Geophysical Signature of the Shallow Water Flow in the Deepwater Basin of the Northern South China Sea |
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| Authors: | Xiaohua Zhang Yunbao Sun Shiguo Wu |
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| Institution: | 1.College of Marine Geosciences,Ocean University of China,Qingao,China;2.Key Laboratory of Gas Hydrate, Ministry of Natural Resources,Qingdao Institute of Marine Geology,Qingdao,China;3.Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,China;4.Institute of Deep-Sea Science and Engineering,Chinese Academy of Sciences,Sanya,China;5.Hainan Key Laboratory of Marine Georesources and Prospecting,Sanya,China;6.University of Chinese Academy of Sciences,Beijing,China;7.Key Laboratory of Marine Hydrocarbon Resource and Geology,Qingdao Institute of Marine Geology,Qingdao,China |
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| Abstract: | Shallow water flow (SWF), a disastrous geohazard in the continental margin, has threatened deepwater drilling operations. Under overpressure conditions, continual flow delivering unconsolidated sands upward in the shallow layer below the seafloor may cause large and long-lasting uncontrolled flows; these flows may lead to control problems and cause well damage and foundation failure. Eruptions from over-pressured sands may result in seafloor craters, mounds, and cracks. Detailed studies of 2D/3D seismic data from a slope basin of the South China Sea (SCS) indicated the potential presence of SWF. It is commonly characterized by lower elastic impedance, a higher Vp/Vs ratio, and a higher Poisson’s ratio than that for the surrounding sediments. Analysis of geological data indicated the SWF zone originated from a deepwater channel system with gas bearing over-pressured fluid flow and a high sedimentation rate. We proposed a fluid flow model for SWF that clearly identifies its stress and pressure changes. The rupture of previous SWF zones caused the fluid flow that occurred in the Baiyun Sag of the northern SCS. |
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