Effect of Chemical Surfactant Composition on the Spreading Coefficient and Capillary Number in Dolomite Oil Reservoir

The main advantages of surfactant flooding, including the reduction of the interfacial tension between the aqueous surfactant solution and the residual oil and wettability alteration, make it a very potential method for the enhanced oil recovery processes. Since the surface activity of surfactants and their critical micelle concentration (CMC) can be improved by mixing them, this study was aimed to evaluate the binary mixture of various surfactants, including cationic quaternary ammonium surfactant (CTAB), anionic surfactant (AOT) and non-ionic (Tween 80) with an imidazolium-based ionic liquid ([C12mim] [Cl]) in the volume ratio of 2:1. Binary surfactant mixtures have been investigated in low and high salt concentrations (650 ppm and 38350 ppm) to see the effect of salt concentration on each of the binary mixtures. After investigation of the interfacial tension of each of these mixtures, the phase behavior of each of them was investigated. In addition, the wettability alteration on dolomitic carbonate rock has been investigated. To simultaneously investigate the two mechanisms including interfacial tension reduction and wettability alteration, the spreading coefficient and capillary number were calculated. The results showed that despite the decrease in the interfacial tension of crude oil from 8.72 mN/m to less than 0.5 mN/m, this improvement has no significant impact on the creation of a favorable microemulsion and change the wettability alteration of dolomitic rock into strongly water wet state, as a result, no significant changes in the capillary number and spreading coefficient were obtained.