Rheological demonstration of micellization changes of internal olefin sulfonate and alcohol alkoxy sulfate commercial surfactants upon interactions with inorganic salts

Abstract

The Enhanced Oil Recovery by Chemical methods (CEOR) is carried out through the injection of polymer and/or surfactant solutions. The polymer allows for the increase of the viscosity of the injected water, while the surfactant decreases the interfacial tension between water and crude-oil under reservoir conditions. However, the salinity of the oilfield water sources significantly reduces the ability of synthetic polymer to increase the viscosity and viscoelasticity of the water. Consequently, their use is limited, especially in those oilfields presenting high ionic strength brines. The rheological behavior of surfactant solutions could be considerably enhanced if formed micellar aggregates are in a sufficient number, adequate size, and the interactions among them are sufficiently strong. In this work, the effect of some inorganic salts on the rheological behavior of surfactant solutions in the absence of polymer molecules is studied. To our knowledge, this is the first time commonly anionic surfactants used in CEOR are tested using several cation valences inorganic salts. Results show a trend to increase or induce a shear-thinning behavior of sufficiently concentrated solutions. Solutions exhibiting higher viscosities profiles may display viscoelastic properties that resemble (or even overcome) those of polymeric solutions with similar viscosity profiles. This can be a very promising technique for oil recovery in the absence of traditional polymer molecules under high salinity conditions.