Preparation and characterization of the quaternary hydrophobically associating polymer HATP for tight oil fracturing fluids

A new polymer thickener HATP was designed to overcome the limitations of guar gum and conventional polyacrylamides in tight oil reservoir fracturing. HATP (P(AM–co–AMPS–co–NVP–co–AHM)) was prepared via micellar copolymerization–redox initiation. It has a composition of 68.8:22.1:7.1:2.0, molecular weight 7.90 × 106 g·mol−1, and thermal decomposition onset at 322 °C. At 0.3 wt% and 170 s−1, its apparent viscosity is 132 ± 4 mPa·s at 25 °C, with viscosity retention of 73.8 ± 2.6% after 60 min at 120 °C, and 88.6% ± 2.4 in 20,000 mg·L−1 NaCl and 79.4% ± 2.7 in simulated formation water. HATP achieves a proppant settling ratio of 3.8 ± 0.3% after 2 h with 40 wt% ceramic proppant, a drag reduction rate of 76.1 ± 2.0% at 0.10 wt%, and fluid loss of 15 ± 1 mL at 90 °C and 3.5 MPa. After oxidative breaking with 0.02 wt% APS at 90 °C for 60 min, residue is only 7.1 ± 0.7 mg·L−1 and regain permeability reaches 91.4 ± 1.2%. Dynamic light scattering and zeta–potential measurements show that HATP forms a reconfigurable associating network: in 20,000 mg·L−1 NaCl the aggregates contract only from 326 nm to 308 nm and remain negatively charged, indicating limited contraction rather than disintegration. The synergy of AMPS hydration shielding, NVP segments, and AHM hydrophobic nodes enables an optimal balance of temperature/salt resistance, proppant transport, drag reduction, low damage, and flowback performance, offering a verifiable design route for clean fracturing–fluid thickeners.