A Surface Reactivity Analysis of the Crude Oil-Brine-Limestone Interface for a Comprehensive Understanding of the Low Salinity Waterflooding Mechanism

Low salinity waterflooding (LSWF) has proven to improve oil recovery in carbonate formations through rock wettability alteration although the underlying mechanism remains elusive. In this work, coreflooding coupled with surface reactivity analysis approach was employed to investigate the interplay of wettability alteration mechanisms such as mineral dissolution, electrostatic force reduction and the effect of pH at in-situ conditions. Improved oil recovery (IOR) in tertiary mode observed by coreflooding in Indiana limestone rocks showed a brine ionic strength dependence, i.e. reducing brine ionic strength resulted in an increase in oil recovery. Coreflooding results showed that the seawater and low salinity brines deprived of Mg2+ ions resulted in the lowest IOR in tertiary mode, indicating the significance of Mg2+ on IOR in limestone rocks. Similar results were observed through contact angle measuring showing the limestone rock wettability state dependence on ionic strength and the effect of Mg2+ ion. Su...