A Study on a Novel Hydrophobic Associative Polymer Thickener for High-Salinity Water in Hydraulic Fracturing

Graphical This study develops a highly salt-resistant, hydrophobic associative polyacrylamide (CHFR) to enhance the reuse of high-salinity flowback fluid. Its microstructure is characterized using FT-IR and ¹H NMR, while rheological analysis confirms its superior thickening properties and salt tolerance. CHFR significantly outperforms conventional systems, providing a novel solution for efficient fluid reuse in high-salinity reservoirs. The reuse of flowback fluid is a critical strategy for mitigating environmental pollution and reducing the costs associated with hydraulic fracturing technology in oil fields. However, in high-salinity formations, the electrostatic shielding effect caused by high-salinity flowback fluid significantly reduces the thickening efficiency of polyacrylamide-based thickeners, thereby hindering the reuse of flowback fluid. In this study, we synthesized a novel, high-salinity-resistant, hydrophobic associative polymer (CHFR) by incorporating the hydrophobic monomer octadecyl polyoxyethylene methacrylate (N1810) into acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and methacryloxyethyl trimethylammonium chloride (DMC). FT-IR and 1 H NMR confirmed the successful synthesis of CHFR. The polymer demonstrated a viscosity retention of 53% in a 20,000 mg/L NaCl solution and 46% in a CaCl 2 solution, exhibiting salt tolerance concentrations that were 10 and 30 times higher than those of conventional PAM/AMPS. At 100 °C and a shear rate of 100 s −1 , CHFR retained 78% of its viscosity. The interaction process between salt and CHFR can be divided into four phases: the initial period, the rapid viscosity decline period, the slow viscosity decline period, and the stable viscosity period. The CHFR polymer exhibits excellent salt resistance, providing a new type of polymer thickener for the reuse of high-salinity flowback fluid.