Revolutionizing self-healing materials: Complex micro-containers (CMC) for delivery of compartmentalized reactive agents

This study presents a Complex Micro-Container (CMC) system designed to transport compartmentalized reaction mixtures containing healing agents. Specifically designed for cementing operations in the oil and gas industry, the CMCs exhibit an autonomous ability to effect successful cement restoration. This is achieved by a mechanism that involves the in-situ formation of a self-expanding polyurethane foam following the rupture of the CMCs and the subsequent cross-linking reaction between the healing agents. The CMC system, consisting of polyurea microcapsules with curing agent embedded in a reactive monomer and encapsulated in an outer polyurethane shell, undergoes a two-step interfacial polymerization process. The system structure is characterized by Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric and differential thermal analyzes (TGA and DTA), and scanning electron microscopy (SEM). Examination of the foam generated by the CMCs reveals an increase in initial volume of up to 165 %, highlighting the inherent expansion capacity of the system. Furthermore, computed tomography studies confirm the complete visual sealing of cracks using computer tomography technique and 19 % restoration of the compressive strength within the cement body loaded with only 5 % wt. CMCs. The synthesized material is shown to be a highly effective means of imparting self-healing properties to cement, which holds great promise for applications in the oil and gas industry by reducing the financial burden associated with costly repairs resulting from cementing failures, while improving well integrity.