Region 8, as defined by the National Petroleum Council's Committee on Future Petroleum Provinces of the United States, includes Wisconsin, Michigan, and the northern parts of Indiana and Ohio. The region includes three geologic provinces: the Wisconsin arch, the Lake Superior basin, and the Michigan basin. The Wisconsin and Lake Superior provinces have no established hydrocarbon production and offer little possibility of future production. The Michigan basin has been an oil- and gas-producing province for more than four decades and is the most likely area for future undiscovered reserves.

The Michigan basin covers about 122,000 sq mi (315,980 sq km) and contains about 108,000 cu mi (450,040 cu km) of sedimentary rock. About 36,800 cu mi (153,350 cu km) of this volume is considered potentially productive. The consolidated rocks filling the basin include Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and remnant Jurassic sediments. The entire rock sequence, including the Jurassic, is estimated to be 14,000-15,000 ft (4,270-4,570 m) thick in the central part of the basin. Pleistocene glacial drift, ranging up to 1,000 ft (305 m) or more in thickness, blankets virtually all bedrock.

The Michigan part of the basin, specifically the Southern Peninsula, had produced nearly 552 million bbl of oil and 580 billion cu ft of gas through 1967. These hydrocarbons have come from about 600 individual pools, most of which are small. The bulk of oil and gas in past years has been produced from Mississippian and Devonian rocks. Silurian and Ordovician rocks also produce and in recent years have become increasingly important as drilling objectives. Cambrian rocks have not produced and their potential is not known. Large areas of the basin are still inadequately explored, especially to formations older than Devonian.

Several estimates were made of the volume of hydrocarbons yet to be found in the Michigan basin. The first estimate, based on oil yield per cubic mile of sedimentary rock, is more than 1 billion bbl. The other estimates, based on actual hydrocarbon yield per square mile of proved area, range from about 673 million to more than 1.2 billion bbl. The latter figures apply only to the Southern Peninsula of Michigan and not the entire Michigan basin as defined. New pools, generally of small size, are found each year in the basin. Exploratory and development drilling always has been cyclic, and is closely related to the number and size of new discoveries. The gradual decline in exploratory drilling in recent years, the results of this drilling as reflected by the number and small size of dis overies, and the sagging annual production do not lend high confidence to the estimates of hydrocarbons yet to be discovered.