Functional Group Synergy in Improving High-Temperature Resistance of Polymers for Water-Based Drilling Fluids

This study aims at the problem of rheological degradation and elevated fluid loss in water-based drilling fluids under high-temperature conditions caused by thermal decomposition of polymeric additives. We systematically investigated six functional groups—acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinylpyrrolidone (NVP), methacryloxyethyltrimethyl ammonium chloride (DMC), acrylic acid (AA), and polyethylene glycol diacrylate (PEGDA)—to establish molecular design principles for enhancing polymer thermal stability. Six copolymer series with systematically varied functional group combinations were synthesized using controlled protocols. The structure-property relationship between molecular architecture and high-temperature performance was elucidated through characterization techniques. The effect of introducing different functional groups on the thermal stability and high-temperature viscosity of polymers was studied through testing methods such as thermogravimetric analysis (TGA). The results demonstrate that sulfonic acid-containing AMPS groups significantly enhance thermal stability through strong intermolecular interactions, whereas NVP groups effectively maintain viscosity retention at elevated temperatures via enhanced molecular chain rigidity. A notable synergistic effect was observed in polymers combining AMPS and NVP functionalities, achieving measurable improvements in both thermal stability and viscosity retention compared to single-functional-group analogues. Further optimization through strategic incorporation of AMPS, NVP, DMC, and PEGDA groups yielded polymer formulations that retained stable viscosity under extreme thermal conditions. These findings provide a molecular design framework for developing advanced polymeric additives, emphasizing the critical role of functional group selection and combinatorial optimization. The study establishes fundamental guidelines for engineering high-performance water-based drilling fluids applicable to deep well operations, addressing a crucial technological gap in high-temperature hydrocarbon resource development.