Abstract: Rifting Controls on Tertiary Petroleum Systems in Bohai Bay Basin, East China

CHEN JIANYU, ZHANG SHULING, and XIONG YIN

Being a giant Tertiary extensional basin, the Bohai Bay Basin has undergone two tectonic stages: rifting during the Paleogene and subsidence during the Neogene. The intensity and history of rifting control the existence, distribution and attributes of the petroleum system in all East China basins. Intense rifting in the Paleogene has broken up the basin into numerous half-graben shaped (less commonly graben - shaped) depressions and subdepressions which often received organic matter rich deposits and evolved into independent petroliferous units. For example, Jiyan superdepression in the basin contains 4 depressions and 16 subdepressions in which most are important productive areas. Three major rifting cycles in the Paleogene have resulted in the deposition of five sets of potential clastic source rocks in the basin, thus forming respectively Eocene, Oligocene and Miocene petroleum systems. The distribution of systems largely varies, relying on the existence of mature source rock. According to the evolutional history in the Paleogene, the depressions can be divided into three categories: inherited, early developed and lately developed. The former two categories may contain 2 - 3 systems and the later only one, or even none. The Miocene system has only limited occurrence in eastern end of the basin.

As an effective migrational path, faults connect not only the deeply buried sources with the Neogene reservoirs, but also connect superposed different systems in the depression, modifying the systems attributes.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria