Applications of ionic liquids in improving CO₂ miscibility in crude oil for enhanced oil recovery and CO₂ sequestration applications

Innovation and sustainability are critical for maximizing reserves in the petroleum industry, especially in deep heavy oil reservoirs where traditional thermal EOR techniques often underperform. CO₂-flooding offers a promising alternative, with its effectiveness dependent on achieving minimum miscibility pressure (MMP). Reducing MMP offers higher recovery factors while avoiding issues due to formation fracturing at high injection pressures. This study evaluates ionic liquids (ILs), 1-methyl-3-octylimidazolium chloride ([MOIM]Cl) and 1-decyl-3-methylimidazolium chloride ([DMIM]Cl), for lowering MMP in CO₂-crude oil systems. Results showed [MOIM]Cl and [DMIM]Cl reduced MMP by 17 % and 13.5 %, outperforming n-butanol and non-ionic surfactants, which achieved 6 % and 9 % reductions, respectively. For extra heavy oil, [MOIM]Cl reduced MMP by 15.5 %. The ILs also lowered first contact miscibility pressure across crude oils with asphaltene content ranging from 6.4 to 36 wt%. These findings highlight ILs' potential to improve CO₂ miscibility in heavy oil reservoirs, providing a sustainable solution for enhanced oil recovery.