Microcontainer-Based Self-Healing Cement Additive to Effectively Seal Cracks by Generating Polyurethane Foam

Abstract Maintaining long-term well integrity is essential for conducting oil and gas production in an economically and ecologically responsible manner. Here, we developed self-healing characteristics in cement by formulating a complex microcontainer (CMC) additive. The mechanical activation of microcontainers during cracking triggers a self-expanding polyurethane foam production mechanism in the fractured region, which leads to the restoration of the well integrity. The complex microcontainers feature a unique structure that includes the main components of the widely used polyurethane foam, which are enclosed and inert to each other: polyol-containing (component A) polyurea microcapsules within the isocyanate phase (component B) in the core of larger polyurethane microcapsules. We obtained the complex microcontainer system in two steps using interphase polymerization, which followed the creation of oil-in-oil and oil-in-water emulsions. FTIR, SEM, optical microscopy and TGA were used to characterize the obtained material. Additionally, we used model cement samples to investigate the material's ability to foam in the presence of water and its self-healing properties. The foaming characteristics in the aqueous system exhibit effective self-expansion, and 5% wt. of self-healing additive is adequate to successfully seal the fractures within 10 days. The implementation of the proposed self-healing cement can save 10 tons of CO2 per deployment by minimizing remedial cementing and hydrocarbon leakage.