Interfacial Property and Minimum Miscibility Pressure of Dimethyl Ether-Assisted CO₂ and Bakken Oil: A Molecular Dynamics Study Available to Purchase

Carbon dioxide (CO₂) flooding in unconventional reservoirs has demonstrated great potential for enhancing oil recovery and reducing greenhouse gas emissions. However, its efficiency is often constrained by the minimum miscibility pressure (MMP), the threshold pressure at which CO₂ becomes fully miscible with crude oil. To address this limitation, dimethyl ether (DME) has been introduced as a cosolvent to improve CO₂-oil miscibility, although the underlying mechanisms remain poorly understood. In this study, molecular dynamics (MD) simulations were used to investigate the effects of DME on the interfacial properties and MMP in the CO₂-Bakken oil system. The results indicate that the addition of DME significantly enhances CO₂ solubility and promotes oil expansion. Specifically, at 30% mol DME, CO₂ solubility increases from 38.80 g/100 g to 58.26 g/100 g, while the oil swelling factor rises from 1.19 to 1.71. Microscope analysis further reveals that DME increases the local concentration of CO₂ molecules around the oil phase, thereby enhancing CO₂ dissolution. In addition, DME reduces the free energy barrier, facilitating mass transfer across the oil/gas interface. As the DME concentration increases, the interfacial tension (IFT) between CO₂ and oil is markedly reduced, resulting in a decrease in MMP from 17.21 MPa to 12.19 MPa in the CO₂-Bakken oil system. Notably, DME enhances CO₂ miscibility more effectively in light oil, reducing the MMP by 43% in light oil and 36% in heavy oil. This study advances the molecular-level understanding of how DME enhances oil/gas miscibility.