Surface and Interfacial Tension Behavior in the Use of Ionic Liquids as Additives for Surfactant-based Enhanced Oil Recovery

Abstract Due to the favorable properties and versatility, the applications of ionic liquids (ILs) have been introduced in petroleum industry for different purposes including Enhanced Oil Recovery (EOR) processes. The ability of ILs to alter surface behavior of surfactant molecules by producing specific interactions with surfactant has motivated further investigation on its application to the important chemical EOR mechanisms, such as surface and interfacial tension lowering under reservoir conditions. The mixtures of in-house surfactant and different types of ILs (imidazolium- and eutectic-based ILs) as additives were formulated using different concentration ratio and prepared in fixed brine salinity. The surface tension (ST) and interfacial tension (IFT) behavior of the formulated mixtures were investigated by performing pendant and spinning drop tests at ambient and high temperature. In general, the extent of ST and IFT reduction was dependent on the type and concentration of ILs. The presence of ILs was able to lower both ST and IFT of surfactant solution and its effect as a function of ILs concentration was found to be more pronounced at high temperature. Of all ILs, eutectic-based IL showed the highest ability to decrease ST at any concentration used. Similarly, the eutectic-based IL was also regarded as the best ILs in lowering the surfactant solution/oil IFT even in the use of low concentration. From this study, it can be concluded that ILs can be proposed as new additives to alter the surface and interfacial behavior which are taking place through some surfactant-IL interactions and eventually improve surfactant performance in reducing ST and IFT. Surfactant solution with a lower ST due to the addition of ILs is expected to provide promising performance for surfactant-based EOR process involving gas mobility control application leading to enhancement of sweep efficiency, while a lower IFT value can provide favorable conditions for better oil displacement efficiency.