The effect of gas and liquid phase composition on miscibility through interfacial tension measurements of model oils in compressed CO2

Abstract Carbon dioxide (CO 2 ) injection is a promising strategy for reducing CO 2 emissions while enhancing oil recovery. Efficient hydrocarbon displacement requires accurate knowledge of Interfacial Tension (IFT) and Minimum Miscibility Pressure (MMP). This study focuses on investigating the IFT and MMP using the pendant drop along with the vanishing interfacial tension (VIT) method in binary systems comprising CO 2 + n-Decane, CO 2 + n-Hexadecane, and ternary systems of CO 2 + (n-Decane + n-Hexadecane) at 313.15 K and 333.15 K as a function of pressure. Furthermore, a novel adaptation of the pendant drop method is presented to investigate the influence of n-Decane concentration in the gas phase on the IFT and MMP of CO 2 + n-Hexadecane and of CO 2 + (n-Decane + n-Hexadecane) systems. The density of the respective CO 2 -saturated alkanes is measured and reported at conditions relevant to the work. The pressure has an inverse relation with IFT, while the influence of temperature depends on the pressure range investigated, and higher MMP is obtained at higher temperatures. Moreover, the molecular weight of the hydrocarbon phase correlates positively with IFT and MMP. The MMP of CO 2 + n-Decane, CO 2 + (n-Decane + n-Hexadecane) and CO 2 + n-Hexadecane systems is 8.7, 9.3 and 13.4 MPa at 313 K, and 10.6, 12.3 and 17.3 MPa at 333 K, respectively. Lastly, the enrichment of the CO 2 phase with n-Decane results in further IFT reduction and consequently a lower MMP is obtained for CO 2 + (n-Decane + n-Hexadecane) and CO 2 + n-Hexadecane systems which is favourable for enhancing the efficiency of processes pertaining CO 2 -enhanced oil recovery.