Four Important Onset Pressures for Mutual Interactions between Each of Three Crude Oils and CO2

Abstract

In this paper, mutual interactions between each of three different crude oils and CO2 are experimentally studied. Three crude oils include two light crude oils and one medium crude oil. First, a series of saturation tests are conducted to determine the onset pressure of asphaltene precipitation for each crude oil−CO2 system. Second, the equilibrium interfacial tension (IFT) between each crude oil and CO2 is measured as a function of the equilibrium pressure. The so-called minimum miscibility pressure (MMP) of each crude oil−CO2 system is determined by applying the vanishing interfacial tension (VIT) technique. Third, the oil-swelling effect and initial strong light-components extraction are observed during the IFT measurements. It is found that the onset pressure of asphaltene precipitation is lower if the asphaltene content of the crude oil is higher. It is also found that the measured equilibrium IFT is reduced almost linearly with the equilibrium pressure in three distinct pressure ranges for the two light crude oil−CO2 systems and in two different pressure ranges for the medium crude oil−CO2 system. The determined MMP is higher if the crude oil is heavier. The oil-swelling effect occurs at a low pressure, but the initial strong light-components extraction becomes dominant at a high pressure.