CO2-Induced <i>In-Situ</i> Rapid Mineralization in Fractures to Remedy CO2 Leakage for Safe Carbon Geo-Sequestration

Abstract Carbon Capture, Utilization, and Storage (CCUS) is a promising strategy to mitigate global climate change. However, the risk of CO2 leakage poses a significant challenge, as conventional sealing materials frequently fail to ensure long-term stability. Therefore, there is an urgent need to explore new sealing technologies to improve the security of geo-sequestration. Inspired by carbon mineralization sequestration in basalts, we propose an innovative method that utilizes in-situ mineralization reactions to remedy leakage pathways. This involves injecting a system containing reactive minerals into fractures, where CO2 leakage triggers mineralization reactions, generating carbonates with cementing properties, thereby effectively preventing and controlling CO2 leakage. Static experiments were conducted in high-temperature and high-pressure reactors to investigate the reaction characteristics of five silicate minerals with CO2. Wollastonite exhibited the best cementation effect and the highest degree of reaction. To evaluate the feasibility of this approach, the sealing performance of the method was evaluated by comparing the permeability of shale cores with simulated fractures before and after reactive system injection. Results showed a significant reduction in gas permeability, with further decreases observed as the reaction progressed. Microscopic techniques, including XRD and SEM, were employed to elucidate the sealing mechanism. XRD spectra showed a mineral phase transformation from silicate minerals to carbonate minerals, while SEM images revealed the accumulation and growth of cubic calcite and rod-shaped aragonite on the rock and fracture walls. These findings confirm that the proposed method effectively seals leakage pathways by promoting the formation of carbonate minerals, which consolidate the fracture surfaces and reduce permeability. This study demonstrates the potential of in-situ mineralization as a reliable and efficient technique for mitigating CO2 leakage in geo-sequestration.