Effect of CO2/N2 Mixture Composition on Interfacial Tension of Crude Oil

摘要

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.