Chia seed-inspired hydrogel-coated proppants for dual function of temporary plugging and propping in ultra-deep reservoir fracturing

Temporary plugging and diverting fracturing is an effective strategy to enhance fracture network complexity and expand the stimulated reservoir volume. However, in ultra-deep reservoirs, temporary plugging agents face a critical contradiction between maintaining high pressure-bearing capacity and achieving rapid deplugging under ultra-high temperatures, as dense structure is usually accompanied by slower degradation rate. And also, after deplugging, fractures tend to close under ultra-high in-situ stress, significantly reducing conductivity. Inspired by the stage-specific functionality and core utilization strategy of chia seeds, this study proposes an innovative, resource-efficient “soft shell–rigid core” plugging structure. A dense yet rapidly self-degradable soft shell, formed from high-temperature-resistant polymers and degradable crosslinkers, is employed to encapsulate a high-strength core to form a core–shell structure. This design balances high pressure resistance with rapid degradation, while providing sustained fracture support post-deplugging. The prepared Gel@CP undergoes a sequential process of “injection-plugging-degradation-fracture support.” It exhibits excellent fluid compatibility and suspension stability in the carrier fluid (static >3 h). Under 200 °C and 170,000 ppm salinity, the material reaches a maximum plugging pressure of 21.5 MPa, maintains 20 MPa for over 240 min, and shows a degradation rate above 99.9 % within 12 h, converting into environmentally benign water-soluble polymer fragments. After degradation, the exposed CP core effectively supports fractures, maintaining conductivity above 876 mD·cm under 70 MPa closure stress. This delicate biomimetic core–shell design endows this material with superior performance simultaneously in pressure bearing, fast degradation, and post-deplugging fracture support, which is reported for the first time, providing an innovative, sustainable, and practical solution for temporary plugging and propping under extreme reservoir conditions.