Application of Organic Alkali for Heavy-Oil Enhanced Oil Recovery (EOR), in Comparison with Inorganic Alkali

Alkali is an important component for alkali/surfactant/polymer technology for enhanced oil recovery (EOR). The mechanism and advantages of traditional inorganic alkali for EOR was reviewed in this paper. The rheological and dynamic properties of the combination of alkali and polymer were analyzed. The results show that the polymer solution with ethanolamine has better shear viscosity and elastic properties at room temperature. Surfactant (Alfaterra 123-8S-90) with concentration of 0.15 wt % was added into each alkali–polymer (AP) solution. No significant change was observed in rheological properties of AP solutions with and without surfactant. Emulsification tests show that ethanolamine has better performance with oil. Injectivity tests were also conducted. The results indicated that the residual resistance factor (RRF) for an ethanolamine–polymer solution is always higher at each flow rate tested, in comparison to a NaOH-based AP solution, which is beneficial for oil recovery. The interfacial tension (IFT) tests results indicated that ethanolamine has better synergy with the surfactant. Polymer adsorption using both static and dynamic measurements was conducted. Polymer solution in an ethanolamine system has lower adsorption for both measurements. The pressure comparison during core flooding experiments shows that it has higher injection pressure in ethanolamine conditions, which result in good sweep efficiency. The ethanolamine–polymer flooding showed a significant increase in oil recovery (15.33%) over NaOH–polymer flooding. After the addition of surfactant, the total recovery improves by 14.8% for ethanolamine–polymer–surfactant flooding over its inorganic counterpart. The better performance indicates that ethanolamine can become a potential alkali and can replace NaOH for EOR.