High-Pressure- and High-Temperature-Resistant Resins as Leakage Control Materials in Drilling Fluids

Well leakage is a recurring hazard in drilling operations that can lead to significant loss of drilling fluids and serious consequences when drilling fluids seep into the formation. Increasing drilling depths correspond to elevated formation temperatures and pressures, which place stringent demands on leakage control materials. In this study, a high-pressure- and high-temperature-resistant branched resin, poly-BDEB, was synthesized using 2,2-bis(4-hydroxyphenyl)propane diepoxyglycidyl ether and epoxy crack adhesive B. The properties of the branched resin poly-BDEB were characterized. Leakage control performance of the branched resin poly-BDEB was evaluated through single-stage and multi-stage crack plugging experiments to determine its effectiveness. The results show that poly-BDEB maintains structural stability under pressures of up to 198.33 MPa. Poly-BDEB has a stable structure and will not be thermally decomposed at 352.25 °C. These properties demonstrate poly-BDEB’s excellent pressure and temperature resistance. The density of branched resin poly-BDEB is 1.07 g/cm3. When its concentration in the drilling fluid reaches 24% (8%A + 8%B + 8%C), it still maintains good sedimentation stability. Poly-BDEB can effectively plug single-stage and multi-stage fractures ranging from 1 to 3 mm in width. Unlike conventional leakage circulation materials (LCMs), poly-BDEB features a branched molecular structure that improves its mechanical strength, thermal stability, and bridging efficiency in fractures. This study can provide technical support for leakage control in deep and ultra-deep wells during drilling.