Development and Evaluation of Temperature-Pressure Sensitive Film-Forming Plugging Agent for Water-Based Drilling Fluids

• A temperature-pressure sensitive film-forming plugging agent for water-based drilling fluid was prepared. • The properties of temperature-pressure sensitive film-forming plugging agent were evaluated. • The temperature-pressure sensitive film-forming plugging agent theory and the plugging mechanism are presented for the first time. Wellbore instability induced by aqueous phase invasion necessitates advanced plugging agents. This study synthesizes a temperature-pressure sensitive film-forming plugging agent (CM-1) via copolymerization of methyl methacrylate and butyl acrylate grafted with 3-(methacryloyloxy)propyltriisopropoxysilane. CM-1 (average size: 243.12 nm) exhibits a regular spherical morphology and disperses uniformly in the aqueous phase. Scanning electron microscopy testing indicates that CM-1 exhibits film-forming properties on solid surfaces. The film-forming mechanism involves the hydrolysis of introduced organosilicon compounds to generate silanol groups, which cause numerous nanoparticles to aggregate through mutual contact. Under high-pressure induction, the sealing agent particles transform from spherical to lamellar shapes, deforming into pressure-sensitive adhesives that fill interstitial voids. Under high-temperature induction, -SiOH groups on different particle surfaces undergo condensation to form a stable three-dimensional Si-O-Si network structure, creating a dense film with high mechanical strength. Performance evaluation results show that CM-1 improves the rheological stability of the bentonite-based mud, and CM-1 exhibits strong temperature-pressure sensitivity. Specifically, the filtration loss reduction rate first increases then decreases with rising temperature, reaching the lowest filtration loss at 120℃ and maintaining resistance up to 180℃. Similarly, the plugging rate initially increases then decreases with increasing pressure, reaching the lowest permeability at 12 MPa and withstanding instantaneous pressures up to 15 MPa. Sandbed plugging tests demonstrate an intrusion depth reduction of 14.2% to 28% compared to similar products, indicating improved plugging performance compared to conventional inert plugging agents. These findings confirm that CM-1 effectively reduces liquid phase intrusion through film-forming plugging, exhibits excellent sealing properties, and provides a feasible optimization strategy for maintaining formation and wellbore stability.