Chemical Verification of the EOR Mechanism by Using Low Saline/Smart Water in Sandstone

Recently, a chemical mechanism for enhanced oil recovery by low salinity water flooding was suggested. The key step in the mechanism was a localized increase in the pH at the day surface due to desorption of active cations, especially Ca2+, as the low saline injection water invaded the porous medium. An increase in pH will remove adsorbed acidic and basic material from the day surface and increase the water wetness of the rock. In the present paper, parametric studies have been performed to verify the different steps in the suggested mechanism. Both dynamic core floods and static adsorption studies of model base and acid on three different day minerals have been performed. The results from the dynamic experiments were supported by the static adsorption/desorption studies. The main observation regarding adsorption/desorption of basic organic material onto days was that changes in pH appeared to play a greater role than the salinity of the brine. Thus, both the dynamic and the static studies supported the suggested chemical mechanism for the low salinity EOR process.