Preparation of Microencapsulated Self-Healing Agent with Core-Shell Structure and Its Self-Healing Performance Evaluation on Oil Well Cement Stone

Cement materials are highly susceptible to micro-cracking due to initial construction flaws and the influence of external loads during use, and the issue of their healing has garnered significant attention. In this study, a core-shell structured microcapsule with crosslinked polystyrene encapsulating epoxy resin was prepared using in-situ polymerization and used as a crack-responsive self-healing agent for oil well cement stone. The effect of microcapsules on the mechanical properties of cement stone was analyzed. In addition, the effects of microcapsule dosage and particle size, cement healing time, and pre-damaged degree on the recovery effect of the cement stone's mechanical properties were conducted through orthogonal experiments. Results indicate that the addition of microcapsules with large particle increases defects in the cement stone and reduces its early strength. While, as the hydration reaction progresses, the compressive strength of the self-healing cement stone gradually approaches that of cement stone without microcapsule. Additionally, as the hydration time of cement increases, the integration between the microcapsules and the cement stone becomes tighter, which is beneficial for the rupture of microcapsules at the crack tips under stress, thereby enhancing the self-healing effect of the cement stone.