The synergism of improving interfacial properties between betaine and crude oil for enhanced oil recovery

Betaine, an emerging surfactant for enhanced oil recovery (EOR), has garnered increased attention and recog-nition. This study focuses on linear alkylbenzene sulfonate betaine (ASB) as the research subject, and different crude oils were utilized to prepare two types of oil-water formulations with high interfacial film strengths but differed interfacial tensions. The interfacial properties were characterized and explored using interfacial dila-tional rheology, droplet squeeze coalescence, interfacial tension, emulsification, microscopic visualization, and other measuring methods. The actual emphasis in interfacial film properties of betaine as a standalone chemical EOR formulation was clarified. The results indicated that betaine had generally high interfacial film strength with selected crude oils, at this time, the slight difference in film strength had a negligible effect on enhancing the recovery. The main contributing factor was the difference in interfacial tension between the oil and water. Ultra -low interfacial tension could increase the stripping efficiency of oil in pore, reduce the energy required to emulsification or oil droplets initiation, and ensure that droplets were displaced and collected in smaller sizes, thereby avoiding large oil droplets trapped in the pore throat and unable to pass. Making good use of the ad-vantages of improving sweep efficiency brought by high interfacial film strength, at the same time giving the system ultra-low oil-water interfacial tension, ensuring the start-up and migration of porous crude oil, is the core construction principle of betaine surfactant applied to EOR.