The deepest well was drilled in 1974 by Exxon USA in Calhoun County, to a depth of 20,222 feet, bottoming in the Precambrian basement. The well, permit number 2503, was dry with a gas show in the Big Lime and oil shows in the Upper Devonian shale and the Marcellus shale. Wells drilled to the Precambrian basement are important to geologists because they provide a “view” of the complete stratigraphic section of sedimentary rocks in a particular area, and they may provide information about the potential of a variety of gas and/or oil reservoirs in the area.