GEOLOGIC STRUCTURE OF JIANFENGBEI BASIN AND ITS PROSPECT FOR PETROLEUM EXPLORATION

Jianfengbei basin is a Cenozoic sedimentary basin which is located in the south continent margin of the South China Sea. This basin consists of five seismic sequences with complex tectonic systems. In the basin,faults are well developed and extend alone NE, EW and NW directions. They can be grouped under normal and shift faults. Normal fault is the most important. The basin has two developing stages:early graben period and late depression period. Affected by the Shenfu movement from Paleocene to Eocene,the basin gave birth to many NE or NEE faults and many small grabens,and during this period the basin accepted sediments of river-lake facies. Influenced by spreading of the central basin of the South China Sea from Oligocene to middle Miocene, Jianfengbei basin subsided and accepted transition facies or marine sediments. At the end of middle Miocene the basin uplifted and some parts of the basin were eroded. Late Miocene was a regional subsiding stage when the basin accepted shallow sea to deep sea sediments, which are distributed broadly and more than 4 500 m in thickness. Such sediments can generate hydrocarbon. The basin has good reservoir and seal condition and also good migration condition, so it has good oil-gas potential.