High Temperature Self‐Regenerative Granular Hydrogels for Fracture Treatments During Subsurface Energy Recovery

The uses of granular hydrogels to assemble macroscopic bulk hydrogels display numerous distinct advantages. However, prior assembly of bulk hydrogels is accomplished by interparticle linking strategy, which compromised mechanical property and thermal stability under hostile conditions. To expand their applications as engineering soft materials, self-regenerative granular hydrogels via a seamless integrating approach to regenerate bulk hydrogels is highly desirable. Herein, covalent regenerative granular hydrogels (CRHs) are prepared at low-temperature synthetic conditions and re-construct bulk seamless hydrogels at high-temperature aqueous environments. The re-formed bulk hydrogels display rubber-like viscoelastic behaviors over a wide range of temperatures from 90 to 150 °C, where the covalent re-crosslinking reactions homogeneously occurr along the periphery and in the matrix of granular hydrogels, accounting for the increased structural integrity at high temperatures. The bulk hydrogel shows increased elasticity and long-term thermal integrity at 150 °C for more than six months in the confined fractures. Moreover, regenerative granular CRH-based bulk hydrogels significantly improve mechanical robustness under destructive pressure. Thus, high temperature water induced regenerative granular hydrogels present the paradigm to treat engineering scenarios such as large fractures for hydraulic fracturing, drilling operation, and disproportionate permeability reduction under extremely hostile conditions during subsurface energy recovery.