Background CO₂ storage in basalts, enjoying distinct advantages of rapid mineralization and high safety, has gradually emerged as a hot research topic both in China and abroad. This study presents a systematic review of the current status of research on the mechanisms of in-situ CO₂ mineralization storage, the evolutionary characteristics of the physical properties of strata under the condition of mineralization reactions, and representative demonstration projects. On this basis, the future research directions are proposed.

Advances in Research  The in-situ CO₂ mineralization storage in basalts is essentially a process of CO₂-water-rock reactions, achieved primarily through both the dissolution of primary silicate minerals and the precipitation of secondary carbonate minerals, with the former limiting the speed of the whole reaction process. Through static autoclave experiments and dynamic core flooding experiments, existing studies have systematically revealed the dissolution and precipitation behavior of minerals in various types of basalts and have identified the mechanisms by which factors such as mineral composition, grain size/specific surface area, pH, temperature, and fluid composition regulate the kinetics and products of CO₂ mineralization reactions. Through the coupling of mineral dissolution and precipitation, CO₂ mineralization reactions alter the composition of minerals in strata while also significantly affecting their macroscopic physical properties, as manifested by pore structure reconstruction, porosity and permeability evolution, and mechanical property enhancement or weakness. These changes jointly determine the efficiency and geological safety of long-term CO₂ storage. The two global representative demonstration projects, i.e., the CarbFix project in Iceland and the Wallula project in the United States, employ two different CO₂ injection techniques. In the CarbFix project, CO₂-unsaturated aqueous solution is injected into basalts, with conversion used as the core logic. In this project, accelerated dissolution and mineralization reactions are employed for rapid CO₂ fixing, while isotope tracing technology is innovatively introduced to monitor the reaction process in real time. In contrast, the Wallula project focuses on CO₂ storage. In this project, supercritical CO₂ is injected into target strata, with caprocks and trap structures playing a key role in ensuring safe CO₂ sequestration. Additionally, geophysical logging is adopted to assess the CO₂ leakage risk. The two projects provide a valuable reference for the siting, design, and monitoring of CO₂ storage in basalts under various geological conditions.

Prospects  Although significant advances have been achieved in in-situ CO₂ mineralization storage in basalts, there is a urgent need to make breakthroughs in some key issues, including (1) the accurate identification and quantitative characterization of secondary minerals; (2) the understanding of the formation mechanisms of passivation layers and their inhibiting effects on reactions; (3) global sensitivity analysis of factors influencing CO₂ mineralization under actual complex geological-chemical coupling conditions; and (4) the decoupling and identification of multi-source and multi-sink reaction pathways in multi-mineral systems. Thoroughly investigating these issues will lay a core foundation for driving the large-scale applications of in-situ CO₂ mineralization storage from demonstration, thus holding great significance for safe and efficient geological CO₂ sequestration in the future.