Core Flooding of Complex Nanoscale Colloidal Dispersions for Enhanced Oil Recovery by in Situ Formation of Stable Oil-in-Water Pickering Emulsions

This study reports a Pickering emulsion flooding system, in which the oil-water interface is structurally stabilized by a complex colloidal layer consisting of silica nanoparticles, dodecyltrimethylammonium bromide (DTAB), and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSS-co-MA). The colloidal layer was generated by adsorption of PSS-co-MA on the silica nanoparticles as a result of the van der Waals attraction and by adsorption of DTAB onto the PSS-co-MA layer as a result of the electrostatic attraction, thus providing the mechanically robust, stable interface. To demonstrate a practical applicability to the enhanced oil recovery, the complex colloidal dispersion fluid was injected into the Berea sandstone for a core flooding experiment. The result revealed that the colloidal dispersion significantly increased the oil recovery by similar to 4% compared to the case of flooding water. This means that the emulsion drops in situ produced in the core could readily flow through the rock pores. We attribute this to the fact that the oil-water interface made with the complex colloidal phase not only increased the structural stability of the emulsion drops but also provided them deformability without any drop breakup or coalescence.