Mechanism of rigid functional groups on the temperature resistance of fluid loss additives for well cementing

To tackle the existing gap in our understanding of the degradation mechanisms of fluid loss additives in high-temperature cement slurry environments and reveal the role of monomers with highly rigid functional groups in improving the stability of polymer chains at high temperature, we synthesized several high-temperature resistant fluid loss additives using monomers with highly rigid functional groups, including sodium styrene sulfonate (SSS) and N-vinyl pyrrolidone (NVP), separately. High-temperature fluid loss control property experiments demonstrated that the introduction of rigid functional groups effectively enhances the temperature resistance of fluid loss additives, while also maintaining favorable dehydration performance at lower dosages. High-temperature fluid loss control property experiments and aging experiments demonstrated that the introduction of rigid functional groups effectively enhances the temperature resistance of fluid loss additives. At 220 °C, the fluid loss decreases to below 64 % of the initial level The effects of introducing rigid functional groups on the interaction between fluid loss additives and cement particles at elevated temperatures were investigated through zeta potential, particle size, and high-resolution microscopy analysis. Additionally, TGA, IR, ¹H NMR, and GPC tests were conducted on the fluid loss additives after aging at 220 °C to examine the impact of rigid groups，while the molecular weight retention rate can increase from 48.03 % to over 62.21 %. The results indicate that branched chain and main chain in high-temperature cement slurry environments critically undermines polymer integrity, ultimately leading to functional failure. At same time, compared with NVP, SSS relies on the temperature resistance of the benzene ring, which enables it to have higher temperature resistance and retain more sulfonic acid groups. This will help improve the performance of water loss agents at high temperatures and provide strategic design principles for the development of high-temperature resistant cement slurry systems.