SYNERGISTIC SYSTEM STUDY OF HYDROPHOBIC ASSOCIATING WATER-SOLUBLE POLYMER AND VISCOELASTIC SURFACTANT APPLIED IN FRACTURING FLUID FOR UNCONVENTIONAL OIL AND GAS

Polymer-based fracturing fluids are widely used in unconventional reservoirs but often fall short in complex conditions. This study synthesizes a novel hydrophobic association water-soluble polymer (PAMNC12) and explores its synergy with viscoelastic surfactants (VESs: oleic acid amide propyl trimethylammonium chloride (OTAC), oleic acid amide propyl sulfobetaine (ODSB), oleic acid amide propyl carboxyl betaine (ODCB)) to optimize fracturing fluid performance. PAMNC12 exhibits critical association concentrations at 1029.2 and 2513.2 mg L–1. Rheological, gel-breaking, and core damage tests reveal that VES-PAMNC12 synergy significantly enhances apparent viscosity, viscoelasticity, drag reduction, heat/shear resistance, and proppant-carrying capacity while reducing residue content and core damage. Optimal dosages are 400 mg L–1 VES and 10,000 mg L–1 KCl. Among the systems, PAMNC12/OTAC shows superior thickening, heat/shear resistance (160 °C), drag reduction (lowest settlement velocity), and minimal residue (30 mg L–1) and core damage (10.1%). PAMNC12/ODSB and PAMNC12/ODCB also demonstrate excellent heat tolerance, sand-carrying, drag reduction, and low formation damage, making them promising for hydraulic fracturing in unconventional reservoirs. This study provides a foundation for developing high-performance fracturing fluids.