Research of the heavy oil displacement mechanism by using alkaline/surfactant flooding system

Alkaline/surfactant flooding has great potential for enhancing the recovery of heavy oil due to the synergistic effect between alkali and surfactant. This research is aimed at developing a new alkaline/surfactant system with a sustainable surfactant called alkyl polyglucoside to improve the heavy oil recovery and clarifying its displacement mechanism. A series of oil/water interfacial tension measurements were conducted to screen the alkaline/surfactant system for the heavy oil sample. The oil/water interfacial tension could be reduced to the value of 10^-2mN/m with only alkyl polyglucoside (0.05%). When some Na₂CO₃ (0.5%) and petroleum sulfonate (0.03%) were applied to the above surfactant solution, the oil/water interfacial tension could be further decreased to 10^-4mN/m. Several sandpack flood tests were conducted, and the results show that the tertiary oil recovery can reach to 19.4% of the initial oil in place by using the suitable alkaline/surfactant system. Self-emulsification experiment and microscopic test were performed to investigate the displacement mechanism for enhancing heavy oil recovery, and the results indicate that alkaline/surfactant system including proper surfactant can form water-in-oil emulsion with heavy oil at the displacement front and oil-in-water emulsion in the swept region, which is necessary to obtain high sweep efficiency and oil washing ratio respectively.