Study on the migration law of CO2 miscible flooding front and the quantitative identification and characterization of gas channeling

Abstract

CO2 miscible flooding can significantly improve crude oil recovery in low permeability reservoirs. At present, research on the migration process of CO2 miscible flooding has mainly focused on the characterization of CO2 concentrations at different locations and the characterization of oil and gas migration velocities, but there have been few quantitative characterization studies on the migration law of CO2 miscible flooding front and the identification of gas channeling time. In view of the above problems, considering the effects of reservoir physical properties, injection parameters and migration mechanisms on the front migration of CO2 miscible flooding, a mathematical model of CO2 miscible flooding is established. Based on the characterization of the CO2 front and miscible zone front, the effects of porosity, initial injection concentration, dispersion and adsorption on the migration law of the CO2 miscible flooding front and gas channeling time are analyzed. The results show that during the migration of CO2, the entire flow area is divided into the CO2 area, miscible area and crude oil area through the CO2 front and miscible zone front, and the miscible area gradually moves to the production end with the increase in injection volume. When the adsorption is weak, the increase in porosity and initial injection concentration accelerates the mass transfer and dispersion process, and the stronger the dispersion is, the larger the miscible area and the earlier the gas breakthrough time. The enhancement of adsorption reduces the miscible area and delays the complete gas channeling time. This study has significance regarding mines for understanding the migration law of CO2 miscible flooding front and the timing of complete gas channeling in low permeability reservoirs.