Effects of Interfacial Tension, Emulsification, and Mobility Control on Tertiary Oil Recovery

Interfacial tension (IFT), emulsification, and sandpack flood tests were conducted to investigate the effects of IFT, emulsification, and mobility control on tertiary oil recovery. The results show that although IFT was reduced to a lower level in the BST-1 flood and the solution viscosity was improved to a higher level in the polymer flood, the tertiary oil recovery obtained in the Na2CO3 flood was the highest. The emulsifying performance of Na2CO3 was better than that of BST-1 or polymer, and thus led to a higher pressure and a higher tertiary oil recovery of the Na2CO3 flood. Tertiary oil recovery and pressure both increased with the increase in chemical agent concentration. Although polymer has an adverse effect on IFT reduction, owing to the favorable mobility control caused by the addition of the polymer, the tertiary oil recovery in the alkaline/polymer or surfactant/polymer flood increased when the polymer concentration increased. The results show that compared with the effect of the low IFT, tertiary oil recovery is always accompanied by a favorable mobility control that can be triggered by a high viscosity of displacement fluid or emulsification.