Dynamic Curing Regulation of a Thermosetting Sealing System for Deep Fractured Formations under High Temperature

Abstract Deep and ultradeep oil reservoirs, characterized by high temperatures, high pressures, and strong formation heterogeneity, have emerged as the primary battleground for crude oil production. However, conventional plugging materials, such as hydrogels and solid particles, face significant challenges in effectively operating within such reservoirs. In this work, a novel epoxy thermosetting plugging resin with good injectability, long gelation time, high strength, and excellent sealing performance is designed and developed, which is composed of epoxy prepolymer diglycidyl ether of bisphenol A, curing agent 4,4′-((methylenebis(4,1-phenylene))bis(azanediyl))bis(4-(furan-2-yl)butan-2-one), and diluent butyl glycidyl ether (BGE). BGE is selected to reduce the initial system viscosity while preserving its mechanical properties after solidification. Upon the addition of 20% BGE, the viscosity significantly decreases from 52,900 mPa·s to 2680 mPa·s, while the compressive strength after curing remains 74.4 MPa, and this addition exerts only a small influence on the gelation process. The gelation time at 150 °C reaches 7.8 h, and the cured product exhibited a 5% mass-loss temperature of 300 °C under the TGA condition. Simulated plugging experiment results show that this system exhibits substantially improved injectability. The breakthrough pressure reaches a value exceeding 12 MPa at 120 °C. Notably, following water breakthrough, the inlet pressure does not undergo a rapid reduction to 0 MPa; rather, it experiences a slight decrease to a constant value in excess of 11 MPa. The improved injectability, long gelation time, high-temperature resistance, and exceptional mechanical properties, as well as the excellent plugging capability, make this epoxy resin a promising novel plugging material for deep and ultradeep reservoirs.