Application of a Hyperbranched Amide Polymer in High-Temperature Drilling Fluids: Inhibiting Barite Sag and Action Mechanisms

Addressing the critical challenges of viscosity loss and barite sag in synthetic-based drilling fluids (SBDFs) under high-temperature, high-pressure (HTHP) conditions, this study innovatively developed a hyperbranched amide polymer (SS-1) through a unique stepwise polycondensation strategy. By integrating dynamic ionic crosslinking for temperature-responsive rheology and rigid aromatic moieties ensuring thermal stability beyond 260°C, SS-1 achieves a molecular-level breakthrough. Performance evaluations demonstrate that adding merely 2.0 wt% SS-1 significantly enhances key properties of 210°C-aged SBDFs: plastic viscosity rises to 45 mPa·s, electrical stability (emulsion voltage) reaches 1426 V, and the sag factor declines to 0.509, outperforming conventional sulfonated polyacrylamide (S-PAM, 0.531) by 4.3%. Mechanistic investigations reveal a trifunctional synergistic anti-sag mechanism involving electrostatic adsorption onto barite surfaces, hyperbranched steric hindrance, and colloid-stabilizing network formation. SS-1 exhibits exceptional HTHP stabilization efficacy, substantially surpassing S-PAM, thereby providing an innovative molecular design strategy and scalable solution for next-generation high-performance drilling fluid stabilizers.