Aqueous two-phase high-viscosity friction reducer for deep reservoir fracturing and its mechanisms of temperature resistance and viscosity enhancement

Abstract

Given the stringent requirements for friction reducers in terms of long-distance friction reduction, efficient proppant transport, temperature resistance and viscosity enhancement in deep oil and gas reservoir fracturing development, an aqueous two-phase high-viscosity friction reducer ANSD-PADA suitable for deep reservoir fracturing was prepared by introducing nanomaterial ANSD and through the aqueous two-phase polymerization. Its mechanisms of temperature resistance, viscosity enhancement, and friction reduction were explored by means of fluorescence spectroscopy, microscopic morphology observation, nanomechanical testing and other analytical methods, and field tests were also carried out. The introduction of hydrophobic monomer N-(3-dimethylaminopropyl) methacrylamide enables PADA (a self-synthesized hydrophobic terpolymer) molecules to entangle, associate and self-assemble into a honeycomb-like network structure under the combined effects of van der Waals forces, electrostatic repulsion and hydrophobic interaction. This structure further increases the hydrodynamic volume, thereby significantly improving the viscosity-enhancing performance of the product. ANSD fills the pores of the polymer network structure, effectively strengthening the network skeleton and association junctions, and remarkably improving the temperature resistance of the system. The friction reducer retains a friction reduction rate of 73.36% at 130 °C, with a temperature resistance up to 150 °C, and it has demonstrated encouraging results in the pilot site at Well XX-HF targeting deep shale oil reservoirs on the northern slope zone of the Gaoyou Sag, Subei Basin, China.