Oil and gas transmission systems and accumulation model in Eastern depression of North Yellow Sea Basin

Oil and gas in the Mesozoic era have been found in the eastern depression of the North Yellow Sea. Besides previous comprehensive studies, there is still a lack of in-depth and systematic understanding of the main controlling transport system for oil and gas accumulation. The hydrocarbon source rocks, reservoirs, and source reservoir cap rock combinations in the eastern depression were analyzed. Based on reservoir porosity, displacement pressure, mercury saturation, and geological structural characteristics, three main types of oil-gas transport systems in the eastern depression were recognized: sand bodies, unconformities, and faults. Results show that the fault transport system is the main pathway for oil-gas accumulation in this area, followed by the sand transport system and unconformity transport system. Oil and gas are mainly transported vertically, with relatively weak horizontal transport capabilities and short migration distances. Based on the petroleum geological conditions and transport system, four oil and gas accumulation models were established: fracture controlling, stratigraphic overlap , buried hill, and unconventional tight sandstone. Among them, fracture controlling model is the main one, followed by stratigraphic overlap, buried hill, and unconventional tight sandstone models. This article provides geological basis for oil and gas exploration in the study area by exploring the transportation system and reservoir formation mode.