Effects of brine valency and concentration on oil displacement by spontaneous imbibition: An interplay between wettability alteration and reduction in the oil-brine interfacial tension

Brine fluids have recently been of high interest to enhanced oil recovery process in both academia and industry. Both diluted formation brines specifically formulated were reported improve crude displacement porous rock, owing either their bulk salinity or brine-type. Mechanisms for such an improvement widely proposed, including microscopic interfacial phenomena: wettability alteration reduction the oil-brine tension (?), although synergistic interlinked contributions vaguely clarified. To elucidate insights into this “low-salinity” recovery, by spontaneous imbibition was conducted current research with focus on effects brine valency concentration. Monovalent (NaCl) divalent (CaCl2) at elevated concentrations (10, 100, 1000 mM) examined as imbibing fluids. Changes three-phase contact angle also investigated. Imbibition results showed that NaCl ‘suitable’ concentration (100 displaced greater (95.8 %) than too-low (10 too-high (1000 concentrations, these monovalent more effective those CaCl2 due oil-wetting a result ion bridging phenomenon. This echoes crucial influences Since no direct individual contribution from ? obtained, interplay between two parameters thought control. The capillary-dominated (capillary number < 2.1 × 10?6), re-confirmed correlations calculated capillary pressures inverse Bond numbers. findings revealed given system required is wettability-dependent: water-wet needs enhance driving capillarity while oil-wet prefers lower weaken resisting force. formula directly attributed ?: secure water-wetting reduced effectively assured oil-wetting. Low-salinity mechanism thus found be contributed effect, which wettability. Paring formulating anticipate challenge.