Mechanisms of Covalent Bonds in Enhancing the Adsorption Stability of Clay–Polymer Gels in High-Temperature Environments

To address the issue of drilling fluid performance drop and wellbore instability induced by desorption between treatment agents and clay in the high-temperature environment of ultra-deep drilling, this study synthesized three organosilicon polymers (ADE, ADM, ADD) with different substituents. The study confirmed that the covalent bond significantly improved the high-temperature adsorption resistance of clay, which is closely related to the interface behavior of gels. Through rolling recovery, rheology, and filtration experiments for performance evaluation, these organic silicon polymers showed excellent high-temperature performance: the shale rolling recovery rate exceeded 80% at 210 °C, and the filtration loss was reduced to 14 mL, with a reduction rate of 53.3%. The adsorption capacity of the three polymers on clay remained unchanged from 150 °C to 210 °C, among which the adsorption amount of trimethoxy groups stabilized at 8-11 mg/g after 150 °C. The adsorption capacity of ethoxy groups increased by 7.9% at 150-210 °C. The adsorption capacity of dimethoxy groups with methyl steric hindrance increased by 28.1% at 150-210 °C. These results indicate that covalent bonds effectively enhance the high-temperature adsorption of clay, allowing for polymer molecules to firmly anchor on the clay surface at high temperatures. This breakthrough overcomes the limitations of traditional inhibitors in high-temperature desorption, and provides a valuable reference for the preparation of high-temperature adsorption resistant functional materials in water-based drilling fluid gel systems.