Effect of Salinity on Microemulsion Used for Residual Oil Recovery and Restoration of Initial Wetting State of a Capillary Medium

Abstract

An important volume of oil remains trapped in the porous medium due to wettability alteration. Microemulsions are widely used in laboratory core flooding experiments to enhance residual oil recovery and restore the initial wetting state. This study presents the formulation of a microemulsion using two surfactants: sodium dodecyl benzene sulfonate (SDBS) and Tergitol 15-S-12, with the optimal salinity determined by Huh's method for draining a capillary system with altered wettability (oil-wet). The results show that the optimal salinity lies between 70 and 90 g/l, with a decrease in interfacial tension of approximately 0.01 mN/m. The percentage of oil recovered after brine drainage is 33.13%, compared with 89.96% after microemulsion injection at 25°C. These results support the use of experimentally prepared surfactant formulations from the laboratory scale to the reservoir rock scale