The U.S. Geological Survey (USGS) completed an assessment of the undiscovered oil and gas potential of the U.S. portions of the Appalachian Basin and the Michigan Basin in 2002 and 2004, respectively. Following the assessments of these two basins, oil and gas allocations were assigned to the U.S. portions of the Great Lakes - Lake Superior (Michigan, Minnesota, and Wisconsin), Lake Michigan (Illinois, Indiana, Michigan, and Wisconsin), Lake Huron (Michigan), Lake Erie (Michigan, New York, Ohio, and Pennsylvania), and Lake Ontario (New York). Allocations for Lake St. Clair (Michigan) were included with those of Lake Erie.
The allocations are based on the geologic elements of each total petroleum system defined in the region and the projected extent of those elements from onshore beneath each of the lakes. These geologic elements include the hydrocarbon source rocks, reservoir rocks, and traps. By using this geologic framework, the USGS defined 8 total petroleum systems and 21 assessment units within the Great Lakes and estimated the quantity of undiscovered technically recoverable oil and gas resources within 16 of the 21 assessment units in the Great Lakes.