win德赢

Supercritical carbon dioxide (scCO₂) microemulsion was formed by supercritical CO₂, H₂O, sodium bis(2-ethylhexyl) sulfosuccinate (AOT, surfactant) and C₂H₅OH (co-surfactant) under pressures higher than 8 MPa at 45 oC. The fundamental characteristics of the scCO₂ microemulsion and the minimum miscibility pressure (MMP) with Daqing oil were investigated with a high-pressure falling sphere viscometer, a high-pressure interfacial tension meter, a PVT cell and a slim tube test. The mechanism of the scCO₂ microemulsion for enhancing oil recovery is discussed. The results showed that the viscosity and density of the scCO₂ microemulsion were higher than those of the scCO₂ fluid at the same pressure and temperature. The results of interfacial tension and slim tube tests indicated that the MMP of the scCO2 microemulsion and crude oil was lower than that of the scCO₂ and crude oil at 45 oC. It is the combined action of viscosity, density and MMP which made the oil recovery efficiency of the scCO₂ microemulsion higher than that of the scCO₂ fluid.