Potential of alkaline flooding to enhance heavy oil recovery through water-in-oil emulsification

Alkaline flooding has great potential for enhancing the recovery of heavy oil, especially for reservoirs in which thermal methods are not suitable. In this study, alkaline flooding tests were performed in micromodels and sandpacks to investigate the microscopic displacement mechanisms for enhancing heavy oil recovery and the effect of the injection parameters on displacement efficiency. The micromodel tests indicate that the penetration of the alkaline solution into the crude oil and the subsequent formation of a water-in-oil (W/O) emulsion reduce the mobility of the water phase and divert the injected water into the unswept region, thereby improving the sweep efficiency. The sandpack flood results show that the tertiary oil recovery can reach about 20% of the initial oil in place (IOIP) using 1.0% NaOH, and the tertiary oil recovery has been found to increase as the alkaline concentration increases. However, there is an optimum slug size and injection rate at which the highest tertiary oil recovery can be obtained during the alkaline flooding process. Continuous alkaline injection can provide a higher tertiary oil recovery compared with a cyclic alkaline injection pattern. These results show that the alkaline flooding, if properly designed and controlled, can lead to enhanced heavy oil recovery through the water-in-oil emulsification.