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

Abstract 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.