Effect of Surfactant Emulsification Capability on Oil Displacement Performance in ASP Flooding Systems

Both indoor and field experiments have shown that emulsification is very beneficial for improving the oil displacement effect of chemical flooding. In the process of chemical flooding, emulsification mainly plays a role in emulsification carrying and emulsion plugging. On the one hand, the adsorption of surfactants at the oil-water interface can form emulsions with certain stability, which can be extracted through the emulsification carrying effect. On the other hand, the viscosity of emulsion is higher than the apparent viscosity of the external phase, which increases the sweep coefficient. Therefore, this paper took a weak alkaline ternary system as its foundation and delves into the oil displacement efficacy of systems featuring varied emulsifying capabilities and reduced interfacial tensions. By fine-tuning the surfactant formulation within the system to enhance its emulsifying capacity, and integrating indicators like interfacial activity and emulsification phase behavior, it correlated these factors with laboratory physical modeling experiments. The experimental results indicated that, by adjusting the surfactant formula, the interface activity of the system was reduced (from 10–3 orders of magnitude to 10–2 orders of magnitude), while improving the emulsification ability of the system, the system could achieve phase transformation in one-dimensional homogeneous Berey core experiments, form a bicontinuous phase with Winsor III phase characteristics, and further improved the recovery rate. In the chemical flooding stage of indoor physical model experiments, the recovery rate was 15% ~ 18% higher than that of conventional weak alkaline ternary systems. Theresearch results could be used to guide the optimization of composite system formulations, fully leverage the oil displacement effect of composite flooding systems, and provide more effective replacement technology support measures for the sustainable development of oilfields, which is of great significance.