Designing binary low IFT surfactant system using HLD concept for oil recovery

Abstract

Surfactant-based microemulsion technology is widely used in tertiary enhanced oil recovery applications (EOR). The formulation of suitable surfactant system is a key success in production and economic feasibility of this technology. The middle phase or Winsor Type III microemulsions, employed for selecting appropriate surfactant system, can offer an optimal salinity at which the high oil solubilization capacity and minimum interfacial tension (IFT) or ultralow IFT (<0.01 mN/m) are obtained. By this technology, more remaining oil in the reservoir can be solubilized and mobilized which leads to an improvement of oil recovery. This study aims to formulate surfactant systems for the oil recovery through microemulsion formulation. The novel mixed anionic surfactant system of a sodium dioctyl sulfosuccinate (AOT) and an internal olefin sulfonates (IOS) with different alkyl chain lengths (C15-18, C19-23, C24-28) were used due to its mixture avoiding the surfactant precipitation. The result found that the binary mixture of AOT and (IOS C15-18 and IOS C19-23) can form the middle phase at the mixing ratios of 5:5 to 9:1 (by molar ratio) with heptane and decane. When the fraction of IOS increased in the mixed AOT/IOS system, the optimal salinity (S*) also increased. For the effects of a carbon tail length of IOS surfactant was observed that the tail length increased with decreasing the optimal salinity. The hydrophilic–lipophilic deviation (HLD) for the mixed surfactant system was investigated to individually determine the K and Cc values for the IOS surfactants. The finding from this work provided a guide for surfactant selection through HLD concept to formulate microemulsion-based surfactant flooding for EOR application.