Comparative study of an acidic deep eutectic solvent and an ionic liquid as chemical agents for enhanced oil recovery

Abstract

Chemical enhanced oil recovery (CEOR) is a viable approach to recover the remaining oil after primary and secondary recovery processes. The present work aims at assessing the performance of two CEOR agents, namely 1-dodecyl-3-methylimidazolium chloride as ionic liquid (IL) and choline chloride:citric acid(1:1) as deep eutectic solvent (DES) through systematic and thorough experimental and theoretical studies. It was also endeavored to figure out their impact on wettability alteration of dolomite samples and also on the reduction of oil-brine interfacial tension (IFT), especially in the presence of cetyltrimethylammonium bromide (CTAB) for the case of DES. Moreover, the adsorption of synthesized IL and DES on dolomite samples was studied through a number of well-known isotherms, including Langmuir, Freundlich, and Temkin, while core flooding experiments with pre-defined soaking periods were carried out to determine oil recovery performance and formation damage tendency of the CEOR agents. It has been revealed that both chemicals, especially IL, were greatly efficient to increase the oil recovery up to 32% that could be further increased by the soaking period after the chemical injection. Furthermore, IFT was significantly reduced following the addition of 5 ppm of CTAB to the DES solution. Finally, the XDLVO theory was also utilized, for the first time, to discern the possible molecular interactions between the oil-wet dolomite surface and the IL/DES-included brines. The results confirmed that the presence of IL and DES-CTAB mixture triggered a stronger adhesion between the brine and oil-wet dolomite surface that was reflected in the total energy of interactions and the work of adhesion calculated for the brine/rock system.