intensive neural network models. We review the two main approaches to optical reservoir computing: networks implemented with multiple discrete optical nodes and the continuous system of a single nonlinear device coupled to delayed feedback.

  15. Modeling 3D Fracture Network in Carbonate NFR : Contribution from an Analogue Dataset, the Cante Perdrix Quarry, Calvisson, SE France

    NARCIS (Netherlands)

    Gauthier, B.D.M.; Bisdom, K.; Bertotti, G.

    2012-01-01

    The full 3D characterization of fracture networks is a key issue in naturally fractured reservoir modeling. Fracture geometry (e.g., orientation, size, spacing), fracture scale (e.g., bed-confined fractures, fracture corridors), lateral and vertical variations, need to be defined from limited,

  16. Role of Geomechanics in Assessing the Feasibility of CO2 Sequestration in Depleted Hydrocarbon Sandstone Reservoirs

    Science.gov (United States)

    Fang, Zhi; Khaksar, Abbas

    2013-05-01

    Carbon dioxide (CO2) sequestration in depleted sandstone hydrocarbon reservoirs could be complicated by a number of geomechanical problems associated with well drilling, completions, and CO2 injection. The initial production of hydrocarbons (gas or oil) and the resulting pressure depletion as well as associated reduction in horizontal stresses (e.g., fracture gradient) narrow the operational drilling mud weight window, which could exacerbate wellbore instabilities while infill drilling. Well completions (casing, liners, etc.) may experience solids flowback to the injector wells when injection is interrupted due to CO2 supply or during required system maintenance. CO2 injection alters the pressure and temperature in the near wellbore region, which could cause fault reactivation or thermal fracturing. In addition, the injection pressure may exceed the maximum sustainable storage pressure, and cause fracturing and fault reactivation within the reservoirs or bounding formations. A systematic approach has been developed for geomechanical assessments for CO2 storage in depleted reservoirs. The approach requires a robust field geomechanical model with its components derived from drilling and production data as well as from wireline logs of historical wells. This approach is described in detail in this paper together with a recent study on a depleted gas field in the North Sea considered for CO2 sequestration. The particular case study shows that there is a limitation on maximum allowable well inclinations, 45° if aligning with the maximum horizontal stress direction and 65° if aligning with the minimum horizontal stress direction, beyond which wellbore failure would become critical while drilling. Evaluation of sanding risks indicates no sand control installations would be needed for injector wells. Fracturing and faulting assessments confirm that the fracturing pressure of caprock is significantly higher than the planned CO2 injection and storage pressures for an ideal

  17. Geothermal Ultrasonic Fracture Imager

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, Doug [Baker-Hughes Oilfield Operation Inc., Houston, TX (United States); Leggett, Jim [Baker-Hughes Oilfield Operation Inc., Houston, TX (United States)

    2013-07-29

    The Geothermal Ultrasonic Fracture Imager project has a goal to develop a wireline ultrasonic imager that is capable of operating in temperatures up to 300°C (572°F) and depths up to 10 km (32,808 ft). This will address one of the critical needs in any EGS development of understanding the hydraulic flow paths in the reservoir. The ultrasonic imaging is well known in the oil and gas industry as one of the best methods for fracture evaluation; providing both high resolution and complete azimuthal coverage of the borehole. This enables fracture detection and characterization, both natural and induced, providing information as to their location, dip direction and dip magnitude. All of these factors are critical to fully understand the fracture system to enable the optimization of the thermal drainage through injectors and producers in a geothermal resource.

  18. Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism

    Science.gov (United States)

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design. PMID:25032240

  19. Hydraulic fracture extending into network in shale: reviewing influence factors and their mechanism.

    Science.gov (United States)

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design.

  20. Combined Percutaneous Iliosacral Screw Fixation With Sacroplasty Using Resorbable Calcium Phosphate Cement for Osteoporotic Pelvic Fractures Requiring Surgery.

    Science.gov (United States)

    Collinge, Cory A; Crist, Brett D

    2016-06-01

    Osteoporotic sacral fractures, including acute and chronic insufficiency fractures, are increasing in frequency and present a number of management problem. Many of these patients are treated nonoperatively with relative immobility (eg, bedrest, wheelchair, or weight-bearing restrictions) and analgesics, which likely make the osteoporotic component worse. Surgery in this patient population may be desirable in some cases with the goals of improving mobility, relieving pain, and healing in an aligned position while minimizing deformity progression. However, internal fixation of the osteoporotic pelvis can be difficult. Large unicortical lag screws are the workhorse of posterior pelvic fixation, and yet fixation in cancellous bone corridors of an osteoporotic sacrum seems unlikely to achieve optimal fixation. As a result, the operative management and clinical results of these difficult injuries may not be uniformly successful. The authors present a technique for treating osteoporotic patients with a sacral fracture when operative treatment is indicated using percutaneous screw fixation combined with screw augmentation using a resorbable calcium phosphate bone substitute or "cement." The guide wire for a 7.3-mm or other large cannulated lag screw is fully inserted along the desired bony sacral corridor as is standard. The lag screw is then inserted over the wire to the depth where cement is desired. The guide wire is removed, and the aqueous calcium phosphate is injected through the screw's cannulation. For acute fractures, cement was applied to the areas distant to the fracture; whereas in insufficiency fractures, the cement was inserted along most of the screw path. The guide wire then can be reinserted and the lag screw fully inserted. The rationale for using these 2 modalities is their synergistic effect: the cannulated screw provides typical screw fixation and also a conduit for cement application. The cement augments the lag screw's purchase in osteoporotic bone

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

    Directory of Open Access Journals (Sweden)

    Jianming He

    2017-05-01

    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.

  2. Analysis of structural heterogeneities on drilled cores: a reservoir modeling oriented methodology; Analyse des heterogeneites structurales sur carottes: une methodologie axee vers la modelisation des reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Cortes, P.; Petit, J.P. [Montpellier-2 Univ., Lab. de Geophysique, Tectonique et Sedimentologie, UMR CNRS 5573, 34 (France); Guy, L. [ELF Aquitaine Production, 64 - Pau (France); Thiry-Bastien, Ph. [Lyon-1 Univ., 69 (France)

    1999-07-01

    The characterization of structural heterogeneities of reservoirs is of prime importance for hydrocarbons recovery. A methodology is presented which allows to compare the dynamic behaviour of fractured reservoirs and the observation of microstructures on drilled cores or surface reservoir analogues. (J.S.)

  3. Reservoir Simulations of Low-Temperature Geothermal Reservoirs

    Science.gov (United States)

    Bedre, Madhur Ganesh

    The eastern United States generally has lower temperature gradients than the western United States. However, West Virginia, in particular, has higher temperature gradients compared to other eastern states. A recent study at Southern Methodist University by Blackwell et al. has shown the presence of a hot spot in the eastern part of West Virginia with temperatures reaching 150°C at a depth of between 4.5 and 5 km. This thesis work examines similar reservoirs at a depth of around 5 km resembling the geology of West Virginia, USA. The temperature gradients used are in accordance with the SMU study. In order to assess the effects of geothermal reservoir conditions on the lifetime of a low-temperature geothermal system, a sensitivity analysis study was performed on following seven natural and human-controlled parameters within a geothermal reservoir: reservoir temperature, injection fluid temperature, injection flow rate, porosity, rock thermal conductivity, water loss (%) and well spacing. This sensitivity analysis is completed by using ‘One factor at a time method (OFAT)’ and ‘Plackett-Burman design’ methods. The data used for this study was obtained by carrying out the reservoir simulations using TOUGH2 simulator. The second part of this work is to create a database of thermal potential and time-dependant reservoir conditions for low-temperature geothermal reservoirs by studying a number of possible scenarios. Variations in the parameters identified in sensitivity analysis study are used to expand the scope of database. Main results include the thermal potential of reservoir, pressure and temperature profile of the reservoir over its operational life (30 years for this study), the plant capacity and required pumping power. The results of this database will help the supply curves calculations for low-temperature geothermal reservoirs in the United States, which is the long term goal of the work being done by the geothermal research group under Dr. Anderson at

  4. Numerical research of two-phase flow in fractured-porous media based on discrete fracture fetwork model

    Science.gov (United States)

    Pyatkov, A. A.; Kosyakov, V. P.; Rodionov, S. P.; Botalov, A. Y.

    2018-03-01

    In this work was the study of the processes of isothermal and non-isothermal flow of high viscosity oil in a fractured-porous reservoir. The numerical experiment was done using our own reservoir simulator with the possibility of modeling of fluid motion in conditions of non-isothermal processes and long fractures in the formation.

  5. Numerical Modeling of Permeability Enhancement by Hydroshearing: the Case of Phase I Reservoir Creation at Fenton Hill

    Science.gov (United States)

    Rutqvist, J.; Rinaldi, A. P.

    2017-12-01

    The exploitation of a geothermal system is one of the most promising clean and almost inexhaustible forms of energy production. However, the exploitation of hot dry rock (HDR) reservoirs at depth requires circulation of a large amount of fluids. Indeed, the conceptual model of an Enhanced Geothermal System (EGS) requires that the circulation is enhanced by fluid injection. The pioneering experiments at Fenton Hill demonstrated the feasibility of EGS by producing the world's first HDR reservoirs. Such pioneering project demonstrated that the fluid circulation can be effectively enhanced by stimulating a preexisting fracture zone. The so-called "hydroshearing" involving shear activation of preexisting fractures is recognized as one of the main processes effectively enhancing permeability. The goal of this work is to quantify the effect of shear reactivation on permeability by proposing a model that accounts for fracture opening and shearing. We develop a case base on a pressure stimulation experiment at Fenton Hill, in which observation suggest that a fracture was jacked open by pressure increase. The proposed model can successfully reproduce such a behavior, and we compare the base case of pure elastic opening with the hydroshearing model to demonstrate that this latter could have occurred at the field, although no "felt" seismicity was observed. Then we investigate on the sensitivity of the proposed model by varying some of the critical parameters such as the maximum aperture, the dilation angle, as well as the fracture density.

  6. Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

    Science.gov (United States)

    Tary, J. B.; van der Baan, M.; Eaton, D. W.

    2014-02-01

    Hydraulic fracturing treatments are often monitored by strings of geophones deployed in boreholes. Instead of picking discrete events only, we here use time-frequency representations of continuous recordings to identify resonances in two case studies. This paper outlines an interpretational procedure to identify their cause using a subdivision into source, path, and receiver-side effects. For the first case study, two main resonances are observed both at depth by the downhole geophones and on the surface by two broadband arrays. The two acquisition networks have different receiver and path effects, yet recorded the same resonances; these resonances are therefore likely generated by source effects. The amplitude pattern at the surface arrays indicates that these resonances are probably due to pumping operations. In the second case study, selective resonances are detected by the downhole geophones. Resonances coming from receiver effects are either lower or higher frequency, and wave propagation modeling shows that path effects are not significant. We identify two possible causes within the source area, namely, eigenvibrations of fractures or non-Darcian flow within the hydraulic fractures. In the first situation, 15-30 m long fluid-filled cracks could generate the observed resonances. An interconnected fracture network would then be required, corresponding to mesoscale deformation of the reservoir. Alternatively, systematic patterns in non-Darcian fluid flow within the hydraulic fracture could also be their leading cause. Resonances can be used to gain a better understanding of reservoir deformations or dynamic fluid flow perturbations during fluid injection into hydrocarbon and geothermal reservoirs, CO2 sequestration, or volcanic eruptions.

  7. Required grades of hull steel plates in consideration of fracture toughness; Hakai jinsei wo koryoshita sentaiyo koban shiyo kubun ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, H.; Yamamoto, M.; Ogaki, Y. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1997-10-01

    This paper discusses the required grades of hull steel plates based on the steel ship rule of Nippon Kaiji Kyokai (NK). The minimum value of the allowable crack length in NK rule (critical safety crack length at 0degC just before brittle unstable crack causing fatal fracture) was estimated. In the case where the estimated crack tip exists in a matrix, the crack length was a minimum of 200-210mm, while nearly 60mm in a fusion line at high-heat-input welded joint. The allowable crack lengths estimated from a specified value in the NK rule were fairly different. The allowable crack length at 0degC was also estimated from the minimum value in V-notch Charpy impact test. The private proposal on the required grades of hull steel plates in consideration of fracture toughness was discussed. Thirty-five percent of crack lengths found in real ships is 100mm or less, however, cracks of 250-400mm long are frequently found suggesting the allowable crack length of 400mm. The required grade integrally considering required values and design conditions is demanded to secure the reliability of hull strength. 5 refs., 5 figs., 2 tabs.

  8. Modeling of 1D Anomalous Diffusion in Fractured Nanoporous Media

    Directory of Open Access Journals (Sweden)

    Albinali Ali

    2016-07-01

    Full Text Available Fractured nanoporous reservoirs include multi-scale and discontinuous fractures coupled with a complex nanoporous matrix. Such systems cannot be described by the conventional dual-porosity (or multi-porosity idealizations due to the presence of different flow mechanisms at multiple scales. More detailed modeling approaches, such as Discrete Fracture Network (DFN models, similarly suffer from the extensive data requirements dictated by the intricacy of the flow scales, which eventually deter the utility of these models. This paper discusses the utility and construction of 1D analytical and numerical anomalous diffusion models for heterogeneous, nanoporous media, which is commonly encountered in oil and gas production from tight, unconventional reservoirs with fractured horizontal wells. A fractional form of Darcy’s law, which incorporates the non-local and hereditary nature of flow, is coupled with the classical mass conservation equation to derive a fractional diffusion equation in space and time. Results show excellent agreement with established solutions under asymptotic conditions and are consistent with the physical intuitions.

  9. Iron Release and Precipitation in Fracture Fluid-Shale Fracturing Systems

    Science.gov (United States)

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

    2015-12-01

    Hydraulic fracturing of unconventional hydrocarbon reservoirs is important to the United States energy portfolio. Hydrocarbon production from new wells generally declines rapidly over the initial months of production. One possible reason for the decrease is the mineralization and clogging of microfracture networks proximal to propped fractures. One important but relatively unexplored class of reactions is oxidation of Fe(II) derived from Fe(II)-bearing mineral dissolution (primarily pyrite and siderite) and subsequent precipitation of Fe(III)-(oxy)hydroxides. To explore this topic, we reacted fracture fluid with sand-sized and whole rock chips from four different geological localities (Marcellus Fm., Barnett Fm., Eagle Ford Fm., and Green River Fm.) containing highly varied concentrations of clays, carbonates, and TOC. Additionally, kerogen was isolated from the Green River Fm. and reacted with fracture fluid. All the shale sands showed an initial release of Fe into solution during the first 96 hours of reaction followed by a plateau or significant drop in Fe indicating that mineral precipitation occurred. Conversely, the Fe concentrations in the kerogen reactors kept increasing throughout the 3-week experiments. The whole rock samples showed a steady increase then a plateau in Fe during the 3-weeks, indicating a slower Fe release and subsequently, slower Fe precipitation. Reactors with Marcellus Fm. Sands contained dilute HCl, water only, the fracture fluid with no headspace, and fracture fluid with no HCl. Results from these experiments show that HCl is the most important additive for the promotion of Fe release into solution. Iron oxidation is not promoted solely by O2 or organics but instead requires a combination of the two for precipitation in these systems. These results indicate that Fe redox cycling is an important and complex part of hydraulic fracturing that most likely results in production slowdown over the life of a well.

  10. Impact of Oxidative Dissolution on Black Shale Fracturing: Implication for Shale Fracturing Treatment Design

    Science.gov (United States)

    You, L.; Chen, Q.; Kang, Y.; Cheng, Q.; Sheng, J.

    2017-12-01

    Black shales contain a large amount of environment-sensitive compositions, e.g., clay minerals, carbonate, siderite, pyrite, and organic matter. There have been numerous studies on the black shales compositional and pore structure changes caused by oxic environments. However, most of the studies did not focus on their ability to facilitate shale fracturing. To test the redox-sensitive aspects of shale fracturing and its potentially favorable effects on hydraulic fracturing in shale gas reservoirs, the induced microfractures of Longmaxi black shales exposed to deionized water, hydrochloric acid, and hydrogen peroxide at room-temperature for 240 hours were imaged by scanning electron microscopy (SEM) and CT-scanning in this paper. Mineral composition, acoustic emission, swelling, and zeta potential of the untreated and oxidative treatment shale samples were also recorded to decipher the coupled physical and chemical effects of oxidizing environments on shale fracturing processes. Results show that pervasive microfractures (Fig.1) with apertures ranging from tens of nanometers to tens of microns formed in response to oxidative dissolution by hydrogen peroxide, whereas no new microfracture was observed after the exposure to deionized water and hydrochloric acid. The trajectory of these oxidation-induced microfractures was controlled by the distribution of phyllosilicate framework and flaky or stringy organic matter in shale. The experiments reported in this paper indicate that black shales present the least resistance to crack initiation and subcritical slow propagation in hydrogen peroxide, a process we refer to as oxidation-sensitive fracturing, which are closely related to the expansive stress of clay minerals, dissolution of redox-sensitive compositions, destruction of phyllosilicate framework, and the much lower zeta potential of hydrogen peroxide solution-shale system. It could mean that the injection of fracturing water with strong oxidizing aqueous solution may

  11. Implicit fracture modelling in FLAC3D: Assessing the behaviour of fractured shales, carbonates and other fractured rock types

    NARCIS (Netherlands)

    Osinga, S.; Pizzocolo, F.; Veer, E.F. van der; Heege, J.H. ter

    2016-01-01

    Fractured rocks play an important role in many types of petroleum and geo-energy operations. From fractured limestone reservoirs to unconventionals, understanding the geomechanical behaviour and the dynamically coupled (dual) permeability system is paramount for optimal development of these systems.

  12. Multiscale Hessian fracture filtering for the enhancement and segmentation of narrow fractures in 3D image data

    Science.gov (United States)

    Voorn, Maarten; Exner, Ulrike; Rath, Alexander

    2013-08-01

    Narrow fractures—or more generally narrow planar features—can be difficult to extract from 3D image datasets, and available methods are often unsuitable or inapplicable. A proper extraction is however in many cases required for visualisation or future processing steps. We use the example of 3D X-ray micro-Computed Tomography (µCT) data of narrow fractures through core samples from a dolomitic hydrocarbon reservoir (Hauptdolomit below the Vienna Basin, Austria). The extraction and eventual binary segmentation of the fractures in these datasets is required for porosity determination and permeability modelling. In this paper, we present the multiscale Hessian fracture filtering technique for extracting narrow fractures from a 3D image dataset. The second-order information in the Hessian matrix is used to distinguish planar features from the dataset. Different results are obtained for different scales of analysis in the calculation of the Hessian matrix. By combining these various scales of analysis, the final output is multiscale; i.e. narrow fractures of different apertures are detected. The presented technique is implemented and made available as macro code for the multiplatform public domain image processing software ImageJ. Serial processing of blocks of data ensures that full 3D processing of relatively large datasets (example dataset: 1670×1670×1546 voxels) is possible on a desktop computer. Here, several hours of processing time are required, but interaction is only required in the beginning. Various post-processing steps (calibration, connectivity filtering, and binarisation) can be applied, depending on the goals of research. The multiscale Hessian fracture filtering technique provides very good results for extracting the narrow fractures in our example dataset, despite several drawbacks inherent to the use of the Hessian matrix. Although we apply the technique on a specific example, the general implementation makes the filter suitable for different

  13. Improvement of tubulars used for fracturing in hot dry rock wells

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, R.W.; Dreesen, D.S.; Turner, W.C.

    1984-04-01

    Completion of hot dry rock wells as it is currently envisioned, requires that hydraulic fracturing be used to develop a heat extraction reservoir and to provide low impedance flow paths between the designated water injection and production wells. Recent fracturing operations at measured depths from 11,400 ft to 15,300 ft at the Fenton Hill Hot Dry Rock Geothermal Test Site have resulted in numerous failures of tubulars caused by the high fracturing pressures, corrosive environment and large treatment volumes at high flow rates. Two new fracturing strings were designed and purchased. Physical and chemical properties exceeding API specifications were demanded and supplied by the manufacturers. These tubulars have performed to design specifications.

  14. Intelligent fracture creation for shale gas development

    KAUST Repository

    Douglas, Craig C.

    2011-05-14

    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.

  15. Constant-pressure well test analysis of finite-conductivity hydraulically fractured gas wells influenced by non-Darcy flow effects

    Energy Technology Data Exchange (ETDEWEB)

    Nashawi, Ibrahim Sami [Department of Petroleum Engineering, College of Engineering and Petroleum, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait)

    2006-09-15

    Non-Darcy flow effects have long been recognized to have serious adverse impact on the performance of high flow rate gas wells. These effects may mask the presence of fractures around the wellbores of naturally fractured reservoirs and may render the effective fracture conductivity and fracture half-length of hydraulically fractured wells much less than the designed parameters. Even though the effects of non-Darcy flow have been identified in the field and properly acknowledged in the well testing literature, little has been done to improve the well test analysis results. This paper presents a new technique that accurately determines the fracture conductivity of hydraulically fractured gas wells producing at constant-bottomhole pressure and provides direct means to calculate the magnitude of turbulence in the fracture around the wellbore from a single well test. A semi-analytical equation that incorporates the effects of non-Darcy flow in the fracture is presented for the first time. A detailed investigation of the various parameters that influence the flow behavior of real gas in the fracture nearby the wellbore is also illustrated. Furthermore, a systematic method for calculating the fracture conductivity and non-Darcy flow coefficient from a single well test is outlined. The final working equations are presented in such a way that permits a straightforward, simple, yet accurate analysis of the variable flow rate with time. No type-curve matching, multirate tests or correlations are required. The methodology of the proposed technique is illustrated using several synthetic examples. (author)

  16. Improved efficiency of miscible CO2 floods and enhanced prospects for CO2 flooding heterogeneous reservoirs. Final report, April 17, 1991--May 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Grigg, R.B.; Schechter, D.S.

    1998-02-01

    From 1986 to 1996, oil recovery in the US by gas injection increased almost threefold, to 300,000 bbl/day. Carbon dioxide (CO{sub 2}) injection projects make up three-quarters of the 191,139 bbl/day production increase. This document reports experimental and modeling research in three areas that is increasing the number of reservoirs in which CO{sub 2} can profitably enhance oil recovery: (1) foams for selective mobility reduction (SMR) in heterogeneous reservoirs, (2) reduction of the amount of CO{sub 2} required in CO{sub 2} floods, and (3) low interfacial tension (97) processes and the possibility of CO{sub 2} flooding in naturally fractured reservoirs. CO{sub 2} injection under miscible conditions can effectively displace oil, but due to differences in density and viscosity the mobility of CO{sub 2} is higher than either oil or water. High CO{sub 2} mobility causes injection gas to finger through a reservoir, causing such problems as early gas breakthrough, high gas production rates, excessive injection gas recycling, and bypassing of much of the reservoir oil. These adverse effects are exacerbated by increased reservoir heterogeneity, reaching an extreme in naturally fractured reservoirs. Thus, many highly heterogeneous reservoirs have not been considered for CO{sub 2} injection or have had disappointing recoveries. One example is the heterogeneous Spraberry trend in west Texas, where only 10% of its ten billion barrels of original oil in place (OOIP) are recoverable by conventional methods. CO{sub 2} mobility can be reduced by injecting water (brine) alternated with CO{sub 2} (WAG) and then further reduced by adding foaming agents-surfactants. In Task 1, we studied a unique foam property, selective mobility reduction (SMR), that effectively reduces the effects of reservoir heterogeneity. Selective mobility reduction creates a more uniform displacement by decreasing CO{sub 2} mobility in higher permeability zones more than in lower permeability zones.

  17. Odontoid Fracture: Computed Tomography

    Directory of Open Access Journals (Sweden)

    Jonathan Peña

    2016-09-01

    Full Text Available History of present illness: An 84-year-old male presented with left-sided posterior head, neck, and back pain after a ground level fall. Exam was notable for left parietal scalp laceration and midline cervical spine tenderness with no obvious deformities. He was neurovascularly intact, and placed in an Aspen Collar with strict spine precautions. Significant findings: Computed Tomography (CT of the cervical spine showed a stable, acute, non-displaced fracture of the odontoid process extending into the body of C2, consistent with a Type III Odontoid Fracture. He was evaluated by orthopedic spine service who recommended conservative, non-operative management. Discussion: The cervical spine is composed of seven vertebrae, with C1 and C2 commonly referred to as the Atlas and Axis, respectively. Unique to C2 is a bony prominence, the Odontoid Process (Dens. Hyperextension or hyperflexion injuries can induce significant stress causing fractures. Odontoid fractures comprise approximately 10% of vertebral fractures, and there are three types with varying stability.1 Type 1 is the rarest and is a fracture involving the superior segment of the Dens. It is considered a stable fracture. Type 2 is the most common and is a fracture involving the base of the odontoid process, below the transverse component of the cruciform ligament. This fracture is unstable and requires operative stabilization. 2 Type 3 odontoid fractures are classified by a fracture of the Odontoid process, as well as the lateral masses of the C2. Determining the stability of a Type III Odontoid fracture requires radiographic evaluation. Strict cervical spine precautions must be adhered to until adequate imaging and surgical consultation is obtained. CT of the of cervical spine fractures poses several advantages to plain film radiography due to the ability to view the anatomy in three planes. 3 However, if there is concern for ligamentous injury, MRI is the preferred modality.3

  18. Dimensional threshold for fracture linkage and hooking

    Science.gov (United States)

    Lamarche, Juliette; Chabani, Arezki; Gauthier, Bertrand D. M.

    2018-03-01

    Fracture connectivity in rocks depends on spatial properties of the pattern including length, abundance and orientation. When fractures form a single-strike set, they hardly cross-cut each other and the connectivity is limited. Linkage probability increases with increasing fracture abundance and length as small fractures connect to each other to form longer ones. A process for parallel fracture linkage is the "hooking", where two converging fracture tips mutually deviate and then converge to connect due to the interaction of their crack-tip stresses. Quantifying the processes and conditions for fracture linkage in single-strike fracture sets is crucial to better predicting fluid flow in Naturally Fractured Reservoirs. For 1734 fractures in Permian shales of the Lodève Basin, SE France, we measured geometrical parameters in 2D, characterizing three stages of the hooking process: underlapping, overlapping and linkage. We deciphered the threshold values, shape ratios and limiting conditions to switch from one stage to another one. The hook set up depends on the spacing (S) and fracture length (Lh) with the relation S ≈ 0.15 Lh. Once the hooking is initiated, with the fracture deviation length (L) L ≈ 0.4 Lh, the fractures reaches the linkage stage only when the spacing is reduced to S ≈ 0.02 Lh and the convergence (C) is < 0.1 L. These conditions apply to multi-scale fractures with a shape ratio L/S = 10 and for fracture curvature of 10°-20°.

  19. Heat Extraction Project, geothermal reservoir engineering research at Stanford

    Energy Technology Data Exchange (ETDEWEB)

    Kruger, P.

    1989-01-01

    The main objective of the SGP Heat Extraction Project is to provide a means for estimating the thermal behavior of geothermal fluids produced from fractured hydrothermal resources. The methods are based on estimated thermal properties of the reservoir components, reservoir management planning of production and reinjection, and the mixing of reservoir fluids: geothermal, resource fluid cooled by drawdown and infiltrating groundwater, and reinjected recharge heated by sweep flow through the reservoir formation. Several reports and publications, listed in Appendix A, describe the development of the analytical methods which were part of five Engineer and PhD dissertations, and the results from many applications of the methods to achieve the project objectives. The Heat Extraction Project is to evaluate the thermal properties of fractured geothermal resource and forecasted effects of reinjection recharge into operating reservoirs.

  20. Reservoir characteristics and control factors of Carboniferous volcanic gas reservoirs in the Dixi area of Junggar Basin, China

    Directory of Open Access Journals (Sweden)

    Ji'an Shi

    2017-02-01

    Full Text Available Field outcrop observation, drilling core description, thin-section analysis, SEM analysis, and geochemistry, indicate that Dixi area of Carboniferous volcanic rock gas reservoir belongs to the volcanic rock oil reservoir of the authigenic gas reservoir. The source rocks make contact with volcanic rock reservoir directly or by fault, and having the characteristics of near source accumulation. The volcanic rock reservoir rocks mainly consist of acidic rhyolite and dacite, intermediate andesite, basic basalt and volcanic breccia: (1 Acidic rhyolite and dacite reservoirs are developed in the middle-lower part of the structure, have suffered strong denudation effect, and the secondary pores have formed in the weathering and tectonic burial stages, but primary pores are not developed within the early diagenesis stage. Average porosity is only at 8%, and the maximum porosity is at 13.5%, with oil and gas accumulation showing poor performance. (2 Intermediate andesite and basic basalt reservoirs are mainly distributed near the crater, which resembles the size of and suggests a volcanic eruption. Primary pores are formed in the early diagenetic stage, secondary pores developed in weathering and erosion transformation stage, and secondary fractures formed in the tectonic burial stage. The average porosity is at 9.2%, and the maximum porosity is at 21.9%: it is of the high-quality reservoir types in Dixi area. (3 The volcanic breccia reservoir has the same diagenetic features with sedimentary rocks, but also has the same mineral composition with volcanic rock; rigid components can keep the primary porosity without being affected by compaction during the burial process. At the same time, the brittleness of volcanic breccia reservoir makes it easily fracture under the stress; internal fracture was developmental. Volcanic breccia developed in the structural high part and suffered a long-term leaching effect. The original pore-fracture combination also made

  1. Data Compression of Hydrocarbon Reservoir Simulation Grids

    KAUST Repository

    Chavez, Gustavo Ivan

    2015-05-28

    A dense volumetric grid coming from an oil/gas reservoir simulation output is translated into a compact representation that supports desired features such as interactive visualization, geometric continuity, color mapping and quad representation. A set of four control curves per layer results from processing the grid data, and a complete set of these 3-dimensional surfaces represents the complete volume data and can map reservoir properties of interest to analysts. The processing results yield a representation of reservoir simulation results which has reduced data storage requirements and permits quick performance interaction between reservoir analysts and the simulation data. The degree of reservoir grid compression can be selected according to the quality required, by adjusting for different thresholds, such as approximation error and level of detail. The processions results are of potential benefit in applications such as interactive rendering, data compression, and in-situ visualization of large-scale oil/gas reservoir simulations.

  2. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Havmøller, Ole; Krogsbøll, Anette

    1997-01-01

    The main objectives of the project are to combine geological description of fractures, chalk types and rock mechanical properties, and to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. Five chalk types, representing two outcrop localities: Stevns...... and Hillerslev, and three reservoir zones: Tyra Maastrictian, Valhall Tor and Valhall Hod are investigated. Different test types are applied in small and large scale in order to investigate the influence on stiffness and strength from natural and induced fractures, stylolites, bedding planes and healed fractures...

  3. Percolation Theory and Modern Hydraulic Fracturing

    Science.gov (United States)

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

    2015-12-01

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

  4. Quantification of a maximum injection volume of CO2 to avert geomechanical perturbations using a compositional fluid flow reservoir simulator

    Science.gov (United States)

    Jung, Hojung; Singh, Gurpreet; Espinoza, D. Nicolas; Wheeler, Mary F.

    2018-02-01

    Subsurface CO2 injection and storage alters formation pressure. Changes of pore pressure may result in fault reactivation and hydraulic fracturing if the pressure exceeds the corresponding thresholds. Most simulation models predict such thresholds utilizing relatively homogeneous reservoir rock models and do not account for CO2 dissolution in the brine phase to calculate pore pressure evolution. This study presents an estimation of reservoir capacity in terms of allowable injection volume and rate utilizing the Frio CO2 injection site in the coast of the Gulf of Mexico as a case study. The work includes laboratory core testing, well-logging data analyses, and reservoir numerical simulation. We built a fine-scale reservoir model of the Frio pilot test in our in-house reservoir simulator IPARS (Integrated Parallel Accurate Reservoir Simulator). We first performed history matching of the pressure transient data of the Frio pilot test, and then used this history-matched reservoir model to investigate the effect of the CO2 dissolution into brine and predict the implications of larger CO2 injection volumes. Our simulation results -including CO2 dissolution- exhibited 33% lower pressure build-up relative to the simulation excluding dissolution. Capillary heterogeneity helps spread the CO2 plume and facilitate early breakthrough. Formation expansivity helps alleviate pore pressure build-up. Simulation results suggest that the injection schedule adopted during the actual pilot test very likely did not affect the mechanical integrity of the storage complex. Fault reactivation requires injection volumes of at least about sixty times larger than the actual injected volume at the same injection rate. Hydraulic fracturing necessitates much larger injection rates than the ones used in the Frio pilot test. Tested rock samples exhibit ductile deformation at in-situ effective stresses. Hence, we do not expect an increase of fault permeability in the Frio sand even in the presence of

  5. Shale Gas Geomechanics for Development and Performance of Unconventional Reservoirs

    Science.gov (United States)

    Domonik, Andrzej; Łukaszewski, Paweł; Wilczyński, Przemysław; Dziedzic, Artur; Łukasiak, Dominik; Bobrowska, Alicja

    2017-04-01

    Mechanical properties of individual shale formations are predominantly determined by their lithology, which reflects sedimentary facies distribution, and subsequent diagenetic and tectonic alterations. Shale rocks may exhibit complex elasto-viscoplastic deformation mechanisms depending on the rate of deformation and the amount of clay minerals, also bearing implications for subcritical crack growth and heterogeneous fracture network development. Thus, geomechanics for unconventional resources differs from conventional reservoirs due to inelastic matrix behavior, stress sensitivity, rock anisotropy and low matrix permeability. Effective horizontal drilling and hydraulic fracturing technologies are required to obtain and maintain high performance. Success of these techniques strongly depends on the geomechanical investigations of shales. An inelastic behavior of shales draws increasing attention of investigators [1], due to its role in stress relaxation between fracturing phases. A strong mechanical anisotropy in the vertical plane and a lower and more variable one in the horizontal plane are characteristic for shale rocks. The horizontal anisotropy plays an important role in determining the direction and effectiveness of propagation of technological hydraulic fractures. Non-standard rock mechanics laboratory experiments are being applied in order to obtain the mechanical properties of shales that have not been previously studied in Poland. Novel laboratory investigations were carried out to assess the creep parameters and to determine time-dependent viscoplastic deformation of shale samples, which can provide a limiting factor to tectonic stresses and control stress change caused by hydraulic fracturing. The study was supported by grant no.: 13-03-00-501-90-472946 "An integrated geomechanical investigation to enhance gas extraction from the Pomeranian shale formations", funded by the National Centre for Research and Development (NCBiR). References: Ch. Chang M. D

  6. Does hydraulic-fracturing theory work in jointed rock masses

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, H.D.; Keppler, H.; Dash, Z.V.

    1983-01-01

    The hypocenter locations of micro-earthquakes (acoustic emissions) generated during fracturing typically are distributed three-dimensionally suggesting that fracturing stimulates a volumetric region, rather than the planar fracture theoretically expected. The hypocenter maps generated at six operating, or potential, HDR reservoirs in the US, Europe and Japan are examined in detail and the fracture dimensions are correlated with fracture injection volumes and formation permeability. Depsite the volumetric appearance of the maps we infer that the induced fractures are mainly planar and may propagate aseismically. The induced seismicity stems from nearby joints, which are not opened significantly by fracturing, but are caused to shear-slip because of local pore pressure.

  7. Reservoir sizing using inert and chemically reacting tracers

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, B.A.; Tester, J.W.; Brown, L.F.

    1984-01-01

    Non-reactive tracer tests in prototype hot dry rock (HDR) geothermal reservoirs indicate multiple fracture flow paths that show increases in volume due to energy extraction. Tracer modal volumes correlate roughly with estimated reservoir heat-transfer capacity. Chemically reactive tracers are proposed which will map the rate of advance of the cooled region of an HDR reservoir, providing advanced warning of thermal drawdown. Critical parameters are examined using a simplified reservoir model for screening purposes. Hydrolysis reactions are a promising class of reactions for this purpose.

  8. Modeling reservoir geomechanics using discrete element method : Application to reservoir monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Alassi, Haitham Tayseer

    2008-09-15

    Understanding reservoir geomechanical behavior is becoming more and more important for the petroleum industry. Reservoir compaction, which may result in surface subsidence and fault reactivation, occurs during reservoir depletion. Stress changes and possible fracture development inside and outside a depleting reservoir can be monitored using time-lapse (so-called '4D') seismic and/or passive seismic, and this can give valuable information about the conditions of a given reservoir during production. In this study we will focus on using the (particle-based) Discrete Element Method (DEM) to model reservoir geomechanical behavior during depletion and fluid injection. We show in this study that DEM can be used in modeling reservoir geomechanical behavior by comparing results obtained from DEM to those obtained from analytical solutions. The match of the displacement field between DEM and the analytical solution is good, however there is mismatch of the stress field which is related to the way stress is measured in DEM. A good match is however obtained by measuring the stress field carefully. We also use DEM to model reservoir geomechanical behavior beyond the elasticity limit where fractures can develop and faults can reactivate. A general technique has been developed to relate DEM parameters to rock properties. This is necessary in order to use correct reservoir geomechanical properties during modeling. For any type of particle packing there is a limitation that the maximum ratio between P- and S-wave velocity Vp/Vs that can be modeled is 3 . The static behavior for a loose packing is different from the dynamic behavior. Empirical relations are needed for the static behavior based on numerical test observations. The dynamic behavior for both dense and loose packing can be given by analytical relations. Cosserat continuum theory is needed to derive relations for Vp and Vs. It is shown that by constraining the particle rotation, the S-wave velocity can be

  9. Pediatric pelvic fractures.

    Science.gov (United States)

    Holden, Candice P; Holman, Joel; Herman, Martin J

    2007-03-01

    Pediatric pelvic fractures account for only 1% to 2% of fractures seen by orthopaedic surgeons who treat children. They are typically associated with high-energy trauma, requiring a comprehensive workup for concomitant life-threatening injuries. Anteroposterior radiographs and rapid-sequence computed tomography are the standards of diagnostic testing to identify the fracture and recognize associated injuries. Treatment is individualized based on patient age, fracture classification, stability of the pelvic ring, extent of concomitant injuries, and hemodynamic stability of the patient. Most pelvic injuries in children are treated nonsurgically, with protected weight bearing and gradual return to activity. Open reduction and internal fixation is required for acetabular fractures with >2 mm of fracture displacement and for any intra-articular or triradiate cartilage fracture displacement >2 mm. To prevent limb-length discrepancies, external fixation is necessary for pelvic ring displacement >2 cm. Fractures involving immature triradiate cartilage may lead to growth disturbance of the acetabulum, resulting in acetabular dysplasia, hip subluxation, or hip joint incongruity. Osteonecrosis of the femoral head may develop after acetabular fractures associated with hip dislocation. Other complications include myositis ossificans and neurologic deficits secondary to sciatic, femoral, and/or lumbosacral plexus nerve injuries.

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

    Science.gov (United States)

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

    2016-08-01

    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. An environmental data base for all Hydro-Quebec reservoirs

    International Nuclear Information System (INIS)

    Demers, C.

    1988-01-01

    Hydro-Quebec has created two management positions specifically for reservoirs, namely Reservoir Ecology Advisor and Reservoir Management Advisor. To assist management decisions, a means was required of bringing together all existing environmental information for each reservoir operated by Hydro-Quebec, including storage reservoirs, auxiliary reservoirs and forebays. A relational database using Reflex software was developed on a network of Macintosh computers. The database contains five blocks of information: general information, and physical, physiochemical, biologic and socioeconomic characteristics for each reservoir. Data will be collected on over 100 sites, and the tool will form the basis for developing a medium-range study program on reservoir ecology. The program must take into account the physical, biological and socioeconomic aspects of the environment, as well as the concerns of management personnel operating the reservoirs, the local population, reservoir users, and various government departments. 2 figs

  12. Characterizing Fractures in Geysers Geothermal Field by Micro-seismic Data, Using Soft Computing, Fractals, and Shear Wave Anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Aminzadeh, Fred [Univ. of Southern California, Los Angeles, CA (United States); Sammis, Charles [Univ. of Southern California, Los Angeles, CA (United States); Sahimi, Mohammad [Univ. of Southern California, Los Angeles, CA (United States); Okaya, David [Univ. of Southern California, Los Angeles, CA (United States)

    2015-04-30

    The ultimate objective of the project was to develop new methodologies to characterize the northwestern part of The Geysers geothermal reservoir (Sonoma County, California). The goal is to gain a better knowledge of the reservoir porosity, permeability, fracture size, fracture spacing, reservoir discontinuities (leaky barriers) and impermeable boundaries.

  13. The Methane Hydrate Reservoir System

    Science.gov (United States)

    Flemings, P. B.; Liu, X.

    2007-12-01

    We use multi phase flow modeling and field examples (Hydrate Ridge, offshore Oregon and Blake Ridge, offshore North Carolina) to demonstrate that the methane hydrate reservoir system links traditional and non- traditional hydrocarbon system components: free gas flow is a fundamental control on this system. As in a traditional hydrocarbon reservoir, gas migrates into the hydrate reservoir as a separate phase (secondary migration) where it is trapped in a gas column beneath the base of the hydrate layer. With sufficient gas supply, buoyancy forces exceed either the capillary entry pressure of the cap rock or the fracture strength of the cap rock, and gas leaks into the hydrate stability zone, or cap rock. When gas enters the hydrate stability zone and forms hydrate, it becomes a very non traditional reservoir. Free gas forms hydrate, depletes water, and elevates salinity until pore water is too saline for further hydrate formation: salinity and hydrate concentration increase upwards from the base of the regional hydrate stability zone (RHSZ) to the seafloor and the base of the hydrate stability zone has significant topography. Gas chimneys couple the free gas zone to the seafloor through high salinity conduits that are maintained at the three-phase boundary by gas flow. As a result, significant amounts of gaseous methane can bypass the RHSZ, which implies a significantly smaller hydrate reservoir than previously envisioned. Hydrate within gas chimneys lie at the three-phase boundary and thus small increases in temperature or decreases in pressure can immediately transport methane into the ocean. This type of hydrate deposit may be the most economical for producing energy because it has very high methane concentrations (Sh > 70%) located near the seafloor, which lie on the three-phase boundary.

  14. Safety Characterization of the Technological Development Plant at Hontomín. Risk Structures: 1. Faults and Fractures

    International Nuclear Information System (INIS)

    Recreo, F.; Hurtado, A.; Eguilior, S.

    2015-01-01

    The safe storage of CO2 requires ensuring seal integrity during the time the CO2 will remain in a supercritical state before dissolving as an aqueous phase, CO2-aq. Geological structures such as faults and fractures that affect storage and seal formations can play an important role in the behaviour of the CO2 plume depending on whether the fracture acts as a barrier to the movement of CO2 or as a preferent conduit. As a consequence, a CO2 geological storage affected by faults or fractures represents a higher degree of uncertainty and its complexity will also be greater for the estimation of the dynamic properties of the flow of CO2 than a not fractured reservoir, increasing uncertainties in assessing both performance and safety In this report an analysis is made on the role that faults and fractures can play on the storage formation flow conditions and on the effects on the behaviour of injected CO2, considering different types of fractures in relation to the fracture inclination angle with the plume flow direction and the fracture conductivity, and presents a simplified model of fracture behaviour in a CO2 storage formation which could be mplemented in the safety assessment probabilistic model that CIUDEN is developing in the framework of the ALM/10/017 project. Finally, an application at the Hontomín site is tested based on the current available geological and geophysical information

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

    Science.gov (United States)

    Jenkins, Andrew

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

  16. Fractures of the distal phalanx in the horse

    International Nuclear Information System (INIS)

    Yovich, J.V.

    1989-01-01

    Fractures of the distal phalanx are an important cause of lameness referable to the foot. Depending on the fracture configuration and articular involvement, conservative or surgical treatment may be required. Fractures of the distal phalanx have been divided into six categories based on fracture configuration. Discussion of clinical features, management, and prognosis for horses with distal phalangeal fractures is presented for each fracture type

  17. Hip Fracture

    Science.gov (United States)

    ... hip fractures in people of all ages. In older adults, a hip fracture is most often a result of a fall from a standing height. In people with very weak bones, a hip fracture can occur simply by standing on the leg and twisting. Risk factors The rate of hip fractures increases substantially with ...

  18. Estimation of Bank Erosion Due To Reservoir Operation in Cascade (Case Study: Citarum Cascade Reservoir

    Directory of Open Access Journals (Sweden)

    Sri Legowo

    2009-11-01

    Full Text Available Sedimentation is such a crucial issue to be noted once the accumulated sediment begins to fill the reservoir dead storage, this will then influence the long-term reservoir operation. The sediment accumulated requires a serious attention for it may influence the storage capacity and other reservoir management of activities. The continuous inflow of sediment to the reservoir will decrease the capacity of reservoir storage, the reservoir value in use, and the useful age of reservoir. Because of that, the rate of the sediment needs to be delayed as possible. In this research, the delay of the sediment rate is considered based on the rate of flow of landslide of the reservoir slope. The rate of flow of the sliding slope can be minimized by way of each reservoir autonomous efforts. This effort can be performed through; the regulation of fluctuating rate of reservoir surface current that does not cause suddenly drawdown and upraising as well. The research model is compiled using the searching technique of Non Linear Programming (NLP.The rate of bank erosion for the reservoir variates from 0.0009 to 0.0048 MCM/year, which is no sigrificant value to threaten the life time of reservoir.Mean while the rate of watershed sediment has a significant value, i.e: 3,02 MCM/year for Saguling that causes to fullfill the storage capacity in 40 next years (from years 2008.

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

    Science.gov (United States)

    Suppachoknirun, Theerapat; Tutuncu, Azra N.

    2017-12-01

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

  20. Pressure Transient Analysis of Dual Fractal Reservoir

    Directory of Open Access Journals (Sweden)

    Xiao-Hua Tan

    2013-01-01

    Full Text Available A dual fractal reservoir transient flow model was created by embedding a fracture system simulated by a tree-shaped fractal network into a matrix system simulated by fractal porous media. The dimensionless bottom hole pressure model was created using the Laplace transform and Stehfest numerical inversion methods. According to the model's solution, the bilogarithmic type curves of the dual fractal reservoirs are illustrated, and the influence of different fractal factors on pressure transient responses is discussed. This semianalytical model provides a practical and reliable method for empirical applications.

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

    NARCIS (Netherlands)

    Meng, C.

    2010-01-01

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

  2. Integrated Experimental and Computational Study of Hydraulic Fracturing and the Use of Alternative Fracking Fluids

    Science.gov (United States)

    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.

    2014-12-01

    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.

  3. Multiscale ensemble filtering for reservoir engineering applications

    NARCIS (Netherlands)

    Lawniczak, W.; Hanea, R.G.; Heemink, A.; McLaughlin, D.

    2009-01-01

    Reservoir management requires periodic updates of the simulation models using the production data available over time. Traditionally, validation of reservoir models with production data is done using a history matching process. Uncertainties in the data, as well as in the model, lead to a nonunique

  4. On the feasibility of inducing oil mobilization in existing reservoirs via wellbore harmonic fluid action

    KAUST Repository

    Jeong, Chanseok

    2011-03-01

    Although vibration-based mobilization of oil remaining in mature reservoirs is a promising low-cost method of enhanced oil recovery (EOR), research on its applicability at the reservoir scale is still at an early stage. In this paper, we use simplified models to study the potential for oil mobilization in homogeneous and fractured reservoirs, when harmonically oscillating fluids are injected/produced within a well. To this end, we investigate first whether waves, induced by fluid pressure oscillations at the well site, and propagating radially and away from the source in a homogeneous reservoir, could lead to oil droplet mobilization in the reservoir pore-space. We discuss both the fluid pore-pressure wave and the matrix elastic wave cases, as potential agents for increasing oil mobility. We then discuss the more realistic case of a fractured reservoir, where we study the fluid pore-pressure wave motion, while taking into account the leakage effect on the fracture wall. Numerical results show that, in homogeneous reservoirs, the rock-stress wave is a better energy-delivery agent than the fluid pore-pressure wave. However, neither the rock-stress wave nor the pore-pressure wave is likely to result in any significant residual oil mobilization at the reservoir scale. On the other hand, enhanced oil production from the fractured reservoir\\'s matrix zone, induced by cross-flow vibrations, appears to be feasible. In the fractured reservoir, the fluid pore-pressure wave is only weakly attenuated through the fractures, and thus could induce fluid exchange between the rock formation and the fracture space. The vibration-induced cross-flow is likely to improve the imbibition of water into the matrix zone and the expulsion of oil from it. © 2011 Elsevier B.V.

  5. Laboratory Visualization Experiments of Temperature-induced Fractures Around a Borehole (Cryogenic Fracturing) in Shale and Analogue Rock Samples

    Science.gov (United States)

    Kneafsey, T. J.; Nakagawa, S.; Wu, Y. S.; Mukhopadhyay, S.

    2014-12-01

    In tight shales, hydraulic fracturing is the dominant method for improving reservoir permeability. However, injecting water-based liquids can induce formation damage and disposal problems, thus other techniques are being sought. One alternative to hydraulic fracturing is producing fractures thermally, using low-temperature fluids (cryogens). The primary consequence of thermal stimulation is that shrinkage fractures are produced around the borehole wall. Recently, cryogenic stimulation produced some promising results when the cryogen (typically liquid nitrogen and cold nitrogen gas) could be brought to reservoir depth. Numerical modeling also showed possible significant increases in gas production from a shale reservoir after cryogenic stimulation. However, geometry and the dynamic behavior of these thermally induced fractures under different stress regimes and rock anisotropy and heterogeneity is not yet well understood.Currently, we are conducting a series of laboratory thermal fracturing experiments on Mancos Shale and transparent glass blocks, by injecting liquid nitrogen under atmospheric pressure into room temperature blocks under various anisotropic stress states. The glass blocks allow clear optical visualization of fracture development and final fracturing patterns. For the shale blocks, X-ray CT is used to image both pre-existing and induced fractures. Also, the effect of borehole orientation with respect to the bedding planes and aligned preexisting fractures is examined. Our initial experiment on a uniaxially compressed glass block showed fracturing behavior which was distinctly different from conventional hydraulic fracturing. In addition to tensile fractures in the maximum principal stress directions, the thermal contraction by the cryogen induced (1) chaotic, spalling fractures around the borehole wall, and (2) a series of disk-shaped annular fractures perpendicular to the borehole. When applied to a horizontal borehole, the propagation plane of the

  6. Numerical Simulation of Fluid Flow through Fractal-Based Discrete Fractured Network

    Directory of Open Access Journals (Sweden)

    Wendong Wang

    2018-01-01

    Full Text Available Abstract: In recent years, multi-stage hydraulic fracturing technologies have greatly facilitated the development of unconventional oil and gas resources. However, a quantitative description of the “complexity” of the fracture network created by the hydraulic fracturing is confronted with many unsolved challenges. Given the multiple scales and heterogeneity of the fracture system, this study proposes a “bifurcated fractal” model to quantitatively describe the distribution of induced hydraulic fracture networks. The construction theory is employed to generate hierarchical fracture patterns as a scaled numerical model. With the implementation of discrete fractal-fracture network modeling (DFFN, fluid flow characteristics in bifurcated fractal fracture networks are characterized. The effects of bifurcated fracture length, bifurcated tendency, and number of bifurcation stages are examined. A field example of the fractured horizontal well is introduced to calibrate the accuracy of the flow model. The proposed model can provide a more realistic representation of complex fracture networks around a fractured horizontal well, and offer the way to quantify the “complexity” of the fracture network in shale reservoirs. The simulation results indicate that the geometry of the bifurcated fractal fracture network model has a significant impact on production performance in the tight reservoir, and enhancing connectivity of each bifurcate fracture is the key to improve the stimulation performance. In practice, this work provides a novel and efficient workflow for complex fracture characterization and production prediction in naturally-fractured reservoirs of multi-stage fractured horizontal wells.

  7. Heat Recovery from Multiple-Fracture Enhanced Geothermal Systems: The Effect of Thermoelastic Fracture Interactions

    DEFF Research Database (Denmark)

    Vik, Hedda Slatlem; Salimzadeh, Saeed; Nick, Hamid

    2018-01-01

    This study investigates the effect of thermoelastic interactions between multiple parallel fractures on energy production from a multiple-fracture enhanced geothermal system. A coupled thermo-hydro-mechanical finite element model has been developed that accounts for non-isothermal fluid flow within...... increased to maximise the net energy production from the system. Otherwise, the multiple-fracture system fails to improve the energy recovery from the geothermal reservoir, as initially intended....

  8. Chalk as a reservoir

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    intervals are to some extent cemented and cannot compact mechanically at realistic effective stresses and only deform elastically. All chalk intervals though, may react by fracturing to changes in shear stress. So where natural fractures are not prevalent, fractures may be generated hydraulically. Fractures...

  9. Advancing Reactive Tracer Methods for Measurement of Thermal Evolution in Geothermal Reservoirs: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell A. Plummer; Carl D. Palmer; Earl D. Mattson; Laurence C. Hull; George D. Redden

    2011-07-01

    The injection of cold fluids into engineered geothermal system (EGS) and conventional geothermal reservoirs may be done to help extract heat from the subsurface or to maintain pressures within the reservoir (e.g., Rose et al., 2001). As these injected fluids move along fractures, they acquire heat from the rock matrix and remove it from the reservoir as they are extracted to the surface. A consequence of such injection is the migration of a cold-fluid front through the reservoir (Figure 1) that could eventually reach the production well and result in the lowering of the temperature of the produced fluids (thermal breakthrough). Efficient operation of an EGS as well as conventional geothermal systems involving cold-fluid injection requires accurate and timely information about thermal depletion of the reservoir in response to operation. In particular, accurate predictions of the time to thermal breakthrough and subsequent rate of thermal drawdown are necessary for reservoir management, design of fracture stimulation and well drilling programs, and forecasting of economic return. A potential method for estimating migration of a cold front between an injection well and a production well is through application of reactive tracer tests, using chemical whose rate of degradation is dependent on the reservoir temperature between the two wells (e.g., Robinson 1985). With repeated tests, the rate of migration of the thermal front can be determined, and the time to thermal breakthrough calculated. While the basic theory behind the concept of thermal tracers has been understood for some time, effective application of the method has yet to be demonstrated. This report describes results of a study that used several methods to investigate application of reactive tracers to monitoring the thermal evolution of a geothermal reservoir. These methods included (1) mathematical investigation of the sensitivity of known and hypothetical reactive tracers, (2) laboratory testing of novel

  10. APPLICATION OF RESERVOIR CHARACTERIZATION AND ADVANCED TECHNOLOGY TO IMPROVE RECOVERY AND ECONOMICS IN A LOWER QUALITY SHALLOW SHELF SANANDRES RESERVOIR

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2003-01-15

    The Class 2 Project at West Welch was designed to demonstrate the use of advanced technologies to enhance the economics of improved oil recovery (IOR) projects in lower quality Shallow Shelf Carbonate (SSC) reservoirs, resulting in recovery of additional oil that would otherwise be left in the reservoir at project abandonment. Accurate reservoir description is critical to the effective evaluation and efficient design of IOR projects in the heterogeneous SSC reservoirs. Therefore, the majority of Budget Period 1 was devoted to reservoir characterization. Technologies being demonstrated include: (1) Advanced petrophysics; (2) Three-dimensional (3-D) seismic; (3) Crosswell bore tomography; (4) Advanced reservoir simulation; (5) Carbon dioxide (CO{sub 2}) stimulation treatments; (6) Hydraulic fracturing design and monitoring; (7) Mobility control agents.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J.; Huang, H.; Deo, M.

    2016-03-01

    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