Natural Gas Hydrates

Title Page
......Page 3
Copyright
......Page 4
CONTENTS......Page 5
PREFACE......Page 7
Definition......Page 8
Composition......Page 9
Amount of Methane......Page 10
Geological Evidence......Page 11
Geophysical Evidence......Page 12
INVENTORY OF GAS HYDRATE......Page 13
REFERENCES......Page 18
1. INTRODUCTION......Page 24
2. THE PALEOGENE STEADY-STATE EXOGENIC CARBON CYCLE......Page 25
3. THE LATEST PALEOCENE CARBON ISOTOPE EXCURSION: THE PROBLEM......Page 27
4. THE GAS HYDRATE DISSOCIATION HYPOTHESIS......Page 28
5. OBSERVATIONS FROM THE BLAKE RIDGE......Page 29
6. A GLOBAL GAS HYDRATE CAPACITOR......Page 32
7. A BASIC SIMULATION OF THE LPTM......Page 36
8. CONCLUSIONS AND FUTURE RESEARCH......Page 39
REFERENCES......Page 40
Models for Pore Fluid Compositional Changes in Sedimentary Pore Spaces......Page 44
Implications for Sediment Pore Fluid Geochemistry......Page 45
Survey of Chloride Anomalies and Gas Hydrate Occurrence......Page 47
A Modern Seawater Baseline......Page 48
An Empirically Determined Baseline......Page 51
Possible Causes of Pore Water Freshening Beneath the BGHS/BSR......Page 52
REFERENCES......Page 53
1. INTRODUCTION......Page 55
3.1. Core Voids......Page 56
3.5 Comparisons Among Core Gas Measurement Techniques......Page 58
3.6. Development of Pressure Core Samplers......Page 59
4.1 Gas Void and Headspace Composition Data......Page 60
4.3 Headspace Data Compared with Methane Solubility......Page 61
5.2 Comparison of Core Gas Measurements and Pressure Core Sample Measurements......Page 63
5.3. Origin and Geochemical Finger Print of Sedimentary Methane......Page 64
6. SUMMARY AND CONCLUSIONS......Page 65
REFERENCES......Page 66
Background......Page 68
Summary of Previous Work......Page 70
Distinct Characteristic of Convergent Margins......Page 71
Gas Hydrate Occurrence, Distribution, and Concentration in Convergent Margins......Page 72
Methane Occurrence and Implications for Gas Hydrate Formation and Distribution......Page 74
Origin of Methane and Yields for Methane Hydrate Formation......Page 77
Methane Yields for Gas Hydrate Formation......Page 79
Pore Fluids Geochemistry and Estimates of Hydrate Abundances......Page 80
RESPONSES OF THE CONVERGENT MARGINS GAS HYDRATE RESERVOIR TO ENVIRONMENTAL STRESSES......Page 82
MAIN CONCLUSIONS......Page 83
REFERENCES......Page 84
1. INTRODUCTION......Page 88
2. METHANE HYDRATE MANIFESTATIONS......Page 90
3. CHLORIDE-ANOMALY PATTERN......Page 93
4. FLOATING HYDRATES: EVIDENCE FROM HYDRATE FABRIC AND LOW BULK DENSITIE......Page 94
6. CONCLUSIONS......Page 97
REFERENCES......Page 98
1. INTRODUCTION......Page 100
2. GEOLOGICAL SETTING AND GEOCHEMICAL ENVIRONMENT OF CARBONATE FORMATION......Page 101
3. CARBONATE COMPLEXES AND SAMPLING SITES......Page 102
4. ANALYTICAL METHODS......Page 103
5.1 Petrographic Description and Classification......Page 105
5.2 Stable Isotope Signatures of C and O......Page 108
5.5 Carbonates of Diagenetic Origin in Sediments of Very Slow Venting: Mudstones......Page 110
5.7 Carbonate Lithologies Generated by Gas Hydrate......Page 112
REFERENCES......Page 113
1. INTRODUCTION......Page 115
2.4. Gas Chromatography GC......Page 117
3.1. Biomarkers: Abundance and Structures......Page 118
3.2. Carbon Isotopes and Isotope Effects Associated with AMO at Hydrate Ridge......Page 120
3.3. Microbial Community Structure and the Process of AMO in Hydrate Ridge Sediments......Page 125
4. CONCLUSIONS......Page 127
REFERENCES......Page 128
1. INTRODUCTION......Page 130
1.1 Geologic Overview......Page 132
2.1 Study Sites......Page 133
3.2 Gas Hydrate......Page 136
4.1 Vent Gases......Page 137
4.3 Structure ii Gas Hydrate......Page 138
5. CONCLUSIONS......Page 139
REFERENCES......Page 140
Fluid and Gas Expulsion on the Northern Gulf of Mexico Continental Slope: Mud-Prone to Mineral-Prone Responses......Page 143
1. INTRODUCTION......Page 144
2. FLUID AND GAS EXPULSION FEATURE SPECTRUM......Page 146
3.1. Rapid Flux Mud Prone Case......Page 147
3.2. Moderate Flux Case......Page 149
3.3. Slow Flux Mineral Prone Case......Page 151
3. SUMMARY......Page 155
REFERENCES......Page 157
1.1 The Role of the Deep-tow Seismic Technique......Page 160
1.2 High-Resolution Deep-Tow Acquisition and Processing......Page 161
1.3. Imaging......Page 162
1.4 Velocity Analysis......Page 163
2.1. Cascadia Margin......Page 165
2.2. The Blake Ridge, Crest and Flank......Page 167
3.1. Sediment P-Wave Velocity......Page 168
3.2 A Model of Hydrate Distribution......Page 169
3.3. Blanking......Page 170
REFERENCES......Page 171
INTRODUCTION......Page 174
A Weighted Equation......Page 175
B Effective Medium Equation......Page 176
POROSITY AND VELOCITY DATA......Page 177
OBSERVATIONS AND PREDICTIONS......Page 178
DISCUSSION......Page 179
REFERENCES......Page 181
INTRODUCTION......Page 183
Formation Imaging Logs......Page 184
Gas Hydrate Reservoir Models......Page 186
WELL-LOG RESPONSE MODELING......Page 187
Gamma-Gamma Density Logs......Page 188
Neutron Porosity Logs......Page 189
Electrical Resistivity Logs......Page 192
Acoustic Transit-Time Logs......Page 193
Neutron Spectroscopy Logs......Page 194
Blake Ridge, Atlantic Ocean......Page 195
Mackenzie River Delta, Canada......Page 199
Porosity Calculations......Page 200
Gas-Hydrate Saturations......Page 202
REFERENCES......Page 203
Seafloor Collapse and Methane Venting Associated with Gas Hydrate on the Blake Ridge ? Causes and Implications to Seafloor Stability and Methane Release......Page 205
METHODS......Page 206
SEISMIC PROFILE AND SIDESCAN SONAR DATA ANALYSIS......Page 207
Structure of the Collapse and Adjacent Areas......Page 218
Cause of the Collapse......Page 220
Hypothesized Developmental Stages......Page 221
Relation to Sealevel Lowstand......Page 222
Volume Loss and Methane Escape......Page 223
SUMMARY AND CONCLUSIONS......Page 224
REFERENCES......Page 225
INTRODUCTION......Page 228
HYDRATE, THE BSR AND BLANKING......Page 230
THE DYNAMIC FREE GAS SYSTEM......Page 237
THE BLAKE RIDGE COLLAPSE: THE VALVE ON A PRESSURE COOKER?......Page 241
CONCLUSIONS......Page 246
REFERENCES......Page 248
Gas Hydrates Along the Peru and Middle America Trench Systems......Page 250
Geologic Setting......Page 251
Distribution of BSRs......Page 252
Thermal Field of the Peruvian Margin......Page 254
Gas Hydrates During DSDP and ODP Legs......Page 256
Distribution of BSRs at the Costa Rica Margin......Page 258
BSRs and Slope Failure......Page 259
Heat Flow Patterns......Page 260
REFERENCES......Page 262
INTRODUCTION......Page 265
SEISMIC DATA......Page 266
Distribution of Hydrate BSR......Page 269
BSR Reflection and Reflection Coefficients for Conventional Multichannel and Single Channel Data......Page 270
Interval Velocity-Depth Profiles......Page 271
Amplitude- Versus-Offset......Page 272
Full Waveform Inversions......Page 274
HEAT FLOW DATA AND DEPTH TO THE BSR......Page 275
THERMAL MODELS FOR SUBDUCTION AND FOR SEDIMENT ACCRETION......Page 276
SEAFLOOR ELECTRICAL PROFILING AND COMPLIANCE ESTIMATES OF HYDRATE......Page 277
Hydrate and Free Gas Concentrations......Page 280
COMPARISONS WITH SEVERAL OTHER HYDRATE AREAS......Page 282
CONCLUSIONS......Page 283
REFERENCES......Page 284
Geologic Setting......Page 288
NEW BATHYMETRIC AND BACKSCATTER DATA......Page 290
INTERPRETAION OF THE NEW MULTIBEAM DATA......Page 291
Regional Distribution of High Backscatter Caused by Flow Phenomena......Page 293
REFERENCES......Page 294
1. INTRODUCTION......Page 295
3. PHYSICAL BEHAVIOUR OF GAS HYDRATE- CHARGEDMARINE SOIL......Page 296
5.1 Sea floor stability......Page 297
5.4 Heavy structures and anchors......Page 298
6. CONCLUSIONS......Page 300
REFERENCES......Page 302