Wettability Alteration During Low Salinity Water Flooding: Effects of Brine Composition and Clay Minerals

Abstract

Low salinity water flooding (LSWF) when injected into the reservoir enhances the oil recovery considerably, and this is attributed to the change of reservoir rock wettability. The process governing these changes is still not well understood. In recent years, the result of extensive research work both in field and laboratory test demonstrated that wettability alteration of rock surface by water salinity concentration and composition can improve significantly the ultimate oil recovery of water flooding. Moreover, the presence of background electrolyte Ca⁺⁺ can largely enhance the adsorption of acidic polar compounds (benzoic acid) onto clays (kaolinite, illite) in contrast to Na^+, and reducing the salinity can lead to the desorption of acidic polar compounds that pre-adsorb onto clays. In his paper, an experimental investigation on the possible mechanisms of LSWF was conducted, contact angles change as function of time, and low salinity using sandstone core and powder of clay minerals (kaolinite, illite) for various injection brines were performed. For the study [5], core slabs were extracted from the core plug, and then, saturated with high salinity water (HSW). Then, the slabs underwent aging process in crude oil at ambient pressure and temperature of 90°. Later, the slabs were removed and immersed in container with low salinity water (LSW) at different ionic compositions, and the wettability was measured by applying the sessile drop method in certain range of time. According to the results, there has been significantly great change of wettability when decreasing the salinity in case of clay minerals.