渤海新构造运动控制晚期油气成藏

NEOTECTONISM AND LATE HYDROCARBON ACCUMULATION IN BOHAI SEA

渤海海域是我国近海最早进行油气钻井勘探的海域，并首先在浅层获得成功，但经历了漫长探索才认识到海域有良好的浅层油气成藏机制。目前浅层的油气储量占总储量的７０％以上，这是由于海域新构造运动控制了晚期成藏，表现为：第四纪沉降中心与Ｎｍ晚期沉降中心不吻合，使得Ｑ与Ｎ之间地层呈角度不整合；玄武岩喷发及岩浆活动频繁；沿渤南及郯庐断裂带天然地震震中有规律分布，晚期（１５～２Ｍａ）断裂极其发育，在Ｎｍ－Ｎｇ组地层内形成众多的背斜圈闭。新构造运动动力分析认为源于岩石圈下地壳深部地幔拱升及板块运动、纵长５０００ｋｍ的郯庐断裂活动所至，特别是郯庐断裂主体正通过海域，晚期活动产生一系列新的地质事件，使得海域既具有陆区的成藏规律，又有自身的独特一面──晚期成藏。综观海域油气前景，将成为我国东部石油稳产重要基地。

Bohai Sea is the first explored area in China Offshore and first oil discovery had been gained from the shallow targets. After a long-term exploration and development,the mechanism of hydrocarbon accumulation at shallow targets is understood. Up to date the reserves discovered at shallow targets has exceeded 70% of total in Bohai Sea. Neotectonism (Bohai movement)is characterized by: (1)different Q and N center of subsidence,and angular unconformity between Q and N; (2)basalt effusion and magma activities frequently; (3) regular distribution of earthquake center; (4)intensive later faults (15-2Ma)forming multitude anticiline in Nm-Ng formations. In accordance to kinetic analysis of tectognesis, neotectonism was caused by mantle rise, plate movements and Tanlu faults,and it controlled the late hydrocarbon accumulation in Bohai Sea. Bohai Sea will play an important role in stabilizing oil and gas production in the eastern China.