Wettability Alteration on Sandstone Reservoirs Containing Clay Minerals By The Addition Anionic Alkyl Ethoxy Carboxylate Surfactant

With the increasing number of maturing fields, surfactant injection as an alternative EOR technique is essential to mobilize the remaining oil. The presence of clay in the sandstone causes the polar components in the oil to be adsorbed on the rock surface, causing a tendency towards wettability towards oil-wet. Therefore, the oil potential remaining in the reservoir, which is the target of surfactant injection, is more significant in oil reservoirs with oil-wet characteristics. For this reason, surfactants are needed that can alter the surface properties of oil-wet to water-wet and the ability of these surfactants to reduce IFT. The wettability alteration mechanism is one thing that needs to be understood more deeply, considering the critical function of surfactant injection in the EOR method. Studies on the effect of adding surfactants on sandstones containing clay minerals of certain types and concentrations need to be developed to assist the application of the oil recovery process at an advanced stage. Laboratory experiments are carried out by measuring the contact angle of sandstone samples conditioned according to reservoir characteristics with several concentrations of clay interacting with fluid. The measurement results show that the initial condition of the sandstone containing montmorillonite clay is water-wet, while the sandstone containing kaolinite clay is oil-wet. The presence of surfactant solutions gives a wettability alteration effect on sandstones containing montmorillonite clay to become more water-wet and sandstones containing kaolinite to be water-wet. Surfactant solution with a concentration of 1wt% gives a more significant wettability alteration effect than surfactants with the attention of 2wt%. The interaction of sandstones containing clay minerals with surfactant solution shows that the addition of surfactants can reduce the interfacial tension between oil and water. In contrast, surfactants with a concentration of 2wt% can reduce IFT greater than surfactants with the attention of 1wt%.