Fundamentals of Gas Shale Reservoirs

Content: Contributors xv    Preface xvii    1 Gas Shale: Global Significance Distribution and Challenges 1    1.1 Introduction 1    1.2 Shale Gas Overview 1    1.2.1 Shale Gas Geology 2    1.2.2 Characteristics of a Producing Shale Gas Play 3    1.3 The Significance of Shale Gas 4    1.4 Global Shale Gas Resources 5    1.4.1 Sources of Information 5    1.4.2 Resource Estimation Methodologies 5    1.5 Global Resource Data 7    1.5.1 China 7    1.5.2 The United States 7    1.5.3 Mexico 7    1.5.4 Southern South America 7    1.5.5 South Africa 8    1.5.6 Australia 8    1.5.7 Canada 8    1.5.8 North Africa 8    1.5.9 Poland 9    1.5.10 France 9    1.5.11 Russia 9    1.5.12 Scandinavia 9    1.5.13 Middle East 9    1.5.14 India 9    1.5.15 Pakistan 10    1.5.16 Northwest Africa 10    1.5.17 Eastern Europe (Outside of Poland) 10    1.5.18 Germany and Surrounding Nations 10    1.5.19 The United Kingdom 10    1.5.20 Northern South America 11    1.5.21 Turkey 11    1.6 Data Assessment 11    1.6.1 Distribution 11    1.6.2 Basin Type 11    1.6.3 Depositional Environment 12    1.6.4 TOC Content 12    1.6.5 Clay Content 13    1.7 Industry Challenges 13    1.7.1 Environmental Challenges 13    1.7.2 Commercial/Economic 14    1.8 Discussion 14    1.9 Conclusions 15    Appendix A.1 Global Shale Gas Resource Data 16    2 Organic Matter  ]Rich Shale Depositional Environments 21    2.1 Introduction 21    2.2 Processes Behind the Deposition of Organic Matter  ]Rich Shale 23    2.2.1 Processes Behind the Transport and Deposition of Mud 23    2.2.2 Production Destruction and Dilution: The Many Roads to Black Shale 23    2.3 Stratigraphic Distribution of Organic Matter  ]Rich Shales 25    2.4 Geographic Distribution of Organic Matter  ]Rich Shales 27    2.4.1 Background 27    2.4.2 Controls on the Geographic Distribution of Black Shales 30    2.5 Organic Matter  ]Rich Shale Depositional Environments 34    2.5.1 Continental Depositional Environments 34    2.5.2 Paralic Depositional Environments 36    2.5.3 Shallow Marine Depositional Environments 37    2.5.4 Deep Marine Depositional Environments 38    2.6 Conclusion 39    3 Geochemical Assessment of Unconventional Shale Gas Resource Systems 47    3.1 Introduction 47    3.2 Objective and Background 49    3.3 Kerogen Quantity and Quality 49    3.4 Sample Type and Quality 51    3.5 Kerogen Type and Compositional Yields 52    3.6 Thermal Maturity 54    3.7 Organoporosity Development 55    3.8 Gas Contents 57    3.9 Expulsion   Retention of Petroleum 57    3.10 Secondary (Petroleum) Cracking 58    3.11 Upper Maturity Limit for Shale Gas 58    3.12 Gas Composition and Carbon Isotopes 59    3.13 Additional Geochemical Analyses for Shale Gas Resource System Evaluation 61    3.14 Oil and Condensate with Shale Gas 63    3.15 Major Shale Gas Resource Systems 64    3.16 Conclusions 65    4 Sequence Stratigraphy of Unconventional Resource Shales 71    4.1 Introduction 71    4.2 General Sequence Stratigraphic Model for Unconventional Resource Shales 71    4.3 Ages of Sea  ]Level Cycles 72    4.4 Water Depth of Mud Transport and Deposition 73    4.5 Criteria to Identify Sequences and Systems Tracts 74    4.6 Paleozoic Resource Shale Examples 74    4.6.1 Barnett Shale (Devonian) 74    4.6.2 Woodford Shale (Late Devonian   Early Mississippian) 74    4.6.3 Marcellus Shale (Devonian) 78    4.6.4 New Albany Shale (Upper Devonian   Lower Mississippian) 78    4.7 Mesozoic Resource Shale Examples 80    4.7.1 Montney Formation (Early Triassic) 80    4.7.2 Haynesville/Bossier Shales (Late Jurassic) 80    4.7.3 Eagle Ford Formation (Cretaceous) 80    4.7.4 LaLuna Formation (Upper Cretaceous) 82    4.8 Cenozoic Resource Shale Example 83    4.9 Conclusions 84    4.10 Applications 84    5 Pore Geometry in Gas Shale Reservoirs 89    5.1 Introduction 89    5.1.1 Gas Shales and Their Challenges 89    5.1.2 Pore Size Classification 90    5.2 Samples Characteristics 90    5.2.1 Sample Collection 90    5.2.2 Mineral Composition 90    5.3 Experimental Methodology 91    5.3.1 Capillary Pressure Profile 91    5.3.2 Nitrogen Adsorption (N2) 92    5.3.3 Low  ]Field NMR 92    5.3.4 Image Acquisition and Analysis 93    5.4 Advantages and Disadvantages of Experimental PSD Methods 95    5.5 Permeability Measurement 95    5.6 Results 96    5.6.1 Pore Size Distribution from MICP Experiments 96    5.6.2 Pore Size Distribution from Nitrogen Adsorption Experiments 98    5.6.3 NMR T2 Relaxation Time 98    5.6.4 Scanning Electron Microscopy 100    5.6.5 Focused Ion Beam/Scanning Electron Microscopy 100    5.6.6 Capillary Pressure and Permeability 102    5.7 Discussion 103    5.7.1 Porosity and PSD Comparisons 103    5.7.2 Interchanging MICP with NMR Data 103    5.7.3 Pore  ]Body to Pore  ]Throat Size Ratio: Pore Geometry Complexity 107    5.7.4 Pore Throat Size and Permeability 107    5.7.5 Mineralogy 108    5.8 Conclusions 112    Appendix 5.A XRD Results 114    6 Petrophysical Evaluation of Gas Shale Reservoirs 117    6.1 Introduction 117    6.2 Key Properties for Gas Shale Evaluation 117    6.2.1 Pore System Characteristics 117    6.2.2 Organic Matter Characteristics 118    6.2.3 Permeability 118    6.2.4 Gas Storage Capacity 119    6.2.5 Shale Composition 120    6.2.6 Geomechanical Properties 120    6.3 Petrophysical Measurements of Gas Shale Reservoirs 121    6.3.1 Pore Structure Evaluation Techniques 121    6.3.2 Fluid Saturation Measurement 122    6.3.3 Permeability Measurement 123    6.3.4 Adsorbed Gas Measurement 124    6.4 Well Log Analysis of Gas Shale Reservoirs 125    6.4.1 Well Log Signatures of Gas Shale Formations 125    6.4.2 Well Log Interpretation of Gas Shale Formations 128    7 Pore Pressure Prediction for Shale Formations Using well Log Data 139    7.1 Introduction 139    7.1.1 Normal Pressure 139    7.1.2 Overpressure 139    7.2 Overpressure-Generating Mechanisms 140    7.2.1 Loading Mechanisms 141    7.2.2 Unloading Mechanisms (Fluid Expansion) 142    7.2.3 World Examples of Overpressures 143    7.2.4 Overpressure Indicators from Drilling Data 144    7.2.5 Identification of Shale Intervals 144    7.3 Overpressure Estimation Methods 146    7.3.1 Overview of the Compaction Theory 146    7.3.2 Eaton   s Method 147    7.3.3 Effective Stress Method 149    7.3.4 Bowers   s Method 150    7.4 The Role of Tectonic Activities on Pore Pressure In Shales 151    7.4.1 Geology of the Study Area 151    7.4.2 Stress Field in the Perth Basin 152    7.4.3 Pore Pressure in Tectonically Active Regions (Uplifted Areas) 154    7.4.4 Pore Pressure in Tectonically Stable Regions 154    7.4.5 Origins of Overpressure in Kockatea Shale 156    7.5 Discussion 160    7.5.1 Significance of Pore Pressure Study 163    7.5.2 Overpressure Detection and Estimation 163    7.5.3 Pore Pressure and Compressional Tectonics 163    7.5.4 Overpressure-Generating Mechanisms 164    7.5.5 Overpressure Results Verifications 164    7.6 Conclusions 165    8 Geomechanics of Gas Shales 169    8.1 Introduction 169    8.2 Mechanical Properties of Gas Shale Reservoirs 170    8.2.1 Gas Shale Reservoir Properties under Triaxial Loading 170    8.2.2 True  ]Triaxial Tests 171    8.2.3 Gas Shale Reservoir Properties under Ultrasonic Tests 172    8.2.4 Nanoindentation Tests on Gas Shale Plays 173    8.2.5 Scratch Tests 174    8.3 Anisotropy 175    8.3.1 Anisotropy in Gas Shale Reservoirs 175    8.4 Wellbore Instability in Gas Shale Reservoirs 176    8.4.1 Structurally Controlled Instability 177    8.4.2 Instability Due to Directional Dependency of Geomechanical Parameters 178    8.4.3 Time  ]Dependent Instability 184    9 Rock Physics Analysis of Shale Reservoirs 191    9.1 Introduction 191    9.2 Laboratory Measurements on Shales: Available Datasets 192    9.3 Organic Matter Effects on Elastic Properties 192    9.4 Partial Saturation Effects 195    9.5 Maturity Effects 197    9.6 Seismic Response of Orss 201    9.7 Conclusions 203    10 Passive Seismic Methods for Unconventional Resource Development 207    10.1 Introduction 207    10.2 Geomechanics and Natural Fracture Basics for Application to Hydraulic Fracturing 209    10.2.1 Basics of Earth Stress and Strain 209    10.2.2 Natural Fracture Basics and Interaction with Hydraulic Fractures 211    10.3 Seismic Phenomena 213    10.3.1 MEQs and Their Magnitudes 213    10.3.2 Earthquake Focal Mechanisms 213    10.3.3 Other Types of Seismic Activity Produced by Hydraulic Fracturing 216    10.4 Microseismic Downhole Monitoring 216    10.4.1 Downhole Monitoring Methodology 216    10.4.2 Advantages and Disadvantages of Downhole Monitoring 220    10.5 Monitoring Passive Seismic Emissions with Surface and Shallow Buried Arrays 222    10.5.1 Recording 222    10.5.2 Seismic Emission Tomography 223    10.5.3 MEQ Methods 229    10.5.4 Imaging Cumulative Seismic Activity 230    10.5.5 Direct Imaging of Fracture Networks 232    10.5.6 Comparison of Downhole Hypocenters and Fracture Images 232    10.5.7 Summary 233    10.6 Integrating Interpreting and Using Passive Seismic Data 235    10.6.1 General Considerations 235    10.6.2 Interpreting Reservoir Stress from Focal Mechanisms 236    10.6.3 Fracture Width Height SRV and Tributary Drainage Volume 240    10.6.4 Using Passive Seismic Results for Frac Well  ]Test and Reservoir Simulation 240    10.7 Conclusions 241    11 Gas Transport Processes in Shale 245    11.1 Introduction 245    11.2 Detection of Nanopores in Shale Samples 247    11.3 Gas Flow in Micropores and Nanopores 248    11.4 Gas Flow in a Network of Pores in Shale 251    11.5 Gas Sorption in Shale 252    11.6 Diffusion in Bulk Kerogen 253    11.7 Measurement of Gas Molecular Diffusion into Kerogen 255    11.8 Pulse  ]Decay Permeability Measurement Test 256    11.8.1 Pulse  ]Decay Pressure Analysis 257    11.8.2 Estimation of Permeability Parameters with the Pulse  ]Decay Experiment 259    11.9 Crushed Sample Test 260    11.9.1 Porosity Measurement 260    11.9.2 Crushed Sample Pressure Analysis for Permeability Measurement 261    11.9.3 Crushed Sample Permeability Estimation with Early  ]Time Pressure Data 262    11.9.4 Crushed Sample Permeability Estimation with Late  ]Time Pressure Data 262    11.10 Canister Desorption Test 262    11.10.1 Permeability Estimation with Early Time Cumulative Desorbed Gas Data 263    11.10.2 Permeability Estimation with Late  ]Time Cumulative Desorbed Gas Data 264    12 A Review of the Critical Issues Surrounding the Simulation of Transport and Storage in Shale Reservoirs 267    12.1 Introduction 267    12.2 Microgeometry of Organic  ]Rich Shale Reservoirs 268    12.3 Gas Storage Mechanisms 269    12.4 Fluid Transport 270    12.5 Capillary Pressure Relaxation to Equilibrium State and Deposition of Stimulation Water 273    12.6 Characterization of Fluid Behavior and Equations of State Valid for Nanoporous Media 274    12.6.1 Viscosity Corrections 276    12.6.2 Corrections for Interfacial Tension 277    12.7 Upscaling Heterogeneous Shale  ]Gas Reservoirs into Large Homogenized Simulation Grid Blocks 277    12.7.1 Upscaling Fine Continuum Model of Shale to Lumped  ]Parameter Leaky Tank Model of Shale 278    12.7.2 Upscaling Finely Detailed Continuum Model of Shale to Coarse Continuum Model of Shale 279    12.8 Final Remarks 280    13 Performance Analysis of Unconventional Shale Reservoirs 283    13.1 Introduction 283    13.2 Shale Reservoir Production 283    13.3 Flow Rate Decline Analysis 284    13.3.1 Decline Curve Analysis in Unconventional Reservoirs 285    13.3.2 Flow Rate Transient Analysis (RTA) and its Relation to Rate Decline Analysis 286    13.3.3 Field Applications 287    13.4 Flow Rate and Pressure Transient Analysis in Unconventional Reservoirs 288    13.4.1 Bilinear Flow Regime in Multistage Hydraulic Fracturing 288    13.4.2 Linear Flow Analysis for Reservoir Permeability 289    13.4.3 Field Applications 290    13.4.4 Type-Curve Matching 290    13.5 Reservoir Modeling and Simulation 292    13.5.1 History Matching and Forecasting 292    13.5.2 Dual-Porosity Single-Phase Modeling 293    13.5.3 Dual-Porosity Multicomponent Gas Modeling 294    13.6 Specialty Short-Term Tests 295    13.6.1 Mini-DST 295    13.6.2 Mini-Frac Test 296    13.7 Enhanced Oil Recovery 297    13.8 Conclusion 298    14 Resource Estimation for Shale Gas Reservoirs 301    14.1 Introduction 301    14.1.1 Unique Properties of Shale 301    14.1.2 Petroleum Resources Management System (PRMS) 301    14.1.3 Energy Information Administration   s Classification System 301    14.1.4 Reserves Estimate Methodology for Unconventional Gas Reservoirs 302    14.1.5 Monte Carlo Probabilistic Approach 302    14.1.6 Analytical Models 303    14.1.7 Economic Analysis 303    14.1.8 Region  ]Level World Shale Gas Resource Assessments 304    14.1.9 Shale Gas OGIP Assessment in North America 305    14.1.10 Recent Shale Gas Production and Activity Trends 306    14.1.11 Drilling Stimulation and Completion Methods in Shale Gas Reservoirs 308    14.2 Methodology 309    14.3 Resource Evaluation of Shale Gas Plays 310    14.3.1 Reservoir Model 310    14.3.2 Well Spacing Determination 310    14.3.3 Reservoir Parameters Sensitivity Analysis 311    14.3.4 Reservoir Parameters 312    14.3.5 Model Verification 312    14.3.6 Resource Assessment 313    14.3.7 Reserve Evaluation 318    14.4 Discussion 320    15 Molecular Simulation of Gas Adsorption in Minerals and Coal: Implications for Gas Occurrence in Shale Gas Reservoirs 325    15.1 Introduction 325    15.1.1 Molecular Dynamics Simulation 325    15.1.2 Major Challenges in Shale Gas Research 326    15.1.3 MS of Gas Adsorption 326    15.1.4 Methodology and Workflow of Molecular Simulation 327    15.1.5 Simulation Algorithms and Software 327    15.2 MS of Gas Adsorption on Minerals 327    15.2.1 MD Simulation of Gas Adsorption on Quartz 328    15.2.2 Molecular Dynamic Simulation of Gas Adsorption on Wyoming  ]Type Montmorillonite 330    15.2.3 MD Simulation of Gas Adsorption on Zeolite 332    15.2.4 MD Simulation of Gas Adsorption on Coal 334    15.3 Conclusions 337    16 Wettability of Gas Shale Reservoirs 341    16.1 Introduction 341    16.2 Wettability 341    16.3 Imbibition in Gas Shales 342    16.4 Factors Influencing Water Imbibition in Shales 343    16.4.1 Sample Expansion 343    16.4.2 Depositional Lamination 346    16.4.3 Chemical Osmosis 346    16.4.4 Water Film and Salt Crystals 348    16.4.5 Water Adsorption (Clay Swelling) 348    16.4.6 Connectivity of Hydrophobic and Hydrophilic Pore Networks 349    16.4.7 Effect of Polymer and Surfactant 351    16.5 Quantitative Interpretation of Imbibition Data 352    16.5.1 Scaling Imbibition Data 352    16.5.2 Modeling Imbibition Data 352    16.6 Estimation of Brine Imbibition at the Field Scale 354    16.7 Initial Water Saturation in Gas Shales 356    16.8 Conclusions 356    17 Gas Shale Challenges Over The Asset Life Cycle 361    17.1 Introduction 361    17.2 The Asset Life Cycle 361    17.2.1 Exploration Phase Objectives   Recommended Practices 361    17.2.2 Appraisal Phase Objectives   Recommended Practices 362    17.2.3 Development Phase Objectives   Recommended Practices 362    17.2.4 Production Phase Objectives   Recommended Practices 362    17.2.5 Rejuvenation Phase Objectives   Recommended Practices 362    17.3 Exploration Phase Discussion 362    17.3.1 Screening Study   Current Practice 362    17.3.2 Screening Study Recommended Practices 363    17.3.3 Reservoir Characterization   Current Practice 363    17.3.4 Reservoir Characterization   Recommended Practices 363    17.3.5 Determining Initial Economic Value and Reservoir Potential 365    17.4 Appraisal Phase Discussion 365    17.4.1 Drill Appraisal Wells   Current Practice 365    17.4.2 Drill Appraisal Wells   Recommended Practices 365    17.4.3 Build Reservoir Models for Simulation   Current Practice 365    17.4.4 Build Reservoir Models for Simulation   Recommended Practices 365    17.4.5 Generate a Field Development Plan   Current Practice 366    17.4.6 Generate a Field Development Plan   Recommended Practices 366    17.4.7 Validate Economics of the Play or Pilot Project 366    17.5 Development Phase Discussion 367    17.5.1 Implement the Field Development Plan 367    17.5.2 Surface Facilities 367    17.5.3 Design Wells and Optimize Drilling Costs   Current Practice 367    17.5.4 Design Wells and Optimize Drilling Costs   Recommended Practice 368    17.5.5 Refine and Optimize Hydraulic Fracturing and Wellbore Completion Design   Current Practices (Characterize the Lateral) 369    17.5.6 Current Hydraulic Fracturing Practices 369    17.5.7 Hydraulic Fracturing   Recommended Practices 370    17.5.8 Characterize the Lateral 372    17.5.9 Current Wellbore Completion Practice 373    17.5.10 Wellbore Completion   Recommended Practices 373    17.5.11 Drilling Considerations for Completion Methods 375    17.5.12 Fracturing Considerations for Completion Method 375    17.6 Production Phase Discussion 375    17.6.1 Monitor and Optimize Producing Rates   Current Practice 375    17.6.2 Monitor and Optimize Producing Rates   Recommended Practices 375    17.6.3 Manage the Water Cycle   Recommended Practices 376    17.6.4 Preventing Corrosion Scaling and Bacterial Contamination in Wells and Facilities 376    17.6.5 Protecting the Environment 376    17.7 Rejuvenation Phase Discussion 376    17.8 Conclusions   Recommended Practices 377    18 Gas Shale Environmental Issues and Challenges 381    18.1 Overview 381    18.2 Water Use 381    18.3 The Disposal and Reuse of Fracking Wastewater 382    18.4 Groundwater Contamination 384    18.5 Methane Emissions 386    18.6 Other Air Emissions 387    18.7 Social Impacts on Shale Gas Communities 388    18.8 Induced Seismicity: Wastewater Injection and Earthquakes 388    18.9 Regulatory Developments 389    18.10 Disclosure of Fracking Chemicals 389    18.11 At the Federal Government Level 390    18.12 Conclusion 391    Index 397