Hydrocarbon accumulation law and exploration practice in the sag areas of Bohai Sea: a case study on west subsag of Bozhong Sag

In order to figure out the hydrocarbon accumulation laws of the Neogene in west subsag of Bozhong Sag, the oil and gas exploration achievements and the hydrocarbon accumulation characteristics in this area were analyzed comprehensively.Then, the joint controlling effect of the size of paleo-uplift and the development degree of fault and mudstone caprock on the areal migration & accumulation and spatial distribution of Neogene oil and gas reservoirs were mainly dissected.And accordingly, it was for the first time to propose the hydrocarbon accumulation pattern of "uplift-fault-caprock" joint control.It is indicated that the paleo-uplift controls the hydrocarbon accumulation location, the development degree of fault dominates the hydrocarbon enrichment horizon in the Neogene, and the thickness of mudstone caprock restricts the hydrocarbon enrichment of Guantao Formation.Obviously, the effective configuration relationship of paleo-uplift, fault and mudstone caprock determines the favorable conditions for the formation of large-scale oil and gas reservoir in the sag area.Under the guidance of this hydrocarbon accumulation pattern, a series of drilling are carried out in Bozhong13A and Longkou 7A structures and they are commercially successful.It is further verified that the hydrocarbon accumulation pattern of "uplift-fault-caprock" joint control is feasible to the exploration in sag areas.The research results are of great significance to deeply understand the hydrocarbon accumulation in sag areas and search for favorable exploration targets further.