47th Annual AAPG-SPE Eastern Section Joint Meeting

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Reservoir Characterization of the Upper Silurian Bass Islands Formation in Northern Michigan for CO2 Storage


Recent research for evaluation of subsurface reservoirs in the northern Michigan Basin through a DOE–funded program called CarbonSafe (DE-FE0029276) identified the Bass Islands Formation as a potential CCS saline reservoir candidate throughout a large area of the northern half of Michigan’s Lower Peninsula. The Bass Islands Formation is a dolomitized brine-filled carbonate reservoir which is underlain by a thick anhydrite and overlain by a cherty carbonate of the Bois Blanc Formation. Porosity values as high as 30% and permeability of >900 md have been observed in core samples The Bois Blanc has high porosity (>15%), but very low permeability and can be considered a leak-off zone and an immediately overlying confining unit. Capillary trapping of CO2 in the Bois Blanc porosity can occur after the pressure during injection diminishes post- injection. The ultimate caprock for the Bass Islands reservoir is the dense, tight limestone of the Amherstberg Formation. Detailed mapping and reservoir analysis using wireline logs throughout a 21-county area in northern Lower Michigan shows relatively uniform thickness (greater than 60 feet) of the porous interval in at least 14 of these counties. Additionally, most of this area lies at depths greater than 2600 feet which is necessary for the CO2 to be maintained in the supercritical phase. Thickness, average porosity, and areas were used along with DOE-NETL standard efficient factors for dolomite to estimate the CO2 resources in Northern Michigan. Results produced a range of 3.5 GT (P10) to 12 GT (P90) with a P50 of 7 GT. The highest potential occurred in Antrim, Otsego, Grand Traverse, and Kalkaska counties. On average, prospective storage was 0.23 MT/km2 which equates to 220 km2 to store 50 MT of CO2. In the highest potential areas, this reduces to 100 km2. There is significant storage potential in the Bass Islands dolomite in northern Michigan, however due to the thickness of the unit, a large radius would be needed to reach injection goals. The Bass Islands dolomite would be a suitable secondary storage zone in a stacked storage scenario.