Experimental Determination of Interfacial Tension and Miscibility of the CO2-Crude Oil System; Temperature, Pressure, and Composition Effects

Interfacial tension (IFT) as one of the main properties for efficient CO2 flooding planning in oil reservoirs depends strongly on pressure, temperature, and composition of the reservoir fluids. Therefore, it is important to measure this property at real reservoir conditions for successful field development plan. In this study, an axisymmetric drop shape analysis (ADSA) has been utilized to measure the equilibrium IFTs between crude oil and CO2 at different temperatures and pressures. Moreover, minimum miscibility pressures (MMP) and first-contact miscibility pressures (P-max) of crude oil/CO2 systems at different temperatures are determined by applying the vanishing interfacial tension (VIT) technique. Besides, the effects of paraffins content and resin to asphaltene ratio of the crude oil on the IFT behavior are investigated. The results show that while the IFT has a decreasing trend with temperature at low pressures region, it has an increasing trend with temperature at high pressures. Also, MMP and P-max were found to increase linearly with temperature. The results indicate that paraffin has a critical effect on the crude oil/CO2 IFT behavior. It was also found that the lower the ratio of resin-to-asphaltene is, the more is the possibility of asphaltene precipitation as determined by examining the IFT behavior of the solution. Moreover, the results verified that the higher is the molecular weight of heavier components of the crude oil, the higher are the MMP values obtained.