According to the U.S. Energy Information Administration (EIA), hydraulically fractured wells (unconventional gas production based on shale gas) accounted for 2/3 of US gas production in 2015. This share is higher than for crude oil production, as hydraulic fracturing ("fracking") accounts for about half of US production.
Unconventional gas production has been soaring in the United States since 2000, when around 26,000 hydraulically fractured wells produced 3.6 bcf/d (102 mcm/d) of gas, i.e. less than 7% of total gas production in the country. The number of hydraulically fractured wells has increased tenfold since then, to an estimated 300,000 in 2015, producing more than 53 bcf/d (1.5 bcm/d), i.e. 67% of total US gas production.
Unconventional gas production mainly comes from shale and tight rocks in the Marcellus and Utica formations of the Appalachian Basin, the Bakken formation in Montana and North Dakota, the Eagle Ford formation in Texas, and the stacked Permian Basin formations in Texas and New Mexico.