Wettability Alteration of Carbonate Reservoir Cores-Laboratory Evaluation Using Complementary Techniques

The objective of this paper was to assess the applicability of relatively low-salinity brine and different surfactants for enhanced oil recovery (EOR) in carbonate reservoirs in the Middle East. Phase behavior, interfacial tension (IFT), contact angle, spontaneous imbibition, and zeta-potential experiments were performed. The experimental work flow included a phase-behavior study followed by IFT, contact-angle measurements, spontaneous-imbibition measurements, and zeta-potential measurements at varying salinities and surfactant concentrations. Contact-angle-measurement results indicated that surfactant solutions, in addition to lowering IFT, tend to change the core wettability from oil-wet or neutral-wet to more water-wet. Furthermore, the best results were achieved by adding an anionic surfactant. Moreover, spontaneous imbibition and zeta-potential measurements provided additional supporting data that diluted seawater (DSW), in a dilute anionic or nonionic surfactant solution, alters the wettability of carbonates to a favorable wetting state for improving oil recovery. This research presents a set of diverse experimental data that confirms adding low concentrations of anionic and nonionic surfactants to DSW improves oil recovery from carbonate reservoirs.