Modeling the long-term fate of injected CO₂ in saline aquifers: An integrated framework coupling multiphase flow, dissolution, reaction, and ripening

Abstract. Geological carbon sequestration (GCS) mitigates climate change by storing anthropogenic carbon dioxide (CO₂) in geological formations. CO₂ undergoes complex physical and chemical transformations in the deep geological formations, governed by various interacting trapping mechanisms. Because the trapping mechanisms operate at wide range of different timescales, their long-term interplay remains unclear. We develop an integrated numerical modeling framework to analyze and track the footprint and phase transition processes that occur throughout the entire cycle of the injected CO₂ in saline aquifers. The key novelty of the modeling framework lies in its capability to accurately describe multiple hydrodynamic processes and their interactions, including injection, dissolution-driven convection, reactive transport, and gravity-induced Ostwald ripening. The results suggest that dissolution reduces the lateral migration of physically trapped CO₂, while mineral reaction provides a preferential channel for CO₂-rich flow. For the scenarios we analyze, after several hundred years of mass transfer, dissolved CO₂ accounts for approximately 40 % of total trapping amount, while mineral trapping contributes less than 1 %. The results also illustrate that low vertical permeability is unfavorable for the long-term transition of CO₂ from the physical state to the dissolution state. When the heterogeneity index γ increases from 0.5 to 10, the total dissolution storage amount within the domain is reduced to one-third over the 500-year simulation period. This integrated modeling framework provides critical insights into the long-term evolution of CO₂ plume migration and phase transition behavior, thereby offering a practical tool to quantitatively assess the long-term fate of the injected CO₂ in saline aquifers.