(6ct) Effect of Salinity on Surfactant Enhanced Oil Recovery with Special Reference to Upper Assam Basin

The effect of salinity gives a new dimension on Surfactant Enhanced Oil Recovery (SEOR). The brine salinity varies from reservoir to reservoir and normally lies in the range of 3000-5000 ppm in case of Upper Assam basin. During SEOR process brine soluble surfactants are introduced into the underground porous media. The brine should be at optimum salinity so as to generate Winsor type III microemulsion. This work aims at determining the optimum salinity of brine in which the surfactant is soluble by way of finding the solubilization ratio in between oil and surfactant and water and surfactant.

It is experimentally observed that at optimal water salinity a middle phase Winsor type III micro-emulsion exist while at salinity below optimum water salinity oil in water (O/W) Winsor type I micro-emulsion exist and at salinity above optimum water salinity water in oil (W/O) Winsor type II microemulsion exist. It is also found that in case of Winsor type I micro-emulsion the IFT between the microemulsion and insufficient water is high, while in case of Winsor type II micro-emulsion the IFT between the microemulsion and insufficient oil is high. In both these cases oil mobilization is hampered and trapping of oil results, thereby reducing the displacement efficiency in the porous media. Therefore the aim of this paper is to generate a Winsor type III micro-emulsion at optimum salinity where the two IFTs in between O/W microemulsion and oil and in between O/W microemulsion and water is less and equal which is one of the most significant parameter in SEOR.