Mineralogical Controls on CO 2 Plume Migration and Mineral Trapping in the United Kingdom Continental Shelf Saline Aquifer

This study investigates the impact of reservoir mineral composition on CO 2 mineralization in saline aquifers of the United Kingdom Continental Shelf (UKCS), one of the most promising regions for large-scale carbon capture and storage (CCS). Using the CMG-GEM simulator, three models with different mineralogical compositions (coarse sandstone, siltstone, and a chamosite-rich variant) were constructed and subjected to 35 years of CO 2 injection followed by 965 years of postinjection monitoring (a total of 1000 years of simulation). The results reveal that CO 2 plume migration is strongly governed by reservoir heterogeneity, with low-permeability layers redirecting plume pathways and restricting vertical migration. In terms of trapping mechanisms, the coarse sandstone model exhibited higher solubility trapping, whereas the siltstone model demonstrated enhanced mineral trapping, dominated by siderite precipitation. Mineralogical analysis identified chamosite dissolution as the primary source of Fe 2+, which facilitated siderite formation; however, excessive dissolution led to pH buffering that limited further mineralization. Sensitivity analysis using CMG-CMOST confirmed that kaolinite and chamosite abundances exert the strongest influences on siderite precipitation, with kaolinite effects being primarily interaction-driven and chamosite showing strong linear control. These findings suggest that mineral composition exerts a decisive role in long-term CO 2 immobilization and highlight the importance of accounting for nonlinear mineral interactions when designing and optimizing CCS projects.