Basin Geodynamics Background of Formation of Huge Petroleum Systems

A new stage of the basic and strategic research of petroleum geology has already started in recent years for discovering significant hydrocarbon accumulation in China. Geologists are facing great challenge and opportunities in this decade and the near future. A critical research field is to recognize the hydrocarbon-rich depressions and their relative petroleum systems in petroliferous basins. Based upon case studies of the Chinese basins, all hydrocarbon-rich depressions have their special basin dynamics background. The Bohaiwan basin is a most important representative one in eastern China. During rifting phase structure framework comprised by a number of half-grabens and associated horsts, rapid subsidence, high geothermal and (overpressured) chambers within source rocks offered excellent conditions for the formation of huge petroleum systems under the lithospheric extension setting. Optimum paleo-climite and lake types in Eocene time may be favorable for the formation of high quality oil source rocks. Two concept models on petroleum system in the Bohaiwan rift basin have been proposed based upon the integrated research of basin evolution and case studies of hydrocarbon accumulation in typical depressions. It is worthy to note that most of important hydrocarbon-generating depressions in large scale superpositional basins of northwest China are also formed in extensional setting, such as the Permian central depression of the junggar basin, the Manjiaer depression of the Tarim basin. The research results elaborate the dynamic processes of hydrocarbon-generating depressions and provide an important theoretical base for the exploration of large oil and gas fields.