Coal Resources in the Michigan Basin: Some Suggestions for Development
CROSS, AUREAL T.
Michigan State University, East Lansing, MI
Coals in the Michigan Basin are in thin, relatively discontinuous, laterally variable seams (mostly a meter or less in thickness) with numerous partings. The coals are of non-coking, high volatile B and C bituminous rank, with a range of 10,300-12,300 Btu, 3-9 percent ash, and 1-3 percent sulfur. The coal-bearing strata, up to 200 m thick, are of Lower to Middle Pennsylvanian age. Bedrock overlying Pennsylvanian strata unconformably in the central and western part of the basin (Jurassic age “Michigan Red Beds”) is comprised of red, gypsiferous shales, gypsum pods, and coarse to fine-grained, pink to tan sandstone with yellow/orange tinge. This sequence is both a caprock seal and in some parts a large aquifer. Elsewhere, Pennsylvanian strata are overlain by unconsolidated Pleistocene and Recent sediments (gravels, silts, clays, and peat) up to 200 m thick.
Remaining reserves are in 100-1500 (mostly less than 250) acre parcels. The principal factors constraining further subsurface development would be the small area available for each mine, the thinness and irregularities of the coal and partings, splitting at the margins of fields, the weak character of roof shales, and the disturbance of significant overlying aquifers.
A three-stage exploration program is proposed: reevaluation of existing logs and cuttings of oil wells penetrating the coal within each parcel selected; the drilling of one test core with geophysical logs within each of thirty townships with demonstrated coal; and determination of gas content of each coal and the sandstone and shale above and below, documenting potential methane recovery.