Hydrocarbon generation and expulsion caused by pressure difference between source rock and reservoir during basin subsiding and uplifting

The evolution history of hydrocarbon-bearing basins can be divided into 3 stages:subsiding (pressure increasing),uplifting (pressure decreasing) and withering (pressure balancing).Through different stages of energy adjustment,the process of hydrocarbon accumulation has been eventually realized.Hydrocarbon generation and expulsion simulations have been carried out with 4 different pressures between source rock and reservoir using formation pore thermocompression simulation instrument.1) During the subsiding stage,hydrocarbon accumulates in sandstones which interbed with source rocks.It is favorable for accumulation in lithologic traps,yet difficult to travel far away.2) During the uplifting stage,the pressure difference between source rock and reservoir promotes the effective discharge and the long-distance migration of hydrocarbon.The bigger the pressure difference is,the higher the discharge effect will be.3 to 6 MPa of pressure difference is the threshold for effective discharge.When uplift and erosion are 300 to 600 m thick,hydrocarbon discharges in large quantity.3) The pressure difference between source rock and reservoir is beneficial for hydrocarbon discharge and source transformation.Hydrocarbon expulsion frequency and power are complementary.If source rock can provide a large quantity of hydrocarbon,the more frequent the hydrocarbon discharges,and the greater the expulsion power is,the higher the hydrocarbon production rate will be.