Characteristics and evolution of composite petroleum systems and the exploration strategy in Junggar basin, northwest China

The composite petroleum system is the aggregate of several petroleum systems in a certain area. In a composite petroleum system, the petroleum systems share the same reservoirs and caprocks and the petroleum accumulations are usually multi sourced. There are 4 composite petroleum systems in Junggar basin including 16 petroleum systems, in which Muhu West well Pen 1, Changji and Dongdaohaizi Dajing composite petroleum systems have the most importance in the basin. The active source rocks in Muhu West well Pen 1 composite petroleum system are Jiamuhe Formation and Fengcheng of Lower Permian and Xiawuerhe Formation of Middle Permian, they formed three petroleum systems. The active source rocks in Changji composite petroleum system are mainly Middle Permian and Lower Jurassic. The active source rocks in Dongdaohaizi Dajing composite petroleum system are Carboniferous and Middle Permian. The multi sourced and multi phase hydrocarbon accumulation makes the most important characteristics of composite petroleum system in Junggar basin. The continuous and successive development of several petroleum systems is the main factor controlling the richness of hydrocarbon in a composite petroleum system. The emphasis of hydrocarbon exploration in Junggar basin should be focused on the uplifts and the related slopes in the three rich composite petroleum systems.