Synthesis and plugging evaluation of a thermoresponsive shape-memory polymer for lost circulation control

Conventional lost circulation materials (LCMs) suffer from limitations such as poor adaptability and low plugging efficiency. This study developed a high-temperature-responsive, shape-memory, expandable lost circulation material. Specifically, using thermosetting epoxy resin as the matrix and organic montmorillonite (OMMT) as reinforcing nanoparticles, an epoxy foam nanocomposite (OMMT/SMPF) was fabricated through chemical foaming combined with hot-press molding techniques. Lab tests demonstrated that the composite (OMMT/SMPF) exhibits excellent mechanical properties and shape memory characteristics. The incorporation of OMMT significantly enhanced the composite’s thermal stability and glass transition temperature (Tg). When the OMMT content was increased to 5%, the thermal decomposition temperature of the OMMT/SMPF composite rose from 314°C (pure resin) to 339.5°C; while its Tg increased from 104.94°C (pure resin) to 137.23°C. The maximum expansion rate at 140°C reached 130%. These improvements significantly broaden its potential for application in high-temperature deep well drilling operations. Simulation experiments for sealing long fractures confirmed that temperature significantly influences the plugging performance of OMMT/SMPF granules. After being stimulated by high temperatures, the OMMT/SMPF rapidly expands to seal fractures, demonstrating significantly superior plugging effectiveness compared to conventional bridging materials. This study provides crucial theoretical underpinnings for the development of high-efficiency circulation materials.