Insights from dynamics, mechanisms, factors and mitigation strategies of salt precipitation for CO2 geo-storage within saline aquifer

Abstract

CO₂ geo-storage in saline aquifers offers significant potential for reducing greenhouse gas emissions. However, salt precipitation resulting from mineral crystallization during gas-liquid percolation affects CO₂ injectivity and storage efficiency. This review synthesizes recent field data, experiments, numerical simulations, and theoretical studies to identify knowledge gaps and improve understanding. It provides insights into the dynamics, mechanisms, factors, and mitigation strategies of salt precipitation for CO₂ geo-storage in saline aquifers. Field data indicate that salt precipitation mainly occurs within 10–30 m of the wellbore, reducing absolute permeability by 60–70 %. Experimental and numerical studies suggest that capillary-driven drying leads to significant pore blockage near the wellbore, while diffusion- or evaporation-driven mechanisms cause more evenly distributed precipitation. Despite a decrease in absolute permeability, CO₂ relative permeability may increase by 5–6 times. Two major challenges contribute to discrepancies between theoretical models and field data: the migration behavior of salt crystallization and dynamic evaporation of the brine. Addressing these challenges requires high-temperature, high-pressure microchip experiments to visualize and quantify brine evaporation dynamics and salt precipitation at the pore scale. Additionally, core flooding tests, coupled with real-time CT/MRI imaging and particle flow simulations, are essential for investigating the interaction between salt precipitation and pore structure damage. Despite the significant impact of reservoir characteristics, brine properties, and injection strategies on salt precipitation dynamics, systematic studies remain limited, and current research is fragmented. This review proposes a comprehensive evaluation framework incorporating multi-factor coupling to better assess salt precipitation risks and improve CO₂ storage efficiency. These findings provide a foundation for managing salt precipitation in subsurface engineering, with broader implications for energy extraction and carbon storage.