Numerical investigation of dimethyl ether impacting the gas–oil minimum miscibility pressure in CO₂-enhanced oil recovery: Insights for water-free and water-saturated conditions.

This article focuses on investigating the effect of dimethyl ether (DME) as an additive on the gas–oil minimum miscibility pressure (MMP) during CO₂-enhanced oil recovery (EOR). Using a two-phase multiple-mixing-cell (MMC) method combined with the Peng–Robinson equation of state and Huron–Vidal mixing rule (PR+HV), the study finds that moderate DME addition can significantly reduce MMP, but excessive DME may increase MMP, especially when the initial MMP is below the oil saturation pressure. The research also reveals that increasing DME concentration shifts the miscibility mechanism from multi-contact to first-contact miscibility, requiring a revised MMP criterion based on the minimum first-contact miscibility pressure (MFCP). Furthermore, the presence of water has a negligible impact on MMP, allowing water-free MMP results to be applied in water-saturated reservoirs, simplifying calculations. The study underscores the importance of optimizing DME concentration to achieve effective MMP reduction in CO₂ flooding processes.