LATE HYDROCARBON ACCUMULATION MECHANISM AND DYNAMICS OFFSHORE THE NORTHERN SOUTH CHINA SEA

Exploration technologies and methods for late hydrocarbon accumulations offshore the northern South China Sea have been summarized in this paper.The late hydrocarbon accumulations are characterized by seismic anomalies such as bottom caves,gas chimneys,"obscure seismic area" and "bright points".Based on geochemical features,three types of accumulations can be identified:biogas in shallow layer,mature-highly mature gas and thermal gas with high CO₂ content.According to neotectonism,late dynamics of petroleum systems related to thrust fault,normal fault as well as diapire-structure and strike-fault have been analyzed.The late movements of faults and the fast thermal subsidence have promoted hydrocarbon migration and redistribution with series of petroleum accumulation distributed along Yingdong ramp and Dongfang-Ledong area in the Yinggehai Basin,No.2 fault zone in the Qiongdongnan Basin and edge ramps of depressions in the Pearl River Mouth Basin.It contributes to the exploration of hydrocarbon and hydrate offshore the northern South China Sea.