Investigation of Surface Forces during Anionic and Cationic Surfactant Flooding in Carbonate Reservoirs

In this study, the effect of anionic and cationic surfactants on enhanced oil recovery was investigated by considering the wettability alteration and interfacial tension. The alpha olefin sulfonate (AOS) and cetrimonium bromide (CTAB) were considered as anionic and cationic surfactants respectively. Firstly, the stability of chemical solutions was evaluated by zeta potential test and so these solutions were used to IFT, wettability, coreflooding, and surfactant adsorption tests. Also, the surface forces were analyzed to investigate the isoelectric point and surfactant adsorption. The results show that the anionic and cationic surfactants can significantly reduce the interfacial tension. Also, the anionic surfactant alters the reservoir wettability from strongly oil wet (159o) to water wet (37o). Based on the isoelectric point, the anionic surfactant adsorption is higher than that for cationic surfactant adsorption. Consequently, the low salinity sea water which includes cationic surfactant, due to no snap-off phenomena, improved the oil recovery factor up to 19 % compared to sea water injection.