FAULTS IN THE ZHU-3 DEPRESSION OF PEARL RIVER MOUTH BASIN AND THEIR CONTROL OVER HYDROCARBON ACCUMULATION

The Zhu-3 depression of the Pearl River Mouth Basin is a stretching petroliferous basin beside the continental margin of the northern South China Sea. Controlled by the tectonic stress field, three periods of faulting activity characterized by three types of fault have been recognized. From Paleocene to early Oligocene, early rifting faults were developed in a direction of Northeast. From late Oligocene to early Miocene, middle strike-slip extensional faults were formed in a direction of approximately East West. And from mid Miocene to present, late strike-slip extensional faults were developed in a direction of Northwest. According to the distribution of the main and secondary faults, there are four combination styles in a plane view, including parallel, pinnate, en echelon, and broom-like. In section, there are three combination styles, including ‘Y’ like, stair-stepping and negative flower-like. Fault activities have significant controlling effects on hydrocarbon generation, migration and accumulation in the Zhu-3 Depression. Major faults control the distribution of hydrocarbon generation sags and the thermal evolution of source rocks. Fault activities generated various traps of hydrocarbons. The long-term active faults provided major pathways for hydrocarbon migration to shallow reservoirs. Zones with major faults are the most favorable areas for multiple reservoir formation. The step-fault zone on the northern slope of the Wenchang A sag and the anticlinal belt of the Qionghai uplift and Yangjiang lower uplift are the most favorable areas for hydrocarbon migration and accumulation.