Accumulative Conditions and Distribution Characteristics of Hydrocarbon in Huanghekou Depression,Offshore Bohai Bay Basin

The hydrocarbon accumulation conditions in the Huanghekou depression are analyzed in this paper,using the latest high-resolution 3D seismic and well logging,combined with the core observation information,from the source rock,reservoirs,reservoir-seal assemblage,traps type and carrier systems.The results show that source rocks are general in the Huanghekou depression,and there develop three sets of hydrocarbon source rocks,and the 3rd Member of the Shahejie Formation and the 3rd Member of the Dongying Formation are the major source rocks.The main reservoir includes Cenozoic clastic reservoir and bedrock reservoir.The main types of source-reservoir-cap rock assemblages include lower-generation middle-accumulation and upper-cap rock,upper-generation lower-accumulation and upper-cap rock,indigenous generation and accumulation.The trap types are mainly fault block traps,and faults dominate the carrier system in the vertical direction.The influence of Neotectonic Movement on the Huanghekou depression brings favorable conditions for the Neogene hydrocarbon accumulation,and the late fault activity plays roles of preservation and secondary distribution of the formed reservoirs.Major reservoirs in the plane are around oil-generating depressions with a zonal distribution in the structural belt.Paleogene reservoirs are in zonated distribution around the eastern sag.The Neogene majorly is in T-shaped distribution.Hydrocarbon accumulates from the periphery to the center,from south to north,from the Paleogene to the Neogene in the Huanghekou depression.