Experimental Study on Low Interfacial Tension Foam for Enhanced Oil Recovery in High-Temperature and High-Salinity Reservoirs

Foam flooding is an important method to enhance oil recovery after water flooding. In this paper, a novel low interfacial tension (LIFT) nitrogen foam was successfully prepared by an amphoteric surfactant and sodium formate. It has good foaming ability and can reduce interfacial tension to a low interfacial tension level (10–1 mN/m order of magnitude) in high-temperature (90 °C) and high-salinity (183 g/L salinity) reservoirs. The influence of surfactant concentration, organic bases concentration, and aging on the performances of the LIFT foam system has been systematically studied through the modified Ross-Miles experiment. Furthermore, the foam displacement in flat-panel sand model and etched-glass micromodels were conducted to investigate the foam displacement mechanisms for enhanced oil recovery. The results of flat-panel sand model experiment showed that the LIFT foam could block high permeability channels and divert following injection fluid to adjacent low permeability areas efficiently. Meanwhile, with the injection of the LIFT foam, the injection pressure of the whole model continued to increase, and the pressure distribution was more uniform. The etched-glass micromodels experiment results showed that the LIFT foam could block the high permeability channels and improve sweep efficiency. Furthermore, comparing with the common foam, the LIFT foam could emulsify oil and strip oil film from model surfaces more easily. So it could enhance the oil recovery more efficiently.