Study on the Intermolecular Action Mechanism and Rheological Properties of A Surfactant‐Modified Hydrophobic Copolymer

ABSTRACT To address the issue of insufficient thickener utilization in high‐temperature, high‐salinity reservoirs, this study employed acrylamide (AM), 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS), acryloxyethyl dimethyloctadecylammonium chloride (AODMAC), and oleoylamidopropyl hydroxysulfonyl betaine (OHSB) via radical polymerization to synthesize a high molecular weight (9 million) hydrophobic associative copolymer ACPM. ACPE without OHSB was used as a control. Results indicate: ACPM exhibits excellent solubility, with a 0.4 wt% solution fully dissolving within 25 min, representing a 60% improvement over ACPE. Salt resistance testing shows that a 0.4 wt% ACPM solution maintains an apparent viscosity of 102 mPa s in a high‐salt system of 20 × 10 4 mg/L NaCl, achieving a viscosity retention rate of 64%, representing a 20% improvement over ACPE. Temperature and shear resistance tests indicated that at 140°C and 170 s −1 , a 0.4 wt% ACPM solution in 4 × 10 4 mg/L NaCl exhibited a final apparent viscosity of 84.58 mPa s after 1 h of shear, with a viscosity retention rate of 50%, representing a 10% improvement over ACPE. Therefore, compared to ACPE, the incorporation of OHSB significantly enhances the solubility, salt tolerance, and temperature‐resistant shear stability of ACPM, making it an efficient thickener suitable for high‐temperature, high‐salinity reservoirs.