Novel Foaming Agent Based on Waterborne Polyurethane for Foam-Assisted Enhanced Oil Recovery

A novel foaming polymer based on waterborne polyurethane (WPUFA) was evaluated for foam-assisted chemical flooding. Compatibility study showed that a solution of 0.5 wt % WPUFA was soluble, stable, and produced foam in the concentration range of 1-11 wt % NaCl at 25 and 60 degrees C. Moreover, the wettability of limestone significantly improved due to the reduction of interfacial tension between WPUFA solution and kerosene from 18.5 mN/m(-1) to 5.8 mN/m(-1) and a decrease in contact angle value from 88.6 degrees to 8.5 degrees at 0.5 wt % WPUFA concentration. Foam scans were carried out using 0.5 wt % WPUFA solution through 50 mD limestone at 1 wt % NaCl at 60 degrees C and a flow rate of 0.3 and 0.4 mL/min. The pressure gradient (dP) was almost constant at 102 psi in the range of 0.2-0.4 gas fraction for 0.3 mL/min and 0.4-0.6 gas fraction for 0.4 mL/min, indicating a shift to higher gas fractions (f(g)) with the increase in the total flow rate. In addition, the displaced solution was collected and reinjected at 0.4 mL/min two times in order to check the foam durability after experiencing multiple heating and frictions during movement through the porous media. The values of dP and apparent viscosity of the solutions after two reinjections were close but slightly lower than the original solution. With the repeating injection, the foam became more homogeneous with stronger lamella structures as a result of the reduction in fluctuations in outlet pressure due to decrease in the bursting of bubbles after the last reinjection. The results of the present study show that the WPUFA can be considered as a promising foaming agent at high salinity conditions for enhanced oil recovery.