Effect of water saturation on the role of polymer elasticity during heavy oil recovery

Abstract

During enhanced oil recovery, polymers are used to improve the sweep efficiency during chemical injection process. Polymers are mainly characterized based on their viscoelasticity response; however, the role of polymer elasticity on heavy oil considering the effect of water saturation in porous media has not been well explored. In this work, four blends of polyacrylamide polymer solutions with similar molecular weight and shear viscosity but different bulk elasticity (due to different molecular weight distribution) were used. A series of flooding experiments were performed using a cylindrical core sand pack saturated with heavy oil designed to simulate linear flow. The flow rate was selected based on the shear rate range present in field applications. Effect of elasticity during the injection of these polymer solutions were compared during tertiary recovery experiments in terms of oil recovery and residual resistance factor at different initial water-flood volumes. The results indicate that the effect of polymer elasticity was more profound in tertiary mode with higher water saturation. An additional pressure drop was required to push a higher elastic solution. The required pressure drop to push the polymer solutions increased with water saturation.