Experimental Study of the Effect of Combined Low Salinity Water and Polymer Injection on Heavy Oil Recovery

In recent years, low salinity polymer injection as an enhanced oil recovery method has drawn more attention by researchers. Combination of other methods with low salinity water injection has also been investigated in the literature. Among them is the combined low salinity water and surfactant or polymer injection which shows its efficiency in enhancing oil recovery. In this study, the combined low salinity water and polymer injection to five sandpack models and its efficiency in oil production is investigated through different flooding experiments. To this end, three and two polymer injection experiments were conducted in tertiary and secondary modes (after and before low salinity water injection), respectively. The results indicates that polymer injection in tertiary mode has better performance than the secondary mode injection experiments as in the former case the oil recovery at breakthrough is about 11% higher than the later one. In tertiary polymer injection experiments, as the concentration of polymer solution increases, the mobility of the displacing fluid decreases leading to an increase in the microscopic efficiency. During the secondary polymer injection, polymer is in contact with the high salinity formation water which increases the adsorption of polymer onto the rock surface and decreases the permeability of the porous medium. As a result, oil recovery decrease. The pH analysis of the produced water shows that during the low salinity water injection experiments, the pH increment is the active mechanism and the wettability alteration toward water-wet increases the oil recovery. Displacement of the polymer and low salinity water are also investigated by measuring the refractive index in the produced water indicating the trend of the salinity change.