Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

Abstract

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10⁻³ mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10⁻² mN/m in this case) interfacial tensions, and also significantly lower retention.

Keywords:

• Interfacial tension
• optimal salinity
• phase behavior
• retention
• salinity

ACKNOWLEDGMENTS

The authors gratefully acknowledge Statoil for supporting EOR research at CIPR, and Shell Global Solutions International for supplying the surfactants.

Notes

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ldis.