Experiment and correlation of the equilibrium interfacial tension for paraffin + CO2 modified with ethanol

•The IFTs of five systems (paraffins + CO2 modified by ethanol) were measured.•The IFTs of paraffin + CO2 were decreased after CO2 was modified with ethanol.•New correlations of paraffins IFTs were presented based on the experimental IFTs.

Carbon dioxide enhanced oil recovery (CO2 EOR) process is widely used in petroleum industry in recent years. But it has some shortcomings, such as early gas breakthrough, fingering, asphaltene precipitations, because of the low viscosity and density of CO2. These problems can be resolved by adding some common solvents as chemical modifiers in CO2 flooding. In this work, ethanol was chosen as the chemical modifier. The effects of ethanol on the equilibrium interfacial tension (IFT) of paraffin + CO2 systems were investigated with different ethanol contents, temperature range 60-100 °C and pressure range 5.06-14.60 MPa, respectively. New correlation for predicting the IFTs of paraffin + modified CO2 systems were proposed based on 150 experimental IFT values. The square of correlation coefficient (R2), root mean square error (RMSE) and average absolute relative deviations (AARD) were 0.9948, 0.15 and 2.49%, respectively. The paraffin IFTs for modified CO2 and pure CO2 flooding were compared by the IFT average absolute decrease ratio (AADR).

Graphical abstractThe IFTs of five paraffins + CO2 modified with ethanol at different temperatures and pressures with different ethanol mole fractions were measured by pendent drop method. The IFTs of paraffin + CO2 were decreased after CO2 was modified with ethanol. New correlation for predicting the IFTs of paraffin + modified CO2 systems were proposed based on experimental IFT values. The R2, RMSE and AARD were 0.9948, 0.15 and 2.49%, respectively. The paraffin IFTs for modified CO2 and pure CO2 flooding were compared by the IFT average absolute decrease ratio (AADR). The AADR increased with the ethanol mole fractions and decreased as the temperature increasing.Download high-res image (122KB)Download full-size image