Determination of Reasonable Recovery Ratio with CO2 Miscible Flooding in Reservoir

In order to determine reasonable recovery for CO2 miscible flooding reservoir,a modified water flooding fractional flow equation is presented in this paper(with more obvious physical factors)to fit CO2 miscible flooding reservoir based on water flooding theory that includes water flooding fractional flow equation,Buckley-Leverett water flooding non-piston theory,and CO2 miscible flooding characteristics(no interfacial tension existed in miscible flooding reservoir,and the permeability of each phase is directly proportional to the saturation of corresponding phase),and derived CO2 gas fractional flow coefficients equation and the equation related to crude oil recovery percentage and cumulative gas injection.The two equations can be used to design and forecast development parameters of CO2 miscible flooding. By deriving the mathematical equation concerning the crude oil recovery percentage and cumulative gas injection,a mathematical model of derivative equation has been established to obtain the reasonable recovery ratio of CO2 miscible flooding,which can provide theoretical reference for calculating reasonable CO2 injection volume and ultimate recovery factor of CO2 miscible flooding.