Hydrocarbon migration characteristics and its controlling effect on hydrocarbon accumulation of weathering crust in slope area of Liaoxi Uplift

With the improvement of the exploration degree, small complex fault block traps have become the key field of oil and gas exploration in the current uplift area. To clarify the reasons for the differential enrichment of oil and gas in the fault block trap in the West Liaoning uplift, the characteristics of weathering crust on the top of the buried hill in the uplift slope area are analysed by using three-dimensional seismic, logging, thin section and other data through three-dimensional streamline quantitative simulation. The "crust-fault" coupling migration model is established to describe the dominant migration path of oil and gas in the slope area to clarify the control effect of hydrocarbon migration along weathered crust on the differential enrichment of oil and gas in the convex fault block. The results show that ① the buried hill in the study area has experienced multistage tectonic movements, and the lithology of the buried hill is mainly lower Paleozoic carbonate rock and Archean granite. The lithology is brittle and easily weathered and denuded. The denudation pores and structural fractures of the weathering crust are widely developed and stably distributed, forming the main channel of lateral long-distance migration of oil and gas in the slope area. ② The middle zone of the slope is controlled by reverse faults to forma fault uplift structure. The migration of oil and gas along the weathering crust is blocked by the slope fault uplift zone, forming a "crust-fault" coupling oil and gas migration model. The fault throw of the fault uplift zone controls the lateral migration ability of oil and gas in the weathering crust. ③ Using the method of three-dimensional streamline quantitative simulation, the four-level dominant oil and gas migration channels in the study area are characterized, and the control effect of different levels of oil and gas migration channels on the degree of oil and gas enrichment in convex fault blocks is clarified. The research results effectively guide the practice of oil and gas exploration in the Liaoxi Uplift and fill the gap of the understanding and research method of oil and gas accumulation in mature uplift areas of oil-rich sags.