Enhancement for drag reducer release efficiency from inverse polymer emulsion using pH-responsive dynamic covalent surfactant

The increasing global fossil resources consumption requires convert the sights into the exploitation of tight oil resources. Polymer emulsion drag reducers are widely used in hydraulic fracturing techniques for inhibition of fluid turbulence and reservoir stimulation for enhanced oil recovery. However, the poor release efficiency and requirement for extra hydrophilic surfactant for phase inversion limit the practical application. Herein, a hydrophobic surfactant oleylamine-4-carboxybenzaldehyde (OA-CBA) was synthesized with oleic amine (OA) and 4-carboxybenzaldehyde (CBA). OA-CBA exhibited pH-responsive behavior, attributing to the existence of dynamic covalent bond in OA-CBA. The OA-CBA stabilized monomer emulsions, consisted of acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and Acrylic acid (AA), suggests remarkable dynamic and storage stability, which supply stable microreactors for polymerization. Furthermore, polymer emulsion with pH-responsive behavior was obtained by inverse emulsion polymerization upon redox initiation. The polymer drag reducer was completely released within 10 s upon adjusting the pH value to 2.26. Notably, the pH-responsive polymer emulsion exhibited 18 times faster release time compared to traditional polymer emulsion stabilized by Span 80, along with a 63.2% drag reduction rate. The rapid release of the polymer was realized by regulating pH merely instead of introduction of extra hydrophilic surfactant, which reconciles the contradiction of stability and release of polymer from emulsions.