CHARACTERISTICS OF COMPOSITE PETROLEUM SYSTEMS OF SUPERIMPOSED BASINS IN CHINA
HE Deng fa, ZHAO Wen zhi, LEI Zhen yu, QU Hui,CHI Ying liu(Chinese Institute of Petroleum Exploration and Development, Beijing 100083,China)
The superimposed petroliferous basins in China are characterized by long evolutionary history, multiple stages of tectonic evolution, and multiple depositional sequences. The petroleum systems in these basins present complexities of multiple kitchens with multiple source rocks, multiple phases of petroleum generation-migration-accumulation, multiple oil and gas intervals, and multiple critical moments involved in their formiations. It is difficult to characterize such petroleum systems by applying the concepts proposed by Magoon Dow (1994). Based on the complexities of the formation and features of the petroleum systems in China, this paper proposes the concept of the composite petroleum system, and the methods of the classification and evaluation. The basic types of composite petroleum systems in China include the stacking, variable migration and accumulation, fault connection, common sealing, and modification etc. Each superimposed basin consists of one or more of petroleum systems. The superimposed basins of foreland and cratonic in western and central China are characterized by fault connection composite petroleum system in fold and thrust belts, and by composite petroleum systems migrating and accumulating along unconformities. The superimposed basins of fault sag and depression in eastern China are characterized by stacking composite petroleum system. The superimposed basins of remnant and new born in southern China are characterized by modified composite petroleum system.The features of composite petroleum system in each type basin are much different, and also for its exploration methods. The characterization of composite petroleum system is the basis for choosing the exploration area. The division and evaluation of petroleum migration and accumulation unit are critical to proposing the prospect of petroleum exploration. Integration of modern exploration techniques plays an important role in the promoting efficiency of oil and gas exploration of the composite petroleum systems in China.