After conventional waterflood processes the residual oil in the reservoir remains as a discontinuous phase in the form of oil drops trapped by capillary forces and is likely to be around 70% of the original oil in place (OOIP). The Enhanced oil Recovery (EOR) method so-called alkaline?surfactant (AS) flooding has proved to be effective in reducing the oil residual saturation in laboratory experiments and field projects through the reduction of interfacial tension (IFT) and mobility ratio between oil and water phases.
The objective of the study is to analyze the microemulsion formed between alkali-surfactant (AS) solution and A crude oil. AS solution was manufactured by using the surfactant purchased from domestic company. C16-PO7-SO4 and sodium carbonate solution were used as surfactant and alkaline. Triethylene glycol butyl ether and isobutyl alcohol were used as co-solvent, respectively.
Solubilization parameters for oil and water were also found to significantly vary with the salinity. Also, the interfacial tension between oil and microemulsion phase is a strong relationship of both concentration of surfactant and salinity.
In this study, the optimum solubilization ratio is 8, and optimal salinity is 18000 ppm in C16-PO7-SO4 1 wt%, TEGBE 4 wt%. The optimum solubilization ratio is 15, and optimal salinity is 9000 ppm in C16-PO7-SO4 2 wt%, IBA 8 wt%. Interfacial tension at optimal salinity is 0.005 mN/m in C16-PO7-SO4 1 wt%, TEGBE 4 wt% and 0.001 mN/m in C16-PO7-SO4 2 wt%, IBA 8 wt% using a Huh’s equation.
The AS solution using a domestic C16-PO7-SO4 surfactant and A crude oil can form a Type III middle phase microemulsion in the presence of salinity. Increasing salinity causes the phase transition of microemulsion from lower (Type I) to middle (Type III) to upper (Type II) phase. The microemulsion is characterized by several concurrent phenomena such as three-phase behavior, minimum interfacial tension and high solubilization of both oil and brine in the microemulsion phase. The domestic surfactant can be applied to enhanced oil recovery because of forming a microemulsion.