The global demand for crude oil, as a primary source of energy, continues to grow. However, primary and secondary recoveries can only extract 20 to 40% of crude oils in mature reservoirs. Accordingly, enhanced oil recovery (EOR) techniques have been identified as promising methods. This study investigates the simultaneous effects of a benzimidazolium cationic Gemini surface active ionic liquid (GSAIL), [C4benzim-C6-benzimC4][Br2], and anionic surfactant sodium dodecyl benzene sulfonate (SDBS) on the emulsification, and wettability alteration of crude oil−water system. Based on the results, significant synergistic effects of the mixture were obtained in emulsification and wettability alteration, respectively 57.5% and 80.2%, with the optimum ionic liquid mole fraction of 0.2. The results indicates that the mixture of GSAIL and SDBS has a high ability to form a stable emulsion of crude oil in water and causes the surface wettability to change from oil-wet to water-wet. Therefore, the mixture of GSAIL and conventional surfactant SDBS can provide excellent synergistic results, considering the different aspects of EOR.
