Contents
Foreword Ⅰ
Foreword Ⅱ
Preface
Chapter 1 Regional Geology and Preliminary Results 1
1.1 Regional Geology 1
1. Tectonic evolution 2
2. Regional sedimentary evolution 6
1.2 History of Makran Gas Hydrate Research 9
1. Pakistani sea area 9
2. Iranian waters 12
1.3 Previous Research Results 14
1. Research results from other countries 14
2. Research results of Qingdao Institute of Marine Geology 16
Chapter 2 Offshore Data Acquisition in the Northwest Indian Ocean 20
2.1 Purpose of the Survey 20
2.2 Research Vessels and Line Layout 21
1. Research vessels and equipments 21
2. Layout of seismic lines and stations 23
2.3 Seismic Acquisition Technical Requirements 24
2.4 Technical Requirements for Geochemical Sample Collection 26
1. Columnar sample 26
2. Pore water 27
3. CTD 29
Chapter 3 Gas Hydrate Seismic Data Processing 30
3.1 Analysis of Raw Seismic Data 30
1. Low frequency background noise 30
2. Trace gaps 31
3. Cable noise 31
4. Multiple analysis 32
5. Spectrum analysis of original data 33
6. Summary of original data analysis 36
3.2 Seismic Data Processing Challenges and Processing Ideas 36
1. Processing challenges 36
2. Processing ideas 37
3.3 Key Technical Measurements 38
1. Cable noise attenuation affected by external forces 38
2. Noise attenuation from endogenous cables 40
3. Blank trace interpolation 41
4. Random noise attenuation 42
5. Multiple suppression 42
6. Velocity selection 48
7. Time migration 49
3.4 Seismic Data Processing Flow 52
3.5 Analysis of Processing Results 53
1. Significant interference and multiple suppression 55
2. High signal-to-noise ratio 55
3. High resolution 56
4. Clear characteristics of the effective wave group 56
5. Good closure condition of the survey line 56
3.6 Presentation of Result Profiles 57
Chapter 4 Analysis of Geochemical Sample Testing for Gas Hydrate 60
4.1 Geological Sample Characteristics 60
4.2 Geochemical Analysis 62
1. Pore water anion and cation analysis 62
2. Pore water isotope analysis 62
3. Sediment geochemical testing 63
4.3 Sediment Geochemical Characteristics 63
1. Geochemical characteristics of major and trace elements 63
2. Geochemical characteristics of pore water 72
4.4 Sulfate-Methane Interface (SMI) and Gas Sources 80
1. Sulphate reduction 80
2. SMI 81
3. Gas sources 82
4.5 Indication of Gas Hydrate Activity by Geochemical Anomalies 82
Chapter 5 Interpretation of Gas Hydrate Seismic Data 86
5.1 Composition and quality of seismic data 86
5.2 Stratigraphic Sequence Characteristics 87
5.3 Thrust Fault Activity and Gas Chimneys 89
5.4 Patterns of Tectonic Evolution 92
5.5 Characterisation of Gas Hydrate Geophysical Anomalies 93
5.6 Characteristics of Free Gas Beneath BSR 94
5.7 Makran Accretionary Prism Gas Hydrate Transport and Accumulation System 96
Chapter 6 Accumulation Models of Gas Hydrate in the Northwest Indian Ocean 98
6.1 Structures Characteristics of Active Continental Margin and Classification of Subduction Zones 98
1. Structural characteristics 98
2. Subduction zone classification 99
6.2 Characteristics of Gas Hydrate Accumulation in High Angle Subduction Zones 101
1. Sedimentary tectonic characteristics 101
2. BSR distribution characteristics 104
3. Gas source genesis and gas hydrate accumulation models 107
6.3 Characteristics of Gas Hydrate Accumulation in Makran Accretionary Prism 112
1. Sedimentary tectonic characteristics 113
2. BSR distribution characteristics 114
3. The genesis of the gas source 117
4. Transportation system 124
6.4 Makran Accretionary Prism Gas Hydrate Accumulation Model 126
1. Genetic types of gas hydrate in Makran Accretionary Prism 128
2. The “two-storey structure” gas hydrate accumulation model 132
3. The science of the “two-storey structure” model and its significance 135
References 141
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