Contents lists available at ScienceDirect Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa Electro-kinetic induced wettability alteration in carbonates: Tailored water chemistry and alkali efects Amani O. Alghamdi ⁎ , Moataz O. Abu-Al-Saud, Mohammed B. Al-Otaibi, Subhash C. Ayirala ⁎ , Ali Alyousef EXPEX ARC Research Center, Saudi Aramco, Dhahran 31311, Saudi Arabia GRAPHICAL ABSTRACT ARTICLE INFO Keywords: SmartWater Alkali ζ-Potential Surface complexation modelling (SCM) Contact angle Wettability alteration ABSTRACT The injection of optimized water in terms of desired salinity range and ionic composition into a reservoir to enhance oil recovery is widely known as SmartWater fooding. The synergistic efects of diferent SmartWater brines with alkali on wettability alteration of carbonates is investigated in this study by measuring the ζ-po- tentials at calcite/brine and oil/brine interfaces. The ζ-potential at calcite/brine/oil interfaces indicate that a higher concentration of sulfates is necessary to result in a favorable wettability alteration. Both alkalis (NaOH and Na 2 CO 3 ) increase the negative ζ-potential at the two interfaces for low salinity Na 2 SO 4 brine. A slight increase in negative charge is observed at the two interfaces using NaCl brine with Na 2 CO 3 alkali while there is no much change in ζ-potentials with alkali in SmartWater (10-times reduced salinity seawater). Sodium carbonate efects on the ζ-potential of calcite is more pronounced when compared to NaOH due to the availability of carbonate ions as excess potential determining ions. The surface complexation modeling results quantitatively agree with the experimental data at the calcite/ brine interface. For the oil/brine interface, a reasonable match is obtained and further calibration of carboxylic acid group and nitrogen based crude oil reactions is recommended to improve these predictions. These results indicate that Na 2 SO 4 brine is highly suitable for alkaline-assisted water-fooding processes in carbonates. The negligible impact of adding alkali on measured dielectric constant as well as strong agreement obtained between the polarity of ζ-potentials at both calcite/brine and oil/brine interfaces with contact angle results confrm the robustness of the reported experimental ζ-potential values. https://doi.org/10.1016/j.colsurfa.2019.123887 Received 16 June 2019; Received in revised form 28 August 2019; Accepted 29 August 2019 ⁎ Corresponding authors. E-mail addresses: amani.alghamdi@aramco.com (A.O. Alghamdi), nethajisubhash.ayirala@aramco.com (S.C. Ayirala). Colloids and Surfaces A 583 (2019) 123887 Available online 29 August 2019 0927-7757/ © 2019 Elsevier B.V. All rights reserved. T