Abstract Existing subsurface data and data from core and logs in a new CO 2 pilot injection test well drilled in northern lower Michigan were used to evaluate the geological carbon sequestration (GCS) potential in Upper Silurian to Middle Devonian saline reservoir and cap-rock units in the Michigan Basin. The Core Energy-State Charlton #4-30 well, Otsego County, Michigan, was drilled as part of ongoing Midwest Region Carbon Sequestration Partnership (MRCSP) phase II studies to investigate GCS potential in these units in the Michigan Basin. Significant GCS potential is recognized in porous dolomite of the Upper Silurian, Bass Islands Group in the new well. Cherty strata of the Bois Blanc Formation are also present in the #4-30 well but may lack suitable injectivity for consideration of GCS. Argillaceous limestone in parts of the superjacent Amherstburg Formation in the test well contains minimal porosity and permeability and constitutes an excellent cap-rock unit in the area. Regional consideration of the Bass Islands sequestration target interval indicates substantial GCS potential throughout most of the Michigan Basin. Preliminary estimates of regional GCS storage capacity range from 1.34 billion metric tonnes at 2% displacement storage efficiency to 6.7 billion metric tonnes of CO 2 at 10% storage efficiency in the study area. These displacement storage capacities equate to approximately 288–1440 t of CO 2 per hectare (117–583 t/ac) given the regional estimates of average thickness and porosity in the target interval used here. Significant drilling fluid loss into the target injection interval observed during drilling of the State Charlton #4-30 well of about 3.2 m 3 /hr (20 bbl/hr) demonstrates substantial injectivity in the pilot test well. Considering the fluid loss during drilling and measurements of conventional petrophysical properties in the injection target, the proposed CO 2 injection test volume of 10,000 t could fill the target interval in an area of at most 35 ha (86 ac) in the subsurface, depending on displacement storage volume efficiency assumptions. These preliminary assumptions and simple calculations indicate that the CO 2 injection plume for the injection test would extend no more than 600 m (1970 ft) away from the borehole in all directions. Preliminary reservoir simulations, using other assumptions, suggest a substantially less extensive invasion of the target interval during the injection test.

ABSTRACT Approximately 200 line-km of high-resolution seismic reflection data, 24 vibracores, historical maps, and aerial photography were used to delineate the geomorphic history, geologic framework, and potential hard mineral resources of the Petit Bois Pass area. Petit Bois Pass is a natural tidal inlet system located between Petit Bois and Dauphin islands at the Mississippi-Alabama state line. Since its opening, the inlet has migrated to the west at rates exceeding 50 m/yr. However, the main channel of Petit Bois Pass has remained relatively stable since 1917, occupying an antecedent topographic depression cut into underlying pre-Holocene deposits. Pre-Holocene deposits form the eastern core of Dauphin Island, where they are subaerially exposed. The pre-Holocene surface dips to the west, providing a platform for the narrow, elongated Holocene spit of Dauphin Island. The pre-Holocene surface crops out on the shoreface at the western end of Dauphin Island 8 to 9 m below mean low water (MLW). Farther to the west, vibracores from the main inlet channel of eastern Petit Bois Pass contain only Holocene sediment, suggesting that the pre-Holocene surface is >11 m below MLW. West of the main tidal channel, the undulating pre-Holocene surface shallows in the central portion of the pass before dipping down to >11 m under Petit Bois Island. It appears that tidal channels associated with Petit Bois Pass occupy pre-Holocene fluvial channels cut by either the Pascagoula, Escatawpa, or Fowl rivers during lower sea level. In the study area, the primary hard mineral resource targets include Holocene tidal inlet channels, ebbtidal deltas, and shoreface sand ridges, while abandoned pre-Holocene fluvial channels are considered secondary.