A Novel Ultra-low Interfacial Tension Foam Flooding Agent to Enhance Heavy Oil Recovery

Abstract

Abstract Foam as a mobility control agent in enhanced oil recovery is becoming more and more attractive. Recently, ASP foam flooding method was proposed, which was based on the mechanism of both lowering interfacial tension to an ultra-low value (10−3mN/m grade) and improving sweep efficiency of displacing fluid. However, the alkali (NaOH or Na2CO3) in the ASP system will bring about scaling in the reservoir and pipelines if the formation water contains a large number of divalent cations such as Ca2+ and Mg2+. Therefore, it is necessary to develop a non-alkali foam flooding system to improve oil recovery. A novel ultra-low interfacial tension foam agent is developed by the combination of surfactant and additives to lower oil-water interfacial tension and the addition of polymer to improve foam stability. Firstly, the concentration of surfactant and non-alkali additives used as the foam agent was determined by interfacial tension contour diagram. Then, the molecular weight and concentration of HPAM to enhance foam stability in the reservoir was screened. The foamability of the formula was measured using airflow method. Furthermore, the effects of temperature, salinity and shearing on the interfacial property and foamability were investigated to know the adaptability of this method to different oilfields. The heavy oil displacement experiments showed that the final oil recovery could be improved approximately 23% initial-oil-in place over waterflood recovery for the heterogenous core model of which permeability variation coefficient is 0.65, more than that of alkaline-surfactant-polymer flooding.