The dominant mechanism of enhanced heavy oil recovery by chemical flooding in a two-dimensional physical model

The dominant mechanism of enhanced heavy oil recovery by chemical flooding is studied by conducting various chemical slug injections in a two-dimensional physical model. In this study, a total of seven single-chemical-slug tests and another seven two-chemical-slug tests are conducted to test the contribution of alkaline, surfactant, polymer, and their combinations to enhanced heavy oil recovery. The relationship between the tertiary oil recovery and the pressure drop of the seven single-slug floods is analyzed, and it is discovered that the two have a good correlation. Comparison of the tertiary oil recoveries of different chemical slug tests shows that the improved waterflood for the heavy oil used in this study is mainly due to the reduction of water mobility. The results of two-chemical-slug tests show that after regular alkaline/surfactant/polymer flooding, the second polymer slug injection can recover more oil, if a water slug injection is applied between the two chemical slugs.