Effect of salinity and surfactant type on spreading coefficient and capillary number of [C12mim] Cl mixtures

The superiority of surfactant flooding, such as the interfacial tension (IFT) reduction and wettability alteration, makes it a very efficient method for enhanced oil recovery. This study aimed to evaluate the effects of mixing various surfactants, including cationic quaternary ammonium surfactant (CTAB), anionic surfactant (AOT), and non-ionic surfactant (Tween 80) with an ionic liquid (IL) based on cationic imidazolium ([C₁₂ mim] Cl) on the interfacial tension, critical micelle concentration (CMC) measurements, microemulsion test, and the wettability alteration on dolomitic carbonate rock through contact angle measurement as well as calculation of spreading coefficient and capillary number. Binary surfactant mixtures have been investigated in low and high salt concentrations (5000 ppm and 39711 ppm) to see the effect of salt concentration on each of the binary mixtures. It was observed that surfactant activity is affected by salt concentration and volume ratio. [C₁₂mim] [Cl] + CTAB at the ratio of 2:1 and low salinity conditions can be considered as the best solution to reduce residual oil saturation due to the ultra-low IFT value, wettability alteration towards water-wet state, and the highest capillary number and acceptable spreading coefficient.