Study of surface complexation and mineral dissolution during water-rock interaction in high salinity waterflooding at elevated temperature

High salinity waterflooding for carbonate reservoirs is efficient and cheap method used for improved oil recovery. Various mechanisms have been proposed including adsorption/desorption on rock surface, mineral dissolution and precipitation, multicomponent ion exchange, interfacial tension reduction, fine migration and double layer expansion. These all process alter the wettability which leads to improved oil recovery.;Objective of this study was to understand processes that occur during water-rock interaction when high salinity water is flooded into the reservoir. In this work, effect of temperature on water-rock interaction is studied along with effect of pH and specific surface areas of calcite at normal and elevated temperatures. To understand processes occurring on surface of rock, reactive transport model for brine-rock interaction was developed. It included surface complexation and mineral dissolution processes which contribute towards wettability alteration. Effect of pH, specific surface area of calcite on surface complexation and mineral dissolution at normal and elevated temperatures showed that rate of mineral dissolution was higher than surface complexation reactions. Calcite dissolved volumes for varied composition of injected brine were compared with oil recovery percentages. The results showed that calcite dissolution increased with increase in oil recovery at higher temperatures. The study showed that improved oil recovery is complicated process which is result of various processes and steps involved. Sensitivity of each process and step for wettability alteration can be different depending on environment.