A novel DMAA/AMPS/VM/IA quadripolymer as a high temperature and salt resistance fluid loss additive for well cementing

Cementing in deep and ultra-deep reservoirs often faces the critical challenge of additive degradation in high-temperature environments. Addressing this, 1-vinylimidazole (VM) was incorporated into the copolymerization of N,N-dimethylacrylamide, itaconic acid, and 2-acrylamido-2-methylpropanesulfonic acid to synthesize a tetrapolymer (PDVI). Using aqueous free radical polymerization optimized by response surface methodology, the resulting PDVI exhibited superior fluid loss reduction in high-temperature and high-salinity conditions. Compared to the control sample PDI, PDVI reduced fluid loss from 64.7 mL to 25 mL at 200°C and from 105.7 mL to 42.5 mL at 240°C, while maintaining filtration below 70 mL in 20% NaCl. Structural characterization via 1 H-NMR and FTIR, combined with TGA and aging tests, confirmed that VM’s rigid five-membered ring significantly enhanced thermal stability; molecular weight retention after aging at 220°C increased from 46.13% to 68.31%. Furthermore, DLS, SEM, and zeta potential analyses indicated that VM’s cationic nature facilitates robust polymer adsorption on cement particles. This mechanism ensures effective particle dispersion and the formation of a dense filter cake even under extreme conditions. These findings provide essential insights for developing high-performance polymeric additives for cementing in complex downhole environments.