Preparation and High‐Temperature Stabilization Mechanism of Quaternary Copolymer Suspension Stabilizer for Cementing Spacer Fluid

Conventional spacer fluids fail at high temperatures in deep wells, causing sedimentation and poor cementing quality. In this study, a quaternary copolymer suspension stabilizer was synthesized via aqueous free‐radical polymerization. Orthogonal tests revealed that the influence of synthesis parameters on sedimentation stability followed the order: pH > reaction temperature > initiator dosage > monomer molar ratio. The optimal conditions were determined as a monomer molar ratio of 1:1.5:0.5:0.2, a reaction temperature of 65°C, an initiator dosage of 0.1 mol%, and a pH of 5.5. The structure was verified by Fourier‐transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy ( 1 H‐NMR). Performance evaluation shows that the stabilizer enables the spacer fluid to maintain excellent sedimentation stability at 200°C. It presents good rheological and thickening compatibility with drilling fluid and cement slurry. Mechanism analysis indicates that the stabilizer provides high‐temperature stability through chemical adsorption and steric hindrance. Viscosity measurements conducted at a shear rate of 170 s −1 over a temperature range of 30°C ~200°C show that the polymer solution retains 45% of its initial viscosity at 200°C, indicating that the main chain remains intact and meets the demands of deep and ultra‐deep well cementing.