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<p>Fracturing operations in low-permeability gas reservoirs impose stringent requirements on the temperature, salt, and shear resistance of friction reducers. Although hydrophobic group structures critically determine these properties, the underlying mechanisms remain poorly understood. This study designed and synthesized two cationic hydrophobic monomers: a rigid monomer containing a benzene ring (AQB) and a flexible monomer featuring a branched alkyl chain (AQL). Through aqueous free-radical polymerization, these were copolymerized with acrylamide and sodium acrylate to prepare rigid (PB) and flexible (PL) hydrophobically associating friction reducers. The polymer structures were characterized using infrared spectroscopy, followed by a systematic comparison of their solubility, rheological behavior, friction reduction efficiency, and salt tolerance. The results indicate that the critical association concentration of PB is 1800&#xa0;mg/L, lower than that of PL (2500&#xa0;mg/L), suggesting that the rigid benzene ring facilitates the formation of an intermolecular association network. Rheological evaluations reveal that PB exhibits a viscosity retention rate of 71% at 90&#xa0;°C and 88% after continuous shearing for 3600&#xa0;s, both outperforming those of PL (58% and 79%, respectively). Scanning electron microscopy observations confirm that PB constructs a more compact and dense three-dimensional network. Furthermore, performance assessments demonstrate that 1000&#xa0;mg/L of PB achieves friction reduction rates of 76.2% in fresh water, 71.8% in 20,000&#xa0;mg/L NaCl brine, and 62.1% in 5000&#xa0;mg/L CaCl<sub>2</sub> brine, which are consistently superior to the corresponding values for PL. Mechanistic analysis proposes that the rigid benzene ring enhances the stability of the hydrophobic association network through steric hindrance. This research elucidates how the rigidity and flexibility of hydrophobic groups influence friction reducer performance, thereby providing a theoretical foundation for the molecular design of high-performance friction reducers tailored for low-permeability gas reservoirs.</p>

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Preparation and properties of a hydrophobically associating friction reducer for fracturing in low-permeability gas reservoirs

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月25日

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  • Enbo Qiu,
  • Xuezhi Ding,
  • Yang Zhang,
  • Lin Ai,
  • Bo Li

摘要

Fracturing operations in low-permeability gas reservoirs impose stringent requirements on the temperature, salt, and shear resistance of friction reducers. Although hydrophobic group structures critically determine these properties, the underlying mechanisms remain poorly understood. This study designed and synthesized two cationic hydrophobic monomers: a rigid monomer containing a benzene ring (AQB) and a flexible monomer featuring a branched alkyl chain (AQL). Through aqueous free-radical polymerization, these were copolymerized with acrylamide and sodium acrylate to prepare rigid (PB) and flexible (PL) hydrophobically associating friction reducers. The polymer structures were characterized using infrared spectroscopy, followed by a systematic comparison of their solubility, rheological behavior, friction reduction efficiency, and salt tolerance. The results indicate that the critical association concentration of PB is 1800 mg/L, lower than that of PL (2500 mg/L), suggesting that the rigid benzene ring facilitates the formation of an intermolecular association network. Rheological evaluations reveal that PB exhibits a viscosity retention rate of 71% at 90 °C and 88% after continuous shearing for 3600 s, both outperforming those of PL (58% and 79%, respectively). Scanning electron microscopy observations confirm that PB constructs a more compact and dense three-dimensional network. Furthermore, performance assessments demonstrate that 1000 mg/L of PB achieves friction reduction rates of 76.2% in fresh water, 71.8% in 20,000 mg/L NaCl brine, and 62.1% in 5000 mg/L CaCl2 brine, which are consistently superior to the corresponding values for PL. Mechanistic analysis proposes that the rigid benzene ring enhances the stability of the hydrophobic association network through steric hindrance. This research elucidates how the rigidity and flexibility of hydrophobic groups influence friction reducer performance, thereby providing a theoretical foundation for the molecular design of high-performance friction reducers tailored for low-permeability gas reservoirs.