Page 11 - Fundamentals of Gas Shale Reservoirs

CONTENTS ix
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