Surfactant–polymer flooding characteristics for heavy oil recovery with varying injection volumes of surfactant and polymer

A laboratory surfactant–polymer flooding experiment was performed to improve the recovery of heavy oil. The surfactant phase behavior tests and a series of flooding experiments were conducted to find the best and optimal additional oil recovery condition after water flooding using a surfactant–polymer slug. Through the phase behavior tests, it was found that a combination of a 2.5 wt% surfactant solution with 1.5 wt% of salinity was the optimal for injection experiments. In the surfactant–polymer flooding, the combination of injected volume which was 0.6 pore volume (PV) of combined slugs of surfactant and polymer was varied in each test. The additional oil recovery obtained by the surfactant–polymer flooding after water flooding ranged from 13.6% to 28.6%. With the same total volume of the surfactant and polymer, the oil recovery decreased as the volume of polymer increased when the volume of polymer was lesser than the volume of surfactant; however, the oil recovery increased with increase in the volume of the polymer when the volume of the polymer was greater than or equal to the volume of the surfactant. The highest oil recovery of 28.6% was obtained by injecting 0.1 PV of surfactant and 0.5 PV of polymer.