A Multi-Parameter Correction Model for Predicting IFT and MMP of CO2–Oil Systems

Abstract

Gas-liquid interfacial behavior in nanoconfined CO2-hydrocarbon systems controls interfacial tension (IFT), minimum miscibility pressure (MMP), and miscibility development in nanoporous media. Most confinement-correction models focus on critical temperature and critical pressure, while changes in the acentric factor, critical volume, binary interaction coefficient, and parachor are less consistently treated. Here, we developed a multi-parameter thermodynamic correction framework that combines a cubic equation of state, flash calculations, and parachor-based IFT prediction. The model reproduced literature and experimental benchmarks with relative deviations of 1.44% for bulk CO2–C6 MMP, less than 3% for confined CO2–C6 MMP, and 3.49% for a CO2-mixed hydrocarbon system. Additional comparisons with experimental MMP/IFT data and SAFT-based calculations showed consistent pressure and pore-size trends. The full-parameter correction gave lower IFT and MMP than correction of only critical temperature and critical pressure. For CO2–C8 at 80 °C in a 5 nm pore, the IFT at 6 MPa decreased from 2.52 to 0.613 mN/m, and the MMP decreased from 12.75 to 11.48 MPa after all parameter shifts were included. The correction effect became stronger in smaller pores, at higher temperatures, and for longer-chain hydrocarbons. Mechanistic analysis showed that pressure and stronger confinement promote gas–liquid compositional homogenization, whereas temperature regulates miscibility non-monotonically. The workflow is most suitable for comparing pore-size, temperature, pressure, and composition effects in CO2-alkane and simplified mixed-hydrocarbon systems. Extension to complex crude oils requires reliable compositional and thermodynamic inputs.