Adsorption-induced wettability alteration in chemical enhanced oil recovery: Interfacial mechanisms, characterization methods, and flow-regulation effects

Wettability alteration is a key mechanism in chemical enhanced oil recovery (C-EOR) because it controls capillary pressure, fluid distribution, residual-oil mobilization, and multiphase flow pathways in porous media. In most chemical-flooding designs, adsorption on reservoir rocks is treated as an unfavorable loss because it reduces the effective concentration of injected agents. However, increasing evidence shows that when adsorption occurs at appropriate interfacial locations and remains stable during flow, it can modify surface energy, adjust oil–water–rock contacts, and change how fluids occupy and transport through pore networks. This review explores adsorption-induced wettability alteration as an interfacial process that links chemical retention with displacement response. It begins with the initial wetting state of reservoir rocks, which is controlled by mineral surface chemistry, adsorbed polar crude-oil components, organic matter, brine ions, and water-film stability. It then compares how different chemical agents alter oil–water–rock interfaces through distinct adsorption modes and evaluates characterization and modeling methods according to whether they quantify adsorption, locate interfacial reconstruction, and connect wettability alteration with dynamic flow behavior. Two EOR pathways are emphasized: microscopic oil mobilization, where adsorption-induced changes in interfacial energy, capillary pressure, and oil–rock adhesion promote oil-film detachment, capillary desaturation, and residual-oil mobilization; and sweep improvement, where adsorption layers, hydration layers, particle deposition, structural disjoining pressure, or disproportionate permeability reduction modify local flow resistance and redistribute injected fluids. Finally, the review distinguishes functional adsorption from excessive adsorption according to adsorption location, persistence under flow, measurable interfacial or flow-regulation benefits, and low-damage performance.