At the turn of the 20th century, Ohio was the largest oil producer in the United States. With the Appalachian Basin, which crosses the eastern part of Ohio, the state may return being a large oil and natural gas producer. The Basin’s Marcellus shale formation contains shale gas and the Utica shale formation contains both shale oil and gas. While production is just beginning in these shale formations in Ohio, it is expected to increase substantially by 2015. Currently, the shale wells account for less than 1 percent of the almost 51,000 gas and oil wells in the state. However, their output in 2012 represented 12 percent of the state's total oil production and 16 percent of the state's total gas production.
