Objective The polymer chain segment used in oilfield chemical working fluids such as fracturing fluid is easy to shear fracture, and the salt-resistant effect needs to be improved. Therefore, the design of a polymer with shear-resistant and salt-resistant is of great significance for the efficient utilization of fracturing fluid.

Method Two associative acrylamide copolymers were synthesized by aqueous polymerization using acrylamide (AM), sodium acrylate (NaAA) and two cationic monomers as raw materials. The structural characterization, microstructure, salt resistance, shear resistance and drag reduction were tested.

Result Infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy confirmed that the prepared copolymers were the target products, and microscopic scanning electron microscopy showed that they had a remarkable spatial network structure. When the mass concentration of the two modified polymers was higher than 3 000 mg/L, the polymers behaved as the high elastic and low viscosity fluids. When the shear rate of 170 s⁻¹ was cut for 60 min, the viscosity retention rate of two polymers was higher than 88%, and the apparent viscosity of two polymers was higher than 25.0 mPa·s at 1 000 s⁻¹, with significant shear-resistant effects. When the mass concentration of P(AM/NaAA/AQAS3) polymer solution was 500 mg/L and the pipeline flow rate was 45 L/min, the drag reduction rate of NaCl with a salinity of 10 000 mg/L was as high as 72.54%, and the drag reduction rate of CaCl₂ with a salinity of 2 500 mg/L was 63.52%. Under the same conditions, the drag reduction rate of P(AM/NaAA/AQAS4) polymer solution in 10 000 mg/L NaCl solution was 72.37%, and that in 2 500 mg/L CaCl₂ solution was 64.72%, which had a good drag reduction effect.

Conclusion By designing associative polymers with different hydrophobic structures, and comparing their salt resistance, shear resistance and other characteristics, a theoretical basis is provided for the development of new salt-resistant and shear-resistant associative polymers with hydrophobic structures, and ideas are also provided for the construction of high-performance shear-resistant and low friction fracturing fluid systems during the shale gas extraction.