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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications ROCK FRACTURES AND FLUID FLOW Contemporary Understanding and Applications Committee on Fracture Characterization and Fluid Flow U.S. National Committee for Rock Mechanics Geotechnical Board Board on Energy and Environmental Systems Commission on Engineering and Technical Systems National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1996
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, D.C. 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This report was prepared with the support of the U.S. Department of Energy (DOE), Grant Nos. DE-AC01-89DP48070, DE-FG22-91BC14837, DE-FG05-91ER40668, and DE-FG08-92NV11227 and Contract No. DE-FG01-92CE31021, and the Nuclear Regulatory Commission (NRC), Grant Nos. NRC-G-04-91-089 and NRC-04-91-089. Any opinions, findings, conclusions, and recommendations expressed herein are those of the authors and do not necessarily reflect the views of DOE or NRC. SPONSORS: This project was sponsored by the following federal agencies: Department of Defense (Air Force Office of Scientific Research, Defense Nuclear Agency); Department of Energy (Office of Energy Research, Office of Environmental Restoration and Waste Management, Office of Fossil Energy, Geothermal Division of the Office of Conservation and Renewable Energy, Office of the Superconducting Super Collider, Yucca Mountain Site Characterization Project Office); Department of the Interior (Bureau of Land Management, Bureau of Mines, Bureau of Reclamation); Environmental Protection Agency (Robert S. Kerr Environmental Research Laboratory, Environmental Monitoring Systems Laboratory); Federal Transit Administration; National Science Foundation; and the Nuclear Regulatory Commission. In addition, the Gas Research Institute and Dowell-Schlumberger, Inc., provided support for this project. The National Research Council, through its Day Fund, extended financial support for the publication and dissemination of the report. Library of Congress Cataloging-in-Publication Data Rock fractures and fluid flow : contemporary understanding and applications / Committee on Fracture Characterization and Fluid Flow … [et al.]. p. cm. Includes bibliographical references and index. ISBN 0-309-04996-2 (alk. paper) 1. Rocks—Fracture. 2. Rock mechanics. 3. Fluid dynamics. 4. Hydrogeology. I. National Research Council (U.S.). Committee on Fracture Characterization and Fluid Flow. TA706.R525 1996 96-14613 624.1′5132—dc20 CIP Copyright 1996 by the National Academy of Sciences. All rights reserved.
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications COMMITTEE ON FRACTURE CHARACTERIZATION AND FLUID FLOW Jane C. S. Long (Chair), Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California Atilla Aydin, Stanford University, Stanford, California Stephen R. Brown, Sandia National Laboratories, Albuquerque, New Mexico Herbert H. Einstein, Massachusetts Institute of Technology, Cambridge Kevin Hestir, Utah State University, Logan Paul A. Hsieh, U.S. Geological Survey, Menlo Park, California Larry R. Myer, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California Kenneth G. Nolte, Dowell-Schlumberger, Tulsa, Oklahoma Denis L. Norton, University of Arizona, Tucson (until October 13, 1993) Olle L. Olsson, Conterra AB, Uppsala, Sweden Frederick L. Paillet, U.S. Geological Survey, Denver, Colorado J. Leslie Smith, University of British Columbia, Vancouver, Canada Leon Thomsen, Amoco Production, Tulsa, Oklahoma Staff Duncan Brown, Study Director Kevin Crowley, Technical Editor Amelia B. Mathis, Senior Secretary/Project Assistant Wendy Lewallen, Project Assistant (from November 1994) Peter H. Smeallie, Study Director (to May 1994) Jennifer T. Estep, Administrative Assistant (to May 1994) Helen Johnson, Administrative Associate (from November 1994 to July 1995) Susanna Clarendon, Administrative Assistant (from November 1995) Theron Feist, Project Assistant (from November 1994 to June 1995) Beth Shevitz, Research Assistant (from December 1994 through February 1995)
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications U.S. NATIONAL COMMITTEE FOR ROCK MECHANICS Jane C. S. Long (Chair), Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California Herbert H. Einstein, Massachusetts Institute of Technology, Cambridge Bezalel C. Haimson, University of Wisconsin, Madison Ronald P. Nordgren, NAE, Rice University, Houston, Texas Miklos G. Salamon, Colorado School of Mines, Golden Lawrence W. Teufel, Sandia National Laboratories, Albuquerque, New Mexico Donald L. Turcotte, NAS, Cornell University, Ithaca, New York Former Members Active During the Course of the Study Bernard Amadei (until 1994), University of Colorado, Boulder Barry H. G. Brady (Chair from 1992 until 1994), Dowell-Schlumberger, Tulsa, Oklahoma Arthur McGarr (until 1992), U.S. Geological Survey, Menlo Park, California James E. Monsees (until 1994), PB/MK Team, Dallas, Texas Wolfgang R. Wawersik (Chair until 1992), Sandia National Laboratories, Albuquerque, New Mexico Lewis V. Wade (until 1994), U.S. Bureau of Mines, Minneapolis, Minnesota Staff Mahadevan Mani, Director Peter H. Smeallie, Director (to May 1994) Jennifer T. Estep, Administrative Assistant (to May 1994) Amelia B. Mathis, Senior Secretary/Project Assistant
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications GEOTECHNICAL BOARD James K. Mitchell, NAE, (Chair) Virginia Polytechnic Institute and State University, Blacksburg Clarence R. Allen, NAE/NAS, California Institute of Technology, Pasadena Joan (Jodie) Z. Bernstein, Waste Management, Oak Brook, Illinois David E. Daniel, University of Texas, Austin William S. Gardner, W. S. Gardner and Associates, Blue Bell, Pennsylvania James P. Gould, NAE, Mueser, Rutledge Consulting Engineers, New York, New York François E. Heuze, Lawrence Livermore National Laboratory, Livermore, California Charles C. Ladd, NAE, Massachusetts Institute of Technology, Cambridge James D. Murff, Exxon Production Research Company, Houston, Texas Shlomo P. Neuman, NAE, University of Arizona, Tucson Thomas D. O'Rourke, NAE, Cornell University, Ithaca, New York Reuben Samuels, Parsons Brinckerhoff, New York, New York Robert L. Schuster, U.S. Geological Survey, Denver, Colorado Don W. Steeples, University of Kansas, Lawrence Liaison Members from the Commission on Engineering and Technical Systems William C. Webster, University of California, Berkeley Robert V. Whitman, Lexington, Massachusetts Former Members Active During the Course of the Study Philip E. LaMoreaux (until 1992), P. E. LaMoreaux and Associates, Inc., Tuscaloosa, Alabama Jean-Claude Roegiers (until 1992), University of Oklahoma, Norman Wilson H. Tang (until 1992), University of Illinois at Urbana-Champaign Staff Mahadevan Mani, Director Peter H. Smeallie, Director (to May 1994) Jennifer T. Estep, Administrative Assistant (to May 1994) Amelia B. Mathis, Senior Secretary/Project Assistant
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications BOARD ON ENERGY AND ENVIRONMENTAL SYSTEMS H. M. (Hub) Hubbard (Chair), President and Chief Executive Officer, Pacific International Center for High Technology Research, Honolulu, Hawaii Richard Meserve (Vice-Chair), Partner, Covington & Burling, Washington, D.C. Stephen D. Ban, President, Gas Research Institute, Chicago, Illinois Robert D. Banks, Program Director, Technology and Environment, World Resources Institute, Washington, D.C. Allen J. Bard, NAS, Professor, Department of Chemistry, University of Texas, Austin Barbara R. Barkovich, Partner, Barkovich and Yap, Consultants, San Rafael, California Jan Beyea, Chief Scientist, National Audubon Society, New York, New York David E. Daniel, L. B. (Preach) Meaders Professor of Civil Engineering, Department of Civil Engineering, University of Texas, Austin Linda C. Dolan, Staff Environmental Engineer, Martin Marietta Electronics and Missiles, Orlando, Florida Robert L. Hirsch, President, Energy Technology Collaborative, Washington, D.C. François E. Heuze, Head, Geotechnical Group, Lawrence Livermore National Laboratory, Livermore, California Charles D. Kolstad, Professor, Department of Economics, University of California, Santa Barbara Jane C. S. Long, Staff Scientist, Earth Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California Seymour Meisel, NAE, Vice-President, Research (Retired), Mobil R&D Corporation, Princeton, New Jersey Shlomo P. Neuman, NAE, Regents' Professor, Hydrology and Water Resources, University of Arizona, Tucson Thomas O'Rourke, NAE, Professor, Civil and Environmental Engineering, Cornell University, Ithaca, New York Lawrence T. Papay, NAE, Vice-President and Manager of Research and Development, Bechtel Group, San Francisco, California Ruth A. Reck, Director, Global Climate Change Program, Argonne National Laboratory, Argonne, Illinois Marc H. Ross, Professor, Department of Physics, University of Michigan, Ann Arbor Harold H. Schobert, Chairman, Fuel Sciences Program, Department of Materials Science and Engineering, Pennsylvania State University, University Park Joel Spira, NAE, Chairman and Director of Research, Lutron Electronics Company, Coopersburg, Pennsylvania Jon M. Veigel, President, Oak Ridge Associated Universities, Oak Ridge, Tennessee
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Liaison Members from the Commission on Engineering and Technical Systems Richard A. Conway, NAE, Senior Corporate Fellow, Union Carbide Corporation, South Charleston, West Virginia Trevor O. Jones, NAE, Chairman of the Board (Retired), Libbey-Owens-Ford Company, Cleveland, Ohio Staff Mahadevan Mani, Director James Zucchetto, Senior Program Officer Tracy Wilson, Senior Program Officer Jill Wilson, Program Officer Helen Johnson, Administrative Associate Susanna Clarendon, Administrative Assistant Amelia Mathis, Senior Secretary/Project Assistant Wendy Lewallen, Administrative Assistant Theron Feist, Project Assistant
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of out-standing engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is interim president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and interim vice-chairman, respectively, of the National Research Council.
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Preface At its meeting in June 1990, the U.S. National Committee for Rock Mechanics (USNCRM), a standing committee of the National Research Council (NRC), identified rock fractures as a subject of great concern to the rock mechanics community. The USNCRM proposed that the NRC undertake a study to review characterization and fluid flow in rock fractures. The Committee on Fracture Characterization and Fluid Flow was appointed by the NRC in April 1991 and met for the first time in May 1991. The committee membership represents many of the disciplines concerned with rock fractures and fluid flow, including rock mechanics, hydrogeology, hydrofractures, geophysics, geology, geostatistics, civil engineering, and seismology. The committee met six times over the course of this study to debate, define, and develop this report. Interest in fluid flow in fractured rock has grown rapidly in the past two decades, as a tool in recovering water and hydrocarbon supplies and geothermal energy, in predicting the flow of pollutants underground, and in engineering structures. Practitioners have recognized that progress in this field can be made only by drawing information from a number of different disciplines. However, a person trained in hydrology may have a limited understanding of what geology, geophysics, or geomechanics can do to help solve a problem in fluid flow. As a result, hydrological modelers often disregard geological or geophysical information that they do not know how to use. Similarly, those trained in geology, geophysics, or geomechanics may fail to understand aspects of fractures that are relevant to fluid flow. Studies produced under these conditions may be fascinating, but peripheral or even irrelevant to the real problems they are intended to address. These attitudes are self-propagating and lead to dead ends.
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications This report is intended to promote a new, interdependent approach. It discusses the varied approaches used to solve problems of fluid flow in fractured rock, so that students, faculty, and practitioners may understand the strengths and limitations, as well as the interdependencies, of the available tools. It also contains recommendations for interdisciplinary research on problems that are not well understood, for the use of policy makers and research program managers. This report has limitations. Its breadth has prohibited a comprehensive treatment of any single disciplinary area, although it does communicate a basic understanding of each area. Experts are unlikely to learn much from the chapters devoted to their fields, but should find much of interest in the other chapters. The report is neither a review of the state of the art nor a literature survey, and does not include references to much important work. However, although the references are not all-inclusive, they are designed to be an entrance to the literature. Committee members served the NRC as volunteers for more than three years to complete this study despite busy schedules and conflicting demands. Committee members responded to the chairman's unending demands and the critiques of their colleagues and of the NRC's staff and reviewers. The committee was supported by an impressive list of outside contributors who responded with enthusiasm to calls such as ''Could you write a brief treatment of the importance of diagenesis?" or "Tell us what you know about two-phase flow in fractures." These individuals made a great difference in the quality of the final report. Steve Martel of the University of Hawaii merits special thanks. He contributed a significant effort to Chapter 2 as well as helping organize a field trip for the committee to look at fracture patterns in crystalline and volcanic rocks. Chris Dyke of British Petroleum wrote an account of diagenesis. Steve Laubach of the Texas Bureau of Economic Geology wrote one about joint systems. Marcelo Lippmann contributed sections on the role of fractures in geothermal energy development. Kenzi Karasaki of Ernest Orlando Lawrence Berkeley National Laboratory contributed a treatment of well test analysis. Bill Foxall of Ernest Orlando Lawrence Berkeley National Laboratory wrote about the San Andreas Fault system. Ernie Majer of Ernest Orlando Lawrence Berkeley National Laboratory gave advice about cross-hole seismic methods. Tom Daley, also of Ernest Orlando Lawrence Berkeley National Laboratory, contributed a treatment of shear-wave anisotropy. Richard Everitt of Atomic Energy of Canada Limited contributed a description of the hydrology of fault zones at the Underground Research Laboratory. Bob Glass of Sandia National Laboratory wrote about two-phase flow in fractures in Chapter 3. Norm Warpinski of Sandia National Laboratory contributed an account of the Multiwell Experiment. Duayne Chesnut of Lawrence Livermore Laboratory and Deborah Hopkins, Robert Zimmerman, and Jahan Noorishad of Ernest Orlando Lawrence Berkeley National Laboratory put time and effort into helping us with the difficulties of Chapter 7. Ki Ha Lee
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications and Karstin Pruess of Lawrence Berkeley National Laboratory also made essential contributions. To all of these people we are grateful. Several individuals were critical to the development and conduct of this study and must be mentioned explicitly. Wolfgang Wawersik, chaired the USNCRM when that committee developed the idea for this study, provided enthusiasm and moral support that sustained the project, and particularly the chairman. Peter Smeallie, as study director, developed the financial support, steered the work through the required procedures of the NRC, and guided the committee with skill, intelligence and tact. Jennifer Estep dealt with the committee's trips, its manuscripts, and its unending trivial requests—all with consistent cheerfulness, intelligence and know-how—and in addition had two beautiful babies during the study! Amelia Mathis doggedly yet cheerfully prepared numerous versions of the manuscript. Kevin Crowley edited the entire document, written by scores of people; he made it a readable and coherent document. Dev Mani became coordinator of the project near its completion and deserves our thanks for his efforts. The end game of this report was skillfully handled by Duncan Brown with help from Wendy Lewallen and Beth Shevitz. Jim Mitchell served as report review coordinator on behalf of the NRC, performing that demanding job with insight and good cheer. Nine anonymous reviewers went through the extensive text and provided comments that significantly improved the product. The study received direct support from a number of federal government agencies concerned with research, resource development, environmental regulation and remediation, and civil infrastructure systems. These agencies were the Department of Energy's Office of Environmental Restoration and Waste Management, Office of Energy Research, Office of Fossil Energy, Geothermal Energy Division, Office of the Super conducting Super Collider, and Yucca Mountain Site Characterization Project Office; the Environmental Protection Agency's Robert S. Kerr Environmental Research Laboratory and the Environmental Monitoring Systems Laboratory; the Nuclear Regulatory Commission; the Department of the Interior's Bureau of Mines, Bureau of Reclamation, and Bureau of Land Management; the Department of Defense's Air Force Office of Scientific Research and the Defense Nuclear Agency; Federal Transit Administration; and the National Science Foundation. In addition, two private-sector organizations contributed to the support of the study: the Gas Research Institute and Dowell-Schlumberger, Inc. The National Research Council, through its Day Fund, extended financial support for the publication and dissemination of the report. The committee and staff gratefully acknowledge the support of each of these agencies and organizations. A number of individuals from the various federal agencies and other organizations that sponsored the study helped the committee by serving as liaisons to the committee and providing data, information, and materials. The committee wishes specifically to acknowledge the contributions of the following: Max Blanchard and Robert Levich, Yucca Mountain Site Characterization Project Office, U.S.
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Department of Energy; Barry H. G. Brady, Dowell-Schlumberger, Inc.; James Carney, Office of the Superconducting Super Collider, U.S. Department of Energy; Peter G. Chamberlain, F. Michael Jenkins, and Robert D. Schmidt, U.S. Bureau of Mines, U.S. Department of the Interior; Alex Crawley and Robert Lemmon, Bartlesville Project Office, U.S. Department of Energy; George Stosur, Office of Fossil Energy, U.S. Department of Energy; Joseph Dlugosz, Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency; Allan Jelacic and Marshall J. Reed, Geothermal Energy Division, U.S. Department of Energy; Stephen Kraemer and Steven G. Schmelling, Robert S. Kerr Environmental Research Laboratory, U.S. Environmental Protection Agency; Eric Lightner and Caroline B. Purdy, Office of Environmental Management, U.S. Department of Energy; Jacob Philip and Thomas Nicholson, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission; Hillary A. Oden, Bureau of Land Management, U.S. Department of the Interior; Kent F. Perry, Gas Research Institute; Byron L. Ristvet, Nevada Operations Office, U.S. Department of Energy; Greg A. Scott, Bureau of Reclamation, U.S. Department of the Interior. This study has been an odyssey, albeit a rewarding one. We hope our readers find equivalent rewards in it. Jane C. S. Long Chairman, Committee on Fracture Characterization and Fluid Flow
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Contents EXECUTIVE SUMMARY 1 1 Rock Fractures and Fluid Flow: Practical Problems 11 Problems Involving Fractures In Engineering Practice 14 Appendix 1.A, Fractures in The Geysers Field 26 Appendix 1.B, Superfund Site: Byron Salvage Yard 27 References 28 2 Physical Characteristics of Fractures and Fracture Patterns 29 Definition and Classification 30 Genesis of Fractures 33 Flaws, Stress Concentration, and Fracture Initiation 35 Fracture Propagation and Internal Structures 42 Fracture Geometries 44 Fracture Sets 48 Interaction and Linkage of Joints 52 Interaction and Linkage of Faults 52 Fracture Zones 56 Multiple Sets of Fractures 63 Scaling Up Fracture Properties 77 Implications for Fracture Network Models 81 Appendix 2.A, Diagenetic Enhancement of Natural Fracture Permeability 84
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Appendix 2.B, Fracture Patterns in Frontier Formation Sandstones, Southwestern Wyoming 88 Appendix 2.C, Role of Pore Fluids in the San Andreas Fault 92 References 93 3 Physical Properties and Fundamental Processes in Fractures 103 Geometric Properties And Stress Effects 104 Single-Phase Fluid Flow in Fractures 118 Solute Transport 126 Two-Phase Immiscible Fluid Flow 127 Seismic Properties 132 Electrical Properties 138 Summary 146 Appendix 3.A, Seismic Displacement Discontinuity Theory 149 Appendix 3.B, Gravity-Driven Infiltration Flow Instability 153 Appendix 3.C, Influence of Two-Phase Structure on Fracture Permeability and Solute Transport 156 References 160 4 Fracture Detection Methods 167 Surface Methods 172 Borehole-Borehole and Borehole-Surface Methods 186 Single-Hole Methods 200 Fluid Flow Monitoring Using Geophysical Methods 219 Discussion 222 Appendix 4.A, Directional Borehole Radar System 224 Appendix 4.B, Summary of Conventional Log Applications in Fracture Studies 226 Appendix 4.C, Flowmeter Case Studies 230 Appendix 4.D, Example of Shear-Wave Anisotropy in Fractured Reservoirs 233 References 236 5 Hydraulic and Tracer Testing of Fractured Rocks 243 Hydraulic Tests 244 Tracer Tests 272 Appendix 5.A, Example of a Conductive Network Exhibiting Fractal Geometry 287 Appendix 5.B, Using a Multiple-Borehole Test to Determine the Hydraulic Conductivity Tensor of a Rock Mass 288 Appendix 5.C, Using a Numerical Model and Inverse Method to Analyze a Multiple-Borehole Hydraulic Test 290
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Appendix 5.D, A Radially Convergent Flow Tracer Test in a Fractured Chalk Formation 292 Appendix 5.E, A Large-Scale Flow and Tracer Experiment in Granite 294 Appendix 5.F, Diagnostic Well Test Analysis at the Fracture Research Investigation 296 Appendix 5.G, The Fracture Zone Project at Finnsjön 303 References 304 6 Field-Scale Flow and Transport Models 307 Development of Conceptual and Mathematical Models 309 Equivalent Continuum Simulation Models 318 Discrete Network Simulation Models 332 Hybrid Methods: Using Discrete Network Models in Building Continuum Approximations 351 Discrete Network Models with Scale-Dependent Properties 358 Models of More Complex Hydrogeological Systems 375 Summary 385 Appendix 6.A, Model Prediction Using a Continuum Approach: The URL Drawdown Experiment 390 Appendix 6.B, Percolation Theory 393 Appendix 6.C, Connectivity 395 References 396 7 Induced Changes to Fracture Systems 405 Changes in Fracture Void Geometry Due to Changes in Effective Stress 406 Changes in Fracture Fluids 426 Addition of Solids 430 Redistribution of Existing Solids by Chemical Processes 439 Engineering Under Uncertain Conditions 443 Summary of Deficiencies and Research Needs 444 Appendix 7.A, Natural Fracturing 446 Appendix 7.B, Drainage Methods in Construction 448 References 450 8 Case Histories 455 Case History I. U.S. Geological Survey Fractured Rock Research Site Near Mirror Lake, New Hampshire 459 Case History II. The Site Characterization and Validation Project: Stripa Mine, Sweden 469 Case History III. Hydrocarbon Production From Fractured Sedimentary Rocks: Multiwell Experiment Site 475
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Rock Fractures and Fluid Flow: Contemporary Understanding and Applications Case History IV. Investigating the Anatomy of a Low-Dipping Fracture Zone in Crystalline Rocks: Underground Research Laboratory, Manitoba 479 Case History V. Fracture Studies in a Geothermal Reservoir: The Geysers Geothermal Field, California 487 References 493 9 Technical Summary 499 How Can Fractures That Are Significant Hydraulic Conductors be Identified, Located, and Characterized? 501 How Do Fluid Flow and Chemical Transport Occur in Fracture Systems? 510 How Can Changes to Fracture Systems be Predicted and Controlled? 519 Reference 524 APPENDIX A: Committee's Statement of Task 525 INDEX 527