FORMATION AND DISTRIBUTION OF SUBTLE RESERVOIRS IN THE SOUTHERN STEEP SLOPE ZONE IN THE BIYANG SAG OF THE NANXIANG BASIN

The southern steep slope zone in the Biyang Sag of the Nanxiang Basin,is characterized by various categories of subtle hydrocarbon reservoirs.In Shuanghe area,the updip pinch-out sandstone reservoir and the fault-lithologic reservoir dominate over others.In Zhaowa-Anpeng region,the updip pinch-out reservoir and the lenticular turbidite reservoir are the major categories.In Xiaermen area,the fault-lithologic reservoir precedes.Near the large boundary faults,a small quantity of the unconformity reservoir and the buried hill bedrock reservoir have also been drilled.The formation and distribution of subtle reservoirs in this region are controlled by various factors,such as the palaeotectonic setting,the migration pathway of hydrocarbon and the source-reservoir-caprock assemblage,of which the fault as a migration pathway of hydrocarbon is the major factor to control the hydrocarbon occurrence.It is significant for the oil and gas exploration to recognize the hydrocarbon-forming model and its primary controlling factor in different area.