Objective Based on the technical principle that rapid replenishment of formation energy can improve the degree of CO2 miscibility,the feasibility of the injection method to improve the degree of CO2 immiscible flooding in low-pressure tight sandstone reservoirs in Ordos Basin was studied.Methods In this paper,the effects of CO2 displacement at various injection rates and volumes were compared under reservoir conditions.The changes of formation pressure,oil change rate,recovery degree,gas-oil ratio and extraction parameters also were investigated.Results Compared with the conventional injection rate and volumes,the formation pressure increased by 4.14 MPa,the oil change rate increased by 0.13,the recovery degree increased by 22%,the gas-oil ratio decreased by 50%,the component content of C4—C12 increased significantly,and the content of recombination component decreased significantly.Field tests of the two well groups showed that the monthly oil production of the well group was increased by 78%,the average formation pressure was 5 MPa,the corresponding well oil pressure was increased by 4.5 MPa,the degree of miscibility was increased by 32.81%,and the oil displacement effect was remarkable.Conclusion The injection method can effectively improve the degree of CO2 miscible flooding and the effect of CO2 immiscible flooding in tight sandstone reservoirs.
tight sandstone reservoirCO2 immiscible floodingCO2 perfusiondegree of miscibility
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