Surfactivity-switchable dynamic covalent trimeric stabilizer for enhanced dissolution efficiency of friction reducer emulsions

Polymer emulsion drag reducers are vital components in slickwater fracturing fluids used for stimulating shale gas reservoirs. Efficient dissolution rates are crucial for maximizing the performance of friction reducers by enabling rapid friction reduction. However, the stability of W/O-type emulsion is compromised in the presence of hydrophilic surfactants, posing a significant challenge for enhancing the dissolution of friction reducers in continuous fracturing processes. Herein, a dynamic covalent trimeric stabilizer, oleylamine - glycerol triglycidyl ether (OLA-GTE), was designed to construct W/O monomer emulsions. The stabilizer underwent pH-induced cleavage of imine bonds, leading to an increased concentration and enhanced surface activity of the cationic surfactant OLA + , which facilitated the transition to reverse emulsion. The stability parameters of the monomer emulsions consisting of oil-water ratio, stabilizer concentration, and pH level were optimized by storage, centrifugation, and heat treatment. Furthermore, the polyacrylamide-based friction reducer emulsions were synthesized through inverse emulsion polymerization. The stimuli-responsive friction reducer emulsions directly dissolved in water with a pH below 5.0, which was attributed to the breakdown of OLA-GTE at the interface, coupled with the phase transition effect of the cationic surfactant OLA + . The formulation of slickwater using friction-reducer emulsions can be completed within 10 s when stimulated by water at pH 5.0, resulting in a friction-reduction rate of up to 76 %. The rapid dissolution capability is a significant advancement for applications in slickwater fracturing for shale gas reservoirs, offering quick and efficient friction reduction.