RELATION BETWEEN GEOTHERMAL-GEOPRESSURE SYSTEM AND PETROLEUM ACCUMULATION IN MOLIQING RIFT IN YITONG BASIN

Based on the data of geothermal, geopressure and acoustic log, the characteristics of geothermal and geopressure fields and geothermal-geopressure system of Moliqing rift in Yitong basin are analyzed by using the theory of geothermal-geopressure system. The relation between geothermal-geopressure system and petroleum accumulation is also discussed on the view of hydrocarbon generation, preservation and distribution in the studied area. The research results show that Moliqing area presents high geothermal gradient which is favorable for organic matter maturation and hydrocarbon generation. Undercompaction mudstone appears in the Shuangyang Formation and it enhances the seal of oil-gas. Abnormal pressure does not occur in the ramp region, and capillary pressure acts as the main control factor for sealing the hydrocarbon. Moliqing rift has a geothermal-geopressure system with low overpressure. Because the fluid energy is similar between the upper and the lower geothermal-geopressure system, the vertical migration and accumulation of hydrocarbon are not obvious and the inner low overpressure system is most favorable for hydrocarbon accumulation. The Es2 petroleum system is the most important object for oil-gas exploration in this studied area.