Seismic evidence and formation mechanism of gas hydrates in the Zhongjiannan Basin,Western margin of the South China Sea |
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| Institution: | 1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China;2. Petrochina Hangzhou Research Institute of Geology, Hangzhou, 310023, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;4. Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao Institute of Marine Geology, Qingdao, 266071, China;5. Evaluation and Detection Technology Laboratory of Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China |
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| Abstract: | An analysis of 3D seismic data from the Zhongjiannan Basin in the western margin of the South China Sea (SCS) reveals seismic evidence of gas hydrates and associated gases, including pockmarks, a bottom simulating reflector (BSR), enhanced reflection (ER), reverse polarity reflection (RPR), and a dim amplitude zone (DAZ). The BSR mainly surrounds Zhongjian Island, covering an area of 350 km2 in this 3D survey area. The BSR area and pockmark area do not match each other; where there is a pockmark developed, there is no BSR. The gas hydrate layer builds upward from the base of the stability zone with a thickness of less than 100 m. A mature pockmark usually consists of an outside trough, a middle ridge, and one or more central pits, with a diameter of several kilometers and a depth of several hundreds of meters. The process of pockmark creation entails methane consumption. Dense faults in the study area efficiently transport fluid from large depths to the shallow layer, supporting the formation of gas hydrate and ultimately the pockmark. |
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| Keywords: | Seismic evidence Gas hydrate Pockmarks Zhongjiannan Basin South China Sea |
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