Experimental Investigation of Acidic Medium Effect on Seawater and Low Salinity Water for Wettability Alteration and Interfacial Tension Reduction: The Presence of Divalent and Trivalent Cations

Research Subject:

 In recent years, smart water flooding has gained attention regarding enhanced oil recovery, and one of its driving mechanisms is wettability alteration. However, the effect of acid presence on smart water performance needs to be clarified. Thus, the main question is whether the presence of acid and potential determining ions can lead to further wettability alteration and interfacial tension (IFT) reduction. Additionally, in this study, trivalent cations were added to smart water for the first time, and the results were compared with those of divalent cations. 

Research approach: 

In this study, seawater (SW), 4-times diluted SW, and 8-times diluted SW were prepared in distilled water, 0.001 normal HCl and 0.01 normal HCl, and the contact angle and IFT experiments were carried out. In addition, concentrations of Ca2+, Mg2+, and Fe3+ were adjusted in 8-times diluted SW prepared in 0.01 normal HCl, and the IFT and contact angle tests were conducted.

The results showed that the presence of acid in distilled water could decrease the IFT values; however, it did have a marginal effect on contact angle reduction. Also, because of synergistic effects between acid and potential determining ions, IFT significantly declined. While adding acid to brines with different salinities resulted in contact angle reduction, the glass surface remained oil-wet. Regarding divalent and trivalent cations, the results revealed that increasing Fe3+ concentration in smart water made the glass surface water-wet. However, adjusting Ca2+ and Mg2+ concentrations changed the wettability from oil-wet to neutral-wet. Moreover, divalent and trivalent cations showed similar behavior in IFT reduction, and a four-times increase in the concentration of each mentioned ion reduced IFT by about 2 mN/m.