Phase behavior study for chemically enhanced waterflooding

During chemical based enhanced oil recovery (EOR) process, ultralow oil-water interfacial tension (IFT) (less than 10-2 mN/m) should be achieved to mobilize the residual oil left behind after conventional recovery methods. This research work studied the phase behaviour of surfactant systems with a view to screen formulations for chemically enhanced waterflooding with ultralow IFT. The phase behaviour tests help to determine the optimum salinity, which is one of the most important parameter in the surfactant flooding because it is at this salinity at which maximum oil recovery can be obtained. The phase behaviour studies of (surfactant + brine + crude oil) systems were performed with various combinations of chemicals with crude oil (31 0API) of an Upper Assam oilfield at reservoir temperature (70 0C). The surfactants considered for the experimental works were Sodium Dodecyl Sulphate (SDS, anionic), TritonX-100 (TX-100, non-ionic) and Black Liquor (BL, natural). Five core flood experiments were done to determine the EOR potential of the surfactants used and to validate the chemical formulations that performed well in phase behavior experiments. Mixed surfactant systems were found to perform better in the phase behavior tests and recovered higher residual oil during core flooding due to synergistic effect.