Investigation of Rock Wettability Alteration by Carbonated Water through Contact Angle Measurements

Abstract

Carbonated (CO2-enriched) water injection has been shown to improve waterflood performance over conventional water flooding. Carbonated water can be purposely injected in an oil reservoir, but it also forms spontaneously during conventional CO2 floods or CO2 water alternating gas (WAG) injection. It is therefore important to understand the rock–fluid and fluid–fluid interactions that take place in an oil reservoir when carbonated water contacts the oil and the reservoir rock. Because of dissolution of CO2 in brine, the pH of injection water is reduced during carbonated water injection. This reduction in brine pH may affect the electric charges on water–rock interfaces and, hence, may alter the wetting characteristics of the surface. This wettability alteration will have a direct effect on oil recovery and the amount of oil remaining after waterflood. To assess and quantify the extent of possible wettability alteration as a result of carbonation of water, a series of contact angle measurements have been pe...