Monitoring the Wettability of Oil Reservoir Rocks by AFM during Surfactant Treatment

Oil recovery from fractured, oil-wet/mixed-wet, carbonate reservoirs by waterflooding is hindered mostly because of the absence of water imbibitions into the matrix blocks. It is believed that the chemical treatments including surfactant flooding improve oil recovery efficiency by wettability alteration and interfacial tension (IFT) reduction. In this paper the effect of surfactants on the wettability of dolomite surfaces are studied. The Two different types of surfactants mainly a cationic (C16TAB) and a non-ionic surfactant (TritonX-100) were used to investigate the wettability alteration utilizing a novel technique of Dynamic contact angle measurement. The treated surfaces which show the most effective changed surfaces are then subjected to the AFM test. Results show that cationic surfactant can remove adsorbed compounds from the surface hence change the wettability. In the case of Non-ionic surfactant as it adsorbs on the surface however the wettability remains unchanged.