TECTONIC SUBSIDENCE AND ITS CONTROL ON HYDROCARBON RESOURCES IN THE WAN'AN BASIN IN THE SOUTH CHINA SEA

The Wan'an basin is a typical Cenozoic shearextensional basin in the southwest of the South China Sea. Inferred from the results of tectonic subsidence modeling for the seismic profiles across the basin and from the calculation of the faulting movement velocity in the basin, it has undergone four tectonic subsidence processes since early Eogene period, and most of the faults are growth ones coming from the basement. The faults were strongly active when the basin underwent shearextension and riftdepression subsidence from late Oligocene to early Miocene. The geological factors and processes for hydrocarbon formation, migration, accumulation and preservation were controlled by the tectonic subsidence stages.