Preparation and Performance Study of Expandable Polymer Plugging Agent for Water‐Based Drilling Fluid

ABSTRACT Expanding polymer materials demonstrate significant application value in oil drilling due to their unique volume expansion effects and deformation sealing performance. To investigate polymers with enhanced water absorption and sealing performance, this study employed AM, MMA, and AMPS as ternary copolymer reactants, using white oil as the dispersion medium and OP‐10 and SDS as emulsifiers. Through inverse emulsion polymerization, a three‐dimensional network‐structured expanding polymer P(AM–MMA–AMPS) was synthesized. Optimal synthesis conditions were determined via orthogonal experiments, and comprehensive material characterization revealed successful functional group incorporation with excellent high‐temperature resistance. The polymer exhibits spherical morphology and a median particle size of 33.2 μm, achieving 71.5 g/g water absorption within 24 h at room temperature and 5 MPa pressure resistance. Under the condition of high temperature and high pressure, the polymer can form a dense film on the surface of the mud cake, thereby reducing the filtration loss of the drilling fluid and effectively improving the wellbore stability.