The density characteristics of CO2 and alkane mixtures using PC‐SAFT EoS

Abstract

AbstractThe density of CO2 + crude oil mixtures is one of the most important parameters influencing CO2 diffusion and migration in oil reservoirs. However, it would be quite time consuming to obtain comprehensive density data for CO2 + alkane mixtures over a wide range of temperatures and pressures via experimental methods, therefore the development of a reliable model for predicting the densities of various CO2 + alkane mixtures with high accuracy is crucial. In this paper, the parameters (m, σ, and ε/k) in the perturbed‐chain statistical associating fluid theory (PC‐SAFT) Equation of State (EoS) were optimized by correlating density data of pure n‐alkanes from heptane to nonadecane (except undecane and hexadecane). For comparison, the G‐S PC‐SAFT and HTHP PC‐SAFT EoS(s) were also employed to fit the densities of these n‐alkanes, and the results demonstrated that the PC‐SAFT EoS with the optimized parameters in this study exhibited superior accuracy. Subsequently, by correlating density data of CO2 + alkane mixtures containing C7–C14 alkanes, the binary interaction parameter kij was optimized. Furthermore, for the first time, correlations between the optimized parameters (m, σ, ε/k, and kij) and alkane carbon number (n) were established. These correlations provided PC‐SAFT EoS with a good universality and scalability for density prediction. Using the parameters calculated from these correlations, the densities of hexadecane and saturated CO2 + alkane mixtures containing C10–C20 alkanes were successfully predicted with relatively high accuracy. This work provides a new way for modeling the thermodynamic properties of CO2 + alkane mixtures. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.