Differences in Temperature and Pressure Evolution and Ordered Distribution Characteristics of Oil Reservoirs in Different Structural Zones of Small Fault Depressions: A Case Study of Beixi Area in Hailar Basin, China

Hailar Basin is composed of multiple small fault depressions, Beixi area is located in Beier fault depression in the central fault depression zone, with diverse structures and complex reservoirs, which urgently requires in-depth research. 3D Basin modeling software is used to carry out single well burial history, thermal history and pressure history evolution simulation, and then carry out planar fluid potential analysis and oil and gas migration and accumulation simulation. In combination with the oil and gas display and reservoir profile of actual drilling wells, the differences in temperature and pressure evolution of three structural zones and the orderly distribution characteristics of oil reservoirs are clarified. The research shows that from trough zone to slope zone to structural zone, the maturity of the source rock of the Nantun Formation ranges from mature to low mature to immature, the hydrocarbon generation pressurization is large to relatively large to small, the migration flow line is dense short distance streamline to longer streamline to long distance streamline, the fluid pressure is high pressure to medium pressure to low pressure, and the ratio of the number of industrial and oil and gas display wells is about 1:2:1, forming an orderly accumulation sequence of lithologic-fault block-structural reservoirs as a whole. The results of Basin modeling are consistent with the actual drilling results, so it is considered that the Nantun Formation in Beixi area can spread exploration and realize full sag oil bearing next step. The dynamic research on accumulation based on 3D seismic, geochemical evaluation, Basin modeling and other technologies can effectively guide the exploration of complex fault basin.