Brine composition effect on the oil recovery in carbonate oil reservoirs: A comprehensive experimental and CFD simulation study

Highlights

• Observed change in IFT and wettability through the presence of ${\text{Mg}}^{2+}$ and ${\text{SO}}_4^{2-}$ ions.

• Insignificant influence of ${\text{Ca}}^{2+}$ ions on both IFT and wettability.

• A neutral-wet surface cause to better recovery compared to water-wet state.

• Computational fluid dynamic is a suitable method to simulate fluid flow in porous media.

Abstract

In order to understand the potential role of divalent ions involved in smart water, fluid-fluid and rock-fluid interactions are studied through contact angle and interfacial tension (IFT) measurements. Then, the suitable brines in changing contact angle and IFT are brought into measurement with spontaneous imbibition experiments to evaluate the co-impact of fluid-fluid and rock-fluid interactions. The results show the importance of ${\text{SO}}_4^{2-}$ ions during smart water injection as removing them from the injection water leads to a sharp drop in ultimate oil recovery. Accordingly, when the concentration of ${\text{SO}}_4^{2-}$ within the injection water increases four times, 10% ultimate oil recovery is recovered. Furthermore, the spontaneous imbibition measurements exhibit the higher ultimate oil recovery from the neutrally-wet core plugs more rather than the strong water-wet plugs. Further elaborating about the effect of wettability on the pore-scale displacement of oil by injection water is conducted through Computational Fluid Dynamics (CFD) modelling. The results confirm that the lowest residual oil saturation is achieved in the model with neutral wettability state as well as the highest oil recovery which is in line with the piston-like displacement in the neutral wet rock medium.