Effect of CO(2)/N(2) Mixture Composition on Interfacial Tension of Crude Oil

[Image: see text] CO(2)-enhanced oil recovery (EOR) has demonstrated significant success over the last decades; it is one of the fastest-growing EOR techniques in the USA accounting for nearly 6% of oil production. A large quantity of CO(2) gas is required for the EOR process and sometimes other gases such as hydrocarbons, air, flue gases, CO(2), N(2), and mixtures of two or more gases are used for injection. It is also realized that the injection of CO(2) and N(2) combines advantage in reducing CO(2) concentrations in the atmosphere and improving the oil recovery by sequestering it underground. However, there are a number of variables involved in the successful design of the CO(2)-EOR process. The objective of this study is to investigate the effect of CO(2)/N(2) mixture composition on interfacial tension (IFT) of crude oil. Experiments were performed to measure the IFT of the CO(2)/N(2) mixtures and crude oil for different compositions of gas by varying the system pressure at a fixed temperature. The effect of CO(2)/N(2) mixture composition and pressure on the IFT of crude oil is evaluated. The experimental results show that an increase in the mole fraction of CO(2) in the gas mixture results in a decrease in IFT between CO(2)–oil, irrespective of the system pressure. However, because of an increase in the mole fraction of N(2) in the gas mixture, an increase in IFT was observed and this change is opposite to the effect of the CO(2) mole fraction. Also, the change in IFT is consistent with the pressure, which means that the IFT decreases with an increase in the pressure at a given temperature. The effect of the CO(2) mole fraction is more profound compared to the N(2) fraction and with the pressure at which experiments were conducted in this study. The finding of this study helps in designing the CO(2)-EOR process in which achieving miscibility conditions is vital for taking advantage of the CO(2) injection. Also, the presence of N(2) and its influence on the IFT that must be considered in the CO(2)-EOR were addressed in this study.