Detailed analysis of the brine-rock interactions during low salinity water injection by a coupled geochemical-transport model

Enhanced Oil Recovery (EOR) methods have been widely used around the world to improve oil production from petroleum reservoirs. Recently, the injection of the low salinity/smart water has gained popularity among the EOR methods. Different mechanisms are believed to exist during low salinity/smart water injection, including dissolution, precipitation, and ion exchange at the rock surface. In this study, a coupled geochemical-transport model is presented for the detailed analysis and investigation of the interactions between brine, sandstone and carbonate rocks. The proposed model presents the coupling of a geochemical software (PHREEQC) and a species transport model. This coupled method makes it possible to model the dissolution, precipitation, and ion exchange caused by geochemical reactions during water flow through porous media. The results show that monovalent cations are released into the brine from the exchanger site, and divalent cations fill their position at the clay surface for the sandstone rock. The porosity and permeability changes are observed in the carbonate rock, where it can be important in the near injection area. The ion exchange results in the carbonate rocks show that the geochemical reactions move in a direction to disagree with the pH increase created by low salinity brine injection.