Interaction of crude oil with halogen-free ionic liquid-based catanionic surfactants

Abstract

Chemical injection has proved to have superior performance in improving oil recovery. The injected chemicals are typically designed to participate in interfacial interactions at liquid–liquid and rock-liquid interfaces while having minimum adsorption onto the rock surface. This study endeavors to investigate the interfacial activity of several environmentally-friendly halogen-free ionic liquid-based catanionic surfactants synthesized via an ion exchange reaction between cationic imidazolium-based ionic liquids, [Cnmim][Cl] (n = 4,8,12), and anionic surfactants, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and dioctyl sodium sulfosuccinate. Results revealed that the catanionic surfactant synthesized with medium-chain ionic liquid (n = 8) and sodium dodecyl sulfate exhibited higher interfacial activity, demonstrating a minimum crude oil-brine interfacial tension of 0.17 mN/m and wettability alteration index of 0.79. The results of the adsorption study also revealed the adsorption density of 2.19 mg/g onto the dolomite surface for 2000 mg/L of catanionic surfactant in seawater, which was considerably lower than cetyltrimethylammonium bromide adsorption (11.55 mg/g) in the control experiment. Finally, the surface energy analysis of liquid-rock interactions was conducted using the concept of work of adhesion to scrutinize the wettability alteration and adsorption processes, where a direct relationship between work of adhesion and adsorption density was proposed. According to the results of this study, medium chain ionic liquid-based catanionic surfactant containing dodecyl sulfate anion, exhibiting excellent interfacial activity and low adsorption tendency onto the dolomite surface, could be considered in future chemical enhanced oil recovery applications.