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Sample records for fractured spraberry reservoir

  1. 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.

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

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    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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. PREFERRED WATERFLOOD MANAGEMENT PRACTICES FOR THE SPRABERRY TREND AREA

    Energy Technology Data Exchange (ETDEWEB)

    David S. Schechter

    2004-08-31

    The naturally fractured Spraberry Trend Area is one of the largest reservoirs in the domestic U.S. and is the largest reservoir in area extent in the world. Production from Spraberry sands is found over a 2,500 sq. mile area and Spraberry reservoirs can be found in an eight county area in west Texas. Over 150 operators produce 65,000 barrels of oil per day (bopd) from the Spraberry Trend Area from more than 9,000 production wells. Recovery is poor, on the order of 7-10% due to the profoundly complicated nature of the reservoir, yet billions of barrels of hydrocarbons remain. We estimate over 15% of remaining reserves in domestic Class III reservoirs are in Spraberry Trend Area reservoirs. This tremendous domestic asset is a prime example of an endangered hydrocarbon resource in need of immediate technological advancements before thousands of wells are permanently abandoned. This report describes the final work of the project, ''Preferred Waterflood Management Practices for the Spraberry Trend Area.'' The objective of this project is to significantly increase field-wide production in the Spraberry Trend in a short time frame through the application of preferred practices for managing and optimizing water injection. Our goal is to dispel negative attitudes and lack of confidence in water injection and to document the methodology and results for public dissemination to motivate waterflood expansion in the Spraberry Trend. This objective has been accomplished through research in three areas: (1) detail historical review and extensive reservoir characterization, (2) production data management, and (3) field demonstration. This provides results of the final year of the three-year project for each of the three areas.

  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. 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

  11. 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.

  12. RECENT ADVANCES IN NATURALLY FRACTURED RESERVOIR MODELING

    OpenAIRE

    ORDOÑEZ, A; PEÑUELA, G; IDROBO, E. A; MEDINA, C. E

    2001-01-01

    Large amounts of oil reserves are contained in naturally fractured reservoirs. Most of these hydrocarbon volumes have been left behind because of the poor knowledge and/or description methodology of those reservoirs. This lack of knowledge has lead to the nonexistence of good quantitative models for this complicated type of reservoirs. The complexity of naturally fractured reservoirs causes the need for integration of all existing information at all scales (drilling, well logging, seismic, we...

  13. 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.

  14. 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.

  15. on GAGD EOR in Naturally Fractured Reservoirs

    Directory of Open Access Journals (Sweden)

    Misagh Delalat

    2013-01-01

    Full Text Available The gas-assisted gravity drainage (GAGD process is designed and practiced based on gravity drainage idea and uses the advantage of density difference between injected CO2 and reservoir oil. In this work, one of Iran western oilfields was selected as a case study and a sector model was simulated based on its rock and fluid properties. The pressure of CO2 gas injection was close to the MMP of the oil, which was measured 1740 psia. Both homogeneous and heterogeneous types of fractures were simulated by creating maps of permeability and porosity. The results showed that homogeneous fractures had the highest value of efficiency, namely 40%; however, in heterogeneous fractures, the efficiency depended on the value of fracture density and the maximum efficiency was around 37%. Also, the effect of injection rate on two different intensities of fracture was studied and the results demonstrated that the model having higher fracture intensity had less limitation in increasing the CO2 injection rate; furthermore, its BHP did not increase intensively at higher injection rates either. In addition, three different types of water influxes were inspected on GAGD performance to simulate active, partial, and weak aquifer. The results showed that strong aquifer had a reverse effect on the influence of GAGD and almost completely disabled the gravity drainage mechanism. Finally, we inventively used a method to weaken the aquifer strength, and thus the gravity drainage revived and efficiency started to increase as if there was no aquifer.

  16. 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.

  17. Naturally fractured reservoirs-yet an unsolved mystery

    International Nuclear Information System (INIS)

    Zahoor, M.K.

    2013-01-01

    Some of the world's most profitable reservoirs are assumed to be naturally fractured reservoirs (NFR). Effective evaluation, prediction and planning of these reservoirs require an early recognition of the role of natural fractures and then a comprehensive study of factors which affect the flowing performance through these fractures is necessary. As NFRs are the combination of matrix and fractures mediums so their analysis varies from non-fractured reservoirs. Matrix acts as a storage medium while mostly fluid flow takes place from fracture network. Many authors adopted different approaches to understand the flow behavior in such reservoirs. In this paper a broad review about the previous work done in naturally fractured reservoirs area is outlined and a different idea is initiated for the NFR simulation studies. The role of capillary pressure in natural fractures is always been a key factor for accurate recovery estimations. Also recovery through these reservoirs is dependent upon grid block shape while doing NFR simulation. Some authors studied above mentioned factors in combination with other rock properties to understand the flow behavior in such reservoirs but less emphasis was given for checking the effects on recovery estimations by the variations of only fracture capillary pressures and grid block shapes. So there is need to analyze the behavior of NFR for the mentioned conditions. (author)

  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. 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.

  20. 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

  1. Characteristic fracture spacing in primary and secondary recovery for naturally fractured reservoirs

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2018-01-01

    If the aperture distribution is broad enough in a naturally fractured reservoir, even one where the fracture network is highly inter-connected, most fractures can be eliminated without significantly affecting the flow through the fracture network. During a waterflood or enhanced-oil-recovery

  2. 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 ...

  3. Optimization of fracture length in gas/condensate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, J.; Sharma, M.M.; Pope, G.A. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Texas Univ., Austin, TX (United States)

    2006-07-01

    A common practice that improves the productivity of gas-condensate reservoirs is hydraulic fracturing. Two important variables that determine the effectiveness of hydraulic fractures are fracture length and fracture conductivity. Although there are no simple guidelines for the optimization of fracture length and the factors that affect it, it is preferable to have an optimum fracture length for a given proppant volume in order to maximize productivity. An optimization study was presented in which fracture length was estimated at wells where productivity was maximized. An analytical expression that takes into account non-Darcy flow and condensate banking was derived. This paper also reviewed the hydraulic fracturing process and discussed previous simulation studies that investigated the effects of well spacing and fracture length on well productivity in low permeability gas reservoirs. The compositional simulation study and results and discussion were also presented. The analytical expression for optimum fracture length, analytical expression with condensate dropout, and equations for the optimum fracture length with non-Darcy flow in the fracture were included in an appendix. The Computer Modeling Group's GEM simulator, an equation-of-state compositional simulator, was used in this study. It was concluded that for cases with non-Darcy flow, the optimum fracture lengths are lower than those obtained with Darcy flow. 18 refs., 5 tabs., 22 figs., 1 appendix.

  4. 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

  5. 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

  6. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs; TOPICAL

    International Nuclear Information System (INIS)

    Seright, Randall S.; Liang, Jenn-Tai; Schrader, Richard; Hagstrom II, John; Wang, Ying; Kumar, Ananad; Wavrik, Kathryn

    2001-01-01

    This report describes work performed during the third and final year of the project, Using Chemicals to Optimize Conformance Control in Fractured Reservoirs. This research project had three objectives. The first objective was 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 was to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective was to develop procedures to optimize blocking agent placement in naturally fractured reservoirs

  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. 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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Naturally fractured tight gas reservoir detection optimization

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-04-30

    In March, work continued on characterizing probabilities for determining natural fracturing associated with the GGRB for the Upper Cretaceous tight gas plays. Structural complexity, based on potential field data and remote sensing data was completed. A resource estimate for the Frontier and Mesa Verde play was also completed. Further, work was also conducted to determine threshold economics for the play based on limited current production in the plays in the Wamsutter Ridge area. These analyses culminated in a presentation at FETC on 24 March 1999 where quantified natural fracture domains, mapped on a partition basis, which establish ''sweet spot'' probability for natural fracturing, were reviewed. That presentation is reproduced here as Appendix 1. The work plan for the quarter of January 1, 1999--March 31, 1999 comprised five tasks: (1) Evaluation of the GGRB partitions for structural complexity that can be associated with natural fractures, (2) Continued resource analysis of the balance of the partitions to determine areas with higher relative gas richness, (3) Gas field studies, (4) Threshold resource economics to determine which partitions would be the most prospective, and (5) Examination of the area around the Table Rock 4H well.

  14. 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

  15. 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.

  16. 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.

  17. Modeling of non-equilibrium effects in solvent-enhanced spontaneous imbibition in fractured reservoirs (poster)

    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.

  18. Tracer Testing for Estimating Heat Transfer Area in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, Karsten; van Heel, Ton; Shan, Chao

    2004-05-12

    A key parameter governing the performance and life-time of a Hot Fractured Rock (HFR) reservoir is the effective heat transfer area between the fracture network and the matrix rock. We report on numerical modeling studies into the feasibility of using tracer tests for estimating heat transfer area. More specifically, we discuss simulation results of a new HFR characterization method which uses surface-sorbing tracers for which the adsorbed tracer mass is proportional to the fracture surface area per unit volume. Sorption in the rock matrix is treated with the conventional formulation in which tracer adsorption is volume-based. A slug of solute tracer migrating along a fracture is subject to diffusion across the fracture walls into the adjacent rock matrix. Such diffusion removes some of the tracer from the fluid in the fractures, reducing and retarding the peak in the breakthrough curve (BTC) of the tracer. After the slug has passed the concentration gradient reverses, causing back-diffusion from the rock matrix into the fracture, and giving rise to a long tail in the BTC of the solute. These effects become stronger for larger fracture-matrix interface area, potentially providing a means for estimating this area. Previous field tests and modeling studies have demonstrated characteristic tailing in BTCs for volatile tracers in vapor-dominated reservoirs. Simulated BTCs for solute tracers in single-phase liquid systems show much weaker tails, as would be expected because diffusivities are much smaller in the aqueous than in the gas phase, by a factor of order 1000. A much stronger signal of fracture-matrix interaction can be obtained when sorbing tracers are used. We have performed simulation studies of surface-sorbing tracers by implementing a model in which the adsorbed tracer mass is assumed proportional to the fracture-matrix surface area per unit volume. The results show that sorbing tracers generate stronger tails in BTCs, corresponding to an effective

  19. 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.

  20. 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

  1. Comparison of pressure transient response in intensely and sparsely fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Johns, R.T.

    1989-04-01

    A comprehensive analytical model is presented to study the pressure transient behavior of a naturally fractured reservoir with a continuous matrix block size distribution. Geologically realistic probability density functions of matrix block size are used to represent reservoirs of varying fracture intensity and uniformity. Transient interporosity flow is assumed and interporosity skin is incorporated. Drawdown and interference pressure transient tests are investigated. The results show distinctions in the pressure response from intensely and sparsely fractured reservoirs in the absence of interporosity skin. Also, uniformly and nonuniformly fractured reservoirs exhibit distinct responses, irrespective of the degree of fracture intensity. The pressure response in a nonuniformly fractured reservoir with large block size variability, approaches a nonfractured (homogeneous) reservoir response. Type curves are developed to estimate matrix block size variability and the degree of fracture intensity from drawdown and interference well tests.

  2. Coupling a fluid flow simulation with a geomechanical model of a fractured reservoir

    OpenAIRE

    Segura Segarra, José María; Paz, C.M.; de Bayser, M.; Zhang, J.; Bryant, P.W.; Gonzalez, Nubia Aurora; Rodrigues, E.; Vargas, P.E.; Carol, Ignacio; Lakshmikantha, Ramasesha Mookanahallipatna; Das, K. C.; Sandha, S.S.; Cerqueira, R.; Mello,, U.

    2013-01-01

    Improving the reliability of integrated reservoir development planning and addressing subsidence, fault reactivation and other environmental impacts, requires increasingly sophisticated geomechanical models, especially in the case of fractured reservoirs where fracture deformation is strongly coupled with its permeability change. Reservoir simulation has historically treated any geomechanical effects by means of a rock compressibility term/table, which can be improved by simulating the actual...

  3. 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

  4. 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.

  5. 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.

  6. Modeling CO2 Storage in Fractured Reservoirs: Fracture-Matrix Interactions of Free-Phase and Dissolved CO2

    Science.gov (United States)

    Oldenburg, C. M.; Zhou, Q.; Birkholzer, J. T.

    2017-12-01

    The injection of supercritical CO2 (scCO2) in fractured reservoirs has been conducted at several storage sites. However, no site-specific dual-continuum modeling for fractured reservoirs has been reported and modeling studies have generally underestimated the fracture-matrix interactions. We developed a conceptual model for enhanced CO2 storage to take into account global scCO2 migration in the fracture continuum, local storage of scCO2 and dissolved CO2 (dsCO2) in the matrix continuum, and driving forces for scCO2 invasion and dsCO2 diffusion from fractures. High-resolution discrete fracture-matrix models were developed for a column of idealized matrix blocks bounded by vertical and horizontal fractures and for a km-scale fractured reservoir. The column-scale simulation results show that equilibrium storage efficiency strongly depends on matrix entry capillary pressure and matrix-matrix connectivity while the time scale to reach equilibrium is sensitive to fracture spacing and matrix flow properties. The reservoir-scale modeling results shows that the preferential migration of scCO2 through fractures is coupled with bulk storage in the rock matrix that in turn retards the fracture scCO2 plume. We also developed unified-form diffusive flux equations to account for dsCO2 storage in brine-filled matrix blocks and found solubility trapping is significant in fractured reservoirs with low-permeability matrix.

  7. Analysis of Flow Behavior for Acid Fracturing Wells in Fractured-Vuggy Carbonate Reservoirs

    Directory of Open Access Journals (Sweden)

    Mingxian Wang

    2018-01-01

    Full Text Available This study develops a mathematical model for transient flow analysis of acid fracturing wells in fractured-vuggy carbonate reservoirs. This model considers a composite system with the inner region containing finite number of artificial fractures and wormholes and the outer region showing a triple-porosity medium. Both analytical and numerical solutions are derived in this work, and the comparison between two solutions verifies the model accurately. Flow behavior is analyzed thoroughly by examining the standard log-log type curves. Flow in this composite system can be divided into six or eight main flow regimes comprehensively. Three or two characteristic V-shaped segments can be observed on pressure derivative curves. Each V-shaped segment corresponds to a specific flow regime. One or two of the V-shaped segments may be absent in particular cases. Effects of interregional diffusivity ratio and interregional conductivity ratio on transient responses are strong in the early-flow period. The shape and position of type curves are also influenced by interporosity coefficients, storativity ratios, and reservoir radius significantly. Finally, we show the differences between our model and the similar model with single fracture or without acid fracturing and further investigate the pseudo-skin factor caused by acid fracturing.

  8. 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

  9. 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.

  10. Hydromechanical and Thermomechanical Behaviour of Elastic Fractures during Thermal Stimulation of Naturally Fractured Reservoirs

    Science.gov (United States)

    Jalali, Mohammadreza; Valley, Benoît

    2015-04-01

    During the last two decades, incentives were put in place in order to feed our societies in energy with reduced CO2 emissions. Various policies have been considered to fulfill this strategy such as replacing coal by natural gas in power plants, producing electricity using CO2 free resources, and CO2 sequestration as a remediation for large point-source emitters (e.g. oil sands facilities, coal-fired power plants, and cement kilns). Naturally fractured reservoirs (NFRs) are among those geological structures which play a crucial role in the mentioned energy revolution. The behavior of fractured reservoirs during production processes is completely different than conventional reservoirs because of the dominant effects of fractures on fluid flux, with attendant issues of fracture fabric complexity and lithological heterogeneity. The level of complexity increases when thermal effects are taking place - as during the thermal stimulation of these stress-sensitive reservoirs in order to enhance the gas production in tight shales and/or increase the local conductivity of the fractures during the development of enhanced geothermal systems - where temperature is introduced as another degree of freedom in addition to pressure and displacement (or effective stress). Study of these stress-pressure-temperature effects requires a thermo-hydro-mechanical (THM) coupling approach, which considers the simultaneous variation of effective stress, pore pressure, and temperature and their interactions. In this study, thermal, hydraulic and mechanical behavior of partially open and elastic fractures in a homogeneous, isotropic and low permeable porous rock is studied. In order to compare the hydromechanical (HM) and thermomechanical (TM) characteristics of these fractures, three different injection scenarios, i.e. constant isothermal fluid injection rate, constant cooling without any fluid injection and constant cold fluid injection, are considered. Both thermomechanical and hydromechanical

  11. 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)

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. OPTIMIZATION OF INFILL DRILLING IN NATURALLY-FRACTURED TIGHT-GAS RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence W. Teufel; Her-Yuan Chen; Thomas W. Engler; Bruce Hart

    2004-05-01

    A major goal of industry and the U.S. Department of Energy (DOE) fossil energy program is to increase gas reserves in tight-gas reservoirs. Infill drilling and hydraulic fracture stimulation in these reservoirs are important reservoir management strategies to increase production and reserves. Phase II of this DOE/cooperative industry project focused on optimization of infill drilling and evaluation of hydraulic fracturing in naturally-fractured tight-gas reservoirs. The cooperative project involved multidisciplinary reservoir characterization and simulation studies to determine infill well potential in the Mesaverde and Dakota sandstone formations at selected areas in the San Juan Basin of northwestern New Mexico. This work used the methodology and approach developed in Phase I. Integrated reservoir description and hydraulic fracture treatment analyses were also conducted in the Pecos Slope Abo tight-gas reservoir in southeastern New Mexico and the Lewis Shale in the San Juan Basin. This study has demonstrated a methodology to (1) describe reservoir heterogeneities and natural fracture systems, (2) determine reservoir permeability and permeability anisotropy, (3) define the elliptical drainage area and recoverable gas for existing wells, (4) determine the optimal location and number of new in-fill wells to maximize economic recovery, (5) forecast the increase in total cumulative gas production from infill drilling, and (6) evaluate hydraulic fracture simulation treatments and their impact on well drainage area and infill well potential. Industry partners during the course of this five-year project included BP, Burlington Resources, ConocoPhillips, and Williams.

  1. Characterization of Fractured Reservoirs Using a Combination of Downhole Pressure and Self-Potential Transient Data

    OpenAIRE

    Yuji Nishi; Tsuneo Ishido

    2012-01-01

    In order to appraise the utility of self-potential (SP) measurements to characterize fractured reservoirs, we carried out continuous SP monitoring using multi Ag-AgCl electrodes installed within two open holes at the Kamaishi Mine, Japan. The observed ratio of SP change to pressure change associated with fluid flow showed different behaviors between intact host rock and fractured rock regions. Characteristic behavior peculiar to fractured reservoirs, which is predicted from numerical simulati...

  2. 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.

  3. 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

  4. 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.

  5. Structural-Diagenetic Controls on Fracture Opening in Tight Gas Sandstone Reservoirs, Alberta Foothills

    Science.gov (United States)

    Ukar, Estibalitz; Eichhubl, Peter; Fall, Andras; Hooker, John

    2013-04-01

    In tight gas reservoirs, understanding the characteristics, orientation and distribution of natural open fractures, and how these relate to the structural and stratigraphic setting are important for exploration and production. Outcrops provide the opportunity to sample fracture characteristics that would otherwise be unknown due to the limitations of sampling by cores and well logs. However, fractures in exhumed outcrops may not be representative of fractures in the reservoir because of differences in burial and exhumation history. Appropriate outcrop analogs of producing reservoirs with comparable geologic history, structural setting, fracture networks, and diagenetic attributes are desirable but rare. The Jurassic to Lower Cretaceous Nikanassin Formation from the Alberta Foothills produces gas at commercial rates where it contains a network of open fractures. Fractures from outcrops have the same diagenetic attributes as those observed in cores fractures relative to fold cores, hinges and limbs, 2) compare the distribution and attributes of fractures in outcrop vs. core samples, 3) estimate the timing of fracture formation relative to the evolution of the fold-and-thrust belt, and 4) estimate the degradation of fracture porosity due to postkinematic cementation. Cathodoluminescence images of cemented fractures in both outcrop and core samples reveal several generations of quartz and ankerite cement that is synkinematic and postkinematic relative to fracture opening. Crack-seal textures in synkinematic quartz are ubiquitous, and well-developed cement bridges abundant. Fracture porosity may be preserved in fractures wider than ~100 microns. 1-D scanlines in outcrop and core samples indicate fractures are most abundant within small parasitic folds within larger, tight, mesoscopic folds. Fracture intensity is lower away from parasitic folds; intensity progressively decreases from the faulted cores of mesoscopic folds to their forelimbs, with lowest intensities within

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Optimum development of a thin box-shaped reservoir with multiply fractured horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Lietard, O.; Hegeman, P.

    1998-12-31

    An improved definition of the productivity index of multiply fractured wells is proposed, based on the use of Dietz`s shape factors for vertical wells centered in independent box-shaped drainage areas of equal size in a reservoir. Pseudo-radial flow around each fracture is taken into account and pressure drops in the reservoir are accurately estimated. By using the corrected Gringarten mathematical approach, it is confirmed that orthogonal fractures provide much better productivity than a single collinear fracture even at constant material usage. Up to five-fold improvements have been registered when the number of fractures was equal to 1.8 times the reservoir shape ratio (length over width). For best results, the well should be cased and cemented, and hydraulic fractures should be propagated one by one through short perforation clusters. 18 refs., 10 figs., 1 appendix.

  11. 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

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

    Science.gov (United States)

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

    2017-04-01

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

  14. 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.

  15. 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.

  16. 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.

  17. Liquid petroleum gas fracturing fluids for unconventional gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, R.S.; Funkhouser, G.P.; Watkins, H.; Attaway, D. [Halliburton Energy Services, Calgary, AB (Canada); Lestz, R.S.; Wilson, L. [Chevron Canada Resources, Calgary, AB (Canada)

    2006-07-01

    This paper presented details of a gelled liquid petroleum gas (LPG) based fracturing fluid designed to address phase trapping concerns by replacing water with a mixture of LPG and a volatile hydrocarbon fluid. The system eliminates the need for water, which is a growing concern in terms of its availability. In the application process, up to 100 per cent gelled LPG is used for the pad and flush. Sand slurry stages are comprised of a mixture of up to 90 per cent LPG, with the balance of the volume being a volatile hydrocarbon base fluid. The fluid system is not adversely affected by shear, which ensures that acceptable fluid rheology is delivered. Viscosity can be adjusted during the treatment because the surfactant gellant and crosslinker are run in a 1:1 ratio and have good tolerance to concentration variations. The application ratio also allows for fast and accurate visual checks on amounts pumped during the treatment. A portion of the LPG in the fluid can be reproduced as a gas, while the remaining LPG is dissolved in the hydrocarbon fluid and is produced back as a miscible mixture through the use of a methane drive mechanism. Clean-up is facilitated by eliminating water and having LPG as up to 80-90 per cent of the total fluid system, even when wells have low permeability and reservoir pressure. However, LPG and optimized base oils are more expensive than other fluids. It was concluded that the higher costs of the system can be recovered through eliminating the need for swabbing, coiled tubing and nitrogen. Higher final stabilized productions rates may also offset initial costs. 7 refs., 2 tabs., 2 figs.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Investigation on the Productivity Behaviour in Deformable Heterogeneous Fractured Reservoirs

    DEFF Research Database (Denmark)

    Kadeethum, Teeratorn; Salimzadeh, Saeed; Nick, Hamid

    reasons for this reduction. Discrete fracture and matrix (DFM) modelling is selected in this investigation because of its ability to represent fracture behaviours more realistically. Moreover, it has become a preferential method for modelling flow in fractured formations for the past decade (Bisdom et al...

  3. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-01

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

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

    Science.gov (United States)

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

    2018-06-01

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

  6. 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.

  7. 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

  8. Oil recovery from naturally fractured reservoirs by steam injection methods. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Reis, J.C.; Miller, M.A.

    1995-05-01

    Oil recovery by steam injection is a proven, successful technology for nonfractured reservoirs, but has received only limited study for fractured reservoirs. Preliminary studies suggest recovery efficiencies in fractured reservoirs may be increased by as much as 50% with the application of steam relative to that of low temperature processes. The key mechanisms enhancing oil production at high temperature are the differential thermal expansion between oil and the pore volume, and the generation of gases within matrix blocks. Other mechanisms may also contribute to increased production. These mechanisms are relatively independent of oil gravity, making steam injection into naturally fractured reservoirs equally attractive to light and heavy oil deposits. The objectives of this research program are to quantify the amount of oil expelled by these recovery mechanisms and to develop a numerical model for predicting oil recovery in naturally fractured reservoirs during steam injection. The experimental study consists of constructing and operating several apparatuses to isolate each of these mechanisms. The first measures thermal expansion and capillary imbibition rates at relatively low temperature, but for various lithologies and matrix block shapes. The second apparatus measures the same parameters, but at high temperatures and for only one shape. A third experimental apparatus measures the maximum gas saturations that could build up within a matrix block. A fourth apparatus measures thermal conductivity and diffusivity of porous media. The numerical study consists of developing transfer functions for oil expulsion from matrix blocks to fractures at high temperatures and incorporating them, along with the energy equation, into a dual porosity thermal reservoir simulator. This simulator can be utilized to make predictions for steam injection processes in naturally-fractured reservoirs. Analytical models for capillary imbibition have also been developed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  10. 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.

  11. Evolution of stress and seismicity in fractured geothermal reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Schoenball, Martin

    2014-05-05

    Heat Mining, Soultz, forms the basis of the studies. The PhD project was conducted partly within the FP7 GEISER (Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs) project, funded by the European Commission and it benefited largely from fruitful collaborations with Universite de Strasbourg, Geowatt AG, Zuerich, GFZ German Research Centre for Geosciences, Potsdam and CSIRO Earth Science and Resources Engineering, Perth. In the first study, I analyze whether interaction of seismicity by static stress transfer plays a significant role on the spatio-temporal evolution of seismicity. I follow an analytical approach to compute the displacement field of a rectangular earthquake source. Through stacking of several sources, realistic slip distributions are obtained. The analysis reveals seemingly random distributed patches of stress increase and stress decrease of less than ± 1 MPa, except for very localized areas. Since the fracture planes have varying orientations, they form a volumetric fracture network. About 60% of hypocenters are found in areas with increased Coulomb stress where their potential for failure was increased by static stress transfer. A different behavior is observed for slippage of neighboring asperities on larger fault zones. Here, failure of asperities leads to a direct stress increase in adjacent asperities, which are then more likely to fail. This is exemplified on a cluster of events occurring on the largest fault zone in Soultz, after shut-in of the well GPK2. Subsequently, the peculiar behavior of seismicity and the hydraulic regime following shut-in of the well GPK2 is highlighted and investigated by further analysis of focal mechanism solutions. An increase of the thrust faulting component following shut-in is observed. The changes of the stress field are derived from spatio-temporally resolved inversions of focal mechanism solutions. A very strong reduction of the maximum horizontal stress and an increase of the

  12. U.S. Geological Survey input-data forms for the assessment of the Spraberry Formation of the Midland Basin, Permian Basin Province, Texas, 2017

    Science.gov (United States)

    Marra, Kristen R.

    2017-10-24

    In 2017, the U.S. Geological Survey (USGS) completed an updated assessment of undiscovered, technically recoverable oil and gas resources in the Spraberry Formation of the Midland Basin (Permian Basin Province) in southwestern Texas (Marra and others, 2017). The Spraberry Formation was assessed using both the standard continuous (unconventional) and conventional methodologies established by the USGS for three assessment units (AUs): (1) Lower Spraberry Continuous Oil Trend AU, (2) Middle Spraberry Continuous Oil Trend AU, and (3) Northern Spraberry Conventional Oil AU. The revised assessment resulted in total estimated mean resources of 4,245 million barrels of oil, 3,112 billion cubic feet of gas, and 311 million barrels of natural gas liquids. The purpose of this report is to provide supplemental documentation of the input parameters used in the USGS 2017 Spraberry Formation assessment.

  13. Numerical simulation of single-phase and multiphase non-Darcy flowin porous and fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Shu

    2000-06-02

    A numerical method as well as a theoretical study of non-Darcy fluid flow of through porous and fractured reservoirs is described. The non-Darcy flow is handled in a three-dimensional, multiphase flow reservoir simulator, while the model formulation incorporates the Forchheimer equation for describing single-phase or multiphase non-Darcy flow and displacement. The numerical scheme has been verified by comparing its results against those of analytical methods. Numerical solutions are used to obtain some insight into the physics of non-Darcy flow and displacement in reservoirs. In addition, several type curves are provided for well-test analyses of non-Darcy flow to demonstrate a methodology for modeling this type of flow in porous and fractured rocks, including flow in geothermal reservoirs.

  14. 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.

  15. Transport of Gas Phase Radionuclides in a Fractured, Low-Permeability Reservoir

    Science.gov (United States)

    Cooper, C. A.; Chapman, J.

    2001-12-01

    The U.S. Atomic Energy Commission (predecessor to the Department of Energy, DOE) oversaw a joint program between industry and government in the 1960s and 1970s to develop technology to enhance production from low-permeability gas reservoirs using nuclear stimulation rather than conventional means (e.g., hydraulic and/or acid fracturing). Project Rio Blanco, located in the Piceance Basin, Colorado, was the third experiment under the program. Three 30-kiloton nuclear explosives were placed in a 2134 m deep well at 1780, 1899, and 2039 m below the land surface and detonated in May 1973. Although the reservoir was extensively fractured, complications such as radionuclide contamination of the gas prevented production and subsequent development of the technology. Two-dimensional numerical simulations were conducted to identify the main transport processes that have occurred and are currently occurring in relation to the detonations, and to estimate the extent of contamination in the reservoir. Minor modifications were made to TOUGH2, the multiphase, multicomponent reservoir simulator developed at Lawrence Berkeley National Laboratories. The simulator allows the explicit incorporation of fractures, as well as heat transport, phase change, and first order radionuclide decay. For a fractured two-phase (liquid and gas) reservoir, the largest velocities are of gases through the fractures. In the gas phase, tritium and one isotope of krypton are the principle radionuclides of concern. However, in addition to existing as a fast pathway, fractures also permit matrix diffusion as a retardation mechanism. Another retardation mechanism is radionuclide decay. Simulations show that incorporation of fractures can significantly alter transport rates, and that radionuclides in the gas phase can preferentially migrate upward due to the downward gravity drainage of liquid water in the pores. This project was funded by the National Nuclear Security Administration, Nevada Operations Office

  16. 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.

  17. 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.

  18. 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.

  19. Integrated workflow for characterizing and modeling fracture network in unconventional reservoirs using microseismic data

    Science.gov (United States)

    Ayatollahy Tafti, Tayeb

    We develop a new method for integrating information and data from different sources. We also construct a comprehensive workflow for characterizing and modeling a fracture network in unconventional reservoirs, using microseismic data. The methodology is based on combination of several mathematical and artificial intelligent techniques, including geostatistics, fractal analysis, fuzzy logic, and neural networks. The study contributes to scholarly knowledge base on the characterization and modeling fractured reservoirs in several ways; including a versatile workflow with a novel objective functions. Some the characteristics of the methods are listed below: 1. The new method is an effective fracture characterization procedure estimates different fracture properties. Unlike the existing methods, the new approach is not dependent on the location of events. It is able to integrate all multi-scaled and diverse fracture information from different methodologies. 2. It offers an improved procedure to create compressional and shear velocity models as a preamble for delineating anomalies and map structures of interest and to correlate velocity anomalies with fracture swarms and other reservoir properties of interest. 3. It offers an effective way to obtain the fractal dimension of microseismic events and identify the pattern complexity, connectivity, and mechanism of the created fracture network. 4. It offers an innovative method for monitoring the fracture movement in different stages of stimulation that can be used to optimize the process. 5. Our newly developed MDFN approach allows to create a discrete fracture network model using only microseismic data with potential cost reduction. It also imposes fractal dimension as a constraint on other fracture modeling approaches, which increases the visual similarity between the modeled networks and the real network over the simulated volume.

  20. 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.

  1. Well test mathematical model for fractures network in tight oil reservoirs

    Science.gov (United States)

    Diwu, Pengxiang; Liu, Tongjing; Jiang, Baoyi; Wang, Rui; Yang, Peidie; Yang, Jiping; Wang, Zhaoming

    2018-02-01

    Well test, especially build-up test, has been applied widely in the development of tight oil reservoirs, since it is the only available low cost way to directly quantify flow ability and formation heterogeneity parameters. However, because of the fractures network near wellbore, generated from artificial fracturing linking up natural factures, traditional infinite and finite conductivity fracture models usually result in significantly deviation in field application. In this work, considering the random distribution of natural fractures, physical model of fractures network is proposed, and it shows a composite model feature in the large scale. Consequently, a nonhomogeneous composite mathematical model is established with threshold pressure gradient. To solve this model semi-analytically, we proposed a solution approach including Laplace transform and virtual argument Bessel function, and this method is verified by comparing with existing analytical solution. The matching data of typical type curves generated from semi-analytical solution indicates that the proposed physical and mathematical model can describe the type curves characteristic in typical tight oil reservoirs, which have up warping in late-term rather than parallel lines with slope 1/2 or 1/4. It means the composite model could be used into pressure interpretation of artificial fracturing wells in tight oil reservoir.

  2. 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

  3. 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.

  4. 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

  5. Oil recovery enhancement from fractured, low permeability reservoirs. [Carbonated Water

    Energy Technology Data Exchange (ETDEWEB)

    Poston, S.W.

    1991-01-01

    The results of the investigative efforts for this jointly funded DOE-State of Texas research project achieved during the 1990-1991 year may be summarized as follows: Geological Characterization - Detailed maps of the development and hierarchical nature the fracture system exhibited by Austin Chalk outcrops were prepared. The results of these efforts were directly applied to the development of production decline type curves applicable to a dual-fracture-matrix flow system. Analysis of production records obtained from Austin Chalk operators illustrated the utility of these type curves to determine relative fracture/matrix contributions and extent. Well-log response in Austin Chalk wells has been shown to be a reliable indicator of organic maturity. Shear-wave splitting concepts were used to estimate fracture orientations from Vertical Seismic Profile, VSP data. Several programs were written to facilitate analysis of the data. The results of these efforts indicated fractures could be detected with VSP seismic methods.Development of the EOR Imbibition Process - Laboratory displacement as well as Magnetic Resonance Imaging, MRI and Computed Tomography, CT imaging studies have shown the carbonated water-imbibition displacement process significantly accelerates and increases recovery from oil saturated, low permeability rocks.Field Tests - Two operators amenable to conducting a carbonated water flood test on an Austin Chalk well have been identified. Feasibility studies are presently underway.

  6. Oil Recovery Enhancement from Fractured, Low Permeability Reservoirs. [Carbonated Water

    Science.gov (United States)

    Poston, S. W.

    1991-01-01

    The results of the investigative efforts for this jointly funded DOE-State of Texas research project achieved during the 1990-1991 year may be summarized as follows: Geological Characterization - Detailed maps of the development and hierarchical nature the fracture system exhibited by Austin Chalk outcrops were prepared. The results of these efforts were directly applied to the development of production decline type curves applicable to a dual-fracture-matrix flow system. Analysis of production records obtained from Austin Chalk operators illustrated the utility of these type curves to determine relative fracture/matrix contributions and extent. Well-log response in Austin Chalk wells has been shown to be a reliable indicator of organic maturity. Shear-wave splitting concepts were used to estimate fracture orientations from Vertical Seismic Profile, VSP data. Several programs were written to facilitate analysis of the data. The results of these efforts indicated fractures could be detected with VSP seismic methods. Development of the EOR Imbibition Process - Laboratory displacement as well as Magnetic Resonance Imaging, MRI and Computed Tomography, CT imaging studies have shown the carbonated water-imbibition displacement process significantly accelerates and increases recovery from oil saturated, low permeability rocks. Field Tests - Two operators amenable to conducting a carbonated water flood test on an Austin Chalk well have been identified. Feasibility studies are presently underway.

  7. An element-based finite-volume method approach for naturally fractured compositional reservoir simulation

    Energy Technology Data Exchange (ETDEWEB)

    Marcondes, Francisco [Federal University of Ceara, Fortaleza (Brazil). Dept. of Metallurgical Engineering and Material Science], e-mail: marcondes@ufc.br; Varavei, Abdoljalil; Sepehrnoori, Kamy [The University of Texas at Austin (United States). Petroleum and Geosystems Engineering Dept.], e-mails: varavei@mail.utexas.edu, kamys@mail.utexas.edu

    2010-07-01

    An element-based finite-volume approach in conjunction with unstructured grids for naturally fractured compositional reservoir simulation is presented. In this approach, both the discrete fracture and the matrix mass balances are taken into account without any additional models to couple the matrix and discrete fractures. The mesh, for two dimensional domains, can be built of triangles, quadrilaterals, or a mix of these elements. However, due to the available mesh generator to handle both matrix and discrete fractures, only results using triangular elements will be presented. The discrete fractures are located along the edges of each element. To obtain the approximated matrix equation, each element is divided into three sub-elements and then the mass balance equations for each component are integrated along each interface of the sub-elements. The finite-volume conservation equations are assembled from the contribution of all the elements that share a vertex, creating a cell vertex approach. The discrete fracture equations are discretized only along the edges of each element and then summed up with the matrix equations in order to obtain a conservative equation for both matrix and discrete fractures. In order to mimic real field simulations, the capillary pressure is included in both matrix and discrete fracture media. In the implemented model, the saturation field in the matrix and discrete fractures can be different, but the potential of each phase in the matrix and discrete fracture interface needs to be the same. The results for several naturally fractured reservoirs are presented to demonstrate the applicability of the method. (author)

  8. Decoupling damage mechanisms in acid-fractured gas/condensate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Bachman, R.C.; Walters, D.A. [Taurus Reservoir Solutions Ltd., Calgary, AB (Canada); Settari, A. [Calgary Univ., AB (Canada); Rahim, Z.; Ahmed, M.S. [Saudi Aramco, Dhahran (Saudi Arabia)

    2006-07-01

    The Khuff is a gas condensate field located 11,500 feet beneath the producing Ghawar oil field in Saudi Arabia. Wells are mainly acid fracture stimulated following drilling with excellent fracture conductivity and length properties. The wells experience a quick production loss however, after tie-in which eventually stabilizes after two to five months. In order to identify the source of productivity loss, such as near well liquid dropout, fracture conductivity loss, reservoir permeability loss due to increased effective stress, a study of a well in the Khuff field was conducted. The study reviewed basic geomechanical and reservoir properties and identified the mechanisms of production loss. The paper presented the methodology, data and preliminary analysis, relative permeability and results of the history matching. It was concluded that traditional production type curves in cases with changing skin may indicate that transient flow is occurring when boundary effects are felt. In addition, stress dependent fracture conductivity and reservoir permeability can be modeled with simpler pressure dependent functions for relatively low overall loss in reservoir pressure. 30 refs., 25 figs., 1 appendix.

  9. 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

  10. 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.

  11. 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

  12. Simulation study of the VAPEX process in fractured heavy oil system at reservoir conditions

    Energy Technology Data Exchange (ETDEWEB)

    Azin, Reza; Ghotbi, Cyrus [Department of Chemical and Petroleum Engineering, Sharif Univ. Tech., Tehran (Iran); Kharrat, Riyaz; Rostami, Behzad [Petroleum University of Technology Research Center, Tehran (Iran); Vossoughi, Shapour [4132C Learned Hall, Department of Chemical and Petroleum Engineering, Kansas University, Lawrence, KS (United States)

    2008-01-15

    The Vapor Extraction (VAPEX) process, a newly developed Enhanced Oil Recovery (EOR) process to recover heavy oil and bitumen, has been studied theoretically and experimentally and is found a promising EOR method for certain heavy oil reservoirs. In this work, a simulation study of the VAPEX process was made on a fractured model, which consists of a matrix surrounded by horizontal and vertical fractures. The results show a very interesting difference in the pattern of solvent flow in fractured model compared with the conventional model. Also, in the fractured system, due to differences in matrix and fracture permeabilities, the solvent first spreads through the fractures and then starts diffusing into matrix from all parts of the matrix. Thus, the solvent surrounds the oil bank, and an oil rather than the solvent chamber forms and shrinks as the process proceeds. In addition, the recovery factor is higher at lower solvent injection rates for a constant pore volume of the solvent injected into the model. Also, the diffusion process becomes important and higher recoveries are obtained at low injection rates, provided sufficient time is given to the process. The effect of inter-connectivity of the surrounding fractures was studied by making the side vertical fractures shorter than the side length of the model. It was observed that inter-connectivity of the fractures affects the pattern of solvent distribution. Even for the case of side fractures being far apart from the bottom fracture, the solvent distribution in the matrix was significantly different than that in the model without fractures. Combination of diffusion phenomenon and gravity segregation was observed to be controlling factors in all VAPEX processes simulated in fractured systems. The early breakthrough of the solvent for the case of matrix surrounded by the fracture partially inhibited diffusion of the solvent into the oil and consequently the VAPEX process became the least effective. It is concluded

  13. Effect of boundary conditions on pressure behavior of finite-conductivity fractures in bounded stratified reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Osman, Mohammed E.; Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, Al-Ain (United Arab Emirates)

    1996-08-15

    In this study, a mathematical model was developed to model the pressure behavior of a well located in a bounded multilayer reservoir and crossed by a finite-conductivity vertical fracture. It was found that the dimensionless pressure function and its derivative strongly depend on fracture conductivity and fracture extension during early times. The effect of reservoir heterogeneity on the pressure function is negligible compared to that on the pressure derivative. Both functions exhibit four flow periods: bilinear, formation linear, pseudoradial and pseudosteady-state which are separated by transition periods. One or more of these flow periods may be missing. Data obtained from a long test and which are characterized by a unit slope line indicate that the well is intercepted by deeply extended fractures. It has been found that the fractional production rates of different layers are a good measure of reservoir and fracture characteristics. Flowmeter survey data can be used to eliminate the non-uniqueness problem when using the type curves presented in this study

  14. Assessment of CO2 Storage Potential in Naturally Fractured Reservoirs With Dual-Porosity Models

    Science.gov (United States)

    March, Rafael; Doster, Florian; Geiger, Sebastian

    2018-03-01

    Naturally Fractured Reservoirs (NFR's) have received little attention as potential CO2 storage sites. Two main facts deter from storage projects in fractured reservoirs: (1) CO2 tends to be nonwetting in target formations and capillary forces will keep CO2 in the fractures, which typically have low pore volume; and (2) the high conductivity of the fractures may lead to increased spatial spreading of the CO2 plume. Numerical simulations are a powerful tool to understand the physics behind brine-CO2 flow in NFR's. Dual-porosity models are typically used to simulate multiphase flow in fractured formations. However, existing dual-porosity models are based on crude approximations of the matrix-fracture fluid transfer processes and often fail to capture the dynamics of fluid exchange accurately. Therefore, more accurate transfer functions are needed in order to evaluate the CO2 transfer to the matrix. This work presents an assessment of CO2 storage potential in NFR's using dual-porosity models. We investigate the impact of a system of fractures on storage in a saline aquifer, by analyzing the time scales of brine drainage by CO2 in the matrix blocks and the maximum CO2 that can be stored in the rock matrix. A new model to estimate drainage time scales is developed and used in a transfer function for dual-porosity simulations. We then analyze how injection rates should be limited in order to avoid early spill of CO2 (lost control of the plume) on a conceptual anticline model. Numerical simulations on the anticline show that naturally fractured reservoirs may be used to store CO2.

  15. 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.

  16. Fracture-related fluid flow in sandstone reservoirs - Insights from outcrop analogues of South-eastern Utah

    NARCIS (Netherlands)

    Ogata, K.; Senger, K.; Braathen, A.; Tveranger, J.; Petrie, E.; Evans, J.P.

    2012-01-01

    Fault- And fold-related fractures influence the fluid circulation in the subsurface, thus being of high importance for CO2 storage site assessment, especially in terms of reservoir connectivity and leakage. In this context, discrete regions of concentrated sub-parallel fracturing known as fracture

  17. 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,

  18. 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.

  19. 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 R.; Hermanson, Jan

    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.

  20. Characterization of Fractured Reservoirs Using a Combination of Downhole Pressure and Self-Potential Transient Data

    Directory of Open Access Journals (Sweden)

    Yuji Nishi

    2012-01-01

    Full Text Available In order to appraise the utility of self-potential (SP measurements to characterize fractured reservoirs, we carried out continuous SP monitoring using multi Ag-AgCl electrodes installed within two open holes at the Kamaishi Mine, Japan. The observed ratio of SP change to pressure change associated with fluid flow showed different behaviors between intact host rock and fractured rock regions. Characteristic behavior peculiar to fractured reservoirs, which is predicted from numerical simulations of electrokinetic phenomena in MINC (multiple interacting continua double-porosity media, was observed near the fractures. Semilog plots of the ratio of SP change to pressure change observed in one of the two wells show obvious transition from intermediate time increasing to late time stable trends, which indicate that the time required for pressure equilibration between the fracture and matrix regions is about 800 seconds. Fracture spacing was estimated to be a few meters assuming several micro-darcies (10-18 m2 of the matrix region permeability, which is consistent with geological and hydrological observations.

  1. 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)

  2. 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.

  3. 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

  4. 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

  5. Oil-water flows in wells with powerful fracture reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, N.P.

    1979-01-01

    The character of two phase liquid flows from powerful layer fractures to bottom holes in Starogrodnen and Malgobek-Voznesenskiy fields in the Chechen-Ingush ASSR found in the late stage of operation. The studies were done with the electrothermometer TEG-36, the manometer MGN-2, the remote control thermal flow meter T-4, the remote control moisture meter VBST-1, the density meter GGP-1M, whose accuracy class is 1.0 and whose working limits are: temperature, up to 150/sup 0/C and pressure, up to 1000 kGs/cm/sup 2/. The breakdown of the linear filtration law and the gravitational division of the water-oil mixture phase occurred during fieldwork. The oil and water, etc., flow intervals were defined. The data from the moisture meter and the gamma density meter coincided.

  6. Effect of Discrete Fracture Network Characteristics on the Sustainability of Heat Production in Enhanced Geothermal Reservoirs

    Science.gov (United States)

    Riahi, A.; Damjanac, B.

    2013-12-01

    Viability of an enhanced or engineered geothermal reservoir is determined by the rate of produced fluid at production wells and the rate of temperature drawdown in the reservoir as well as that of the produced fluid. Meeting required targets demands sufficient permeability and flow circulation in a relatively large volume of rock mass. In-situ conditions such overall permeability of the bedrock formation, magnitude and orientation of stresses, and the characteristics of the existing Discrete Fracture Network (DFN) greatly affect sustainable heat production. Because much of the EGS resources are in formations with low permeability, different stimulation techniques are required prior to the production phase to enhance fluid circulation. Shear stimulation or hydro-shearing is the method of injecting a fluid into the reservoir with the aim of increasing the fluid pressure in the naturally fractured rock and inducing shear failure or slip events. This mechanism can enhance the system's permeability through permanent dilatational opening of the sheared fractures. Using a computational modeling approach, the correlation between heat production and DFN statistical characteristics, namely the fracture length distribution, fracture orientation, and also fracture density is studied in this paper. Numerical analyses were completed using two-dimensional distinct element code UDEC (Itasca, 2011), which represents rock masses as an assembly of interacting blocks separated by fractures. UDEC allows for simulation of fracture propagation along the predefined planes only (i.e., the trajectory of the hydraulic fracture is not part of the solution of the problem). Thus, the hydraulic fracture is assumed to be planar, aligned with the direction of the major principal stress. The pre-existing fractures were represented explicitly. They are discontinuities which deform elastically, but also can open and slip (Coulomb slip law) as a function of pressure and total stress changes. The fluid

  7. 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.

  8. PP and PS seismic response from fractured tight gas reservoirs: a case study

    International Nuclear Information System (INIS)

    Jianming, Tang; Shaonan, Zhang; Li, Xiang-Yang

    2008-01-01

    In this paper, we present an example of using PP and PS converted-wave data recorded by digital micro-eletro-mechanical-systems (MEMS) to evaluate a fractured tight gas reservoir from the Xinchang gas field in Sichuan, China. For this, we analyse the variations in converted shear-wave splitting, Vp/Vs ratio and PP and PS impedance, as well as other attributes based on absorption and velocity dispersion. The reservoir formation is tight sandstone, buried at a depth of about 5000 m, and the converted-wave data reveal significant shear-wave splitting over the reservoir formation. We utilize a rotation technique to extract the shear-wave polarization and time delay from the data, and a small-window correlation method to build time-delay spectra that allow the generation of a time-delay section. At the reservoir formation, the shear-wave time delay is measured at 20 ms, about 15% shear-wave anisotropy, correlating with the known gas reservoirs. Furthermore, the splitting anomalies are consistent with the characteristics of other attributes such as Vp/Vs ratio and P- and S-wave acoustic and elastic impedance. The P-wave shows consistent low impedance over the reservoir formation, whilst the S-wave impedance shows relatively high impedance. The calculated gas indicator based on absorption and velocity dispersion yields a high correlation with the gas bearing formations. This confirms the benefit of multicomponent seismic data from digital MEMS sensors

  9. 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

  10. 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

  11. Fracture characterization and discrimination criteria for karst and tectonic fractures in the Ellenburger Group, West Texas: Implications for reservoir and exploration models

    Energy Technology Data Exchange (ETDEWEB)

    Hoak, T.E. [Science Applications International Corp., Germantown, MD (United States)]|[Kestrel Geoscience, Littleton, CO (United States); Sundberg, K.R. [Phillips Petroleum Co., Bartlesville, OK (United States); Deyhim, P. [Oklahoma State Univ., Stillwater, OK (United States); Ortoleva, P. [Indiana Univ., Bloomington, IN (United States). Lab. for Computational Geodynamics

    1998-12-31

    In the Ellenburger Group fractured dolomite reservoirs of West Texas, it is extremely difficult to distinguish between multiple phases of karst-related fracturing, modifications to the karst system during burial, and overprinting tectonic fractures. From the analyses of drill core, the authors developed criteria to distinguish between karst and tectonic fractures. In addition, they have applied these criteria within the context of a detailed diagenetic cement history that allows them to further refine the fracture genesis and chronology. In these analyses, the authors evaluated the relationships between fracture intensity, morphologic attributes, host lithology, fracture cement, and oil-staining. From this analysis, they have been able to characterize variations in Ellenburger tectonic fracture intensity by separating these fractures from karst-related features. In general, the majority of fracturing in the Ellenburger is caused by karst-related fracturing although a considerable percentage is caused by tectonism. These findings underscore the importance of considering the complete geologic evolution of a karst reservoir during exploration and field development programs. The authors have been able to more precisely define the spatial significance of the fracture data sets by use of oriented core from Andector Field. They have also demonstrated the importance of these results for exploration and reservoir development programs in West Texas, and the potential to extrapolate these results around the globe. Given the historic interest in the large hydrocarbon reserves in West Texas carbonate reservoirs, results of this study will have tremendous implications for exploration and production strategies targeting vuggy, fractured carbonate systems not only in West Texas, but throughout the globe.

  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. Naturally fractured tight gas reservoir detection optimization. Annual report, September 1993--September 1994

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1994-10-01

    This report is an annual summarization of an ongoing research in the field of modeling and detecting naturally fractured gas reservoirs. The current research is in the Piceance basin of Western Colorado. The aim is to use existing information to determine the most optimal zone or area of fracturing using a unique reaction-transport-mechanical (RTM) numerical basin model. The RTM model will then subsequently help map subsurface lateral and vertical fracture geometries. The base collection techniques include in-situ fracture data, remote sensing, aeromagnetics, 2-D seismic, and regional geologic interpretations. Once identified, high resolution airborne and spaceborne imagery will be used to verify the RTM model by comparing surficial fractures. If this imagery agrees with the model data, then a further investigation using a three-dimensional seismic survey component will be added. This report presents an overview of the Piceance Creek basin and then reviews work in the Parachute and Rulison fields and the results of the RTM models in these fields.

  14. 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

  15. Investigation of gas-oil gravity drainage in naturally fractured reservoirs using discrete fracture and matrix numerical model

    International Nuclear Information System (INIS)

    Bazr-Afkan, S.

    2012-01-01

    To simulate fluid flow in Naturally Fractured Reservoirs (NFRs), a new Descrete Fracture and Matrix (DFM) simulation technique is developed as a physically more realistic alternative to the dual continuum approach. This Finite-Element Centered Finite-Volume method (FECFVM) has the advantage over earlier FECFVM approaches that it honors saturation dicontinuities that can arise at material interfaces from the interplay of viscous, capillary and gravitational forces. By contrast with an earlier embedded-discontinuity DFEFVM method, the FECFVM achieves this without introducing additional degrees of freedom. It also allows to simulate capillary- and other fracture-matrix exchange processes using a lower dimensional representation of fractures, simplifying model construction and unstructured meshing as well as speeding up computations. A further step-up is obtained by solving the two-phase fluid-flow and saturation transport equations only on 'active elements'. This also diminishes round-off and truncation errors, reducing numerical diffusion during the solution of the transport equation. The FECFVM is verified by comparing IMPES operator-splitting sequential solutions with analytical ones, as well as benchmarking it against commercial reservoir simulators on simple geometries that these can represent. This testing confirms that my 2D FECFVM implementation simulates gravitational segregation, capillary redistribution, capillary barriers, and combinations thereof physically realistically, achieving (at least) first-order solution accuracy. Following this verification, the FECFVM is applied to study Gas-Oil Gravity Drainage (GOGD) process in cross-sectional models of layered NFRs. Here comparisons with dual continua simulations show that these do not capture a range of block-to-block effects, yielding over-optimistic drainage rates. Observations made on individual matrix blocks in the DFM simulations further reveal that their saturation evolution is at odds with the

  16. 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

  17. 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 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 that methanogen species like Methanohalophilus or Methanolobus could be the possible sources of biogenic methane in these shale reservoirs. The evidence of microbial methanogenesis raises the possibility of enhanced gas recovery from these shales using biological amendments.

  18. Effects of different block size distributions in pressure transient response of naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Montazeri, G.H. [Islamic Azad University, Mahshahr (Iran, Islamic Republic of). Dept. of Chemical and Petroleum Engineering], E-mail: montazeri_gh@yahoo.com; Tahami, S.A. [Mad Daneshgostar Tabnak Co. (MDT),Tehran (Iran, Islamic Republic of); Moradi, B.; Safari, E. [Iranian Central Oil Fields Co, Tehran (Iran, Islamic Republic of)], E-mail: morady.babak@gmail.com

    2011-07-15

    This paper presents a model for pressure transient and derivative analysis for naturally fractured reservoirs by a formulation of inter porosity flow incorporating variations in matrix block size, which is inversely related to fracture intensity. Geologically realistic Probability Density Functions (PDFs) of matrix block size, such as uniform, bimodal, linear and exponential distributions, are examined and pseudo-steady-state and transient models for inter porosity flow are assumed. The results have been physically interpreted, and, despite results obtained by other authors, it was found that the shape of pressure derivative curves for different PDFs are basically identical within some ranges of block size variability, inter porosity skin, PDFs parameters and matrix storage capacity. This tool can give an insight on the distribution of block sizes and shapes, together with other sources of information such as Logs and geological observations. (author)

  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. 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.

  1. Assessment of undiscovered oil and gas resources in the Spraberry Formation of the Midland Basin, Permian Basin Province, Texas, 2017

    Science.gov (United States)

    Marra, Kristen R.; Gaswirth, Stephanie B.; Schenk, Christopher J.; Leathers-Miller, Heidi M.; Klett, Timothy R.; Mercier, Tracey J.; Le, Phuong A.; Tennyson, Marilyn E.; Finn, Thomas M.; Hawkins, Sarah J.; Brownfield, Michael E.

    2017-05-15

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean resources of 4.2 billion barrels of oil and 3.1 trillion cubic feet of gas in the Spraberry Formation of the Midland Basin, Permian Basin Province, Texas.

  2. A new method for pressure test analysis of a vertically fractured well producing commingled zones in bounded square reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Osman, Mohammed E.; Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, Al-Ain (United Arab Emirates)

    1997-07-15

    Although hydraulically or naturally fractured wells located in stratified bounded reservoirs are common, reliable techniques available to analyze the pressure test data for such reservoirs are lacking. This paper presents a mathematical model that describes the pressure behavior of a vertically fractured well located in a stratified, bounded, square reservoir. The fracture can be either a uniform flux or an infinite conductivity fracture. It was found that the dimensionless pressure function and its derivative and the fractional production rate from the different layers are mainly controlled by the fracture penetration into the formation, and that transmissibility and storativity affect the fractional production rate and the pressure derivative but have little effect on the dimensionless pressure function. Type curves of dimensionless pressure and dimensionless pressure derivative can be used to evaluate the reservoir characteristics. The selection of the appropriate type curve is guided by the behavior of the layer fractional production rate obtained from flow rate survey carried out during well testing. Type curves for uniform flux and infinite conductivity fractures exhibit similar features. Two examples are presented to demonstrate the application of the new method of analysis presented in this paper

  3. 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.

  4. 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

  5. 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

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

    Science.gov (United States)

    Wei, Mingzhen; Liu, Hong

    2018-01-01

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

  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 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.

  10. Gas hydrate saturations estimated from fractured reservoir at Site NGHP-01-10, Krishna-Godavari Basin, India

    Science.gov (United States)

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

    2009-01-01

    During the Indian National Gas Hydrate Program Expedition 01 (NGHP-Ol), one of the richest marine gas hydrate accumulations was discovered at Site NGHP-01-10 in the Krishna-Godavari Basin. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Assuming the resistivity of gas hydratebearing sediments is isotropic, th?? conventional Archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50% (as high as ???80%) of the pore space for the depth interval between ???25 and ???160 m below seafloor. On the other hand, gas hydrate saturations estimated from pressure cores from nearby wells were less than ???26% of the pore space. Although intrasite variability may contribute to the difference, the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high-angle fractures. Archie's law can be used to estimate gas hydrate saturations in anisotropic reservoir, with additional information such as elastic velocities to constrain Archie cementation parameters m and the saturation exponent n. Theory indicates that m and n depend on the direction of the measurement relative to fracture orientation, as well as depending on gas hydrate saturation. By using higher values of m and n in the resistivity analysis for fractured reservoirs, the difference between saturation estimates is significantly reduced, although a sizable difference remains. To better understand the nature of fractured reservoirs, wireline P and S wave velocities were also incorporated into the analysis.

  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. 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.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. Geochemical Interaction of Middle Bakken Reservoir Rock and CO2 during CO2-Based Fracturing

    Science.gov (United States)

    Nicot, J. P.; Lu, J.; Mickler, P. J.; Ribeiro, L. H.; Darvari, R.

    2015-12-01

    This study was conducted to investigate the effects of geochemical interactions when CO2 is used to create the fractures necessary to produce hydrocarbons from low-permeability Middle Bakken sandstone. The primary objectives are to: (1) identify and understand the geochemical reactions related to CO2-based fracturing, and (2) assess potential changes of reservoir property. Three autoclave experiments were conducted at reservoir conditions exposing middle Bakken core fragments to supercritical CO2 (sc-CO2) only and to CO2-saturated synthetic brine. Ion-milled core samples were examined before and after the reaction experiments using scanning electron microscope, which enabled us to image the reaction surface in extreme details and unambiguously identify mineral dissolution and precipitation. The most significant changes in the reacted rock samples exposed to the CO2-saturated brine is dissolution of the carbonate minerals, particularly calcite which displays severely corrosion. Dolomite grains were corroded to a lesser degree. Quartz and feldspars remained intact and some pyrite framboids underwent slight dissolution. Additionally, small amount of calcite precipitation took place as indicated by numerous small calcite crystals formed at the reaction surface and in the pores. The aqueous solution composition changes confirm these petrographic observations with increase in Ca and Mg and associated minor elements and very slight increase in Fe and sulfate. When exposed to sc-CO2 only, changes observed include etching of calcite grain surface and precipitation of salt crystals (halite and anhydrite) due to evaporation of residual pore water into the sc-CO2 phase. Dolomite and feldspars remained intact and pyrite grains were slightly altered. Mercury intrusion capillary pressure tests on reacted and unreacted samples shows an increase in porosity when an aqueous phase is present but no overall porosity change caused by sc-CO2. It also suggests an increase in permeability

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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

  3. 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

  4. Estimation of Dry Fracture Weakness, Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

    Science.gov (United States)

    Chen, Huaizhen; Zhang, Guangzhi

    2017-05-01

    Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann's (Vier. der Natur. Gesellschaft Zürich 96:1-23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.

  5. 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.

  6. 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

    2015-01-01

    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. Key Points: 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 PMID

  7. Heavy-oil recovery in naturally fractured reservoirs with varying wettability by steam solvent co-injection

    Energy Technology Data Exchange (ETDEWEB)

    Al Bahlani, A. [Alberta Univ., Edmonton, AB (Canada); Babadagli, T. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[Alberta Univ., Edmonton, AB (Canada)

    2008-10-15

    Steam injection may not be an efficient oil recovery process in certain circumstances, such as in deep reservoirs, where steam injection may be ineffective because of hot-water flooding due to excessive heat loss. Steam injection may also be ineffective in oil-wet fractured carbonates, where steam channels through fracture zones without effectively sweeping the matrix oil. Steam flooding is one of the many solutions for heavy oil recovery in unconsolidated sandstones that is in commercial production. However, heavy-oil fractured carbonates are more challenging, where the recovery is generally limited only to matrix oil drainage gravity due to unfavorable wettability or thermal expansion if heat is introduced during the process. This paper proposed a new approach to improve steam/hot-water injection and efficiency for heavy-oil fractured carbonate reservoirs. The paper provided background information on oil recovery from fractured carbonates and provided a statement of the problem. Three phases were described, including steam/hot-waterflooding phase (spontaneous imbibition); miscible flooding phase (diffusion); and steam/hot-waterflooding phase (spontaneous imbibition or solvent retention). The paper also discussed core preparation and saturation procedures. It was concluded that efficient oil recovery is possible using alternate injection of steam/hot water and solvent. 43 refs., 1 tab., 13 figs.

  8. 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

  9. 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.

  10. 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

    1997-12-31

    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.

  11. 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

  12. Computerized X-ray Microtomography Observations and Fluid Flow Measurements of the Effect of Effective Stress on Fractured Reservoir Seal Shale

    Science.gov (United States)

    Welch, N.; Crawshaw, J.; Boek, E.

    2014-12-01

    The successful storage of carbon dioxide in geologic formations requires an in-depth understanding of all reservoir characteristics and morphologies. An intact and substantial seal formation above a storage reservoir is required for a significant portion of the initial sealing mechanisms believed to occur during carbon dioxide storage operations. Shales are a common seal formation rock types found above numerous hydrocarbon reservoirs, as well as potential saline aquifer storage locations. Shales commonly have very low permeability, however they also have the tendency to be quite fissile, and the formation of fractures within these seals can have a significant detrimental effect on the sealing potential of a reservoir and amount to large areas of high permeability and low capillary pressures compared to the surrounding intact rock. Fractured shales also have an increased current interest due to the increasing development of shale gas reservoirs using hydraulic fracturing techniques. This work shows the observed changes that occur within fractured pieces of reservoir seal shale samples, along with quarry analogues, using an in-situ micro-CT fluid flow imaging apparatus with a Hassler type core holder. Changes within the preferential flow path under different stress regimes as well as physical changes to the fracture geometry are reported. Lattice Boltzmann flow simulations were then performed on the extracted flow paths and compared to experiment permeability measurements. The preferential flow path of carbon dioxide through the fracture network is also observed and compared to the results two-phase Lattice Boltzmann fluid flow simulations.

  13. 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

  14. 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

    2004-05-01

    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

  15. 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

    2004-07-01

    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

  16. The role of mineral heterogeneity on the hydrogeochemical response of two fractured reservoir rocks in contact with dissolved CO2

    Science.gov (United States)

    Garcia Rios, Maria; Luquot, Linda; Soler, Josep M.; Cama, Jordi

    2017-04-01

    In this study we compare the hydrogeochemical response of two fractured reservoir rocks (limestone composed of 100 wt.% calcite and sandstone composed of 66 wt.% calcite, 28 wt.% quartz and 6 wt.% microcline) in contact with CO2-rich sulfate solutions. Flow-through percolation experiments were performed using artificially fractured limestone and sandstone cores and injecting a CO2-rich sulfate solution under a constant volumetric flow rate (from 0.2 to 60 mL/h) at P = 150 bar and T = 60 °C. Measurements of the pressure difference between the inlet and the outlet of the samples and of the aqueous chemistry enabled the determination of fracture permeability changes and net reaction rates. Additionally, X-ray computed microtomography (XCMT) was used to characterize and localized changes in fracture volume induced by dissolution and precipitation reactions. In all reacted cores an increase in fracture permeability and in fracture volume was always produced even when gypsum precipitation happened. The presence of inert silicate grains in sandstone samples favored the occurrence of largely distributed dissolution structures in contrast to localized dissolution in limestone samples. This phenomenon promoted greater dissolution and smaller precipitation in sandstone than in limestone experiments. As a result, in sandstone reservoirs, the larger increase in fracture volume as well as the more extended distribution of the created volume would favor the CO2 storage capacity. The different distribution of created volume between limestone and sandstone experiments led to a different variation in fracture permeability. The progressive stepped permeability increase for sandstone would be preferred to the sharp permeability increase for limestone to minimize risks related to CO2 injection, favor capillary trapping and reduce energetic storage costs. 2D reactive transport simulations that reproduce the variation in aqueous chemistry and the fracture geometry (dissolution pattern

  17. Numerical investigation of electricity generation potential from fractured granite reservoir through a single vertical well 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

    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 well there mainly produces liquid and steam two-phase flow. In this work we numerically investigated the electricity generation potential from the fractured granite reservoir through a single vertical well, analyzed the process and mechanism of the two-phase flow, and evaluated main factors affecting the heat production and electricity generation. The results show that under the reference conditions the system attains a pump power of 0.02 ~ 0.16 MW, an electrical power of 2.71 ~ 2.69 MW, and an energy efficiency of 68.06 ~ 16.34, showing favorable electricity generation performance. During the production period, the bottomhole production pressure gradually decreases, and this makes the pump power increasing and the energy efficiency decreasing. When the bottomhole pressure is lower than the saturated vapor pressure, the liquid water begins to evaporate and the bottomhole wellbore begins to produce the mixture of liquid and steam. Main factors affecting the performance are reservoir porosity, permeability and fluid production rate. Higher reservoir porosity or higher permeability or lower fluid production rate will increase the bottomehole pressure, decrease the pump power and improve the energy efficiency. - Highlights: • We established a numerical model of a single vertical well heat mining system. • Desirable electricity production performance can be obtained under suitable conditions. • The system attains an electric power of 2.71 ~ 2.69 MW with an efficiency of about 68.06 ~ 16.34. • Electric power mainly depends on the reservoir porosity and water production rate. • Higher permeability within a certain range is favorable for electricity generation.

  18. 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.

  19. Efficient and robust compositional two-phase reservoir simulation in fractured media

    Science.gov (United States)

    Zidane, A.; Firoozabadi, A.

    2015-12-01

    Compositional and compressible two-phase flow in fractured media has wide applications including CO2 injection. Accurate simulations are currently based on the discrete fracture approach using the cross-flow equilibrium model. In this approach the fractures and a small part of the matrix blocks are combined to form a grid cell. The major drawback is low computational efficiency. In this work we use the discrete-fracture approach to model the fractures where the fracture entities are described explicitly in the computational domain. We use the concept of cross-flow equilibrium in the fractures (FCFE). This allows using large matrix elements in the neighborhood of the fractures. We solve the fracture transport equations implicitly to overcome the Courant-Freidricks-Levy (CFL) condition in the small fracture elements. Our implicit approach is based on calculation of the derivative of the molar concentration of component i in phase (cαi ) with respect to the total molar concentration (ci ) at constant volume V and temperature T. This contributes to significant speed up of the code. The hybrid mixed finite element method (MFE) is used to solve for the velocity in both the matrix and the fractures coupled with the discontinuous Galerkin (DG) method to solve the species transport equations in the matrix, and a finite volume (FV) discretization in the fractures. In large scale problems the proposed approach is orders of magnitude faster than the existing models.

  20. 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

  1. GPU-Based Computation of Formation Pressure for Multistage Hydraulically Fractured Horizontal Wells in Tight Oil and Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Rongwang Yin

    2018-01-01

    Full Text Available A mathematical model for multistage hydraulically fractured horizontal wells (MFHWs in tight oil and gas reservoirs was derived by considering the variations in the permeability and porosity of tight oil and gas reservoirs that depend on formation pressure and mixed fluid properties and introducing the pseudo-pressure; analytical solutions were presented using the Newman superposition principle. The CPU-GPU asynchronous computing model was designed based on the CUDA platform, and the analytic solution was decomposed into infinite summation and integral forms for parallel computation. Implementation of this algorithm on an Intel i5 4590 CPU and NVIDIA GT 730 GPU demonstrates that computation speed increased by almost 80 times, which meets the requirement for real-time calculation of the formation pressure of MFHWs.

  2. 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

  3. 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)

  4. Overview of naturally permeable fractured reservoirs in the central and southern Upper Rhine Graben: Insights from geothermal wells

    OpenAIRE

    Vidal , Jeanne; Genter , Albert

    2018-01-01

    International audience; Since the 1980′s, more than 15 geothermal wells have been drilled in the Upper Rhine Graben (URG), representing more than 60 km of drill length. Although some early concepts were related to purely matrix-porosity reservoirs or Hot Dry Rock systems, most projects in the URG are currently exploiting the geothermal resources that are trapped in fracture networks at the base of the sedimentary cover and in the granitic basement. Lessons-learnt from the European EGS referen...

  5. 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.

  6. 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

  7. Understanding the fracture role on hydrocarbon accumulation and distribution using seismic data: A case study on a carbonate reservoir from Iran

    Science.gov (United States)

    Karimpouli, Sadegh; Hassani, Hossein; Malehmir, Alireza; Nabi-Bidhendi, Majid; Khoshdel, Hossein

    2013-09-01

    The South Pars, the largest gas field in the world, is located in the Persian Gulf. Structurally, the field is part of the Qatar-South Pars arch which is a regional anticline considered as a basement-cored structure with long lasting passive folding induced by salt withdrawal. The gas-bearing reservoir belongs to Kangan and Dalan formations dominated by carbonate rocks. The fracture role is still unknown in gas accumulation and distribution in this reservoir. In this paper, the Scattering Index (SI) and the semblance methods based on scattered waves and diffraction signal studies, respectively, were used to delineate the fracture locations. To find the relation between fractures and gas distribution, desired facies containing the gas, were defined and predicted using a method based on Bayesian facies estimation. The analysis and combination of these results suggest that preference of fractures and/or fractured zones are negligible (about 1% of the total volume studied in this paper) and, therefore, it is hard to conceive that they play an important role in this reservoir. Moreover, fractures have no considerable role in gas distribution (less than 30%). It can be concluded from this study that sedimentary processes such as digenetic, primary porosities and secondary porosities are responsible for the gas accumulation and distribution in this reservoir.

  8. 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.

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

    KAUST Repository

    Ping, Jing; Al-Hinai, Omar; Wheeler, Mary F.

    2017-01-01

    -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

  10. 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.

  11. Insights on fluid-rock interaction evolution during deformation from fracture network geochemistry at reservoir-scale

    Science.gov (United States)

    Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Bellahsen, Nicolas; Emmanuel, Laurent

    2015-04-01

    Fluid migration and fluid-rock interactions during deformation is a challenging problematic to picture. Numerous interplays, as between porosity-permeability creation and clogging, or evolution of the mechanical properties of rock, are key features when it comes to monitor reservoir evolution, or to better understand seismic cycle n the shallow crust. These phenomenoms are especially important in foreland basins, where various fluids can invade strata and efficiently react with limestones, altering their physical properties. Stable isotopes (O, C, Sr) measurements and fluid inclusion microthermometry of faults cement and veins cement lead to efficient reconstruction of the origin, temperature and migration pathways for fluids (i.e. fluid system) that precipitated during joints opening or faults activation. Such a toolbox can be used on a diffuse fracture network that testifies the local and/or regional deformation history experienced by the rock at reservoir-scale. This contribution underlines the advantages and limits of geochemical studies of diffuse fracture network at reservoir-scale by presenting results of fluid system reconstruction during deformation in folded structures from various thrust-belts, tectonic context and deformation history. We compare reconstructions of fluid-rock interaction evolution during post-deposition, post-burial growth of basement-involved folds in the Sevier-Laramide American Rocky Mountains foreland, a reconstruction of fluid-rock interaction evolution during syn-depostion shallow detachment folding in the Southern Pyrenean foreland, and a preliminary reconstruction of fluid-rock interactions in a post-deposition, post-burial development of a detachment fold in the Appenines. Beyond regional specification for the nature of fluids, a common behavior appears during deformation as in every fold, curvature-related joints (related either to folding or to foreland flexure) connected vertically the pre-existing stratified fluid system

  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; 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

  13. 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.

  14. 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.

  15. 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...

  16. Evolution of pores and fractures in an unconventional Upper Carboniferous reservoir analogue, Westphalian D, W-Germany

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne, M.; Schurk, K.; Hilgers, C. [RWTH Aachen Univ. (Germany). Reservoir-Petrology, Energy and Mineral Resources Group (EMR); Koehrer, B. [Wintershall Holding GmbH, Barnstorf (Germany); Bertier, P. [RWTH Aachen Univ. (Germany). Inst. of Clay and Interface Mineralogy

    2013-08-01

    Uncertainties in reservoir characterization of tight gas sandstones can be significantly reduced by using quantitative data from outcrops. The active Piesberg quarry near Osnabrueck exposes Upper Carboniferous strata and therefore provides a reservoir outcrop analog to the gas-bearing tight gas fields in NW-Germany. This study focused on variations of sedimentary facies, porosity, diagenesis and structural inventory in the quarry. The Westphalian D strata at Piesberg consist of siliciclastic, coarse- to fine-grained sandstones with a strong cementation, intercalated with coal seams, siltstones and mudstones. Petrography shows shale-, mudstone and clay rip-up fragments squeezed into primary porosity during eodiagenesis. Sandstone types commonly show low porosities (<10 %) and very low permeabilities (<0.01 mD) mainly due to intense quartz cementation. Scarce authigenic carbonates are euhedral ankerites formed during burial. Secondary porosity resulted mostly from detrital carbonate leaching and limited dissolution of feldspars. Within a zone of up to several meters around faults, porosity is much higher. Feldspars are almost completely altered to illite and locally to kaolinite. Partly dissolved detrital carbonates show Fe-oxide margins around intragranular pores, indicative of Fe-rich compositions formed during telo-diagenesis. Both joints and faults were mapped throughout the quarry and strike, slip and throw of the latter were documented. Cemented fractures prevail around faults and may thus be associated with the structural and diagenetic evolution of the Upper Carboniferous of the Piesberg area. This study is embedded into a larger outcrop analog study of RWTH Aachen in cooperation with Wintershall. Its aim is to unravel the impact of structural diagenesis on the alteration and evolution of pore space and thus reservoir quality. Results can be used to develop datadriven exploration strategies and improved development options for analogous subsurface tight gas

  17. 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.

  18. 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.

  19. Fracture analysis of an Eocene reservoir in Eastern Tunisia by coupling Terrestrial Laser Scanning with GigaPan Technology and seismic attribute

    Science.gov (United States)

    Mastouri, Raja; Guerin, Antoine; Marchant, Robin; Derron, Marc-Henri; Boulares, Achref; Lazzez, Marzouk; Marillier, François; Jaboyedoff, Michel; Bouaziz, Samir

    2015-04-01

    It is usually not possible to study in situ fractures and faults of oil reservoirs. Then outcropping reservoir analogues are used instead. For this purpose, Terrestrial Laser Scanning (TLS) has been increasingly used for some years in the petroleum sector. The formations El Garia and Reineche make the Eocene oil reservoir of Eastern Tunisia. The fracturing of these formations has been analyzed on the surface by TLS on a reservoir analogue outcrop and in the depth by 3D seismic data. TLS datasets provide clear information on fracture geometry distribution (spacing and persistence), connectivity and joint orientation. These results were then compared to structures observed in depth with seismic data. The reservoir analogues are the Ousselat cliff (formation El Garia) and the Damous quarry (formation Reineche). Those two sites are made of marine limestone rich in large foraminifers, gastropods and nummulites. Fieldwork, TLS acquisitions and high-resolution GigaPan panoramas were put together to create digital outcrop models. A total of 9 scans at 3 different survey positions were carried out. Firstly, the data processing (cleaning, alignment and georeferencing of the raw point clouds) was carried out using the Polyworks software. Secondly, we draped Gigapixel pictures on the triangular mesh generated with 3DReshaper to produce relief shading. This process produces a photorealistic model that gives a 3D representation of the outcrop. Finally, Coltop3D was used to identify the different sets of discontinuities and to measure their orientations. Furthermore, we used some 3D seismic attribute data to interpret approximately 60 fractures and faults at the top of the Eocene reservoir. The Coltop3D analysis of the Ousselat cliff shows 5 sets of joints and fractures, with different dips and dip directions. They all strike in directions NW-SE, NNE-SSW, NE-SW and ENE-WSW. Using the photorealistic model, we measured approximately 120 fracture spacings ranging from 1.75m to 10m

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

    Science.gov (United States)

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

    2013-12-01

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

  1. Effect of heterogeneity in a horizontal well with multiple fractures on the long term forecast in shale gas reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Nobakht, M.; Ambrose, R.; Clarkson, C.R. [Society of Petroleum Engineers (Canada)

    2011-07-01

    Multiple fracture horizontal wells (MFHWs) are the most popular type of method used for exploiting shale gas reservoirs. When analyzing MFHW's a homogeneous completion model is often used, but this rarely occurs in the field. This paper develops a hybrid method for forecasting MFHWs based on a heterogeneous completion and investigates the effect of completion heterogeneity on production forecasts. First, a current forecasting method for homogeneous completions was modified for heterogeneous completions. The new forecasting method was then validated using a numerical simulation. A relationship between Arps' hyperbolic decline exponent and the heterogeneity of a completion for a particular case was then developed. Lastly, a field case was analyzed to compare the impact of forecasting with and without taking a heterogeneous completion into consideration. Through analysis and simulations this paper found that the long-term forecast of MFHWs can be greatly impacted should heterogeneity of the completion be ignored.

  2. Coulomb stress change during and after tensile fracture opening in a geothermal reservoir

    NARCIS (Netherlands)

    Urpi, L.; Blöcher, G.; Zimmermann, G.; Wees, J.D. van; Fokker, P.

    2013-01-01

    Stress shadowing and the ratio of shear to normal stress in the rock surrounding a newly created tensile fracture are investigated. Shearing on plane of weakness near the stimulated volume can be inhibited or promoted by change in poro- and thermo-elastic stress, while pore pressure increase tends

  3. Numerical solution of fractured horizontal wells in shale gas reservoirs considering multiple transport mechanisms

    Science.gov (United States)

    Zhao, Yu-long; Tang, Xu-chuan; Zhang, Lie-hui; Tang, Hong-ming; Tao, Zheng-Wu

    2018-06-01

    The multiscale pore size and specific gas storage mechanism in organic-rich shale gas reservoirs make gas transport in such reservoirs complicated. Therefore, a model that fully incorporates all transport mechanisms and employs an accurate numerical method is urgently needed to simulate the gas production process. In this paper, a unified model of apparent permeability was first developed, which took into account multiple influential factors including slip flow, Knudsen diffusion (KD), surface diffusion, effects of the adsorbed layer, permeability stress sensitivity, and ad-/desorption phenomena. Subsequently, a comprehensive mathematical model, which included the model of apparent permeability, was derived to describe gas production behaviors. Thereafter, on the basis of unstructured perpendicular bisection grids and finite volume method, a fully implicit numerical simulator was developed using Matlab software. The validation and application of the new model were confirmed using a field case reported in the literature. Finally, the impacts of related influencing factors on gas production were analyzed. The results showed that KD resulted in a negligible impact on gas production in the proposed model. The smaller the pore size was, the more obvious the effects of the adsorbed layer on the well production rate would be. Permeability stress sensitivity had a slight effect on well cumulative production in shale gas reservoirs. Adsorbed gas made a major contribution to the later flow period of the well; the greater the adsorbed gas content, the greater the well production rate would be. This paper can improve the understanding of gas production in shale gas reservoirs for petroleum engineers.

  4. 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

  5. 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

  6. PRODUCTION WELL WATER SHUT-OFF TREATMENT IN A HIGHLY FRACTURED SANDSTONE RESERVOIR; TOPICAL

    International Nuclear Information System (INIS)

    Lyle A. Johnson, Jr.

    2001-01-01

    As domestic oil and gas fields approach maturity or even abandonment, new methods are being tested to add life to the fields. One area being addressed is the reduction of water production to extend the economic life of a field. In many fields a very common problem is permeability heterogeneity from matrix variations, fractures, or both. Conventional procedures to remediate high water rates in fractured networks, including cement squeezing, openhole packers, and liners are generally unsuccessful. The objective of this project was to test the viability of using sequential treatment of a production well with a cross-linked polymer to restrict water production from highly permeable and fractured zones. The field used for testing was the Ashley Valley field in northeastern Utah. The process proposed for testing in this field was the sequential application of small batches of a cross-linked polymer, chromium (III) polyacrylamide polymer (Marcit(trademark)). First, the highest permeability fractures were to be blocked, followed progressively by smaller fractures, and finally the higher permeability matrix channels. The initial application of this polymer in September 1997 in the Ashley Valley (AV) well No.2 did increase oil production while decreasing both water production and the relative permeability to water. The successive application of the polymer was considered as a method to increase both daily and ultimate oil production and reduce produced water. The second polymer treatment was conducted in October 1999 in AV No.2. The treatment consisted of 4,994 barrels of 1,500-mg/l to 9,000-mg/l polymer at surface injection pressures no higher than 380 psig. During injection, four offset wells showed polymer breakthrough and were shut in during the remaining treatment. Present oil and water production rates for AV No.2 are 14 BOPD and 2,700 BWPD, which is a 44% decrease in the oil rate and a 40% reduction in water from the rates after the first treatment. The decrease in

  7. 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.

  8. 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.

  9. 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.

  10. Elastic-Brittle-Plastic Behaviour of Shale Reservoirs and Its Implications on Fracture Permeability Variation: An Analytical Approach

    Science.gov (United States)

    Masoudian, Mohsen S.; Hashemi, Mir Amid; Tasalloti, Ali; Marshall, Alec M.

    2018-05-01

    are considered to be elastic and are defined using a Langmuir-like curve, which is directly related to the reservoir pressure. The models are used to evaluate the stress distribution and the induced change in permeability within a reservoir. Results show that development of a plastic zone near the wellbore can significantly impact fracture permeability and gas production. The capabilities and limitations of the models are discussed and potential future developments related to modelling of permeability in brittle shales under elastoplastic deformations are identified.

  11. 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.

  12. Use of TOUGHREACT to Simulate Effects of Fluid Chemistry onInjectivity in Fractured Geothermal Reservoirs with High Ionic StrengthFluids

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Zhang, Guoxiang; Pruess, Karsten

    2005-02-09

    Recent studies suggest that mineral dissolution/precipitation and clay swelling effects could have a major impact on the performance of hot dry rock (HDR) and hot fractured rock (HFR) reservoirs. A major concern is achieving and maintaining adequate injectivity, while avoiding the development of preferential short-circuiting flow paths. A Pitzer ionic interaction model has been introduced into the publicly available TOUGHREACT code for solving non-isothermal multi-phase reactive geochemical transport problems under conditions of high ionic strength, expected in typical HDR and HFR systems. To explore chemically-induced effects of fluid circulation in these systems, we examine ways in which the chemical composition of reinjected waters can be modified to improve reservoir performance. We performed a number of coupled thermo-hydrologic-chemical simulations in which the fractured medium was represented by a one-dimensional MINC model (multiple interacting continua). Results obtained with the Pitzer activity coefficient model were compared with those using an extended Debye-Hueckel equation. Our simulations show that non-ideal activity effects can be significant even at modest ionic strength, and can have major impacts on permeability evolution in injection-production systems. Alteration of injection water chemistry, for example by dilution with fresh water, can greatly alter precipitation and dissolution effects, and can offer a powerful tool for operating hot dry rock and hot fractured rock reservoirs in a sustainable manner.

  13. 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.

  14. Relationship between fracturing and porogenesis in a carbonate reservoir: Example from the Middle Turonian Bireno Member in Jebel M'rhila, Central Tunisia

    Science.gov (United States)

    Haj Ali, Hajer; Belghithi, Hanen; Ouali, Jamel Abdennaceur; Touir, Jamel

    2016-09-01

    relationship between fracturing and the reservoir potentiality of dolomites and the dolomitization process. Although the porosity in dolomites is not important enough, its gradual lateral variation with the distance from the fractures reflects the role of the latter in the porogenesis. The field observation and the results of the petrographic and petrophysical analysis show that the fractures must have played a substantial role in conducting the meteoric waters from the emerged platform surface to its base and laterally, resulting in a cementing dolomitization and a solution-related porogenesis. Therefore, it seems that if the dolomitic Bireno Member is rather a good potential reservoir due to the associated fractures networks.

  15. 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.

  16. 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

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

    KAUST Repository

    Qin, Guan; Bi, Linfeng; Popov, Peter; Efendiev, Yalchin; Espedal, Magne

    2010-01-01

    , 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

  18. 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

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

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

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

  20. Nagylengyel: an interesting reservoir. [Yugoslovia

    Energy Technology Data Exchange (ETDEWEB)

    Dedinszky, J

    1971-04-01

    The Nagylengyel oil field, discovered in 1951, has oil-producing formations mostly in the Upper-Triassic dolomites, in the Norian-Ractian transition formations, in the Upper-Cretaceous limestones and shales, and in the Miocene. The formation of the reservoir space occurred in many stages. A porous, cavernous fractured reservoir is developed in the Norian principal dolomite. A cavernous fractured reservoir exists in the Cretaceous limestone and in the Cretaceous shale and porous fractured reservoir is developed in the Miocene. The derivation of the model of the reservoir, and the conservative evaluation of the volume of the reservoir made it possible to use secondary recovery.

  1. Assessing Past Fracture Connectivity in Geothermal Reservoirs Using Clumped Isotopes: Proof of Concept in the Blue Mountain Geothermal Field, Nevada USA

    Science.gov (United States)

    Huntington, K. W.; Sumner, K. K.; Camp, E. R.; Cladouhos, T. T.; Uddenberg, M.; Swyer, M.; Garrison, G. H.

    2015-12-01

    Subsurface fluid flow is strongly influenced by faults and fractures, yet the transmissivity of faults and fractures changes through time due to deformation and cement precipitation, making flow paths difficult to predict. Here we assess past fracture connectivity in an active hydrothermal system in the Basin and Range, Nevada, USA, using clumped isotope geochemistry and cold cathodoluminescence (CL) analysis of fracture filling cements from the Blue Mountain geothermal field. Calcite cements were sampled from drill cuttings and two cores at varying distances from faults. CL microscopy of some of the cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements record variations in the composition and source of fluids that moved through the fractures as they opened episodically. CL microscopy, δ13C and δ18O values were used to screen homogeneous samples for clumped isotope analysis. Clumped isotope thermometry of most samples indicates paleofluid temperatures of around 150°C, with several wells peaking at above 200°C. We suggest that the consistency of these temperatures is related to upwelling of fluids in the convective hydrothermal system, and interpret the similarity of the clumped isotope temperatures to modern geothermal fluid temperatures of ~160-180°C as evidence that average reservoir temperatures have changed little since precipitation of the calcite cements. In contrast, two samples, one of which was associated with fault gauge observed in drill logs, record significantly cooler temperatures of 19 and 73°C and anomalous δ13C and δ18Owater values, which point to fault-controlled pathways for downwelling meteoric fluid. Finally, we interpret correspondence of paleofluid temperatures and δ18Owater values constrained by clumped isotope thermometry of calcite from different wells to suggest past connectivity of fractures among wells within the geothermal field. Results show the ability of clumped isotope

  2. Verification survey of geothermal exploration technology, etc. Report on the result of the developmental research on the development of the fracture type reservoir exploration method; Chinetsu tansa gijutsu nado kensho chosa. Danretsugata choryuso tansaho kaihatsu kenkyu kaihatsu seika sokatsu hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    For the purpose of grasping fracture groups forming geothermal reservoirs with accuracy, the development of the fracture type reservoir exploration method has advanced the technical development of exploration methods of seismic wave use, electromagnetic induction use, and micro-earthquake use. This paper summarized main results of the development and problems to be solved in the future. In the development of the seismic wave use exploration method, the high accuracy reflection method using seismic wave, VSP and seismic tomography were adopted to the geothermal field, and technology effective for the exploration of fracture type reservoirs was developed. In the development of the electromagnetic induction use exploration method, the array CSMT method which can measure multiple stations along the traverse line at the same time was developed with the aim of grasping effectively and accurately fracture groups forming geothermal reservoirs as changes of resistivity in the shallow-deep underground. In the fracture group forming geothermal reservoirs, micro-earthquakes are generated by movement of thermal water and pressure variations. In the development of the micro-earthquake use exploration method, developed was the micro-earthquake data processing and analysis system (MEPAS). 179 refs., 117 figs., 28 tabs.

  3. Understanding the True Stimulated Reservoir Volume in Shale Reservoirs

    KAUST Repository

    Hussain, Maaruf; Saad, Bilal; Negara, Ardiansyah; Sun, Shuyu

    2017-01-01

    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

  4. 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

  5. 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

  6. 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

  7. Oil recovery enhancement from fractured, low permeability reservoirs. Part 2, Annual report, October 1, 1990--September 31, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Poston, S.W.

    1991-12-31

    The results of the investigative efforts for this jointly funded DOE-State of Texas research project achieved during the 1990--1991 year may be summarized as follows: Geological Characterization -- Detailed maps of the development and hierarchical nature the fracture system exhibited by Austin Chalk outcrops were prepared. These results of these efforts were directly applied to the development of production decline type curves applicable to a dual fracture-matrix flow system. Analysis of production records obtained from Austin Chalk operators illustrated the utility of these type curves to determine relative fracture/matrix contributions and extent. Well-log response in Austin Chalk wells has been shown to be a reliable indicator of organic maturity. (VSP) Vertical-Seismic Profile data was used to use shear-wave splitting concepts to estimate fracture orientations. Several programs were to be written to facilitate analysis of the data. The results of these efforts indicated fractures could be detected with VSP seismic methods. Development of the (EOR) Enhanced Oil Recovery Imbibition Process -- Laboratory displacement as well as MRI and CT imaging studies have shown the carbonated water-imbibition displacement process significantly accelerates and increases recovery of an oil saturated, low permeability core material, when compared to that of a normal brine imbibition displacement process. A study of oil recovery by the application of a cyclic carbonated water imbibition process, followed by reducing the pressure below the bubble point of the CO{sub 2}-water solution, indicated the possibility of alternate and new enhanced recovery method. The installation of an artificial solution gas drive significantly increased oil recovery. The extent and arrangement of micro-fractures in Austin Chalk horizontal cores was mapped with CT scanning techniques. The degree of interconnection of the micro-fractures was easily visualized.

  8. Oil recovery enhancement from fractured, low permeability reservoirs. Annual report, October 1, 1990--September 31, 1991, Annex 4

    Energy Technology Data Exchange (ETDEWEB)

    Poston, S.W.

    1991-01-01

    The results of the investigative efforts for this jointly funded DOE-State of Texas research project achieved during the 1990-1991 year may be summarized as follows: Geological Characterization - Detailed maps of the development and hierarchical nature the fracture system exhibited by Austin Chalk outcrops were prepared. The results of these efforts were directly applied to the development of production decline type curves applicable to a dual-fracture-matrix flow system. Analysis of production records obtained from Austin Chalk operators illustrated the utility of these type curves to determine relative fracture/matrix contributions and extent. Well-log response in Austin Chalk wells has been shown to be a reliable indicator of organic maturity. Shear-wave splitting concepts were used to estimate fracture orientations from Vertical Seismic Profile, VSP data. Several programs were written to facilitate analysis of the data. The results of these efforts indicated fractures could be detected with VSP seismic methods.Development of the EOR Imbibition Process - Laboratory displacement as well as Magnetic Resonance Imaging, MRI and Computed Tomography, CT imaging studies have shown the carbonated water-imbibition displacement process significantly accelerates and increases recovery from oil saturated, low permeability rocks.Field Tests - Two operators amenable to conducting a carbonated water flood test on an Austin Chalk well have been identified. Feasibility studies are presently underway.

  9. 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.

  10. 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.

  11. Electricity generation from enhanced geothermal systems by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells: A case study in Xujiaweizi area in Daqing Oilfield, China

    International Nuclear Information System (INIS)

    Zhang, Yan-Jun; Li, Zheng-Wei; Guo, Liang-Liang; Gao, Ping; Jin, Xian-Peng; Xu, Tian-Fu

    2014-01-01

    In this paper, the feasibility of generating electricity from EGS (enhanced geothermal systems) by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells is investigated based on the geological data of Xujiaweizi area, located in the Daqing Oilfield, northeast China. HDR (hot dry rock) resource potential assessment is carried out by using volumetric method. Reservoir stimulation is numerically simulated based on the geological data of well YS-1 and field fracturing experience in this region. Geometric dimensions and flow conductivity of the resulting fracture are imported into the hydro-thermal model to calculate the electricity generation potential of the proposed EGS power plant. An EGS design scheme is proposed based on the simulation results. The system is also evaluated from the economic and environmental aspects. The results indicate that HDR resource in Xujiaweizi area is of great potential for development. Through the staged fracturing technology for horizontal wells, electricity generation power of the proposed EGS project can roughly meet the commercial standard. For 20 years of continuous production, power generation from the proposed EGS power plant is economic feasible. Meanwhile, significant reductions in greenhouse gas emissions can be achieved. - Highlights: • Staged fracturing technology for horizontal well is used in HDR (hot dry rock) development. • Fracturing simulations and heat production simulations are combined. • A 3 MW power plant is designed in Xujiaweizi based on the simulation results

  12. 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.

  13. 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

  14. 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.

  15. 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

    2018-05-01

    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.

  16. Contribution of the exploration of deep crystalline fractured reservoir of Soultz to the knowledge of enhanced geothermal systems (EGS)

    Science.gov (United States)

    Genter, Albert; Evans, Keith; Cuenot, Nicolas; Fritsch, Daniel; Sanjuan, Bernard

    2010-07-01

    Over the past 20 years, the Soultz experimental geothermal site in Alsace, France, has been explored in detail by the drilling of five boreholes, three of which extend to 5 km depth. Data on geology, fluid geochemistry, temperature, microseismicity, hydraulics and geomechanics have been collected and interpreted by the various teams from the participating European countries and their international collaborators. Two reservoirs have been developed within granite at depths of 3.5 and 5 km. The reservoir at 3.5 km was formed from two wells, 450 m apart, both of which were subjected to hydraulic stimulation injections. The system was circulated continuously for 4 months at 25 kg/s in 1997 using a downhole pump, and yielded results that were extremely encouraging. The impedance reduced to 0.1 MPa/l/s, the first time this long-standing target had been attained. Construction of a deeper system began shortly afterwards with the drilling of 3 deviated wells to 5 km true vertical depth, where the temperature was 200 °C. The wells were drilled in a line, 600 m apart at reservoir depth, and all were hydraulically stimulated and subjected to acidization injections. The 3-well system was circulated under buoyancy drive for 5 months in 2005 with injection in the central well, GPK-3, and production from the two outer wells, GPK-2 and GPK-4. This showed good linkage between one doublet pair, but not the other. Further acidization operations on the low-productivity well led to its productivity increasing to almost the same level as the other wells. Construction of a power plant at the site was completed in 2008 and a trial circulation with a production pump in one well and the other shut-in was conducted with power production. Downhole pumps are now installed in both production wells in preparation for long-term circulation of the system. In this article we present an overview of the principal accomplishments at Soultz over the past two decades, and highlight the main results

  17. 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

  18. 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

  19. Fiscal 1996 verification survey of geothermal exploration technology. Development of the fracture type reservoir exploration method (development of the elastic wave use exploration method); 1996 nendo chinetsu tansa gijutsu nado kensho chosa. Danretsugata choryuso tansaho kaihatsu (danseiha riyo tansaho kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    For the purpose of exploring accurately fracture groups greatly restricting the fluid flow of geothermal reservoirs, technical development was made for applying the elastic wave exploration technology such as the high precision reflection method, VSP, elastic wave tomography to the geothermal exploration. The Okiri area, Kagoshima prefecture was selected as a demonstrative field of a typical type where the steep and predominant fracture rules the geothermal reservoir, and experiments were conducted using the high precision reflection method and VSP. Fracture models were made, and the analysis results were studied by a survey using the array CSMT/MT method and by a comparison with existing data. Reformation of the underground receiving system used for VSP and elastic tomography is made for improvement of its viability, and was applied to the VSP experiment. The treatment/analysis system of the core analyzer was improved, and cores of the demonstrative field were analyzed/measured. Further, the exploration results, core analysis results and existing data were synthetically analyzed, and fracture models of the demonstrative field were constructed. Also, effectiveness and viability of the elastic wave use exploration method were studied. 90 refs., 418 figs., 24 tabs.

  20. 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

  1. Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

    Directory of Open Access Journals (Sweden)

    Adelinet M.

    2016-05-01

    Full Text Available The recent tomography results obtained within the scope of the Enhanced Geothermal System (EGS European Soultz project led us to revisit the meso-fracturing properties of Soultz test site. In this paper, we develop a novel approach coupling effective medium modeling and shear-wave splitting to characterize the evolution of crack properties throughout the hydraulic stimulation process. The stimulation experiment performed in 2000 consisted of 3 successive injection steps spanning over 6 days. An accurate 4-D tomographic image was first carried out based upon the travel-times measured for the induced seismicity [Calò M., Dorbath C., Cornet F.H., Cuenot N. (2011 Large-scale aseismic motion identified through 4-D P-wave tomography, Geophys. J. Int. 186, 1295-1314]. The current study shows how to take advantage of the resulting compressional wave (Calò et al., 2011 and shear-wave velocity models. These are given as input data to an anisotropic effective medium model and converted into crack properties. In short, the effective medium model aims to estimate the impact of cracks on velocities. It refers to a crack-free matrix and 2 families of penny-shaped cracks with orientations in agreement with the main observed geological features: North-South strike and dip of 65°East and 65°West [Genter A., Traineau H. (1996 Analysis of macroscopic fractures in granite in the HDR geothermal well EPS-1, Soultz-sous-Forêts, France, J. Vol. Geoth. Res. 72, 121-141], respectively. The resulting output data are the spatial distributions of crack features (lengths and apertures within the 3-D geological formation. We point out that a flow rate increase results in a crack shortening in the area imaged by both compressional and shear waves, especially in the upper part of the reservoir. Conversely, the crack length, estimated during continuous injection rate phases, is higher than during the increasing injection rate phases. A possible explanation for this is that

  2. 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.

  3. Fiscal 1997 report on the survey of verification of geothermal exploration technology, etc. 1. Development of the reservoir variation exploration method (development of the fracture hydraulic exploration method); 1997 nendo chinetsu tansa gijutsu nado kensho chosa. Choryuso hendo tansaho kaihatsu (danretsu suiri tansaho kaihatsu) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    The paper described the fiscal 1997 result of the fracture hydraulic exploration method as the variation exploration method of geothermal reservoirs. By elucidating hydraulic characteristics of the fracture system forming reservoir, technologies are established which are effective for the reservoir evaluation in early stages of development, maintenance of stable power after operational start-up, and extraction of peripheral reservoirs. As for the pressure transient test method, a test supporting system was basically designed to obtain high accuracy hydraulic parameters. As to the tiltmeter fracture monitoring method, a simulation was made for distribution of active fractures and evaluation of hydraulic constants without drilling wells. In relation to the two-phase flow measuring method, for stable steam production, the use of the orifice plate, the existing flow measuring method, etc. was forecast as a simple measuring method of the two-phase state of reservoir. Concerning the hydrophone VSP method, a feasibility study was made of the practical VSP for high temperature which can analyze hydraulic characteristics and geological structures around the well at the same time which the existing methods were unable to grasp, and brought the results. Moreover, to make high accuracy reservoir modeling possible, Doppler borehole televiewer was made in each reservoir. 80 refs., 147 figs., 22 tabs.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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

  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

    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

  13. 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

  14. 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 neural 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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.

  1. Lower Palaeozoic reservoirs of North Africa

    Energy Technology Data Exchange (ETDEWEB)

    Crossley, R.; McDougall, N. [Robertson Research International Ltd., Llandudno, Conwy (United Kingdom)

    1998-12-31

    This paper provides an overview of features considered significant in the exploration and development of Lower Palaeozoic reservoirs of North Africa. Information is derived from a review of literature on the Lower Palaeozoic successions of North Africa, combined with outcrop observations from the Anti Atlas mountains of Morocco. The focus of the exploration-oriented part of the review is on identification of potential traps other than two-way structural dip closure. Stratigraphic elements described include depositional models of reservoir facies, tectonic unconformities and possible eustatic unconformities. Cases of established or potential trapping by post-depositional faulting by diagenesis and by hydrodynamic flow are examined. Development-related topics highlighted include the impact on reservoir matrix quality of burial diagenesis and of palaeo-weathering at the Hercynian unconformity. Other issues discussed which additionally affect producibility from the reservoir matrix include tectonic fracturing, palaeotopography and unloading fracturing at the Hercynian unconformity, and induced fracturing within the present stress regimes. (author)

  2. 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.

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

    African Journals Online (AJOL)

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

  4. 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

  5. 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

  6. 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.

  7. Method of extracting heat from dry geothermal reservoirs

    Science.gov (United States)

    Potter, R.M.; Robinson, E.S.; Smith, M.C.

    1974-01-22

    Hydraulic fracturing is used to interconnect two or more holes that penetrate a previously dry geothermal reservoir, and to produce within the reservoir a sufficiently large heat-transfer surface so that heat can be extracted from the reservoir at a usefully high rate by a fluid entering it through one hole and leaving it through another. Introduction of a fluid into the reservoir to remove heat from it and establishment of natural (unpumped) convective circulation through the reservoir to accomplish continuous heat removal are important and novel features of the method. (auth)

  8. Growth Kinematics of Opening-Mode Fractures

    Science.gov (United States)

    Eichhubl, P.; Alzayer, Y.; Laubach, S.; Fall, A.

    2014-12-01

    Fracture aperture is a primary control on flow in fractured reservoirs of low matrix permeability including unconventional oil and gas reservoirs and most geothermal systems. Guided by principles of linear elastic fracture mechanics, fracture aperture is generally assumed to be a linear function of fracture length and elastic material properties. Natural opening-mode fractures with significant preserved aperture are observed in core and outcrop indicative of fracture opening strain accommodated by permanent solution-precipitation creep. Fracture opening may thus be decoupled from length growth if the material effectively weakens after initial elastic fracture growth by either non-elastic deformation processes or changes in elastic properties. To investigate the kinematics of fracture length and aperture growth, we reconstructed the opening history of three opening-mode fractures that are bridged by crack-seal quartz cement in Travis Peak Sandstone of the SFOT-1 well, East Texas. Similar crack-seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement. We imaged crack-seal cement textures for bridges sampled at varying distance from the tips using scanning electron microscope cathodoluminescence, and determined the number and thickness of crack-seal cement increments as a function of position along the fracture length and height. Observed trends in increment number and thickness are consistent with an initial stage of fast fracture propagation relative to aperture growth, followed by a stage of slow propagation and pronounced aperture growth. Consistent with fluid inclusion observations indicative of fracture opening and propagation occurring over 30-40 m.y., we interpret the second phase of pronounced aperture growth to result from fracture opening strain accommodated by solution-precipitation creep and concurrent slow, possibly subcritical, fracture propagation. Similar deformation

  9. 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.)

  10. Fiscal 1999 research and verification of geothermal energy exploring technologies and the like. Development of reservoir mass and heat flow characterization (Development of fracture hydrological properties characterization technology - Summary); 1999 nendo chinetsu tansa gijutsu nado kensho chosa hokokusho (yoyaku). Choryuso hendo tansaho kaihatsu (danretsu suiri tansaho kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Efforts are under way to develop reservoir change evaluation technologies to be effective in evaluating reservoirs at their initial stage of development, in stabilizing the output of power stations after their commencement of service operation, and in probing into reservoirs in already-developed areas. One of them concerns the characterization of the hydrological properties of fractures. The development efforts involve (1) a pressure transient test method (measurement of the response of reservoirs to changes in borehole internal pressure), (2) a tiltmeter observation method (ground surface deformation measurement), and (3) a 2-phase flow metering method (metering of spurting fluids). Under item (1), a computer-aided borehole hydrology test system is built and field-tested to isolate problems. Also, a pressure transient test system is built by way of trial by use of which compressor-aided control is performed over air pressure in the borehole. Under item (2), it is made clear that changes, several MPa in scale, in the pressure in a borehole is detected by simulation and that a sufficiently capable system is realized using a tiltmeter available on the market. Under item (3), a device is fabricated which is a combination of a laser flowmeter and a void fraction meter, and a field test is conducted to assess its feasibility and to identify problems. (NEDO)

  11. Tuning Fractures With Dynamic Data

    Science.gov (United States)

    Yao, Mengbi; Chang, Haibin; Li, Xiang; Zhang, Dongxiao

    2018-02-01

    Flow in fractured porous media is crucial for production of oil/gas reservoirs and exploitation of geothermal energy. Flow behaviors in such media are mainly dictated by the distribution of fractures. Measuring and inferring the distribution of fractures is subject to large uncertainty, which, in turn, leads to great uncertainty in the prediction of flow behaviors. Inverse modeling with dynamic data may assist to constrain fracture distributions, thus reducing the uncertainty of flow prediction. However, inverse modeling for flow in fractured reservoirs is challenging, owing to the discrete and non-Gaussian distribution of fractures, as well as strong nonlinearity in the relationship between flow responses and model parameters. In this work, building upon a series of recent advances, an inverse modeling approach is proposed to efficiently update the flow model to match the dynamic data while retaining geological realism in the distribution of fractures. In the approach, the Hough-transform method is employed to parameterize non-Gaussian fracture fields with continuous parameter fields, thus rendering desirable properties required by many inverse modeling methods. In addition, a recently developed forward simulation method, the embedded discrete fracture method (EDFM), is utilized to model the fractures. The EDFM maintains computational efficiency while preserving the ability to capture the geometrical details of fractures because the matrix is discretized as structured grid, while the fractures being handled as planes are inserted into the matrix grids. The combination of Hough representation of fractures with the EDFM makes it possible to tune the fractures (through updating their existence, location, orientation, length, and other properties) without requiring either unstructured grids or regridding during updating. Such a treatment is amenable to numerous inverse modeling approaches, such as the iterative inverse modeling method employed in this study, which is

  12. Flow and contaminant transport in fractured rocks

    International Nuclear Information System (INIS)

    Bear, J.; Tsang, C.F.; Marsily, G. de

    1993-01-01

    This book is a compilation of nine articles dealing with various aspect of flow in fractured media. Articles range from radionuclide waste to multiphase flow in petroleum reservoirs to practical field test methods. Each chapter contains copious figures to aid the reader, but is also a detailed in-depth analysis of some major flow problem. The subjects covered are as follows: an introduction to flow and transport models; solute transport in fractured rock with application to radioactive waste repositories; solute transport models through fractured networks; theoretical view of stochastic models of fracture systems; numerical models of tracers; multiphase flow models in fractured systems and petroleum reservoirs; unsaturated flow modeling; comparative analysis of various flow modeling techniques in fractured media; and, a summary of field methods for measuring transfers of mass, heat, contaminant, momentum, and electrical charge in fractured media

  13. 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.

  14. Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method

    OpenAIRE

    Huang Bo; Cheng Hao; He Yidong; Fu Yanming

    2017-01-01

    The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc.), high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the ...

  15. 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.

  16. Geophysical monitoring in a hydrocarbon reservoir

    Science.gov (United States)

    Caffagni, Enrico; Bokelmann, Goetz

    2016-04-01

    Extraction of hydrocarbons from reservoirs demands ever-increasing technological effort, and there is need for geophysical monitoring to better understand phenomena occurring within the reservoir. Significant deformation processes happen when man-made stimulation is performed, in combination with effects deriving from the existing natural conditions such as stress regime in situ or pre-existing fracturing. Keeping track of such changes in the reservoir is important, on one hand for improving recovery of hydrocarbons, and on the other hand to assure a safe and proper mode of operation. Monitoring becomes particularly important when hydraulic-fracturing (HF) is used, especially in the form of the much-discussed "fracking". HF is a sophisticated technique that is widely applied in low-porosity geological formations to enhance the production of natural hydrocarbons. In principle, similar HF techniques have been applied in Europe for a long time in conventional reservoirs, and they will probably be intensified in the near future; this suggests an increasing demand in technological development, also for updating and adapting the existing monitoring techniques in applied geophysics. We review currently available geophysical techniques for reservoir monitoring, which appear in the different fields of analysis in reservoirs. First, the properties of the hydrocarbon reservoir are identified; here we consider geophysical monitoring exclusively. The second step is to define the quantities that can be monitored, associated to the properties. We then describe the geophysical monitoring techniques including the oldest ones, namely those in practical usage from 40-50 years ago, and the most recent developments in technology, within distinct groups, according to the application field of analysis in reservoir. This work is performed as part of the FracRisk consortium (www.fracrisk.eu); this project, funded by the Horizon2020 research programme, aims at helping minimize the

  17. 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

  18. 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

  19. 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.

  20. 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°.

  1. 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.

  2. 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.

  3. 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

  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. SILTATION IN RESERVOIRS

    African Journals Online (AJOL)

    Keywords: reservoir model, siltation, sediment, catchment, sediment transport. 1. Introduction. Sediment ... rendered water storage structures useless in less than 25 years. ... reservoir, thus reducing the space available for water storage and ...

  6. Reservoir fisheries of Asia

    International Nuclear Information System (INIS)

    Silva, S.S. De.

    1990-01-01

    At a workshop on reservoir fisheries research, papers were presented on the limnology of reservoirs, the changes that follow impoundment, fisheries management and modelling, and fish culture techniques. Separate abstracts have been prepared for three papers from this workshop

  7. 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

  8. Large reservoirs: Chapter 17

    Science.gov (United States)

    Miranda, Leandro E.; Bettoli, Phillip William

    2010-01-01

    Large impoundments, defined as those with surface area of 200 ha or greater, are relatively new aquatic ecosystems in the global landscape. They represent important economic and environmental resources that provide benefits such as flood control, hydropower generation, navigation, water supply, commercial and recreational fisheries, and various other recreational and esthetic values. Construction of large impoundments was initially driven by economic needs, and ecological consequences received little consideration. However, in recent decades environmental issues have come to the forefront. In the closing decades of the 20th century societal values began to shift, especially in the developed world. Society is no longer willing to accept environmental damage as an inevitable consequence of human development, and it is now recognized that continued environmental degradation is unsustainable. Consequently, construction of large reservoirs has virtually stopped in North America. Nevertheless, in other parts of the world construction of large reservoirs continues. The emergence of systematic reservoir management in the early 20th century was guided by concepts developed for natural lakes (Miranda 1996). However, we now recognize that reservoirs are different and that reservoirs are not independent aquatic systems inasmuch as they are connected to upstream rivers and streams, the downstream river, other reservoirs in the basin, and the watershed. Reservoir systems exhibit longitudinal patterns both within and among reservoirs. Reservoirs are typically arranged sequentially as elements of an interacting network, filter water collected throughout their watersheds, and form a mosaic of predictable patterns. Traditional approaches to fisheries management such as stocking, regulating harvest, and in-lake habitat management do not always produce desired effects in reservoirs. As a result, managers may expend resources with little benefit to either fish or fishing. Some locally

  9. 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 ...

  10. Application of Reservoir Characterization and Advanced Technology to Improve Recovery and Economics in a Lower Quality Shallow Shelf Carbonate Reservoir

    International Nuclear Information System (INIS)

    Taylor, Archie R.

    1996-01-01

    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) Cross-well bore tomography; (4) Advanced reservoir simulation; (5) Carbon dioxide (CO 2 ) stimulation treatments; (6) Hydraulic fracturing design and monitoring; and (7) Mobility control agents

  11. 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

  12. Importance of water Influx and waterflooding in Gas condensate reservoir

    OpenAIRE

    Ali, Faizan

    2014-01-01

    The possibility of losing valuable liquid and lower gas well deliverability have made gas condensate reservoirs very important and extra emphasizes are made to optimize hydrocarbon recovery from a gas condensate reservoir. Methods like methanol treatments, wettability alteration and hydraulic fracturing are done to restore the well deliverability by removing or by passing the condensate blockage region. The above mentioned methods are applied in the near wellbore region and only improve the w...

  13. Quantifying Discrete Fracture Network Connectivity in Hydraulic Fracturing Stimulation

    Science.gov (United States)

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

    2017-12-01

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

  14. 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.

  15. Advances in carbonate exploration and reservoir analysis

    Science.gov (United States)

    Garland, J.; Neilson, J.; Laubach, S.E.; Whidden, Katherine J.

    2012-01-01

    The development of innovative techniques and concepts, and the emergence of new plays in carbonate rocks are creating a resurgence of oil and gas discoveries worldwide. The maturity of a basin and the application of exploration concepts have a fundamental influence on exploration strategies. Exploration success often occurs in underexplored basins by applying existing established geological concepts. This approach is commonly undertaken when new basins ‘open up’ owing to previous political upheavals. The strategy of using new techniques in a proven mature area is particularly appropriate when dealing with unconventional resources (heavy oil, bitumen, stranded gas), while the application of new play concepts (such as lacustrine carbonates) to new areas (i.e. ultra-deep South Atlantic basins) epitomizes frontier exploration. Many low-matrix-porosity hydrocarbon reservoirs are productive because permeability is controlled by fractures and faults. Understanding basic fracture properties is critical in reducing geological risk and therefore reducing well costs and increasing well recovery. The advent of resource plays in carbonate rocks, and the long-standing recognition of naturally fractured carbonate reservoirs means that new fracture and fault analysis and prediction techniques and concepts are essential.

  16. Using reservoir engineering data to solve geological ambiguities : a case study of one of the Iranian carbonate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Kord, S. [National Iranian South Oil Co. (Iran, Islamic Republic of)

    2006-07-01

    A fractured carbonate reservoir in southwest Iran was studied with reference to reserve estimation, risk analysis, material balance and recovery factor. The 40 km long and 4 km wide reservoir consists of 2 parts with crest depths of 3780 and 3749 mss respectively. The eastern part is smaller and more productive than the western part which has high water saturation and absolutely no production. Economic production from the reservoir began in 1977. By 2004, the cumulative production had reached 12.064 MMSTB. Of the 6 wells drilled, only 2 wells in the eastern part are productive. This study addressed the main uncertainty of whether the 2 parts of the reservoir are sealed or not. The reservoir is under-saturated but the current pressure is near saturation pressure. The reservoir is divided into the following 4 zones: zones 1 and 2 are productive and consist mainly of carbonate rocks; zone 3 has thin beds of sand and shale; and, zone 4 consists of layers of carbonate, shale, marn, and dolomite. Although there are no faults, mud loss suggests that the reservoir has hairline fractures. Oil in place and reserves were estimated for both parts based on calculated reservoir engineering parameters. Material balance calculations were then performed to analyze and simulate the reservoir. The communication between the 2 parts of the reservoir were examined according to core analysis, rock type, fluid characterization, pressure analysis, water-oil contacts, production history and petrophysical evaluations. The porosity was found to be the same in both parts, but the water saturation and net to gross ratios were different between the eastern and western parts. The petrophysical evaluation revealed that there is no communication between the two parts of the reservoir. 4 refs., 2 figs., 2 appendices.

  17. 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.

  18. Rib Fractures

    Science.gov (United States)

    ... Video) Achilles Tendon Tear Additional Content Medical News Rib Fractures By Thomas G. Weiser, MD, MPH, Associate Professor, ... Tamponade Hemothorax Injury to the Aorta Pulmonary Contusion Rib Fractures Tension Pneumothorax Traumatic Pneumothorax (See also Introduction to ...

  19. Root fractures

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

    2012-01-01

    The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

  20. Fortescue reservoir development and reservoir studies

    Energy Technology Data Exchange (ETDEWEB)

    Henzell, S.T.; Hicks, G.J.; Horden, M.J.; Irrgang, H.R.; Janssen, E.J.; Kable, C.W.; Mitchell, R.A.H.; Morrell, N.W.; Palmer, I.D.; Seage, N.W.

    1985-03-01

    The Fortescue field in the Gippsland Basin, offshore southeastern Australia is being developed from two platforms (Fortescue A and Cobia A) by Esso Australia Ltd. (operator) and BHP Petroleum. The Fortescue reservoir is a stratigraphic trap at the top of the Latrobe Group of sediments. It overlies the western flank of the Halibut and Cobia fields and is separated from them by a non-net sequence of shales and coals which form a hydraulic barrier between the two systems. Development drilling into the Fortescue reservoir commenced in April 1983 with production coming onstream in May 1983. Fortescue, with booked reserves of 44 stock tank gigalitres (280 million stock tank barrels) of 43/sup 0/ API oil, is the seventh major oil reservoir to be developed in the offshore Gippsland Basin by Esso/BHP. In mid-1984, after drilling a total of 20 exploration and development wells, and after approximately one year of production, a detailed three-dimensional, two-phase reservoir simulation study was performed to examine the recovery efficiency, drainage patterns, pressure performance and production rate potential of the reservoir. The model was validated by history matching an extensive suite of Repeat Formation Test (RFT) pressure data. The results confirmed the reserves basis, and demonstrated that the ultimate oil recovery from the reservoir is not sensitive to production rate. This result is consistent with studies on other high quality Latrobe Group reservoirs in the Gippsland Basin which contain undersaturated crudes and receive very strong water drive from the Basin-wide aquifer system. With the development of the simulation model during the development phase, it has been possible to more accurately define the optimal well pattern for the remainder of the development.

  1. Improved characterization of reservoir behavior by integration of reservoir performances data and rock type distributions

    Energy Technology Data Exchange (ETDEWEB)

    Davies, D.K.; Vessell, R.K. [David K. Davies & Associates, Kingwood, TX (United States); Doublet, L.E. [Texas A& M Univ., College Station, TX (United States)] [and others

    1997-08-01

    An integrated geological/petrophysical and reservoir engineering study was performed for a large, mature waterflood project (>250 wells, {approximately}80% water cut) at the North Robertson (Clear Fork) Unit, Gaines County, Texas. The primary goal of the study was to develop an integrated reservoir description for {open_quotes}targeted{close_quotes} (economic) 10-acre (4-hectare) infill drilling and future recovery operations in a low permeability, carbonate (dolomite) reservoir. Integration of the results from geological/petrophysical studies and reservoir performance analyses provide a rapid and effective method for developing a comprehensive reservoir description. This reservoir description can be used for reservoir flow simulation, performance prediction, infill targeting, waterflood management, and for optimizing well developments (patterns, completions, and stimulations). The following analyses were performed as part of this study: (1) Geological/petrophysical analyses: (core and well log data) - {open_quotes}Rock typing{close_quotes} based on qualitative and quantitative visualization of pore-scale features. Reservoir layering based on {open_quotes}rock typing {close_quotes} and hydraulic flow units. Development of a {open_quotes}core-log{close_quotes} model to estimate permeability using porosity and other properties derived from well logs. The core-log model is based on {open_quotes}rock types.{close_quotes} (2) Engineering analyses: (production and injection history, well tests) Material balance decline type curve analyses to estimate total reservoir volume, formation flow characteristics (flow capacity, skin factor, and fracture half-length), and indications of well/boundary interference. Estimated ultimate recovery analyses to yield movable oil (or injectable water) volumes, as well as indications of well and boundary interference.

  2. Stress Fractures

    Science.gov (United States)

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

  3. Transport of reservoir fines

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander; Stenby, Erling Halfdan

    Modeling transport of reservoir fines is of great importance for evaluating the damage of production wells and infectivity decline. The conventional methodology accounts for neither the formation heterogeneity around the wells nor the reservoir fines’ heterogeneity. We have developed an integral...... dispersion equation in modeling the transport and the deposition of reservoir fines. It successfully predicts the unsymmetrical concentration profiles and the hyperexponential deposition in experiments....

  4. 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....... aperture in the adjacent fracture, and facilitates the creation of favourable flow pathways between the injection and production wells. These flow paths reduce the energy production from the system. The effects of fracture spacing, reservoir temperature gradient and mechanical properties of the rock matrix...

  5. Paragenetic evolution of reservoir facies, Middle Triassic Halfway Formation, PeeJay Field, northeastern British Columbia: controls on reservoir quality

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, M. L. [Alberta Univ., Dept. of Earth and Atmospheric Sciences, Edmonton, AB (Canada); Moslow, T. F. [Ulster Petroleum Ltd., Calgary, AB (Canada)

    1998-09-01

    Because of the obvious importance of reservoir quality to reservoir performance, diagenetic controls on reservoir quality of Middle Triassic reservoir facies are investigated by comparing two reservoir lithofacies. The implications of porosity structure on the efficiency of primary and secondary hydrocarbon recovery are also assessed. Halfway reservoir facies are composed of bioclastic grainstones (lithofacies G) and litharenites/sublitharenites (lithofacies H), both of which are interpreted as tidal inlet fills. Although paragenetic evolution was similar for the two reservoir facies, subtle differences in reservoir quality are discernible. These are controlled by sedimentary structures, porosity type, grain constituents, and degree of cementation. Reservoir quality in lithofacies G is a function of connectivity of the pore network. In lithofacies H, secondary granular porosity creates a more homogeneous interconnected pore system, wide pore throats and low aspect ratios. The high porosity and low permeability values of the bioclastic grainstones are suspected to cause inefficient flushing of hydrocarbons during waterflooding. However, it is suggested that recovery may be enhanced by induced hydraulic fracturing and acidization of lower permeability calcareous cemented zones. 52 refs., 15 figs.

  6. Hydrogen fracture toughness tester completion

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Michael J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-09-30

    The Hydrogen Fracture Toughness Tester (HFTT) is a mechanical testing machine designed for conducting fracture mechanics tests on materials in high-pressure hydrogen gas. The tester is needed for evaluating the effects of hydrogen on the cracking properties of tritium reservoir materials. It consists of an Instron Model 8862 Electromechanical Test Frame; an Autoclave Engineering Pressure Vessel, an Electric Potential Drop Crack Length Measurement System, associated computer control and data acquisition systems, and a high-pressure hydrogen gas manifold and handling system.

  7. Compartmentalization analysis using discrete fracture network models

    Energy Technology Data Exchange (ETDEWEB)

    La Pointe, P.R.; Eiben, T.; Dershowitz, W. [Golder Associates, Redmond, VA (United States); Wadleigh, E. [Marathon Oil Co., Midland, TX (United States)

    1997-08-01

    This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph the theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.

  8. Microseismic Velocity Imaging of the Fracturing Zone

    Science.gov (United States)

    Zhang, H.; Chen, Y.

    2015-12-01

    Hydraulic fracturing of low permeability reservoirs can induce microseismic events during fracture development. For this reason, microseismic monitoring using sensors on surface or in borehole have been widely used to delineate fracture spatial distribution and to understand fracturing mechanisms. It is often the case that the stimulated reservoir volume (SRV) is determined solely based on microseismic locations. However, it is known that for some fracture development stage, long period long duration events, instead of microseismic events may be associated. In addition, because microseismic events are essentially weak and there exist different sources of noise during monitoring, some microseismic events could not be detected and thus located. Therefore the estimation of the SRV is biased if it is solely determined by microseismic locations. With the existence of fluids and fractures, the seismic velocity of reservoir layers will be decreased. Based on this fact, we have developed a near real time seismic velocity tomography method to characterize velocity changes associated with fracturing process. The method is based on double-difference seismic tomography algorithm to image the fracturing zone where microseismic events occur by using differential arrival times from microseismic event pairs. To take into account varying data distribution for different fracking stages, the method solves the velocity model in the wavelet domain so that different scales of model features can be obtained according to different data distribution. We have applied this real time tomography method to both acoustic emission data from lab experiment and microseismic data from a downhole microseismic monitoring project for shale gas hydraulic fracturing treatment. The tomography results from lab data clearly show the velocity changes associated with different rock fracturing stages. For the field data application, it shows that microseismic events are located in low velocity anomalies. By

  9. Reservoir Engineering Management Program

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J.H.; Schwarz, W.J.

    1977-12-14

    The Reservoir Engineering Management Program being conducted at Lawrence Berkeley Laboratory includes two major tasks: 1) the continuation of support to geothermal reservoir engineering related work, started under the NSF-RANN program and transferred to ERDA at the time of its formation; 2) the development and subsequent implementation of a broad plan for support of research in topics related to the exploitation of geothermal reservoirs. This plan is now known as the GREMP plan. Both the NSF-RANN legacies and GREMP are in direct support of the DOE/DGE mission in general and the goals of the Resource and Technology/Resource Exploitation and Assessment Branch in particular. These goals are to determine the magnitude and distribution of geothermal resources and reduce risk in their exploitation through improved understanding of generically different reservoir types. These goals are to be accomplished by: 1) the creation of a large data base about geothermal reservoirs, 2) improved tools and methods for gathering data on geothermal reservoirs, and 3) modeling of reservoirs and utilization options. The NSF legacies are more research and training oriented, and the GREMP is geared primarily to the practical development of the geothermal reservoirs. 2 tabs., 3 figs.

  10. Acetabular Fracture

    Directory of Open Access Journals (Sweden)

    Chad Correa

    2017-09-01

    Full Text Available History of present illness: A 77-year-old female presented to her primary care physician (PCP with right hip pain after a mechanical fall. She did not lose consciousness or have any other traumatic injuries. She was unable to ambulate post-fall, so X-rays were ordered by her PCP. Her X-rays were concerning for a right acetabular fracture (see purple arrows, so the patient was referred to the emergency department where a computed tomography (CT scan was ordered. Significant findings: The non-contrast CT images show a minimally displaced comminuted fracture of the right acetabulum involving the acetabular roof, medial and anterior walls (red arrows, with associated obturator muscle hematoma (blue oval. Discussion: Acetabular fractures are quite rare. There are 37 pelvic fractures per 100,000 people in the United States annually, and only 10% of these involve the acetabulum. They occur more frequently in the elderly totaling an estimated 4,000 per year. High-energy trauma is the primary cause of acetabular fractures in younger individuals and these fractures are commonly associated with other fractures and pelvic ring disruptions. Fractures secondary to moderate or minimal trauma are increasingly of concern in patients of advanced age.1 Classification of acetabular fractures can be challenging. However, the approach can be simplified by remembering the three basic types of acetabular fractures (column, transverse, and wall and their corresponding radiologic views. First, column fractures should be evaluated with coronally oriented CT images. This type of fracture demonstrates a coronal fracture line running caudad to craniad, essentially breaking the acetabulum into two halves: a front half and a back half. Secondly, transverse fractures should be evaluated by sagittally oriented CT images. By definition, a transverse fracture separates the acetabulum into superior and inferior halves with the fracture line extending from anterior to posterior

  11. Hydraulic fracturing proppants

    Directory of Open Access Journals (Sweden)

    V. P. P. de Campos

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

  12. Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method

    Directory of Open Access Journals (Sweden)

    Huang Bo

    2017-01-01

    Full Text Available The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc., high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the fracturing success rate. 4 out of 12 fracturing wells in the field have failed to add enough proppants due to fluid loss. In order to increase the success rate and efficiency of hydraulic fracturing for deep volcanic reservoir, based on theoretical and experimental method, the mechanism of fracturing fluid leak-off is deeply studied. We propose a dualistic proppant scheme and employ the fluid loss reducer to control the fluid leak-off in macro-fractures and micro-fractures respectively. The proposed technique remarkably improved the success rate in deep volcanic rock fracturing. It bears important theoretical value and practical significance to improve the hydraulic fracturing design for deep volcanic reservoir.

  13. Scale Model Simulation of Enhanced Geothermal Reservoir Creation

    Science.gov (United States)

    Gutierrez, M.; Frash, L.; Hampton, J.

    2012-12-01

    Geothermal energy technology has successfully provided a means of generating stable base load electricity for many years. However, implementation has been spatially limited to limited availability of high quality traditional hydro-thermal resources possessing the combination of a shallow high heat flow anomaly and an aquifer with sufficient permeability and continuous fluid recharge. Enhanced Geothermal Systems (EGS) has been proposed as a potential solution to enable additional energy production from the non-conventional hydro-thermal resources. Hydraulic fracturing is considered the primary means of creating functional EGS reservoirs at sites where the permeability of the rock is too limited to allow cost effective heat recovery. EGS reservoir creation requires improved fracturing methodology, rheologically controllable fracturing fluids, and temperature hardened proppants. Although large fracture volumes (several cubic km) have been created in the field, circulating fluid through these full volumes and maintaining fracture volumes have proven difficult. Stimulation technology and methodology as used in the oil and gas industry for sedimentary formations are well developed; however, they have not sufficiently been demonstrated for EGS reservoir creation. Insufficient data and measurements under geothermal conditions make it difficult to directly translate experience from the oil and gas industries to EGS applications. To demonstrate the feasibility of EGS reservoir creation and subsequent geothermal energy production, and to improve the understanding of hydraulic and propping in EGS reservoirs, a heated true-triaxial load cell with a high pressure fluid injection system was developed to simulate an EGS system from stimulation to production. This apparatus is capable of loading a 30x30x30 cubic cm rock sample with independent principal stresses up to 13 MPa while simultaneously providing heating up to 180 degree C. Multiple orientated boreholes of 5 to 10 mm

  14. Sedimentary facies control on mechanical and fracture stratigraphy in turbidites

    NARCIS (Netherlands)

    Ogata, Kei; Storti, Fabrizio; Balsamo, Fabrizio; Tinterri, Roberto; Bedogni, Enrico; Fetter, Marcos; Gomes, Leonardo; Hatushika, Raphael

    2017-01-01

    Natural fracture networks exert a first-order control on the exploitation of resources such as aquifers, hydrocarbons, and geothermal reservoirs, and on environmental issues like underground gas storage and waste disposal. Fractures and the mechanical stratigraphy of layered sequences have been

  15. Geological model of supercritical geothermal reservoir related to subduction system

    Science.gov (United States)

    Tsuchiya, Noriyoshi

    2017-04-01

    Following the Great East Japan Earthquake and the accident at the Fukushima Daiichi Nuclear power station on 3.11 (11th March) 2011, geothermal energy came to be considered one of the most promising sources of renewable energy for the future in Japan. The temperatures of geothermal fields operating in Japan range from 200 to 300 °C (average 250 °C), and the depths range from 1000 to 2000 m (average 1500 m). In conventional geothermal reservoirs, the mechanical behavior of the rocks is presumed to be brittle, and convection of the hydrothermal fluid through existing network is the main method of circulation in the reservoir. In order to minimize induced seismicity, a rock mass that is "beyond brittle" is one possible candidate, because the rock mechanics of "beyond brittle" material is one of plastic deformation rather than brittle failure. Supercritical geothermal resources could be evaluated in terms of present volcanic activities, thermal structure, dimension of hydrothermal circulation, properties of fracture system, depth of heat source, depth of brittle factures zone, dimension of geothermal reservoir. On the basis of the GIS, potential of supercritical geothermal resources could be characterized into the following four categories. 1. Promising: surface manifestation d shallow high temperature, 2 Probability: high geothermal gradient, 3 Possibility: Aseismic zone which indicates an existence of melt, 4 Potential : low velocity zone which indicates magma input. Base on geophysical data for geothermal reservoirs, we have propose adequate tectonic model of development of the supercritical geothermal reservoirs. To understand the geological model of a supercritical geothermal reservoir, granite-porphyry system, which had been formed in subduction zone, was investigated as a natural analog of the supercritical geothermal energy system. Quartz veins, hydrothermal breccia veins, and glassy veins are observed in a granitic body. The glassy veins formed at 500-550

  16. Mandible Fractures.

    Science.gov (United States)

    Pickrell, Brent B; Serebrakian, Arman T; Maricevich, Renata S

    2017-05-01

    Mandible fractures account for a significant portion of maxillofacial injuries and the evaluation, diagnosis, and management of these fractures remain challenging despite improved imaging technology and fixation techniques. Understanding appropriate surgical management can prevent complications such as malocclusion, pain, and revision procedures. Depending on the type and location of the fractures, various open and closed surgical reduction techniques can be utilized. In this article, the authors review the diagnostic evaluation, treatment options, and common complications of mandible fractures. Special considerations are described for pediatric and atrophic mandibles.

  17. Sediment management for reservoir

    International Nuclear Information System (INIS)

    Rahman, A.

    2005-01-01

    All natural lakes and reservoirs whether on rivers, tributaries or off channel storages are doomed to be sited up. Pakistan has two major reservoirs of Tarbela and Managla and shallow lake created by Chashma Barrage. Tarbela and Mangla Lakes are losing their capacities ever since first impounding, Tarbela since 1974 and Mangla since 1967. Tarbela Reservoir receives average annual flow of about 62 MAF and sediment deposits of 0.11 MAF whereas Mangla gets about 23 MAF of average annual flows and is losing its storage at the rate of average 34,000 MAF annually. The loss of storage is a great concern and studies for Tarbela were carried out by TAMS and Wallingford to sustain its capacity whereas no study has been done for Mangla as yet except as part of study for Raised Mangla, which is only desk work. Delta of Tarbala reservoir has advanced to about 6.59 miles (Pivot Point) from power intakes. In case of liquefaction of delta by tremor as low as 0.12g peak ground acceleration the power tunnels I, 2 and 3 will be blocked. Minimum Pool of reservoir is being raised so as to check the advance of delta. Mangla delta will follow the trend of Tarbela. Tarbela has vast amount of data as reservoir is surveyed every year, whereas Mangla Reservoir survey was done at five-year interval, which has now been proposed .to be reduced to three-year interval. In addition suspended sediment sampling of inflow streams is being done by Surface Water Hydrology Project of WAPDA as also some bed load sampling. The problem of Chasma Reservoir has also been highlighted, as it is being indiscriminately being filled up and drawdown several times a year without regard to its reaction to this treatment. The Sediment Management of these reservoirs is essential and the paper discusses pros and cons of various alternatives. (author)

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

    Directory of Open Access Journals (Sweden)

    Yongming Li

    2018-02-01

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

  19. Coupled Fracture and Flow in Shale in Hydraulic Fracturing

    Science.gov (United States)

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

    2014-12-01

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

  20. Optimising reservoir operation

    DEFF Research Database (Denmark)

    Ngo, Long le

    Anvendelse af optimeringsteknik til drift af reservoirer er blevet et væsentligt element i vandressource-planlægning og -forvaltning. Traditionelt har reservoirer været styret af heuristiske procedurer for udtag af vand, suppleret i en vis udstrækning af subjektive beslutninger. Udnyttelse af...... reservoirer involverer en lang række interessenter med meget forskellige formål (f.eks. kunstig vanding, vandkraft, vandforsyning mv.), og optimeringsteknik kan langt bedre lede frem til afbalancerede løsninger af de ofte modstridende interesser. Afhandlingen foreslår en række tiltag, hvormed traditionelle...

  1. Facial Fractures.

    Science.gov (United States)

    Ghosh, Rajarshi; Gopalkrishnan, Kulandaswamy

    2018-06-01

    The aim of this study is to retrospectively analyze the incidence of facial fractures along with age, gender predilection, etiology, commonest site, associated dental injuries, and any complications of patients operated in Craniofacial Unit of SDM College of Dental Sciences and Hospital. This retrospective study was conducted at the Department of OMFS, SDM College of Dental Sciences, Dharwad from January 2003 to December 2013. Data were recorded for the cause of injury, age and gender distribution, frequency and type of injury, localization and frequency of soft tissue injuries, dentoalveolar trauma, facial bone fractures, complications, concomitant injuries, and different treatment protocols.All the data were analyzed using statistical analysis that is chi-squared test. A total of 1146 patients reported at our unit with facial fractures during these 10 years. Males accounted for a higher frequency of facial fractures (88.8%). Mandible was the commonest bone to be fractured among all the facial bones (71.2%). Maxillary central incisors were the most common teeth to be injured (33.8%) and avulsion was the most common type of injury (44.6%). Commonest postoperative complication was plate infection (11%) leading to plate removal. Other injuries associated with facial fractures were rib fractures, head injuries, upper and lower limb fractures, etc., among these rib fractures were seen most frequently (21.6%). This study was performed to compare the different etiologic factors leading to diverse facial fracture patterns. By statistical analysis of this record the authors come to know about the relationship of facial fractures with gender, age, associated comorbidities, etc.

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

    Directory of Open Access Journals (Sweden)

    Keming Sun

    2016-03-01

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

  3. Log-based identification of sweet spots for effective fracs in shale reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Hashmy, K.; Barnett, C.; Jonkers, J. [Weatherford (United States); Abueita, S. [Anadarko Petroleum (United States)

    2011-07-01

    Shale reservoir exploitation requires horizontal hydro-fracturing, often in a multi-stage configuration. Fracture stages are usually evenly spaced along the horizontal well, regardless of reservoir characteristics, even though wireline logs or logging-while-drilling (LWD) methods could be used to determine sweet spots for more cost-effective fracturing locations. This paper aims to show how failure to take into consideration a reservoir's geological properties can lead to less effective exploitation, and then goes on to describe logging techniques, LWD and wireline logs combined, and their usefulness in effectively placing fracturing stages on a reservoir's sweet spots. By studying logs from different LWD and wireline log techniques, such as gamma ray, resistivity, X-ray fluorescence or shockwave sonic measurements for different existing wells, the study shows how sweet spots, where kerogen concentration is higher, with higher porosity, can be determined. These logging techniques, requiring low investments, offer a variety of methods for identifying sweet spots in shale reservoirs, and fracturing only these spots will avoid unnecessary expenditure on frac stages in zones with poor reservoir characteristics.

  4. Study on the enhancement of hydrocarbon recovery by characterization of the reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Tae-Jin; Kwak, Young-Hoon; Huh, Dae-Gee [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    The reservoir geochemistry is to understand the origin of these heterogeneities and distributions of the bitumens within the reservoir and to use them not only for exploration but for the development of the petroleums. Methods and principles of the reservoir geochemistry, which are applicable to the petroleum exploration and development, are reviewed in the study. In addition, a case study was carried out on the gas, condensate, water and bitumen samples in the reservoir, taken from the Haenam, Pohang areas and the Ulleung Basin offshore Korea. Mineral geothermometers were studied to estimate the thermal history in sedimentary basins and successfully applied to the Korean onshore and offshore basins. The opal silica-to-quartz transformation was investigated in the Pohang basin as a geothermometer. In Korean basins, the smectite-to-illite changes indicate that smectite and illite can act as the geothermometer to estimate the thermal history of the basins. The albitization reaction was also considered as a temperature indicator. Naturally fractured reservoir is an important source of oil and gas throughout the world. The properties of matrix and fracture are the key parameters in predicting the performances of naturally fractured reservoirs. A new laboratory equipment has been designed and constructed by pressure pulse method to determine the properties, which are (1) the porosity of matrix, (2) the permeability of matrix, (3) the effective width of the fractures, and the permeability of the fractures. (author). 97 refs.

  5. Non-linear imaging condition to image fractures as non-welded interfaces

    NARCIS (Netherlands)

    Minato, S.; Ghose, R.

    2014-01-01

    Hydraulic properties of a fractured reservoir are often controlled by large fractures. In order to seismically detect and characterize them, a high-resolution imaging method is necessary. We apply a non-linear imaging condition to image fractures, considered as non-welded interfaces. We derive the

  6. Reservoir characterization of Pennsylvanian sandstone reservoirs. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, M.

    1995-02-01

    This final report summarizes the progress during the three years of a project on Reservoir Characterization of Pennsylvanian Sandstone Reservoirs. The report is divided into three sections: (i) reservoir description; (ii) scale-up procedures; (iii) outcrop investigation. The first section describes the methods by which a reservoir can be described in three dimensions. The next step in reservoir description is to scale up reservoir properties for flow simulation. The second section addresses the issue of scale-up of reservoir properties once the spatial descriptions of properties are created. The last section describes the investigation of an outcrop.

  7. Appraisal of transport and deformation in shale reservoirs using natural noble gas tracers

    Energy Technology Data Exchange (ETDEWEB)

    Heath, Jason E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kuhlman, Kristopher L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Robinson, David G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bauer, Stephen J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gardner, William Payton [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Univ. of Montana, Missoula, MT (United States)

    2015-09-01

    This report presents efforts to develop the use of in situ naturally-occurring noble gas tracers to evaluate transport mechanisms and deformation in shale hydrocarbon reservoirs. Noble gases are promising as shale reservoir diagnostic tools due to their sensitivity of transport to: shale pore structure; phase partitioning between groundwater, liquid, and gaseous hydrocarbons; and deformation from hydraulic fracturing. Approximately 1.5-year time-series of wellhead fluid samples were collected from two hydraulically-fractured wells. The noble gas compositions and isotopes suggest a strong signature of atmospheric contribution to the noble gases that mix with deep, old reservoir fluids. Complex mixing and transport of fracturing fluid and reservoir fluids occurs during production. Real-time laboratory measurements were performed on triaxially-deforming shale samples to link deformation behavior, transport, and gas tracer signatures. Finally, we present improved methods for production forecasts that borrow statistical strength from production data of nearby wells to reduce uncertainty in the forecasts.

  8. Fracture sacrum.

    Directory of Open Access Journals (Sweden)

    Dogra A

    1995-04-01

    Full Text Available An extremely rare case of combined transverse and vertical fracture of sacrum with neurological deficit is reported here with a six month follow-up. The patient also had an L1 compression fracture. The patient has recovered significantly with conservative management.

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

    Directory of Open Access Journals (Sweden)

    Jianming He

    2016-12-01

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

  10. Seismic reservoir characterization: how can multicomponent data help?

    International Nuclear Information System (INIS)

    Li, Xiang-Yang; Zhang, Yong-Gang

    2011-01-01

    This paper discusses the concepts of multicomponent seismology and how it can be applied to characterize hydrocarbon reservoirs, illustrated using a 3D three-component real-data example from southwest China. Hydrocarbon reservoirs formed from subtle lithological changes, such as stratigraphic traps, may be delineated from changes in P- and S-wave velocities and impedances, whilst hydrocarbon reservoirs containing aligned fractures are anisotropic. Examination of the resultant split shear waves can give us a better definition of their internal structures. Furthermore, frequency-dependent variations in seismic attributes derived from multicomponent data can provide us with vital information about fluid type and distribution. Current practice and various examples have demonstrated the undoubted potential of multicomponent seismic in reservoir characterization. Despite all this, there are still substantial challenges ahead. In particular, the improvement and interpretation of converted-wave imaging are major hurdles that need to be overcome before multicomponent seismic becomes a mainstream technology

  11. Seismic reservoir characterization: how can multicomponent data help?

    Science.gov (United States)

    Li, Xiang-Yang; Zhang, Yong-Gang

    2011-06-01

    This paper discusses the concepts of multicomponent seismology and how it can be applied to characterize hydrocarbon reservoirs, illustrated using a 3D three-component real-data example from southwest China. Hydrocarbon reservoirs formed from subtle lithological changes, such as stratigraphic traps, may be delineated from changes in P- and S-wave velocities and impedances, whilst hydrocarbon reservoirs containing aligned fractures are anisotropic. Examination of the resultant split shear waves can give us a better definition of their internal structures. Furthermore, frequency-dependent variations in seismic attributes derived from multicomponent data can provide us with vital information about fluid type and distribution. Current practice and various examples have demonstrated the undoubted potential of multicomponent seismic in reservoir characterization. Despite all this, there are still substantial challenges ahead. In particular, the improvement and interpretation of converted-wave imaging are major hurdles that need to be overcome before multicomponent seismic becomes a mainstream technology.

  12. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Krogsbøll, Anette; Jakobsen, Finn; Madsen, Lena

    1997-01-01

    The main objective of the project is to combine geological descriptions of fractures, chalk types and rock mechanical properties in order to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. This report deals with 1) geological descriptions of outcrop locality...

  13. 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...

  14. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  15. Formation evaluation of fractured basement, Cambay Basin, India

    International Nuclear Information System (INIS)

    Gupta, Saurabh Datta; Farooqui, M Y; Chatterjee, Rima

    2012-01-01

    Unconventional reservoirs such as fractured basalts, shale gas and tight sand are currently playing an important role in producing a significant amount of hydrocarbon. The Deccan Trap basaltic rocks form the basement of the Cambay Basin, India, and hold commercially producible hydrocarbon. In this study two wells drilled through fractured basalts are chosen for evaluating the lithology, porosity and oil saturation of the reservoir sections. Well logs, such as gamma ray, high resolution resistivity, litho density, compensated neutron and elemental capture spectroscopy, have been used in cross-plotting techniques for lithology and mineral identification. Formation micro imagery log data have been analysed to quantify the fractures and porosity in the fractured reservoirs for a well in the south Ahmedabad block of the Cambay Basin. The results of the analysis of two wells are presented and discussed and they are found to be in good agreement with geological and production data. (paper)

  16. Forming mechanism of the Ordovician karst carbonate reservoirs on the northern slope of central Tarim Basin

    Directory of Open Access Journals (Sweden)

    Heng Fu

    2017-07-01

    Full Text Available The Ordovician karst carbonate reservoirs on the northern slope of central Tarim Basin are important oil and gas exploration targets in the basin, but their dissolution mechanisms are in controversy. In this paper, based on the integrated study of sedimentation, sequence and reservoir, together with microscopic analysis and macroscopic seismic data analysis, the carbonate karst reservoirs in the study area were divided into three types: dissolved pore-cavity limestone reservoir, pore-cavity dolomite reservoir and fracture-cavity siliceous reservoir, and their forming mechanisms were discussed respectively. Some findings were obtained. First, dissolved pore-cavity limestone reservoirs are distributed in the upper Yingshan Fm and Yijianfang Fm of the Ordovician vertically, while pore-cavity dolomite reservoirs are mainly developed in the Penglai Fm and lower Yingshan Fm of the Ordovician with great thickness. Second, dissolved pore-cavity limestone reservoirs were formed by karstification on the third-order sequence boundary (lowstand tract, while pore-cavity dolomite reservoirs were formed by deep burial dolomitization controlled by karstification on the third-order sequence boundary, both of which are distributed in the highstand tract below the third-order sequence boundary. Third, siliceous reservoirs are developed under the control of faulting, as a result of reworking of deep hydrothermal fluids along faults to the limestone, and the siliceous reservoirs and their hydrothermal solution fracture-cavity systems are distributed near faults. It is further predicted that, in addition to the three types of reservoir above, platform-margin reef-flat reservoirs are developed in the Ordovician on the northern slope of central Tarim Basin.

  17. Strain-dependent partial slip on rock fractures under seismic-frequency torsion

    Science.gov (United States)

    Saltiel, Seth; Bonner, Brian P.; Ajo-Franklin, Jonathan B.

    2017-05-01

    Measurements of nonlinear modulus and attenuation of fractures provide the opportunity to probe their mechanical state. We have adapted a low-frequency torsional apparatus to explore the seismic signature of fractures under low normal stress, simulating low effective stress environments such as shallow or high pore pressure reservoirs. We report strain-dependent modulus and attenuation for fractured samples of Duperow dolomite (a carbon sequestration target reservoir in Montana), Blue Canyon Dome rhyolite (a geothermal analog reservoir in New Mexico), and Montello granite (a deep basement disposal analog from Wisconsin). We use a simple single effective asperity partial slip model to fit our measured stress-strain curves and solve for the friction coefficient, contact radius, and full slip condition. These observations have the potential to develop into new field techniques for measuring differences in frictional properties during reservoir engineering manipulations and estimate the stress conditions where reservoir fractures and faults begin to fully slip.

  18. A Novel Method for Performance Analysis of Compartmentalized Reservoirs

    Directory of Open Access Journals (Sweden)

    Shahamat Mohammad Sadeq

    2016-05-01

    Full Text Available This paper presents a simple analytical model for performance analysis of compartmentalized reservoirs producing under Constant Terminal Rate (CTR and Constant Terminal Pressure (CTP. The model is based on the well-known material balance and boundary dominated flow equations and is written in terms of capacitance and resistance of a production and a support compartment. These capacitance and resistance terms account for a combination of reservoir parameters which enable the developed model to be used for characterizing such systems. In addition to considering the properties contrast between the two reservoir compartments, the model takes into account existence of transmissibility barriers with the use of resistance terms. The model is used to analyze production performance of unconventional reservoirs, where the multistage fracturing of horizontal wells effectively creates a Stimulated Reservoir Volume (SRV with an enhanced permeability surrounded by a non-stimulated region. It can also be used for analysis of compartmentalized conventional reservoirs. The analytical solutions provide type curves through which the controlling reservoirs parameters of a compartmentalized system can be estimated. The contribution of the supporting compartment is modeled based on a boundary dominated flow assumption. The transient behaviour of the support compartment is captured by application of “distance of investigation” concept. The model shows that depletion of the production and support compartments exhibit two unit slopes on a log-log plot of pressure versus time for CTR. For CTP, however, the depletions display two exponential declines. The depletion signatures are separated by transition periods, which depend on the contribution of the support compartment (i.e. transient or boundary dominated flow. The developed equations can be implemented easily in a spreadsheet application, and are corroborated with the use of a numerical simulation. The study

  19. APPLICATION OF RESERVOIR CHARACTERIZATION AND ADVANCED TECHNOLOGY TO IMPROVE RECOVERY AND ECONOMICS IN A LOWER QUALITY SHALLOW SHELF SAN ANDRES RESERVOIR

    International Nuclear Information System (INIS)

    Raj Kumar; Keith Brown; Hickman, T. Scott; Justice, James J.

    2000-01-01

    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 2 ) stimulation treatments; (6) Hydraulic fracturing design and monitoring; and (7) Mobility control agents

  20. APPLICATION OF RESERVOIR CHARACTERIZATION AND ADVANCED TECHNOLOGY TO IMPROVE RECOVERY AND ECONOMICS IN A LOWER QUALITY SHALLOW SHELF SAN ANDRES RESERVOIR

    International Nuclear Information System (INIS)

    Hickman, T. Scott

    2003-01-01

    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 2 ) stimulation treatments; (6) Hydraulic fracturing design and monitoring; and (7) Mobility control agents

  1. APPLICATION OF RESERVOIR CHARACTERIZATION AND ADVANCED TECHNOLOGY TO IMPROVE RECOVERY AND ECONOMICS IN A LOWER QUALITY SHALLOW SHELF SAN ANDRES RESERVOIR

    International Nuclear Information System (INIS)

    Hickman, T. Scott; Justice, James J.

    2001-01-01

    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 2 ) stimulation treatments; (6) Hydraulic fracturing design and monitoring; and (7) Mobility control agents

  2. APPLICATION OF RESERVOIR CHARACTERIZATION AND ADVANCED TECHNOLOGY TO IMPROVE RECOVERY AND ECONOMICS IN A LOWER QUALITY SHALLOW SHELF SAN ANDRES RESERVOIR

    Energy Technology Data Exchange (ETDEWEB)

    T. Scott Hickman; James J. Justice

    2001-06-16

    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; and (7) Mobility control agents.

  3. Integration of Adaptive Neuro-Fuzzy Inference System, Neural Networks and Geostatistical Methods for Fracture Density Modeling

    Directory of Open Access Journals (Sweden)

    Ja’fari A.

    2014-01-01

    Full Text Available Image logs provide useful information for fracture study in naturally fractured reservoir. Fracture dip, azimuth, aperture and fracture density can be obtained from image logs and have great importance in naturally fractured reservoir characterization. Imaging all fractured parts of hydrocarbon reservoirs and interpreting the results is expensive and time consuming. In this study, an improved method to make a quantitative correlation between fracture densities obtained from image logs and conventional well log data by integration of different artificial intelligence systems was proposed. The proposed method combines the results of Adaptive Neuro-Fuzzy Inference System (ANFIS and Neural Networks (NN algorithms for overall estimation of fracture density from conventional well log data. A simple averaging method was used to obtain a better result by combining results of ANFIS and NN. The algorithm applied on other wells of the field to obtain fracture density. In order to model the fracture density in the reservoir, we used variography and sequential simulation algorithms like Sequential Indicator Simulation (SIS and Truncated Gaussian Simulation (TGS. The overall algorithm applied to Asmari reservoir one of the SW Iranian oil fields. Histogram analysis applied to control the quality of the obtained models. Results of this study show that for higher number of fracture facies the TGS algorithm works better than SIS but in small number of fracture facies both algorithms provide approximately same results.

  4. Exploitation and Optimization of Reservoir Performance in Hunton Formation, Oklahoma, Budget Period I, Class Revisit

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, Mohan

    2002-04-02

    This report explains the unusual characteristics of West Carney Field based on detailed geological and engineering analyses. A geological history that explains the presence of mobile water and oil in the reservoir was proposed. The combination of matrix and fractures in the reservoir explains the reservoir?s flow behavior. We confirm our hypothesis by matching observed performance with a simulated model and develop procedures for correlating core data to log data so that the analysis can be extended to other, similar fields where the core coverage may be limited.

  5. Analytical Estimation of Water-Oil Relative Permeabilities through Fractures

    Directory of Open Access Journals (Sweden)

    Saboorian-Jooybari Hadi

    2016-05-01

    Full Text Available Modeling multiphase flow through fractures is a key issue for understanding flow mechanism and performance prediction of fractured petroleum reservoirs, geothermal reservoirs, underground aquifers and carbon-dioxide sequestration. One of the most challenging subjects in modeling of fractured petroleum reservoirs is quantifying fluids competition for flow in fracture network (relative permeability curves. Unfortunately, there is no standard technique for experimental measurement of relative permeabilities through fractures and the existing methods are very expensive, time consuming and erroneous. Although, several formulations were presented to calculate fracture relative permeability curves in the form of linear and power functions of flowing fluids saturation, it is still unclear what form of relative permeability curves must be used for proper modeling of flow through fractures and consequently accurate reservoir simulation. Basically, the classic linear relative permeability (X-type curves are used in almost all of reservoir simulators. In this work, basic fluid flow equations are combined to develop a new simple analytical model for water-oil two phase flow in a single fracture. The model gives rise to simple analytic formulations for fracture relative permeabilities. The model explicitly proves that water-oil relative permeabilities in fracture network are functions of fluids saturation, viscosity ratio, fluids density, inclination of fracture plane from horizon, pressure gradient along fracture and rock matrix wettability, however they were considered to be only functions of saturations in the classic X-type and power (Corey [35] and Honarpour et al. [28, 29] models. Eventually, validity of the proposed formulations is checked against literature experimental data. The proposed fracture relative permeability functions have several advantages over the existing ones. Firstly, they are explicit functions of the parameters which are known for

  6. a Fractal Network Model for Fractured Porous Media

    Science.gov (United States)

    Xu, Peng; Li, Cuihong; Qiu, Shuxia; Sasmito, Agus Pulung

    2016-04-01

    The transport properties and mechanisms of fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of fractured porous media, where a fractal tree-like network model is used to characterize the fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of fracture system and fractured porous media, tortuosity, fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for fracture length and aperture have significant effect on the equivalent hydraulic properties of fractured porous media. The effective permeability of fracture system can be increased with the increase of fractal dimensions for fracture length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the fracture density and fractal dimension for fracture length has been found, where the scaling exponent depends on the fracture number. The present fractal dual-porosity model may shed light on the transport physics of fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.

  7. Fracture mechanics

    CERN Document Server

    Perez, Nestor

    2017-01-01

    The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

  8. Fracture analysis

    International Nuclear Information System (INIS)

    Ueng, Tzoushin; Towse, D.

    1991-01-01

    Fractures are not only the weak planes of a rock mass, but also the easy passages for the fluid flow. Their spacing, orientation, and aperture will affect the deformability, strength, heat transmittal, and fluid transporting properties of the rock mass. To understand the thermomechanical and hydrological behaviors of the rock surrounding the heater emplacement borehole, the location, orientation, and aperture of the fractures of the rock mass should be known. Borehole television and borescope surveys were performed to map the location, orientation, and aperture of the fractures intersecting the boreholes drilled in the Prototype Engineered Barrier System Field Tests (PEBSFT) at G-Tunnel. Core logging was also performed during drilling. However, because the core was not oriented and the depth of the fracture cannot be accurately determined, the results of the core logging were only used as reference and will not be discussed here

  9. Facial Fractures.

    Science.gov (United States)

    Ricketts, Sophie; Gill, Hameet S; Fialkov, Jeffery A; Matic, Damir B; Antonyshyn, Oleh M

    2016-02-01

    After reading this article, the participant should be able to: 1. Demonstrate an understanding of some of the changes in aspects of facial fracture management. 2. Assess a patient presenting with facial fractures. 3. Understand indications and timing of surgery. 4. Recognize exposures of the craniomaxillofacial skeleton. 5. Identify methods for repair of typical facial fracture patterns. 6. Discuss the common complications seen with facial fractures. Restoration of the facial skeleton and associated soft tissues after trauma involves accurate clinical and radiologic assessment to effectively plan a management approach for these injuries. When surgical intervention is necessary, timing, exposure, sequencing, and execution of repair are all integral to achieving the best long-term outcomes for these patients.

  10. Gasbuggy reservoir evaluation - 1969 report

    International Nuclear Information System (INIS)

    Atkinson, C.H.; Ward, Don C.; Lemon, R.F.

    1970-01-01

    The December 10, 1967, Project Gasbuggy nuclear detonation followed the drilling and testing of two exploratory wells which confirmed reservoir characteristics and suitability of the site. Reentry and gas production testing of the explosive emplacement hole indicated a collapse chimney about 150 feet in diameter extending from the 4,240-foot detonation depth to about 3,900 feet, the top of the 300-foot-thick Pictured Cliffs gas sand. Production tests of the chimney well in the summer of 1968 and during the last 12 months have resulted in a cumulative production of 213 million cubic feet of hydrocarbons, and gas recovery in 20 years is estimated to be 900 million cubic feet, which would be an increase by a factor of at least 5 over estimated recovery from conventional field wells in this low permeability area. At the end of production tests the flow rate was 160,000 cubic feet per day, which is 6 to 7 times that of an average field well in the area. Data from reentry of a pre-shot test well and a new postshot well at distances from the detonation of 300 and 250 feet, respectively, indicate low productivity and consequently low permeability in any fractures at these locations. (author)

  11. Gasbuggy reservoir evaluation - 1969 report

    Energy Technology Data Exchange (ETDEWEB)

    Atkinson, C H; Ward, Don C [Bureau of Mines, U.S. Department of the Interior (United States); Lemon, R F [El Paso Natural Gas Company (United States)

    1970-05-01

    The December 10, 1967, Project Gasbuggy nuclear detonation followed the drilling and testing of two exploratory wells which confirmed reservoir characteristics and suitability of the site. Reentry and gas production testing of the explosive emplacement hole indicated a collapse chimney about 150 feet in diameter extending from the 4,240-foot detonation depth to about 3,900 feet, the top of the 300-foot-thick Pictured Cliffs gas sand. Production tests of the chimney well in the summer of 1968 and during the last 12 months have resulted in a cumulative production of 213 million cubic feet of hydrocarbons, and gas recovery in 20 years is estimated to be 900 million cubic feet, which would be an increase by a factor of at least 5 over estimated recovery from conventional field wells in this low permeability area. At the end of production tests the flow rate was 160,000 cubic feet per day, which is 6 to 7 times that of an average field well in the area. Data from reentry of a pre-shot test well and a new postshot well at distances from the detonation of 300 and 250 feet, respectively, indicate low productivity and consequently low permeability in any fractures at these locations. (author)

  12. A three-dimensional coupled thermo-hydro-mechanical model for deformable fractured geothermal systems

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Paluszny, Adriana; Nick, Hamidreza M.

    2018-01-01

    A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled to a mec......A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled....... The model has been validated against several analytical solutions, and applied to study the effects of the deformable fractures on the injection of cold water in fractured geothermal systems. Results show that the creation of flow channelling due to the thermal volumetric contraction of the rock matrix...

  13. Pisiform fractures

    International Nuclear Information System (INIS)

    Fleege, M.A.; Jebson, P.J.; Renfrew, D.L.; El-Khoury, G.Y.; Steyers, C.M. Jr.

    1991-01-01

    Fractures of the pisiform are often missed due to improper radiographic evaluation and a tendency to focus on other, more obvious injuries. Delayed diagnosis may result in disabling sequelae. A high index of clinical suspicion and appropriate radiographic examination will establish the correct diagnosis. Ten patients with pisiform fracture are presented. The anatomy, mechanism of injury, clinical presentation, radiographic features, and evaluation of this injury are discussed. (orig.)

  14. Stress fractures

    International Nuclear Information System (INIS)

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

    1985-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kerbouc, P

    1968-01-01

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

  16. Geothermal reservoir engineering

    CERN Document Server

    Grant, Malcolm Alister

    2011-01-01

    As nations alike struggle to diversify and secure their power portfolios, geothermal energy, the essentially limitless heat emanating from the earth itself, is being harnessed at an unprecedented rate.  For the last 25 years, engineers around the world tasked with taming this raw power have used Geothermal Reservoir Engineering as both a training manual and a professional reference.  This long-awaited second edition of Geothermal Reservoir Engineering is a practical guide to the issues and tasks geothermal engineers encounter in the course of their daily jobs. The bo

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

    Directory of Open Access Journals (Sweden)

    Jianming He

    2018-03-01

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

  18. Scaphoid Fracture

    Directory of Open Access Journals (Sweden)

    Esther Kim, BS

    2018-04-01

    Full Text Available History of present illness: A 25-year-old, right-handed male presented to the emergency department with left wrist pain after falling from a skateboard onto an outstretched hand two-weeks prior. He otherwise had no additional concerns, including no complaints of weakness or loss of sensation. On physical exam, there was tenderness to palpation within the anatomical snuff box. The neurovascular exam was intact. Plain films of the left wrist and hand were obtained. Significant findings: The anteroposterior (AP plain film of this patient demonstrates a full thickness fracture through the middle third of the scaphoid (red arrow, with some apparent displacement (yellow lines and subtle angulation of the fracture fragments (blue line. Discussion: The scaphoid bone is the most commonly fractured carpal bone accounting for 70%-80% of carpal fractures.1 Classically, it is sustained following a fall onto an outstretched hand (FOOSH. Patients should be evaluated for tenderness with palpation over the anatomical snuffbox, which has a sensitivity of 100% and specificity of 40%.2 Plain films are the initial diagnostic modality of choice and have a sensitivity of 70%, but are commonly falsely negative in the first two to six weeks of injury (false negative of 20%.3 The Mayo classification organizes scaphoid fractures as involving the proximal, mid, and distal portions of the scaphoid bone with mid-fractures being the most common.3 The proximal scaphoid is highly susceptible to vascular compromise because it depends on retrograde blood flow from the radial artery. Therefore, disruption can lead to serious sequelae including osteonecrosis, arthrosis, and functional impairment. Thus, a low threshold should be maintained for neurovascular evaluation and surgical referral. Patients with non-displaced scaphoid fractures should be placed in a thumb spica splint.3 Patients with even suspected scaphoid fractures should be placed in a thumb spica splint and re

  19. Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

    Directory of Open Access Journals (Sweden)

    Ferdinand Stoeckhert

    2015-06-01

    Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

  20. Reservoir Space Evolution of Volcanic Rocks in Deep Songliao Basin, China

    Science.gov (United States)

    Zheng, M.; Wu, X.; Zheng, M.; HU, J.; Wang, S.

    2015-12-01

    Recent years, large amount of natural gas has been discovered in volcanic rock of Lower Crataceous of Songliao basin. Volcanic reservoirs have become one of the important target reservoir types of eastern basin of China. In order to study the volcanic reservoirs, we need to know the main factors controlling the reservoir space. By careful obsercation on volcanic drilling core, casting thin sections and statistical analysis of petrophysical properties of volcanic reservoir in Songliao basin, it can be suggested that the igneous rock reservoir in Yingcheng formation of Lower Crataceous is composed of different rock types, such ad rohylite, rohylitic crystal tuff, autoclastic brecciation lava and so on. There are different reservoirs storage space in in various lithological igneous rocks, but they are mainly composed of primary stoma, secondary solution pores and fractures.The evolution of storage space can be divided into 3 stage: the pramary reservoir space,exogenic leaching process and burial diagenesis.During the evolution process, the reservoir space is effected by secondary minerals, tectonic movement and volcanic hydrothermal solution. The pore of volcanic reservoirs can be partially filled by secondary minerals, but also may be dissoluted by other chemical volcanic hydrothermal solution. Therefore, the favorable places for better-quality volcanic reservoirs are the near-crater facies of vocanic apparatus and dissolution zones on the high position of paleo-structures.

  1. Volume fracturing of deep shale gas horizontal wells

    Directory of Open Access Journals (Sweden)

    Tingxue Jiang

    2017-03-01

    Full Text Available Deep shale gas reservoirs buried underground with depth being more than 3500 m are characterized by high in-situ stress, large horizontal stress difference, complex distribution of bedding and natural cracks, and strong rock plasticity. Thus, during hydraulic fracturing, these reservoirs often reveal difficult fracture extension, low fracture complexity, low stimulated reservoir volume (SRV, low conductivity and fast decline, which hinder greatly the economic and effective development of deep shale gas. In this paper, a specific and feasible technique of volume fracturing of deep shale gas horizontal wells is presented. In addition to planar perforation, multi-scale fracturing, full-scale fracture filling, and control over extension of high-angle natural fractures, some supporting techniques are proposed, including multi-stage alternate injection (of acid fluid, slick water and gel and the mixed- and small-grained proppant to be injected with variable viscosity and displacement. These techniques help to increase the effective stimulated reservoir volume (ESRV for deep gas production. Some of the techniques have been successfully used in the fracturing of deep shale gas horizontal wells in Yongchuan, Weiyuan and southern Jiaoshiba blocks in the Sichuan Basin. As a result, Wells YY1HF and WY1HF yielded initially 14.1 × 104 m3/d and 17.5 × 104 m3/d after fracturing. The volume fracturing of deep shale gas horizontal well is meaningful in achieving the productivity of 50 × 108 m3 gas from the interval of 3500–4000 m in Phase II development of Fuling and also in commercial production of huge shale gas resources at a vertical depth of less than 6000 m.

  2. The Bakken - An Unconventional Petroleum and Reservoir System

    Energy Technology Data Exchange (ETDEWEB)

    Sarg, J.

    2011-12-31

    An integrated geologic and geophysical study of the Bakken Petroleum System, in the Williston basin of North Dakota and Montana indicates that: (1) dolomite is needed for good reservoir performance in the Middle Bakken; (2) regional and local fractures play a significant role in enhancing permeability and well production, and it is important to recognize both because local fractures will dominate in on-structure locations; and (3) the organic-rich Bakken shale serves as both a source and reservoir rock. The Middle Bakken Member of the Bakken Formation is the target for horizontal drilling. The mineralogy across all the Middle Bakken lithofacies is very similar and is dominated by dolomite, calcite, and quartz. This Member is comprised of six lithofacies: (A) muddy lime wackestone, (B) bioturbated, argillaceous, calcareous, very fine-grained siltstone/sandstone, (C) planar to symmetrically ripple to undulose laminated, shaly, very fine-grained siltstone/sandstone, (D) contorted to massive fine-grained sandstone, to low angle, planar cross-laminated sandstone with thin discontinuous shale laminations, (E) finely inter-laminated, bioturbated, dolomitic mudstone and dolomitic siltstone/sandstone to calcitic, whole fossil, dolomitic lime wackestone, and (F) bioturbated, shaly, dolomitic siltstone. Lithofacies B, C, D, and E can all be reservoirs, if quartz and dolomite-rich (facies D) or dolomitized (facies B, C, E). Porosity averages 4-8%, permeability averages 0.001-0.01 mD or less. Dolomitic facies porosity is intercrystalline and tends to be greater than 6%. Permeability may reach values of 0.15 mD or greater. This appears to be a determinant of high productive wells in Elm Coulee, Parshall, and Sanish fields. Lithofacies G is organic-rich, pyritic brown/black mudstone and comprises the Bakken shales. These shales are siliceous, which increases brittleness and enhances fracture potential. Mechanical properties of the Bakken reveal that the shales have similar

  3. Laboratory testing on infiltration in single synthetic fractures

    Science.gov (United States)

    Cherubini, Claudia; Pastore, Nicola; Li, Jiawei; Giasi, Concetta I.; Li, Ling

    2017-04-01

    An understanding of infiltration phenomena in unsaturated rock fractures is extremely important in many branches of engineering for numerous reasons. Sectors such as the oil, gas and water industries are regularly interacting with water seepage through rock fractures, yet the understanding of the mechanics and behaviour associated with this sort of flow is still incomplete. An apparatus has been set up to test infiltration in single synthetic fractures in both dry and wet conditions. To simulate the two fracture planes, concrete fractures have been moulded from 3D printed fractures with varying geometrical configurations, in order to analyse the influence of aperture and roughness on infiltration. Water flows through the single fractures by means of a hydraulic system composed by an upstream and a downstream reservoir, the latter being subdivided into five equal sections in order to measure the flow rate in each part to detect zones of preferential flow. The fractures have been set at various angles of inclination to investigate the effect of this parameter on infiltration dynamics. The results obtained identified that altering certain fracture parameters and conditions produces relevant effects on the infiltration process through the fractures. The main variables influencing the formation of preferential flow are: the inclination angle of the fracture, the saturation level of the fracture and the mismatch wavelength of the fracture.

  4. Parallel reservoir simulator computations

    International Nuclear Information System (INIS)

    Hemanth-Kumar, K.; Young, L.C.

    1995-01-01

    The adaptation of a reservoir simulator for parallel computations is described. The simulator was originally designed for vector processors. It performs approximately 99% of its calculations in vector/parallel mode and relative to scalar calculations it achieves speedups of 65 and 81 for black oil and EOS simulations, respectively on the CRAY C-90

  5. unconventional natural gas reservoirs

    International Nuclear Information System (INIS)

    Correa G, Tomas F; Osorio, Nelson; Restrepo R, Dora P

    2009-01-01

    This work is an exploration about different unconventional gas reservoirs worldwide: coal bed methane, tight gas, shale gas and gas hydrate? describing aspects such as definition, reserves, production methods, environmental issues and economics. The overview also mentioned preliminary studies about these sources in Colombia.

  6. Numerical simulation and fracture identification of dual laterolog in organic shale

    Science.gov (United States)

    Maojin, Tan; Peng, Wang; Qiong, Liu

    2012-09-01

    Fracture is one of important spaces in shale oil and shale gas reservoirs, and fractures identification and evaluation are an important part in organic shale interpretation. According to the fractured shale gas reservoir, a physical model is set up to study the dual laterolog logging responses. First, based on the principle of dual laterolog, three-dimensional finite element method (FEM) is used to simulate the dual laterolog responses in various formation models with different fractures widths, different fracture numbers, different fractures inclination angle. All the results are extremely important for the fracture identification and evaluation in shale reservoirs. Appointing to different base rock resistivity models, the fracture models are constructed respectively through a number of numerical simulation, and the fracture porosity can be calculated by solving the corresponding formulas. A case study about organic shale formation is analyst and discussed, and the fracture porosity is calculated from dual laterolog. The fracture evaluation results are also be validated right by Full borehole Micro-resistivity Imaging (FMI). So, in case of the absence of borehole resistivity imaging log, the dual laterolog resistivity can be used to estimate the fracture development.

  7. Simulated evolution of fractures and fracture networks subject to thermal cooling: A coupled discrete element and heat conduction model

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hai; Plummer, Mitchell; Podgorney, Robert

    2013-02-01

    Advancement of EGS requires improved prediction of fracture development and growth during reservoir stimulation and long-term operation. This, in turn, requires better understanding of the dynamics of the strongly coupled thermo-hydro-mechanical (THM) processes within fractured rocks. We have developed a physically based rock deformation and fracture propagation simulator by using a quasi-static discrete element model (DEM) to model mechanical rock deformation and fracture propagation induced by thermal stress and fluid pressure changes. We also developed a network model to simulate fluid flow and heat transport in both fractures and porous rock. In this paper, we describe results of simulations in which the DEM model and network flow & heat transport model are coupled together to provide realistic simulation of the changes of apertures and permeability of fractures and fracture networks induced by thermal cooling and fluid pressure changes within fractures. Various processes, such as Stokes flow in low velocity pores, convection-dominated heat transport in fractures, heat exchange between fluid-filled fractures and solid rock, heat conduction through low-permeability matrices and associated mechanical deformations are all incorporated into the coupled model. The effects of confining stresses, developing thermal stress and injection pressure on the permeability evolution of fracture and fracture networks are systematically investigated. Results are summarized in terms of implications for the development and evolution of fracture distribution during hydrofracturing and thermal stimulation for EGS.

  8. Non-darcy flow behavior mean high-flux injection wells in porous and fractured formations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Shu

    2003-04-25

    This paper presents a study of non-Darcy fluid flow through porous and fractured rock, which may occur near wells during high-flux injection of waste fluids into underground formations. Both numerical and analytical models are used in this study. General non-Darcy flow is described using the Forchheimer equation, implemented in a three-dimensional, multiphase flow reservoir simulator. The non-Darcy flow through a fractured reservoir is handled using a general dual continuum approach, covering commonly used conceptual models, such as double porosity, dual permeability, explicit fracture, etc. Under single-phase flow conditions, an approximate analytical solution, as an extension of the Warren-Root solution, is discussed. The objectives of this study are (1) to obtain insights into the effect of non-Darcy flow on transient pressure behavior through porous and fractured reservoirs and (2) to provide type curves for well test analyses of non-Darcy flow wells. The type curves generated include various types of drawdown, injection, and buildup tests with non-Darcy flow occurring in porous and fractured reservoirs. In addition, non-Darcy flow into partially penetrating wells is also considered. The transient-pressure type curves for flow in fractured reservoirs are based on the double-porosity model. Type curves provided in this work for non-Darcy flow in porous and fractured reservoirs will find their applications in well test interpretation using a type-curve matching technique.

  9. Identification Method of Mud Shale Fractures Base on Wavelet Transform

    Science.gov (United States)

    Xia, Weixu; Lai, Fuqiang; Luo, Han

    2018-01-01

    In recent years, inspired by seismic analysis technology, a new method for analysing mud shale fractures oil and gas reservoirs by logging properties has emerged. By extracting the high frequency attribute of the wavelet transform in the logging attribute, the formation information hidden in the logging signal is extracted, identified the fractures that are not recognized by conventional logging and in the identified fracture segment to show the “cycle jump”, “high value”, “spike” and other response effect is more obvious. Finally formed a complete wavelet denoising method and wavelet high frequency identification fracture method.

  10. Mimetic Finite Differences for Flow in Fractures from Microseismic Data

    KAUST Repository

    Al-Hinai, Omar; Srinivasan, Sanjay; Wheeler, Mary F.

    2015-01-01

    We present a method for porous media flow in the presence of complex fracture networks. The approach uses the Mimetic Finite Difference method (MFD) and takes advantage of MFD's ability to solve over a general set of polyhedral cells. This flexibility is used to mesh fracture intersections in two and three-dimensional settings without creating small cells at the intersection point. We also demonstrate how to use general polyhedra for embedding fracture boundaries in the reservoir domain. The target application is representing fracture networks inferred from microseismic analysis.

  11. Mimetic Finite Differences for Flow in Fractures from Microseismic Data

    KAUST Repository

    Al-Hinai, Omar

    2015-01-01

    We present a method for porous media flow in the presence of complex fracture networks. The approach uses the Mimetic Finite Difference method (MFD) and takes advantage of MFD\\'s ability to solve over a general set of polyhedral cells. This flexibility is used to mesh fracture intersections in two and three-dimensional settings without creating small cells at the intersection point. We also demonstrate how to use general polyhedra for embedding fracture boundaries in the reservoir domain. The target application is representing fracture networks inferred from microseismic analysis.

  12. Numerical Investigation of Fracture Propagation in Geomaterials

    Science.gov (United States)

    Newell, P.; Borowski, E.; Major, J. R.; Eichhubl, P.

    2015-12-01

    Fracture in geomaterials is a critical behavior that affects the long-term structural response of geosystems. The processes involving fracture initiation and growth in rocks often span broad time scales and size scales, contributing to the complexity of these problems. To better understand fracture behavior, the authors propose an initial investigation comparing the fracture testing techniques of notched three-point bending (N3PB), short rod (SR), and double torsion (DT) on geomaterials using computational analysis. Linear softening cohesive fracture modeling (LCFM) was applied using ABAQUS to computationally simulate the three experimental set-ups. By applying material properties obtained experimentally, these simulations are intended to predict single-trace fracture growth. The advantages and limitations of the three testing techniques were considered for application to subcritical fracture propagation taking into account the accuracy of constraints, load applications, and modes of fracture. This work is supported as part of the Geomechanics of CO2 Reservoir Seals, a DOE-NETL funded under Award Number DE-FOA-0001037. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

    Science.gov (United States)

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

    2018-03-01

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

  14. Acidization of shales with calcite cemented fractures

    Science.gov (United States)

    Kwiatkowski, Kamil; Szymczak, Piotr; Jarosiński, Marek

    2017-04-01

    wormholes is the strongest when coating thickness is a few times larger than the initial aperture of the fracture. This leads to formation of favorable complex networks of wormholes which provide adequate transport of reactive fluids to fracture surfaces and - at the same time - are capable of supporting fracture surfaces. As a conclusion, acidization of the reactivated fractures with hydrochloric acid seems to be an attractive treatment to apply at fracking stage or later on as EGR. The results contribute to the discussion on the use of acidization to enhance the gas production in the shale reservoirs. This communication stresses the importance of the dissolution of calcite cement in natural fractures in shale formations, which are initially sealed and become reactivated during fracking. While this research is based on the analysis of fractures in the Pomeranian shale basin its results are general enough to be applicable to different formations worldwide.

  15. Trochanteric fractures

    International Nuclear Information System (INIS)

    Herrlin, K.; Stroemberg, T.; Lidgren, L.; Walloee, A.; Pettersson, H.; Lund Univ.

    1988-01-01

    Four hundred and thirty trochanteric factures operated upon with McLaughlin, Ender or Richard's osteosynthesis were divided into 6 different types based on their radiographic appearance before and immediately after reposition with special reference to the medial cortical support. A significant correlation was found between the fracture type and subsequent mechanical complications where types 1 and 2 gave less, and types 4 and 5 more complications. A comparison of the various osteosyntheses showed that Richard's had significantly fewer complications than either the Ender or McLaughlin types. For Richard's osteosynthesis alone no correlation to fracture type could be made because of the small number of complications in this group. (orig.)

  16. Fracture Blisters

    Directory of Open Access Journals (Sweden)

    Uebbing, Claire M

    2011-02-01

    Full Text Available Fracture blisters are a relatively uncommon complication of fractures in locations of the body, such as the ankle, wrist elbow and foot, where skin adheres tightly to bone with little subcutaneous fat cushioning. The blister that results resembles that of a second degree burn.These blisters significantly alter treatment, making it difficult to splint or cast and often overlying ideal surgical incision sites. Review of the literature reveals no consensus on management; however, most authors agree on early treatment prior to blister formation or delay until blister resolution before attempting surgical correction or stabilization. [West J Emerg Med. 2011;12(1;131-133.

  17. Formation fracturing by energy waves

    Energy Technology Data Exchange (ETDEWEB)

    Brandon, C W

    1966-11-28

    A method described for recovering oil from an oil strata penetrated by a well bore includes a step of applying fluid pressure to the interior of the well bore across the face of the stratum, and alternately varying the applied fluid pressure, first above and then below the reservoir pressure. This is in order to fracture and break up the face of the strata from internal pressure exerted on the strata. The pressure is affected using liquefied gas at low pressure across the formation.

  18. Carbon Sequestration in Unconventional Reservoirs: Geophysical, Geochemical and Geomechanical Considerations

    Science.gov (United States)

    Zakharova, Natalia V.

    In the face of the environmental challenges presented by the acceleration of global warming, carbon capture and storage, also called carbon sequestration, may provide a vital option to reduce anthropogenic carbon dioxide emissions, while meeting the world's energy demands. To operate on a global scale, carbon sequestration would require thousands of geologic repositories that could accommodate billions of tons of carbon dioxide per year. In order to reach such capacity, various types of geologic reservoirs should be considered, including unconventional reservoirs such as volcanic rocks, fractured formations, and moderate-permeability aquifers. Unconventional reservoirs, however, are characterized by complex pore structure, high heterogeneity, and intricate feedbacks between physical, chemical and mechanical processes, and their capacity to securely store carbon emissions needs to be confirmed. In this dissertation, I present my contribution toward the understanding of geophysical, geochemical, hydraulic, and geomechanical properties of continental basalts and fractured sedimentary formations in the context of their carbon storage capacity. The data come from two characterization projects, in the Columbia River Flood Basalt in Washington and the Newark Rift Basin in New York, funded by the U.S. Department of Energy through Big Sky Carbon Sequestration Partnerships and TriCarb Consortium for Carbon Sequestration. My work focuses on in situ analysis using borehole geophysical measurements that allow for detailed characterization of formation properties on the reservoir scale and under nearly unaltered subsurface conditions. The immobilization of injected CO2 by mineralization in basaltic rocks offers a critical advantage over sedimentary reservoirs for long-term CO2 storage. Continental flood basalts, such as the Columbia River Basalt Group, possess a suitable structure for CO2 storage, with extensive reservoirs in the interflow zones separated by massive impermeable

  19. EXPLOITATION AND OPTIMIZATION OF RESERVOIR PERFORMANCE IN HUNTON FORMATION, OKLAHOMA

    Energy Technology Data Exchange (ETDEWEB)

    Mohan Kelkar

    2002-03-31

    The West Carney Field in Lincoln County, Oklahoma is one of few newly discovered oil fields in Oklahoma. Although profitable, the field exhibits several unusual characteristics. These include decreasing water-oil ratios, decreasing gas-oil ratios, decreasing bottomhole pressures during shut-ins in some wells, and transient behavior for water production in many wells. This report explains the unusual characteristics of West Carney Field based on detailed geological and engineering analyses. We propose a geological history that explains the presence of mobile water and oil in the reservoir. The combination of matrix and fractures in the reservoir explains the reservoir's flow behavior. We confirm our hypothesis by matching observed performance with a simulated model and develop procedures for correlating core data to log data so that the analysis can be extended to other, similar fields where the core coverage may be limited.

  20. Spatial arrangement of faults and opening-mode fractures

    Science.gov (United States)

    Laubach, S. E.; Lamarche, J.; Gauthier, B. D. M.; Dunne, W. M.; Sanderson, David J.

    2018-03-01

    Spatial arrangement is a fundamental characteristic of fracture arrays. The pattern of fault and opening-mode fracture positions in space defines structural heterogeneity and anisotropy in a rock volume, governs how faults and fractures affect fluid flow, and impacts our understanding of the initiation, propagation and interactions during the formation of fracture patterns. This special issue highlights recent progress with respect to characterizing and understanding the spatial arrangements of fault and fracture patterns, providing examples over a wide range of scales and structural settings. Five papers describe new methods and improvements of existing techniques to quantify spatial arrangement. One study unravels the time evolution of opening-mode fracture spatial arrangement, which are data needed to compare natural patterns with progressive fracture growth in kinematic and mechanical models. Three papers investigate the role of evolving diagenesis in localizing fractures by mechanical stratigraphy and nine discuss opening-mode fracture spatial arrangement. Two papers show the relevance of complex cluster patterns to unconventional reservoirs through examples of fractures in tight gas sandstone horizontal wells, and a study of fracture arrangement in shale. Four papers demonstrate the roles of folds in fracture localization and the development spatial patterns. One paper models along-fault friction and fluid pressure and their effects on fault-related fracture arrangement. Contributions address deformation band patterns in carbonate rocks and fault size and arrangement above a detachment fault. Three papers describe fault and fracture arrangements in basement terrains, and three document fracture patterns in shale. This collection of papers points toward improvement in field methods, continuing improvements in computer-based data analysis and creation of synthetic fracture patterns, and opportunities for further understanding fault and fracture attributes in

  1. Chalk as a reservoir

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    , and the best reservoir properties are typically found in mudstone intervals. Chalk mudstones vary a lot though. The best mudstones are purely calcitic, well sorted and may have been redeposited by traction currents. Other mudstones are rich in very fine grained silica, which takes up pore space and thus...... basin, so stylolite formation in the chalk is controlled by effective burial stress. The stylolites are zones of calcite dissolution and probably are the source of calcite for porefilling cementation which is typical in water zone chalk and also affect the reservoirs to different extent. The relatively...... have hardly any stylolites and can have porosity above 40% or even 50% and thus also have relatively high permeability. Such intervals have the problem though, that increasing effective stress caused by hydrocarbon production results in mechanical compaction and overall subsidence. Most other chalk...

  2. Work reservoirs in thermodynamics

    International Nuclear Information System (INIS)

    Anacleto, Joaquim

    2010-01-01

    We stress the usefulness of the work reservoir in the formalism of thermodynamics, in particular in the context of the first law. To elucidate its usefulness, the formalism is then applied to the Joule expansion and other peculiar and instructive experimental situations, clarifying the concepts of configuration and dissipative work. The ideas and discussions presented in this study are primarily intended for undergraduate students, but they might also be useful to graduate students, researchers and teachers.

  3. Work reservoirs in thermodynamics

    Science.gov (United States)

    Anacleto, Joaquim

    2010-05-01

    We stress the usefulness of the work reservoir in the formalism of thermodynamics, in particular in the context of the first law. To elucidate its usefulness, the formalism is then applied to the Joule expansion and other peculiar and instructive experimental situations, clarifying the concepts of configuration and dissipative work. The ideas and discussions presented in this study are primarily intended for undergraduate students, but they might also be useful to graduate students, researchers and teachers.

  4. Elbow Fractures

    Science.gov (United States)

    ... is also an important factor when treating elbow fractures. Casts are used more frequently in children, as their risk of developing elbow stiffness is small; however, in an adult, elbow stiffness is much more likely. Rehabilitation directed by your doctor is often used to ...

  5. Wrist Fractures

    Science.gov (United States)

    ... All Topics A-Z Videos Infographics Symptom Picker Anatomy Bones Joints Muscles Nerves Vessels Tendons About Hand Surgery What is a Hand Surgeon? What is a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Wrist Fractures Email to a friend * required fields ...

  6. Shoulder Fractures

    Science.gov (United States)

    ... All Topics A-Z Videos Infographics Symptom Picker Anatomy Bones Joints Muscles Nerves Vessels Tendons About Hand Surgery What is a Hand Surgeon? What is a Hand Therapist? Media Find a Hand Surgeon Home Anatomy Shoulder Fractures Email to a friend * required fields ...

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

    Directory of Open Access Journals (Sweden)

    Youwei He

    2018-02-01

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

  8. Final Report to DOE EERE – Geothermal Technologies Program Project Title: Monitoring and modeling of fluid flow in a developing enhanced geothermal system (EGS) reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Fehler, Michael [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2017-04-19

    The primary objective of this project was to improve our ability to predict performance of an Enhanced Geothermal System (EGS) reservoir over time by relating, in a quantitative manner, microseismic imaging with fluid and temperature changes within the reservoir. Historically, microseismic data have been used qualitatively to place bounds on the growth of EGS reservoirs created by large hydraulic fracturing experiments. Previous investigators used an experimentally based fracture opening relationship (fracture aperture as a function of pressure), the spatial extent of microseismic events, and some assumptions about fracture frequency to determine the size of an EGS reservoir created during large pumping tests. We addressed a number of issues (1) locating microearthquakes that occur during hydraulic fracturing, (2) obtaining more information about a reservoir than the microearthquake locations from the microearthquake data, for example, information about the seismic velocity structure of the reservoir or the scattering of seismic waves within the reservoir, (3) developing an improved methodology for estimating properties of fractures that intersect wellbores in a reservoir, and (4) developing a conceptual model for explaining the downward growth of observed seismicity that accompanies some hydraulic injections into geothermal reservoirs. We used two primary microseismic datasets for our work. The work was motivated by a dataset from the Salak Geothermal Field in Indonesia where seismicity accompanying a hydraulic injection was observed to migrate downward. We also used data from the Soultz EGS site in France. We also used Vertical Seismic Profiling data from a well in the United States. The work conducted is of benefit for characterizing reservoirs that are created by hydraulic fracturing for both EGS and for petroleum recovery.

  9. Advantageous Reservoir Characterization Technology in Extra Low Permeability Oil Reservoirs

    Directory of Open Access Journals (Sweden)

    Yutian Luo

    2017-01-01

    Full Text Available This paper took extra low permeability reservoirs in Dagang Liujianfang Oilfield as an example and analyzed different types of microscopic pore structures by SEM, casting thin sections fluorescence microscope, and so on. With adoption of rate-controlled mercury penetration, NMR, and some other advanced techniques, based on evaluation parameters, namely, throat radius, volume percentage of mobile fluid, start-up pressure gradient, and clay content, the classification and assessment method of extra low permeability reservoirs was improved and the parameter boundaries of the advantageous reservoirs were established. The physical properties of reservoirs with different depth are different. Clay mineral variation range is 7.0%, and throat radius variation range is 1.81 μm, and start pressure gradient range is 0.23 MPa/m, and movable fluid percentage change range is 17.4%. The class IV reservoirs account for 9.56%, class II reservoirs account for 12.16%, and class III reservoirs account for 78.29%. According to the comparison of different development methods, class II reservoir is most suitable for waterflooding development, and class IV reservoir is most suitable for gas injection development. Taking into account the gas injection in the upper section of the reservoir, the next section of water injection development will achieve the best results.

  10. Use of black oil simulator for coal bed methane reservoir model

    Energy Technology Data Exchange (ETDEWEB)

    Sonwa, R.; Enachescu, C.; Rohs, S. [Golder Associates GmbH, Celle (Germany)

    2013-08-01

    This paper starts from the work done by Seidle et al. (1990) and other authors on the topic of coal degasification and develops a more accurate representative naturally fractured CBM-reservoir by using a Discrete Fracture Network modeling approach. For this issue we firstly calibrate the reservoir simulator tNAVIGATOR by showing his ability to reproduce the work done by Seidle et al. and secondly generate a DFN model using FracMan in accordance with the distribution and orientation of the cleats. tNavigator was then used to simulate multiphase flow through the DFN- Model. (orig.)

  11. Numerical modeling of fracking fluid and methane migration through fault zones in shale gas reservoirs

    Science.gov (United States)

    Taherdangkoo, Reza; Tatomir, Alexandru; Sauter, Martin

    2017-04-01

    Hydraulic fracturing operation in shale gas reservoir has gained growing interest over the last few years. Groundwater contamination is one of the most important environmental concerns that have emerged surrounding shale gas development (Reagan et al., 2015). The potential impacts of hydraulic fracturing could be studied through the possible pathways for subsurface migration of contaminants towards overlying aquifers (Kissinger et al., 2013; Myers, 2012). The intent of this study is to investigate, by means of numerical simulation, two failure scenarios which are based on the presence of a fault zone that penetrates the full thickness of overburden and connect shale gas reservoir to aquifer. Scenario 1 addresses the potential transport of fracturing fluid from the shale into the subsurface. This scenario was modeled with COMSOL Multiphysics software. Scenario 2 deals with the leakage of methane from the reservoir into the overburden. The numerical modeling of this scenario was implemented in DuMux (free and open-source software), discrete fracture model (DFM) simulator (Tatomir, 2012). The modeling results are used to evaluate the influence of several important parameters (reservoir pressure, aquifer-reservoir separation thickness, fault zone inclination, porosity, permeability, etc.) that could affect the fluid transport through the fault zone. Furthermore, we determined the main transport mechanisms and circumstances in which would allow frack fluid or methane migrate through the fault zone into geological layers. The results show that presence of a conductive fault could reduce the contaminant travel time and a significant contaminant leakage, under certain hydraulic conditions, is most likely to occur. Bibliography Kissinger, A., Helmig, R., Ebigbo, A., Class, H., Lange, T., Sauter, M., Heitfeld, M., Klünker, J., Jahnke, W., 2013. Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2. Environ Earth Sci 70, 3855

  12. Bimalleolar ankle fracture with proximal fibular fracture

    NARCIS (Netherlands)

    Colenbrander, R. J.; Struijs, P. A. A.; Ultee, J. M.

    2005-01-01

    A 56-year-old female patient suffered a bimalleolar ankle fracture with an additional proximal fibular fracture. This is an unusual fracture type, seldom reported in literature. It was operatively treated by open reduction and internal fixation of the lateral malleolar fracture. The proximal fibular

  13. Multi-Site Application of the Geomechanical Approach for Natural Fracture Exploration

    Energy Technology Data Exchange (ETDEWEB)

    R. L. Billingsley; V. Kuuskraa

    2006-03-31

    In order to predict the nature and distribution of natural fracturing, Advanced Resources Inc. (ARI) incorporated concepts of rock mechanics, geologic history, and local geology into a geomechanical approach for natural fracture prediction within mildly deformed, tight (low-permeability) gas reservoirs. Under the auspices of this project, ARI utilized and refined this approach in tight gas reservoir characterization and exploratory activities in three basins: the Piceance, Wind River and the Anadarko. The primary focus of this report is the knowledge gained on natural fractural prediction along with practical applications for enhancing gas recovery and commerciality. Of importance to tight formation gas production are two broad categories of natural fractures: (1) shear related natural fractures and (2) extensional (opening mode) natural fractures. While arising from different origins this natural fracture type differentiation based on morphology is sometimes inter related. Predicting fracture distribution successfully is largely a function of collecting and understanding the available relevant data in conjunction with a methodology appropriate to the fracture origin. Initially ARI envisioned the geomechanical approach to natural fracture prediction as the use of elastic rock mechanics methods to project the nature and distribution of natural fracturing within mildly deformed, tight (low permeability) gas reservoirs. Technical issues and inconsistencies during the project prompted re-evaluation of these initial assumptions. ARI's philosophy for the geomechanical tools was one of heuristic development through field site testing and iterative enhancements to make it a better tool. The technology and underlying concepts were refined considerably during the course of the project. As with any new tool, there was a substantial learning curve. Through a heuristic approach, addressing these discoveries with additional software and concepts resulted in a stronger set

  14. Outcropping analogs and multiscale fracture patterns in the Jandaíra formation

    NARCIS (Netherlands)

    Bertotti, G.; Bezerra, F.H.; Bisdom, K.; Cazarin, C.; Reijmer, J.

    2013-01-01

    Outcropping analogs can provide key information on the 3D organization of fracture networks affecting carbonate reservoirs. Such information, however, needs to be integrated in a consistent work flow which includes i) 3D geometric model of the reservoir architecture, ii) mechanic modeling to

  15. Borehole imaging tool detects well bore fractures

    International Nuclear Information System (INIS)

    Ma, T.A.; Bigelow, E.L.

    1993-01-01

    This paper reports on borehole imaging data which can provide high quality geological and petrophysical information to improve fracture identification, dip computations, and lithology determinations in a well bore. The ability to visually quantify the area of a borehole wall occupied by fractures and vugs enhances reservoir characterization and well completion operations. The circumferential borehole imaging log (CBIL) instrument is an acoustic logging device designed to produce a map of the entire borehole wall. The visual images can confirm computed dips and the geological features related to dip. Borehole geometry, including breakout, are accurately described by complete circumferential caliper measurements, which is important information for drilling and completion engineers. In may reservoirs, the images can identify porosity type, bedding characteristics, and petrophysical parameters

  16. Tracer Methods for Characterizing Fracture Creation in Engineered Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Rose, Peter [Energy & Geoscience Institute at the University of Utah, Salt Lake City, UT (United States); Harris, Joel [Univ. of Utah, Salt Lake City, UT (United States)

    2014-05-08

    The aim of this proposal is to develop, through novel high-temperature-tracing approaches, three technologies for characterizing fracture creation within Engineered Geothermal Systems (EGS). The objective of a first task is to identify, develop and demonstrate adsorbing tracers for characterizing interwell reservoir-rock surface areas and fracture spacing. The objective of a second task is to develop and demonstrate a methodology for measuring fracture surface areas adjacent to single wells. The objective of a third task is to design, fabricate and test an instrument that makes use of tracers for measuring fluid flow between newly created fractures and wellbores. In one method of deployment, it will be used to identify qualitatively which fractures were activated during a hydraulic stimulation experiment. In a second method of deployment, it will serve to measure quantitatively the rate of fluid flowing from one or more activated fracture during a production test following a hydraulic stimulation.

  17. Gypsy Field project in reservoir characterization

    Energy Technology Data Exchange (ETDEWEB)

    Castagna, John P.; Jr., O' Meara, Daniel J.

    2000-01-12

    The overall objective of this project was to use extensive Gypsy Field Laboratory and data as a focus for developing and testing reservoir characterization methods that are targeted at improved recovery of conventional oil. This report describes progress since project report DOE/BC/14970-7 and covers the period June 1997-September 1998 and represents one year of funding originally allocated for the year 1996. During the course of the work previously performed, high resolution geophysical and outcrop data revealed the importance of fractures at the Gypsy site. In addition, personnel changes and alternative funding (OCAST and oil company support of various kinds) allowed the authors to leverage DOE contributions and focus more on geophysical characterization.

  18. Fracture mechanics

    International Nuclear Information System (INIS)

    Miannay, D.P.

    1995-01-01

    This book entitle ''Fracture Mechanics'', the first one of the monograph ''Materiologie'' is geared to design engineers, material engineers, non destructive inspectors and safety experts. This book covers fracture mechanics in isotropic homogeneous continuum. Only the monotonic static loading is considered. This book intended to be a reference with the current state of the art gives the fundamental of the issues under concern and avoids the developments too complicated or not yet mastered for not making reading cumbersome. The subject matter is organized as going from an easy to a more complicated level and thus follows the chronological evolution in the field. Similarly the microscopic scale is considered before the macroscopic scale, the physical understanding of phenomena linked to the experimental observation of the material preceded the understanding of the macroscopic behaviour of structures. In this latter field the relatively recent contribution of finite element computations with some analogy with the experimental observation is determining. However more sensitive analysis is not skipped

  19. Rock music : a living legend of simulation modelling solves a reservoir problem by playing a different tune

    Energy Technology Data Exchange (ETDEWEB)

    Cope, G.

    2008-07-15

    Tight sand gas plays are low permeability reservoirs that have contributed an output of 5.7 trillion cubic feet of natural gas per year in the United States alone. Anadarko Petroleum Corporation has significant production from thousands of wells in Texas, Colorado, Wyoming and Utah. Hydraulic fracturing is the key to successful tight sand production. Production engineers use modelling software to calculate a well stimulation program in which large volumes of water are forced under high pressure in the reservoir, fracturing the rock and creating high permeability conduits for the natural gas to escape. Reservoir engineering researchers at the University of Calgary, led by world expert Tony Settari, have improved traditional software modelling of petroleum reservoirs by combining fracture analysis with geomechanical processes. This expertise has been a valuable asset to Anadarko, as the dynamic aspect can have a significant effect on the reservoir as it is being drilled. The challenges facing reservoir simulation is the high computing time needed for analyzing fluid production based on permeability, porosity, gas and fluid properties along with geomechanical analysis. Another challenge has been acquiring high quality field data. Using Anadarko's field data, the University of Calgary researchers found that water fracturing creates vertical primary fractures, and in some cases secondary fractures which enhance permeability. However, secondary fracturing is not permanent in all wells. The newly coupled geomechanical model makes it possible to model fracture growth more accurately. The Society of Petroleum Engineers recently awarded Settari with an award for distinguished achievement in improving the technique and practice of finding and producing petroleum. 1 fig.

  20. An optimal design of cluster spacing intervals for staged fracturing in horizontal shale gas wells based on the optimal SRVs

    Directory of Open Access Journals (Sweden)

    Lan Ren

    2017-09-01

    Full Text Available When horizontal well staged cluster fracturing is applied in shale gas reservoirs, the cluster spacing is essential to fracturing performance. If the cluster spacing is too small, the stimulated area between major fractures will be overlapped, and the efficiency of fracturing stimulation will be decreased. If the cluster spacing is too large, the area between major fractures cannot be stimulated completely and reservoir recovery extent will be adversely impacted. At present, cluster spacing design is mainly based on the static model with the potential reservoir stimulation area as the target, and there is no cluster spacing design method in accordance with the actual fracturing process and targets dynamic stimulated reservoir volume (SRV. In this paper, a dynamic SRV calculation model for cluster fracture propagation was established by analyzing the coupling mechanisms among fracture propagation, fracturing fluid loss and stress. Then, the cluster spacing was optimized to reach the target of the optimal SRVs. This model was applied for validation on site in the Jiaoshiba shale gasfield in the Fuling area of the Sichuan Basin. The key geological engineering parameters influencing the optimal cluster spacing intervals were analyzed. The reference charts for the optimal cluster spacing design were prepared based on the geological characteristics of south and north blocks in the Jiaoshiba shale gasfield. It is concluded that the cluster spacing optimal design method proposed in this paper is of great significance in overcoming the blindness in current cluster perforation design and guiding the optimal design of volume fracturing in shale gas reservoirs. Keywords: Shale gas, Horizontal well, Staged fracturing, Cluster spacing, Reservoir, Stimulated reservoir volume (SRV, Mathematical model, Optimal method, Sichuan basin, Jiaoshiba shale gasfield

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

    Directory of Open Access Journals (Sweden)

    Lianchong Li

    2016-03-01

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

  2. 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.

  3. Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad Ghassemi

    2009-10-01

    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. Therefore, knowledge of the conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fractures are created in the reservoir using hydraulic fracturing. 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 developed advanced poro-thermo-chemo-mechanical fracture models for rock fracture research in support of EGS design. The fracture propagation models are based on a regular displacement discontinuity formulation. The fracture propagation studies include modeling interaction of induced fractures. In addition to the fracture propagation studies, two-dimensional solution algorithms have been developed and used to estimate the impact of pro-thermo-chemical processes on fracture permeability and reservoir pressure. Fracture permeability variation is studied using a coupled thermo-chemical model with quartz reaction kinetics. The model is applied to study quartz precipitation

  4. Surface and Subsurface Geodesy Combined with Active Borehole Experimentation for the Advanced Characterization of EGS Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Elsworth, Derek [Pennsylvania State Univ., University Park, PA (United States); Im, Kyungjae [Pennsylvania State Univ., University Park, PA (United States); Guglielmi, Yves [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Mattioli, Glen [Univ. of Texas, Arlington, TX (United States). UNAVCO

    2016-11-14

    We explore the utility of combining active downhole experimentation with borehole and surface geodesy to determine both the characteristics and evolving state of EGS reservoirs during stimulation through production. The study is divided into two parts. We demonstrate the feasibility of determining in situ reservoir characteristics of reservoir size, strain and fracture permeability and their dependence on feedbacks of stress and temperature using surface and borehole geodetic measurements (Part I). We then define the opportunity to apply the unique hydraulic pulse protocol (HPP) borehole tool to evaluate reservoir state. This can be accomplished by monitoring and co-inverting measured reservoir characteristics (from the HPP tool) with surface geodetic measurements of deformation, tilt and strain with continuous measurements of borehole-wall strain (via optical fiber and fiber Bragg gratings) and measured flow rates (Part II).

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

    Science.gov (United States)

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

    2018-06-01

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

  6. Encapsulated microsensors for reservoir interrogation

    Science.gov (United States)

    Scott, Eddie Elmer; Aines, Roger D.; Spadaccini, Christopher M.

    2016-03-08

    In one general embodiment, a system includes at least one microsensor configured to detect one or more conditions of a fluidic medium of a reservoir; and a receptacle, wherein the receptacle encapsulates the at least one microsensor. In another general embodiment, a method include injecting the encapsulated at least one microsensor as recited above into a fluidic medium of a reservoir; and detecting one or more conditions of the fluidic medium of the reservoir.

  7. Optimized CO{sub 2} miscible hydrocarbon fracturing fluids

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, R.S.; Funkhouser, G.P.; Fyten, G.; Attaway, D.; Watkins, H. [Halliburton Energy Services, Calgary, AB (Canada); Lestz, R.S. [Chevron Canada Resources, Calgary, AB (Canada); Loree, D. [FracEx Inc. (Canada)

    2006-07-01

    Carbon dioxide (CO{sub 2}) miscible hydrocarbon fracturing fluids address issues of fluid retention in low-permeability gas reservoirs, including undersaturated and underpressured reservoirs. An optimized surfactant gel technology using carbon dioxide (CO{sub 2}) hydrocarbon fracturing fluids applicable to all gas-well stimulation applications was discussed in this paper. The crosslinked surfactant gel technology improved proppant transport, leakoff control, and generation of effective fracture half-length. Tests indicated that application of the surfactant cooled the fracture face, which had the effect of extending break times and increasing viscosity during pumping periods. Rapid recovery of the fracturing fluid eliminated the need for swabbing in some cases, and the fluid system was not adversely affected by shear. However, rheological test equipment capable of mixing liquid CO{sub 2} and viscosified hydrocarbons at downhole temperatures is required to determine rheology and required chemical concentrations. It was recommended that to achieve an effective methane-drive cleanup mechanism, treatments should be designed so that the gellant system can be effective with up to 50 per cent CO{sub 2} dissolved in oil. It was concluded that it should be possible to apply the technology to low permeability gas reservoirs. Viscosity curves and friction data were presented. Issues concerning the selection of tubulars and flowback procedures were also discussed. It was suggested that the cost of the hydrocarbon fracturing fluid can be recovered by the sale of recovered load fluid. 6 refs., 4 figs.

  8. Poromechanical response of naturally fractured sorbing media

    Science.gov (United States)

    Kumar, Hemant

    The injection of CO2 in coal seams has been utilized for enhanced gas recovery and potential CO2 sequestration in unmineable coal seams. It is advantageous because as it enhances the production and significant volumes of CO2 may be stored simultaneously. The key issues for enhanced gas recovery and geologic sequestration of CO2 include (1) Injectivity prediction: The chemical and physical processes initiated by the injection of CO2 in the coal seam leads to permeability/porosity changes (2) Up scaling: Development of full scale coupled reservoir model which may predict the enhanced production, associated permeability changes and quantity of sequestered CO2. (3) Reservoir Stimulation: The coalbeds are often fractured and proppants are placed into the fractures to prevent the permeability reduction but the permeability evolution in such cases is poorly understood. These issues are largely governed by dynamic coupling of adsorption, fluid exchange, transport, water content, stress regime, fracture geometry and physiomechanical changes in coals which are triggered by CO 2 injection. The understanding of complex interactions in coal has been investigated through laboratory experiments and full reservoir scale models are developed to answer key issues. (Abstract shortened by ProQuest.).

  9. Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Dengliang

    2013-03-01

    In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

  10. All-optical reservoir computing.

    Science.gov (United States)

    Duport, François; Schneider, Bendix; Smerieri, Anteo; Haelterman, Marc; Massar, Serge

    2012-09-24

    Reservoir Computing is a novel computing paradigm that uses a nonlinear recurrent dynamical system to carry out information processing. Recent electronic and optoelectronic Reservoir Computers based on an architecture with a single nonlinear node and a delay loop have shown performance on standardized tasks comparable to state-of-the-art digital implementations. Here we report an all-optical implementation of a Reservoir Computer, made of off-the-shelf components for optical telecommunications. It uses the saturation of a semiconductor optical amplifier as nonlinearity. The present work shows that, within the Reservoir Computing paradigm, all-optical computing with state-of-the-art performance is possible.

  11. The mechanics of shallow magma reservoir outgassing

    Science.gov (United States)

    Parmigiani, A.; Degruyter, W.; Leclaire, S.; Huber, C.; Bachmann, O.

    2017-08-01

    Magma degassing fundamentally controls the Earth's volatile cycles. The large amount of gas expelled into the atmosphere during volcanic eruptions (i.e., volcanic outgassing) is the most obvious display of magmatic volatile release. However, owing to the large intrusive:extrusive ratio, and considering the paucity of volatiles left in intrusive rocks after final solidification, volcanic outgassing likely constitutes only a small fraction of the overall mass of magmatic volatiles released to the Earth's surface. Therefore, as most magmas stall on their way to the surface, outgassing of uneruptible, crystal-rich magma storage regions will play a dominant role in closing the balance of volatile element cycling between the mantle and the surface. We use a numerical approach to study the migration of a magmatic volatile phase (MVP) in crystal-rich magma bodies ("mush zones") at the pore scale. Our results suggest that buoyancy-driven outgassing is efficient over crystal volume fractions between 0.4 and 0.7 (for mm-sized crystals). We parameterize our pore-scale results for MVP migration in a thermomechanical magma reservoir model to study outgassing under dynamical conditions where cooling controls the evolution of the proportion of crystal, gas, and melt phases and to investigate the role of the reservoir size and the temperature-dependent viscoelastic response of the crust on outgassing efficiency. We find that buoyancy-driven outgassing allows for a maximum of 40-50% volatiles to leave the reservoir over the 0.4-0.7 crystal volume fractions, implying that a significant amount of outgassing must occur at high crystal content (>0.7) through veining and/or capillary fracturing.

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

    Science.gov (United States)

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

    2014-12-01

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

  13. Cesium reservoir and interconnective components

    International Nuclear Information System (INIS)

    1994-03-01

    The program objective is to demonstrate the technology readiness of a TFE (thermionic fuel element) suitable for use as the basic element in a thermionic reactor with electric power output in the 0.5 to 5.0 MW range. A thermionic converter must be supplied with cesium vapor for two reasons. Cesium atoms adsorbed on the surface of the emitter cause a reduction of the emitter work function to permit high current densities without excessive heating of the emitter. The second purpose of the cesium vapor is to provide space-charge neutralization in the emitter-collector gap so that the high current densities may flow across the gap unattenuated. The function of the cesium reservoir is to provide a source of cesium atoms, and to provide a reserve in the event that cesium is lost from the plasma by any mechanism. This can be done with a liquid cesium metal reservoir in which case it is heated to the desired temperature with auxiliary heaters. In a TFE, however, it is desirable to have the reservoir passively heated by the nuclear fuel. In this case, the reservoir must operate at a temperature intermediate between the emitter and the collector, ruling out the use of liquid reservoirs. Integral reservoirs contained within the TFE will produce cesium vapor pressures in the desired range at typical electrode temperatures. The reservoir material that appears to be the best able to meet requirements is graphite. Cesium intercalates easily into graphite, and the cesium pressure is insensitive to loading for a given intercalation stage. The goals of the cesium reservoir test program were to verify the performance of Cs-graphite reservoirs in the temperature-pressure range of interest to TFE operation, and to test the operation of these reservoirs after exposure to a fast neutron fluence corresponding to seven year mission lifetime. In addition, other materials were evaluated for possible use in the integral reservoir

  14. Hip fracture - discharge

    Science.gov (United States)

    ... neck fracture repair - discharge; Trochanteric fracture repair - discharge; Hip pinning surgery - discharge ... in the hospital for surgery to repair a hip fracture, a break in the upper part of ...

  15. Reservoir sedimentation; a literature survey

    NARCIS (Netherlands)

    Sloff, C.J.

    1991-01-01

    A survey of literature is made on reservoir sedimentation, one of the most threatening processes for world-wide reservoir performance. The sedimentation processes, their impacts, and their controlling factors are assessed from a hydraulic engineering point of view with special emphasis on

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

    Directory of Open Access Journals (Sweden)

    R.R. Ibatullin

    2017-09-01

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

  17. 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.

  18. Proximal femoral fractures.

    Science.gov (United States)

    Webb, Lawrence X

    2002-01-01

    Fractures of the proximal femur include fractures of the head, neck, intertrochanteric, and subtrochanteric regions. Head fractures commonly accompany dislocations. Neck fractures and intertrochanteric fractures occur with greatest frequency in elderly patients with a low bone mineral density and are produced by low-energy mechanisms. Subtrochanteric fractures occur in a predominantly strong cortical osseous region which is exposed to large compressive stresses. Implants used to address these fractures must be able to accommodate significant loads while the fractures consolidate. Complications secondary to these injuries produce significant morbidity and include infection, nonunion, malunion, decubitus ulcers, fat emboli, deep venous thrombosis, pulmonary embolus, pneumonia, myocardial infarction, stroke, and death.

  19. Multiphase flow models for hydraulic fracturing technology

    Science.gov (United States)

    Osiptsov, Andrei A.

    2017-10-01

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

  20. Three types of gas hydrate reservoirs in the Gulf of Mexico identified in LWD data

    Science.gov (United States)

    Lee, Myung Woong; Collett, Timothy S.

    2011-01-01

    High quality logging-while-drilling (LWD) well logs were acquired in seven wells drilled during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II in the spring of 2009. These data help to identify three distinct types of gas hydrate reservoirs: isotropic reservoirs in sands, vertical fractured reservoirs in shale, and horizontally layered reservoirs in silty shale. In general, most gas hydratebearing sand reservoirs exhibit isotropic elastic velocities and formation resistivities, and gas hydrate saturations estimated from the P-wave velocity agree well with those from the resistivity. However, in highly gas hydrate-saturated sands, resistivity-derived gas hydrate-saturation estimates appear to be systematically higher by about 5% over those estimated by P-wave velocity, possibly because of the uncertainty associated with the consolidation state of gas hydrate-bearing sands. Small quantities of gas hydrate were observed in vertical fractures in shale. These occurrences are characterized by high formation resistivities with P-wave velocities close to those of water-saturated sediment. Because the formation factor varies significantly with respect to the gas hydrate saturation for vertical fractures at low saturations, an isotropic analysis of formation factor highly overestimates the gas hydrate saturation. Small quantities of gas hydrate in horizontal layers in shale are characterized by moderate increase in P-wave velocities and formation resistivities and either measurement can be used to estimate gas hydrate saturations.

  1. Thermal shale fracturing simulation using the Cohesive Zone Method (CZM)

    KAUST Repository

    Enayatpour, Saeid; van Oort, Eric; Patzek, Tadeusz

    2018-01-01

    Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

  2. Thermal shale fracturing simulation using the Cohesive Zone Method (CZM)

    KAUST Repository

    Enayatpour, Saeid

    2018-05-17

    Extensive research has been conducted over the past two decades to improve hydraulic fracturing methods used for hydrocarbon recovery from tight reservoir rocks such as shales. Our focus in this paper is on thermal fracturing of such tight rocks to enhance hydraulic fracturing efficiency. Thermal fracturing is effective in generating small fractures in the near-wellbore zone - or in the vicinity of natural or induced fractures - that may act as initiation points for larger fractures. Previous analytical and numerical results indicate that thermal fracturing in tight rock significantly enhances rock permeability, thereby enhancing hydrocarbon recovery. Here, we present a more powerful way of simulating the initiation and propagation of thermally induced fractures in tight formations using the Cohesive Zone Method (CZM). The advantages of CZM are: 1) CZM simulation is fast compared to similar models which are based on the spring-mass particle method or Discrete Element Method (DEM); 2) unlike DEM, rock material complexities such as scale-dependent failure behavior can be incorporated in a CZM simulation; 3) CZM is capable of predicting the extent of fracture propagation in rock, which is more difficult to determine in a classic finite element approach. We demonstrate that CZM delivers results for the challenging fracture propagation problem of similar accuracy to the eXtended Finite Element Method (XFEM) while reducing complexity and computational effort. Simulation results for thermal fracturing in the near-wellbore zone show the effect of stress anisotropy in fracture propagation in the direction of the maximum horizontal stress. It is shown that CZM can be used to readily obtain the extent and the pattern of induced thermal fractures.

  3. Compressional acoustics in a borehole. Measurement of fracture permeability

    International Nuclear Information System (INIS)

    Samaden, G.

    1987-04-01

    The detection of open fracturation of reservoirs or underground formations is very important for hydrogeology, geothermal energy and underground waste storage. The refracted compressional P wave only is studied because being faster there is less noise from interferences detection is relatively simple and easy for computer programming. 12 refs [fr

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Um, Evan; Moridis, George

    2014-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-01

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

  6. Field data provide estimates of effective permeability, fracture spacing, well drainage area and incremental production in gas shales

    KAUST Repository

    Eftekhari, Behzad; Marder, M.; Patzek, Tadeusz

    2018-01-01

    the external unstimulated reservoir. This allows us to estimate for the first time the effective permeability of the unstimulated shale and the spacing of fractures in the stimulated region. From an analysis of wells in the Barnett shale, we find

  7. Understanding hydraulic fracturing: a multi-scale problem

    Science.gov (United States)

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

    2016-01-01

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

  8. Analysis of real-time reservoir monitoring : reservoirs, strategies, & modeling.

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Seethambal S.; van Bloemen Waanders, Bart Gustaaf; Cooper, Scott Patrick; Jakaboski, Blake Elaine; Normann, Randy Allen; Jennings, Jim (University of Texas at Austin, Austin, TX); Gilbert, Bob (University of Texas at Austin, Austin, TX); Lake, Larry W. (University of Texas at Austin, Austin, TX); Weiss, Chester Joseph; Lorenz, John Clay; Elbring, Gregory Jay; Wheeler, Mary Fanett (University of Texas at Austin, Austin, TX); Thomas, Sunil G. (University of Texas at Austin, Austin, TX); Rightley, Michael J.; Rodriguez, Adolfo (University of Texas at Austin, Austin, TX); Klie, Hector (University of Texas at Austin, Austin, TX); Banchs, Rafael (University of Texas at Austin, Austin, TX); Nunez, Emilio J. (University of Texas at Austin, Austin, TX); Jablonowski, Chris (University of Texas at Austin, Austin, TX)

    2006-11-01

    The project objective was to detail better ways to assess and exploit intelligent oil and gas field information through improved modeling, sensor technology, and process control to increase ultimate recovery of domestic hydrocarbons. To meet this objective we investigated the use of permanent downhole sensors systems (Smart Wells) whose data is fed real-time into computational reservoir models that are integrated with optimized production control systems. The project utilized a three-pronged approach (1) a value of information analysis to address the economic advantages, (2) reservoir simulation modeling and control optimization to prove the capability, and (3) evaluation of new generation sensor packaging to survive the borehole environment for long periods of time. The Value of Information (VOI) decision tree method was developed and used to assess the economic advantage of using the proposed technology; the VOI demonstrated the increased subsurface resolution through additional sensor data. Our findings show that the VOI studies are a practical means of ascertaining the value associated with a technology, in this case application of sensors to production. The procedure acknowledges the uncertainty in predictions but nevertheless assigns monetary value to the predictions. The best aspect of the procedure is that it builds consensus within interdisciplinary teams The reservoir simulation and modeling aspect of the project was developed to show the capability of exploiting sensor information both for reservoir characterization and to optimize control of the production system. Our findings indicate history matching is improved as more information is added to the objective function, clearly indicating that sensor information can help in reducing the uncertainty associated with reservoir characterization. Additional findings and approaches used are described in detail within the report. The next generation sensors aspect of the project evaluated sensors and packaging

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

    Science.gov (United States)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

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

  10. Evaluation of natural recharge of Chingshui geothermal reservoir using tritium as a tracer

    International Nuclear Information System (INIS)

    Cheng, W.; Kuo, T.; Su, C.; Chen, C.; Fan, K.; Liang, H.; Han, Y.

    2010-01-01

    Naturally existing tritium in groundwater was applied as a tracer to evaluate the natural recharge of the Chingshui geothermal reservoir. The residence time (or, age) of Chingshui geothermal water was first determined with tritium data at 15.2 and 11.3 year using the plug flow and dispersive model, respectively. The annual natural recharge was then estimated by combining the use of the residence time and the fluid-in-place of the Chingshui geothermal reservoir. The natural recharge for Chingshui geothermal reservoir was estimated at 5.0 x 10 5 and 6.7 x 10 5 m 3 year -1 using the plug flow and dispersive model, respectively. Chingshui geothermal water is largely from a fractured zone in the Jentse Member of the Miocene Lushan Formation. The dispersive model more adequately represents the fracture flow system than the simple plug flow model.

  11. The three-zone composite productivity model for a multi-fractured horizontal shale gas well

    Science.gov (United States)

    Qi, Qian; Zhu, Weiyao

    2018-02-01

    Due to the nano-micro pore structures and the massive multi-stage multi-cluster hydraulic fracturing in shale gas reservoirs, the multi-scale seepage flows are much more complicated than in most other conventional reservoirs, and are crucial for the economic development of shale gas. In this study, a new multi-scale non-linear flow model was established and simplified, based on different diffusion and slip correction coefficients. Due to the fact that different flow laws existed between the fracture network and matrix zone, a three-zone composite model was proposed. Then, according to the conformal transformation combined with the law of equivalent percolation resistance, the productivity equation of a horizontal fractured well, with consideration given to diffusion, slip, desorption, and absorption, was built. Also, an analytic solution was derived, and the interference of the multi-cluster fractures was analyzed. The results indicated that the diffusion of the shale gas was mainly in the transition and Fick diffusion regions. The matrix permeability was found to be influenced by slippage and diffusion, which was determined by the pore pressure and diameter according to the Knudsen number. It was determined that, with the increased half-lengths of the fracture clusters, flow conductivity of the fractures, and permeability of the fracture network, the productivity of the fractured well also increased. Meanwhile, with the increased number of fractures, the distance between the fractures decreased, and the productivity slowly increased due to the mutual interfere of the fractures.

  12. Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs

    Directory of Open Access Journals (Sweden)

    Sonja Leonie Philipp

    2013-12-01

    Full Text Available Fractures generated by internal fluid pressure, for example, dykes, mineral veins, many joints and man-made hydraulic fractures, are referred to as hydrofractures. Together with shear fractures, they contribute significantly to the permeability of fluid reservoirs such as those of petroleum, geothermal water, and groundwater. Analytical and numerical models show that – in homogeneous host rocks – any significant overpressure in hydrofractures theoretically generates very high crack tip tensile stresses. Consequently, overpressured hydrofractures should propagate and help to form interconnected fracture systems that would then contribute to the permeability of fluid reservoirs. Field observations, however, show that in heterogeneous and anisotropic, e.g., layered, rocks many hydrofractures become arrested or offset at layer contacts and do not form vertically interconnected networks. The most important factors that contribute to hydrofracture arrest are discontinuities (including contacts, stiffness changes between layers, and stress barriers, where the local stress field is unfavourable to hydrofracture propagation. A necessary condition for a hydrofracture to propagate to the surface is that the stress field along its potential path is everywhere favourable to extension-fracture formation so that the probability of hydrofracture arrest is minimised. Mechanical layering and the resulting heterogeneous stress field largely control whether evolving hydrofractures become confined to single layers (strata¬bound frac¬tures or not (non-stratabound fractures and, there¬fore, if a vertically intercon¬nec¬ted fracture system forms. Non-stratabound hydrofractures may propagate through many layers and generate interconnected fracture systems. Such systems commonly reach the percolation threshold and largely control the overall permeability of the fluid reservoirs within which they develop.

  13. 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

  14. Evaluation of permeable fractures in rock aquifers

    Science.gov (United States)

    Bok Lee, Hang

    2015-04-01

    In this study, the practical usefulness and fundamental applicability of a self-potential (SP) method for identifying the permeable fractures were evaluated by a comparison of SP methods with other geophysical logging methods and hydraulic tests. At a 10 m-shallow borehole in the study site, the candidates of permeable fractures crossing the borehole were first determined by conventional geophysical methods such as an acoustic borehole televiwer, temperature, electrical conductivity and gamma-gamma loggings, which was compared to the analysis by the SP method. Constant pressure injection and recovery tests were conducted for verification of the hydraulic properties of the fractures identified by various logging methods. The acoustic borehole televiwer and gamma-gamma loggings detected the open space or weathering zone within the borehole, but they cannot prove the possibility of a groundwater flow through the detected fractures. The temperature and electrical conductivity loggings had limitations to detect the fractured zones where groundwater in the borehole flows out to the surrounding rock aquifers. Comparison of results from different methods showed that there is a best correlation between the distribution of hydraulic conductivity and the variation of the SP signals, and the SP logging can estimate accurately the hydraulic activity as well as the location of permeable fractures. Based on the results, the SP method is recommended for determining the hydraulically-active fractures rather than other conventional geophysical loggings. This self-potential method can be effectively applied in the initial stage of a site investigation which selects the optimal location and evaluates the hydrogeological property of fractures in target sites for the underground structure including the geothermal reservoir and radioactive waste disposal.

  15. Particle Swarms in Fractures: Open Versus Partially Closed Systems

    Science.gov (United States)

    Boomsma, E.; Pyrak-Nolte, L. J.

    2014-12-01

    In the field, fractures may be isolated or connected to fluid reservoirs anywhere along the perimeter of a fracture. These boundaries affect fluid circulation, flow paths and communication with external reservoirs. The transport of drop like collections of colloidal-sized particles (particle swarms) in open and partially closed systems was studied. A uniform aperture synthetic fracture was constructed using two blocks (100 x 100 x 50 mm) of transparent acrylic placed parallel to each other. The fracture was fully submerged a tank filled with 100cSt silicone oil. Fracture apertures were varied from 5-80 mm. Partially closed systems were created by sealing the sides of the fracture with plastic film. The four boundary conditions study were: (Case 1) open, (Case 2) closed on the sides, (Case 3) closed on the bottom, and (Case 4) closed on both the sides and bottom of the fracture. A 15 μL dilute suspension of soda-lime glass particles in oil (2% by mass) were released into the fracture. Particle swarms were illuminated using a green (525 nm) LED array and imaged with a CCD camera. The presence of the additional boundaries modified the speed of the particle swarms (see figure). In Case 1, enhanced swarm transport was observed for a range of apertures, traveling faster than either very small or very large apertures. In Case 2, swarm velocities were enhanced over a larger range of fracture apertures than in any of the other cases. Case 3 shifted the enhanced transport regime to lower apertures and also reduced swarm speed when compared to Case 2. Finally, Case 4 eliminated the enhanced transport regime entirely. Communication between the fluid in the fracture and an external fluid reservoir resulted in enhanced swarm transport in Cases 1-3. The non-rigid nature of a swarm enables drag from the fracture walls to modify the swarm geometry. The particles composing a swarm reorganize in response to the fracture, elongating the swarm and maintaining its density. Unlike a

  16. Diagenetic effect on permeabilities of geothermal sandstone reservoirs

    DEFF Research Database (Denmark)

    Weibel, Rikke; Olivarius, Mette; Kristensen, Lars

    The Danish subsurface contains abundant sedimentary deposits, which can be utilized for geothermal heating. The Upper Triassic – Lower Jurassic continental-marine sandstones of the Gassum Formation has been utilised as a geothermal reservoir for the Thisted Geothermal Plant since 1984 extracting...... and permeability is caused by increased diagenetic changes of the sandstones due to increased burial depth and temperatures. Therefore, the highest water temperatures typically correspond with the lowest porosities and permeabilities. Especially the permeability is crucial for the performance of the geothermal......-line fractures. Continuous thin chlorite coatings results in less porosity- and permeability-reduction with burial than the general reduction with burial, unless carbonate cemented. Therefore, localities of sandstones characterized by these continuous chlorite coatings may represent fine geothermal reservoirs...

  17. Traumatic thoracolumbar spine fractures

    NARCIS (Netherlands)

    J. Siebenga (Jan)

    2013-01-01

    textabstractTraumatic spinal fractures have the lowest functional outcomes and the lowest rates of return to work after injury of all major organ systems.1 This thesis will cover traumatic thoracolumbar spine fractures and not osteoporotic spine fractures because of the difference in fracture

  18. Fractures in multiple sclerosis

    DEFF Research Database (Denmark)

    Stenager, E; Jensen, K

    1991-01-01

    In a cross-sectional study of 299 MS patients 22 have had fractures and of these 17 after onset of MS. The fractures most frequently involved the femoral neck and trochanter (41%). Three patients had had more than one fracture. Only 1 patient had osteoporosis. The percentage of fractures increase...

  19. Geological Model of Supercritical Geothermal Reservoir on the Top of the Magma Chamber

    Science.gov (United States)

    Tsuchiya, N.

    2017-12-01

    We are conducting supercritical geothermal project, and deep drilling project named as "JBBP: Japan Beyond Brittle Project" The temperatures of geothermal fields operating in Japan range from 200 to 300 °C (average 250 °C), and the depths range from 1000 to 2000 m (average 1500 m). In conventional geothermal reservoirs, the mechanical behavior of the rocks is presumed to be brittle, and convection of the hydrothermal fluid through existing network is the main method of circulation in the reservoir. In order to minimize induced seismicity, a rock mass that is "beyond brittle" is one possible candidate, because the rock mechanics of "beyond brittle" material is one of plastic deformation rather than brittle failure. To understand the geological model of a supercritical geothermal reservoir, granite-porphyry system, which had been formed in subduction zone, was investigated as a natural analog of the supercritical geothermal energy system. Quartz veins, hydrothermal breccia veins, and glassy veins are observed in a granitic body. The glassy veins formed at 500-550 °C under lithostatic pressures, and then pressures dropped drastically. The solubility of silica also dropped, resulting in formation of quartz veins under a hydrostatic pressure regime. Connections between the lithostatic and hydrostatic pressure regimes were key to the formation of the hydrothermal breccia veins, and the granite-porphyry system provides useful information for creation of fracture clouds in supercritical geothermal reservoirs. A granite-porphyry system, associated with hydrothermal activity and mineralization, provides a suitable natural analog for studying a deep-seated geothermal reservoir where stockwork fracture systems are created in the presence of supercritical geothermal fluids. I describe fracture networks and their formation mechanisms using petrology and fluid inclusion studies in order to understand this "beyond brittle" supercritical geothermal reservoir, and a geological

  20. Assessment of fracture risk

    International Nuclear Information System (INIS)

    Kanis, John A.; Johansson, Helena; Oden, Anders; McCloskey, Eugene V.

    2009-01-01

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  1. Estimation of fracture parameters using elastic full-waveform inversion

    KAUST Repository

    Zhang, Zhendong

    2017-08-17

    Current methodologies to characterize fractures at the reservoir scale have serious limitations in spatial resolution and suffer from uncertainties in the inverted parameters. Here, we propose to estimate the spatial distribution and physical properties of fractures using full-waveform inversion (FWI) of multicomponent surface seismic data. An effective orthorhombic medium with five clusters of vertical fractures distributed in a checkboard fashion is used to test the algorithm. A shape regularization term is added to the objective function to improve the estimation of the fracture azimuth, which is otherwise poorly constrained. The cracks are assumed to be penny-shaped to reduce the nonuniqueness in the inverted fracture weaknesses and achieve a faster convergence. To better understand the inversion results, we analyze the radiation patterns induced by the perturbations in the fracture weaknesses and orientation. Due to the high-resolution potential of elastic FWI, the developed algorithm can recover the spatial fracture distribution and identify localized “sweet spots” of intense fracturing. However, the fracture azimuth can be resolved only using long-offset data.

  2. Hydraulic fracture considerations in oil sand overburden dams

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-01

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

  3. Estimating