Migration and accumulation model of slope area in big depression with outside source rock:An example from Fuyu oil layer in Chang 10 area,Songliao Basin

Chang 10 area is of the typical accumulation outside effective hydrocarbon source on slope of depression.The cores,well loggings and seismic data were used to analyze the main controlling factors such as oil origin,sand body distribution,structural features and oil and water distribution.The result shows that oil was generated from syncline source rocks of the first member of Qingshankou Formation in Sanzhao Sag;T2 fault concentrates into belts in plane,and oil sources faults that was active accumulation are border faults around concentrated belts;Fuyu oil layer developed river-dominated delta under Baokang source from southwest,and microfacies were mainly distributary channels with a sedimentary evolution of reliction to transgression overlaying in vertical;oil was distributed on the top of Fuyu oil layer in vertical,and decreased from structurally low position to high position,distributing in step shape,under the effect of insufficient supply on the slope.Accumulation mode is that oil which was generated from source rock in the first member of Qingshankou Formation first downward migrated to Fuyu oil layer through oil-source faults under the action of overpressure,then laterally migrated through preferential migration pathways formed by matching between channel sand developed during the largest retrogradation(bottom of FuⅠ) and oil faults under the action of buoyancy,and oil accumulated in fault-concentrated belts in plane while distributed in upper preferential transforming layers in the vertical.