Page 10 - Fundamentals of Gas Shale Reservoirs

viii CONTENTS

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