Shale gas in the United States is rapidly increasing as an available source of natural gas. Led by new applications of hydraulic fracturing technology and horizontal drilling, development of new sources of shale gas has offset declines in production from conventional gas reservoirs, and has led to major increases in reserves of US natural gas. Largely due to shale gas discoveries, estimated reserves of natural gas in the United States in 2008 were 35% higher than in 2006.
In 2007, shale gas fields included the #2 (Barnett/Newark East) and #13 (Antrim) sources of natural gas in the United States in terms of gas volumes produced. The number of unconventional natural gas wells in the US rose from 18,485 in 2004 to 25,145 in 2007 and is expected to continue increasing until about 2040.
The economic success of shale gas in the United States since 2000 has led to rapid development of shale gas in Canada, and, more recently, has spurred interest in shale gas possibilities in Europe, Asia, and Australia. It has been postulated that there may be a 100-year supply of natural gas in the United States, but only 11 years of gas supply is in the form of proved reserves.