Impact of Ionic Exchanges between Active and Non-active Ions on Displacement Efficiency in Smart Waterflood Application

Abstract

Smart waterflooding in carbonate reservoirs could be an effective IOR process to improve oil recovery through alteration of rock wettability. This paper presents the impact of ionic exchange between the active and non-active ions in smart water on carbonate sample. Coreflooding experiment was conducted by sequential injection of formation brine and smart brines and the effluent ionic composition was analyzed to verify the activity of these ions on improving recovery. In addition, zeta potential and contact angle measurement were conducted to examine the wettability alteration process and correlated to coreflood results. The results were analyzed in terms of additional displacement efficiency beyond the secondary waterflood. Zeta potential showed that absence of non-active ions increased the reactivity of active ions which lowered the rock surface charge, which in turn, made the rock more water-wet. Also contact angle measurement showed more water-wet behavior. Significant improvement in oil recovery was also observed during flooding and effluent ionic analysis demonstrated that the ionic interaction between the active ions and the rock surface led to the observed wettability alteration and improved recovery.