Utilization of ionic liquids and deep eutectic solvents in oil operations: Progress and challenges

Abstract

Unique properties of ionic liquids (ILs) and deep eutectic solvents (DESs) have given impetus for widespread application in various fields of science, including the oil industry. This review paper provides a state-of-the-art review of existing literature focused on the current applications of these novel chemicals in the oil industry, specifically in upstream oil operations. The effective mechanisms and interpretations behind the interfacial tension (IFT) reduction, wettability modification, mobility control enhancements, and other interesting characteristics of the ILs and DESs, as well as the economic analysis of their utilization in field scale, have been discussed to scrutinize the limitations and challenges related to their applications. Additionally, the utilization of these green chemicals in drilling and production engineering and flow assurance studies has been discussed. According to the literature, the effectiveness of both fluid types at elevated pressures and temperatures and in high salinity formation brines has been demonstrated. In this respect, ultra-low IFT values in the presence of surface-active ILs have been reported by several authors, giving rise to the formation of Winsor III microemulsion that resulted in increased oil recovery. Significant wettability alterations from oil- toward water-wetness with DESs have also been reported. In drilling operations, ILs and DESs proved to be potent alternatives to surfactants for shale inhibition and mud loss control purposes. ILs and DESs have even found applications in CO2 capture and kerogen extractions fields. Based on this study, ILs and DESs, being recyclable and having tunable properties, could be considered as green and cost-effective alternatives for toxic chemicals used in the upstream oil industry though further studies are still required before deciding their role as alternatives.