A Review of Different Self-Healing Cement Composites for Wellbore Integrity

Abstract Wellbore integrity is paramount in the oil and gas sector, directly influencing operational safety, environmental protection, and economic viability. The cementing process, designed to secure wellbore systems and prevent fluid migration, often faces significant challenges due to extreme subsurface conditions, including high temperatures, pressure variations, and chemical aggressiveness. In recent years, innovative self-healing cement composites have emerged as a promising solution to enhance wellbore integrity, integrating advanced materials capable of autonomously repairing cracks and defects. This paper explores recent advancements in self-healing cement composites, focusing on innovative materials designed to improve durability and well integrity. The paper covers polymer-cement composites, which use polymers to repair cracks, and microbial cement slurries from dairy wastewater that heal cracks via microbial activity. It also examines geopolymer cement composites for their sustainable self-healing properties, bacterial cement composites for calcium carbonate precipitation, and engineered cementitious composites (ECCs) for their exceptional crack-healing abilities and ductility, offering promising solutions for enhancing cement performance. Polymer-cement composites demonstrate improved mechanical properties and thermal stability by incorporating polymeric materials, making them particularly suitable for geothermal and oil well applications. Geopolymer cement composites have high resistance to chemical attack and low cost, low energy requirements, and low gas emissions. Bacterial cement composites utilize microbial activity to induce calcium carbonate precipitation, effectively sealing micro-cracks and prolonging wellbore life. Additionally, the potential reuse of dairy wastewater as a nutrient source for bacteria addresses environmental concerns while reducing cultivation costs, presenting a dual benefit for wellbore integrity and wastewater management. Meanwhile, ECCs leverage fiber reinforcement to provide ductility and controlled crack formation, improving durability under mechanical stress. Despite the advantages of these advanced materials, challenges remain, including their performance under extreme conditions, economic considerations, and regulatory compliance regarding the use of microbial agents and wastewater. This is the first paper that presents novel insights into all advanced self-healing cement composites, exploring sustainable materials like microbial slurries from dairy wastewater and engineered cementitious composites (ECCs). By integrating these cutting-edge technologies, the paper offers practical solutions for enhancing well integrity and durability, providing practicing engineers with new strategies for improving cement performance and sustainability.