Novel encapsulated surfactants for enhanced oil recovery in carbonate reservoir conditions: Interfacial and wetting behavior

Surfactant encapsulation presents a novel strategy for the targeted delivery of active molecules to oil reservoirs. This study investigates the interfacial tension, wettability alteration, static adsorption and oil displacement performance of two novel encapsulated surfactants, anionic alkyl ether carboxylate and non-ionic alkyl polyglucoside, in water-oil and water-oil-carbonate rock systems. A refined synthesis yielded silica carriers with dimensions appropriate for transport through carbonate reservoir pore networks, preventing pore blockage while enabling effective delivery. A synergism between the surfactants and silica nanoparticles, released upon carrier rupture, was confirmed. The cooperative action of silica nanoparticles and surfactant molecules, facilitated by multiple intermolecular forces, including hydrogen bonding, electrostatic, and hydrophobic, enhanced the efficiency of interfacial adsorption, leading to a significant reduction in interfacial tension compared to pure surfactant systems. Furthermore, silica nanoparticles accelerated the alteration in wettability towards a hydrophilic state via disjoining pressure and competitive adsorption on the carbonate surface. Consequently, the simultaneous enhancement of interfacial behavior and mitigation of static adsorption due to encapsulation translated into more efficient oil displacement compared to use of the pure surfactants. This work demonstrates that encapsulation not only reduces adsorption but also enhances interfacial performance and displacement efficiency, supporting its potential application in chemical enhanced oil recovery.