Print this pageEvolution and Petroleum Systems of the Ying-Qiong Basin
ZHANG, QIMING
The Ying-Qiong Basin, a newly-discovered large gas province in China, lies west and south off the Hainan Island. Although the Yinggehai Basin and the Qiongdongnan Basin are different in genesis, the rapid subsidence and the fast deposition since 5 Ma made both of them sharing the same environments of overtemperature and overpressure, which resulted in different petroleum systems from others in China.
The gas fields discovered in the Ying-Qiong Basin belong to two different petroleum systems. Both of them have relationship with the overpressure built up during the process of basin evolution. One is the upper petroleum system, which was charged by the source rocks of the Sanya, Meishan, and part of the Ying-Huang formations inside the overpressure system. Due to heat flow movements result from mud diapir movements since 5 Ma, hydrocarbons migrated along the syngenetic faults of mud diapirs upwards to the above zones with normal pressure and were entrapped in the Pliocene-Quaternary mud-diapir-related anticlines. The other one is the lower petroleum system with two charging sources: one is the coaly clastics of the Yacheng Formation and the other one is the Meishan Formation inside the overpressure system of the Yinggehai Basin. Gas pools were formed with vertical and lateral charges inside the growth faulted anticlines which were developed on the sandstone basement of Late Oligocene Lingshui Formation. The overpressured strata act as the barrier at the updipping and immediately above areas of the gas pools.