Novel Resin‐Cement Composite for Sustained Annulus Pressure Mitigation: Mechanism, Performance, and Solution Design

ABSTRACT Sustained Annulus Pressure (SAP) compromises wellbore integrity due to leakage and corrosion, posing significant safety and environmental risks. Traditional cement‐based materials lack toughness and acid resistance, limiting their long‐term sealing performance. This study develops a novel waterborne epoxy resin–ultrafine cement composite, enhanced with a silane coupling agent (KH‐550), to address these limitations. With 20.0 wt% epoxy resin, the material achieves 236.0 mm fluidity (a 52.3% increase over pure cement), maintains compressive strength > 21.0 MPa at 140°C, and exhibits a 3.7‐fold higher strain capacity. It demonstrates exceptional thermal stability (decomposition temperature > 440°C), superior resistance to seawater and acidic environments (< 6.28% strength loss after 30 days), and effective gas sealing performance (< 100 mL·min −1 leakage at 25.0 MPa). Microstructural analysis reveals that the epoxy resin fills microcracks and forms Si–O–Si bonds with cement hydrates, creating a reinforced interpenetrating network. Based on the specific conditions of Well A4S2, a targeted four‐step remediation method is designed. Key innovations include the ternary composite design, the elucidated physical–chemical‐microstructural reinforcement mechanism, and the integrated field solution protocol. This work provides a scientifically grounded, field‐ready solution for SAP mitigation, advancing the design of high‐performance, durable sealing materials for oil and gas wells.