Mechanically Tough and Chemically Degradable Glassy Hydrogels for Wellbore Strengthening and Fracture Sealing

Hydrogels have emerged as promising plugging agents for mitigating fluid loss in fractured formations during drilling; however, their practical downhole application remains constrained by insufficient compressive strength and limited fracture toughness. This study presents a high-strength glassy hydrogel based on poly(methacrylamide-co-methacrylic acid) [P(MAAm-co-MAAc)] specifically engineered for robust sealing under complex subsurface conditions. A free-radical copolymerization route was developed, with optimization of key parameters: total monomer concentration, MAAm:MAAc molar ratio, ammonium persulfate (APS) initiator and N,N,N',N'-tetramethylethylenediamine (TMEDA) accelerator concentrations, and reaction temperature. The optimized formulation exhibits a superior compressive strength of 8.02 MPa alongside highly tunable gelation kinetics. The hydrogel exhibits minimal swelling in both freshwater and saline media, while maintaining complete alkaline degradability. In simulated fracture-sealing evaluations, the hydrogel successfully sustained a differential pressure of 8 MPa with zero fluid loss for a duration of 60 min. Moreover, the granite fragment composites cemented with the glassy hydrogel showed a particle-size-dependent strength, with a maximum compressive strength of 7.20 MPa. These attributes position the P(MAAm-co-MAAc) glassy hydrogel as a promising, tunable, and environmentally adaptable plugging agent for wellbore stabilization and lost circulation control in challenging fractured reservoirs.