Synergistic Effects of Mechanical Properties and Self-Healing in Borate-Based Hydrogen-Bond Dynamic Crosslinked Gels in High-Temperature Water-Based Drilling Fluids

Engineering practices employ sealing materials such as rigid bridge plugs, cementation, and polymer gels to address leaking formations; however, each has limitations: particulate-based materials rely on a match between particle size and fracture width, while chemical cementation is constrained by temperature. Although polymer gels combine elasticity with filling capacity, conventional gels have a fixed crosslinked network prone to microcracking and volume loss under sudden load changes and high temperatures. This has prompted researchers to introduce self-healing gels with reversible crosslinking characteristics; yet, under extreme deep-well conditions, simultaneously achieving high mechanical strength, self-healing, and sufficient pressure-bearing capacity remains challenging. This study synthesized a self-healing gel through dynamic covalent crosslinking. High-temperature, high-pressure tests showed that a 5% gel achieved a burst pressure of 10 MPa at 120 °C. In cyclic tensile tests, the intact gel at 200% strain showed 37 kPa, whereas for gels lacking acrylamide or tannic acid components, the stress dropped to 5 kPa or lower, confirming that the crosslinked network confers excellent tensile properties and repeatable self-healing capability. In rheological experiments, after aging at 180 °C, the storage modulus (G’) of the gel remains at approximately 1000 Pa, maintaining its gel state and possessing high-temperature sealing potential. This gel offers a novel solution for sealing drilling leaks.