Evaluating Underground CO₂ Storage Potential across Sedimentary Facies of the Michigan Basin

Rising atmospheric CO₂ concentrations demand scalable and geologically reliable carbon capture and storage solutions. The Michigan Basin, with its well-characterized Paleozoic sedimentary sequences and proximity to major industrial emission sources, represents a promising target for underground CO₂ storage. This study systematically evaluates the CO₂ storage potential of nine distinct sedimentary rock facies retrieved from the Consumers Brine Disposal 139 (BD-139) well, providing a facies-resolved framework for assessing subsurface sequestration capacity. High-pressure isochoric CO₂ adsorption experiments were conducted across three temperature isotherms (25 °C, 35 °C, and 45 °C) and six pressure points (10-35 bar), complemented by comprehensive material characterization, including Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM-EDS), and thermogravimetric analysis (TGA). Based on their inferred mineralogical composition and thermal behavior, the nine facies were classified into three distinct groups: silicate-rich organic-bearing rocks (Group 1), siliciclastic assemblages with a subordinate carbonate component (Group 2), and carbonate-bearing dolomitic facies (Group 3). Facies 3 exhibited the highest apparent CO₂ uptake, 855.7 mg/g at 35 bar and 25 °C, and all facies gave heats of sorption below 60 kJ/mol, consistent with predominantly physical interactions and with favorable reversibility for storage cycling. Because the measurements were performed on pulverized material, and because the apparent uptake of the highest-performing facies exceeds the volumetric capacity of its own pore system, these quantities are reported and interpreted throughout as apparent isochoric uptake determined under identical conditions. They provide a quantitative relative ranking of the facies rather than absolute in situ storage capacities, and the bounds governing their interpretation are set out in Section 3.5.3. Complementary CO₂ absorption experiments in synthetic brine solutions yielded a solid precipitate on depressurization, indicating a potential mineral trapping pathway under high-pressure conditions. The findings establish a direct link between facies-level geological heterogeneity and CO₂ storage performance, offering a practical screening framework for site selection and reservoir evaluation within the Michigan Basin and analogous sedimentary systems.