Effects of Four Important Factors on the Measured Minimum Miscibility Pressure and First-Contact Miscibility Pressure

The vanishing interfacial tension (VIT) technique is applied to determine the minimum miscibility pressures (MMPs) and first-contact miscibility pressures (Pmax) of five light crude oil–CO2 systems from the measured equilibrium interfacial tensions (IFTs) at different equilibrium pressures. The equilibrium IFTs are measured under various experimental conditions by applying the axisymmetric drop shape analysis technique for the pendant drop case. It is found that in each IFT test, the measured equilibrium IFT is reduced almost linearly with the equilibrium pressure in two pressure ranges. The MMP of each light crude oil–CO2 system is thus determined from the measured equilibrium IFTs in range I by applying the VIT technique. The first-contact miscibility pressure (Pmax) of each light crude oil–CO2 system is extrapolated from the measured equilibrium IFTs in range II. Moreover, the test temperature, crude oil composition (dead/live oil), gas composition (pure/impure CO2), and initial gas–oil ratio (GOR) are studied to examine their specific effects. The experimental data show that the measured MMPs and Pmax values of five light crude oil–CO2 systems increase linearly with the temperature. The presence of CH4 in the CO2 phase results in substantially higher MMP and Pmax. An increased initial GOR leads to marginally higher MMP and Pmax.