Experimental Investigation of the Combined Effects of Ions and Surfactant to Improve Surface Properties of Crude oil/Low Salinity-Surfactant Water/Rock

More than half of the discovered hydrocarbon reservoirs of the world are naturally fractured oil-wet carbonate. Oil production from these reservoirs is challenging because of their complex nature. Due to the significant decline in oil prices in recent years, the combination of cost-effective and operative methods for enhanced oil recovery seems essential. Surface-active materials and wettability controller ions can be used to alter wettability to desirable state for enhanced recovery. However, to enhance efficiency of the technique, the type and amount of substances in the water needs to be optimized. Also, it is important to characterize the mechanisms involved in wettability alteration processes. In this study, first, the point of zero charge of the rock was determined to find out changes of rock surface charge by pH of the environment. Then, the effect of the type and concentration of influencing ions on improving wettability and interfacial tension in the absence and presence of cationic surfactant in operational range of pH was investigated. The co-presence of magnesium, calcium and sulfate both in the presence and absence of cationic surfactant resulted in significant reduction of IFT and contact angle. This can be attributed to the release of carboxylate groups on the rock surface through making complex by surfactant or interaction of divalent cation and carboxylate groups. Reducing IFT and altering wettability by surfactant/ potential determining ions or combination of them is more noticeable at lower salinity.