As mentioned, the EIA estimates that 25 percent of current natural gas production comes from shale plays using fracking methods. Many states within the United States have been exploring shale formations and extracting the natural gas located there.
The states with the largest shale plays are Ohio, Pennsylvania, New York, West Virginia, and Virginia (where the Marcellus play is located); Texas, Louisiana, Alabama, and Oklahoma (the large Eagle Ford and Barnett plays are located in Texas); and Montana, North Dakota (home of the large Bakken play), Wyoming, Colorado, and Utah. There are other states involved as well, but these states represent some of the greatest activity in the field.
Outside the United States, the countries that contain the largest recoverable natural gas deposits in shale, according to the EIA, are Canada, Mexico, China, South Africa, Argentina, and Brazil.