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OBS/MCS Imaging of Petroleum and Gas-Hydrate West of Dongsha Atoll in the Northern South China Sea

Deng, Jia-Ming 1; Chan, Chang-Shun 1; Chiu, Mao-Hsiang 1; Wang, Tan-Kin 1; Liu, Char-Shine 1; Lee, Chao-Shing 2
1 Institute of Applied Geosciences, National Taiwan Ocean University, Keelung, Taiwan.
2 Institute of Oceanography, National Taiwan University, Taipei, Taiwan.

In September 2007, twenty-nine micro-ocean-bottom seismometers (MicrOBS) and several multi-channel seismic (MCS) profiling were implemented along the continental slope west of the Dongsha Atoll in the northern South China Sea (SCS). In particular, one N-S line with continuous bottom-simulating reflectors (BSRs) along the continental slope off Hong-Kong was across the drilling sites for acquiring gas hydrates from China in May 2007. First, an initial velocity-interface model was built from reflection times of the MCS data. Subsequently, we picked refracted, reflected and head-wave arrivals from hydrophone and vertical components of MicrOBS data to invert the velocity-interface structure layer-by-layer. From the MicrOBS data modeling, BSRs were found at a depth of about 150 m below the sea floor in most of the seismic profiles except those along some of the lower continental slopes or near the Dongsha Atoll. We also observed sediments with a thickness of 1.5-3.5 km over buried anticlines and rouged basements (P-wave velocity greater than 5 km/s) which may have been resulted from the post-spreading magmatism of the SCS. We suggest that petroleum reservoirs are prevailed near these buried, anticline ridges in the continental margin west of the DongSha Atoll.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009