Orderly distribution and differential enrichment of conventional and unconventional hydrocarbons in the Cretaceous Qingshankou Formation, northern Songliao Basin, NE China

Based on the petroleum exploration in the Cretaceous Qingshankou Formation, northern Songliao Basin, NE China, integrated with seismic, drilling and logging data, this study investigates the characteristics and genetic mechanisms of orderly distribution and the differential enrichment patterns of conventional and unconventional hydrocarbons in the formation. Key findings involve five aspects. First, the conventional and unconventional hydrocarbons coexist orderly. Laterally, conventional oil, tight oil, and shale oil form a pattern of orderly accumulation from basin margins to the center. Vertically, shale oil, tight oil, and conventional oil develop progressively upward. Second, the coupled tectonic-sedimentary processes govern sedimentary facies differentiation and diagenesis, influencing reservoir physical properties and lithology, thereby controlling the orderly distribution of conventional and unconventional hydrocarbons in space. Third, the coupling of source rock hydrocarbon generation evolution, fault sealing capacity, and reservoir densification determines the orderly coexistence pattern of conventional and unconventional hydrocarbons. Fourth, sequential variations in reservoir physical properties generate distinct dynamic fields that regulate hydrocarbon orderly accumulation. Fifth, enrichment controls are different depending on hydrocarbon types: buoyancy-driven, fault-transport, sandbody-connected, and trap-concentrated, for above-source conventional oil; overpressure-driven, fault-transport, multi-stacked sandbodies, and quasi-continuous distribution for near-source tight oil and gas; self-sourced reservoirs, retention through self-sealing, in-situ accumulation or micro-migration driven by hydrocarbon-generation overpressure for inner-source shale oil. From exploration practices, these findings will effectively guide the integrated deployment and three-dimensional exploration of conventional and unconventional hydrocarbon resources in the Qingshankou Formation, northern Songliao Basin.