Potential of Imidazolium-Based Ionic Liquids for Sustainable Enhancement of Oil Recovery in Emirati Tight Reservoirs

In response to the increasing global demand for energy and the limitations of conventional oil recovery methods, this study investigates the potential of imidazolium-based ionic liquids (ILs) as novel agents for enhanced oil recovery (EOR). The effects of four imidazolium ILs─1-decyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride, 1-dodecyl-3-methylimidazolium tetrafluoroborate, and 1-hexadecyl-3-methyl imidazolium bromide (C₁₆mimBr)─on phase behavior, interfacial tension (IFT), and wettability between oil, water and rock were examined in the context of Emirati tight oil reservoirs. In addition, the thermal stability of these ILs was investigated under extreme temperatures of up to 600 °C using thermogravimetric analysis. Experiments were conducted across a range of temperatures (up to 110 °C), IL concentrations (0, 500, 1500, and 3000 ppm), and salinities (seawater and formation brine). In particular, the IL with the longer alkyl chain (C₁₆mimBr) effectively reduced the IFT by >99% in formation brine at 3000 ppm and 110 °C and altered contact angles to as low as 15.37°. Emulsification experiments were conducted with the emulsions analyzed under a microscope to measure the size of water droplets within the microemulsions. It was observed that all imidazolium ILs tested at 500 ppm successfully stabilized oil/brine emulsions, maintaining complete phase integrity for at least 48 h. Imidazolium ILs with longer chains and bulky anions (C₁₂mimBF₄) showed adsorption as low as 2.71 mg/g, reducing chemical loss and enhancing EOR effectiveness. The findings indicate that the choice of IL and its concentration significantly impact the economic reduction of IFT and optimize EOR processes.