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Gas Shales
Gas shales are currently one of the hottest plays in the United States as a result of high gas prices, the remarkable success in the Barnett Shale in the Fort Worth Basin, technological advancements in drilling and completions, and predicted near-term shortages of natural gas.
Furthermore, gas shales occur behind pipe in many developed basins where conventional production is declining, an underutilized gathering infrastructure exists and markets are accessible.
US Production
There are over 35,000 producing gas shale wells in the United States, with a current cumulative production of about 600 bcf/year. Total gas shale resources in the United States have been estimated in the range of 500-600 tcf.
Outside the United States gas shales have received little attention. Gas shales resources in Canada are estimated to be over 1,000 tcf, and many operators are assessing potential gas shales either as potential incremental production or as stand alone, Barnett-type prospects.
Barnett Shale Play
By far the biggest gas shale success story is the Mississippian-aged Barnett Shale of the Fort Worth Basin. The undiscovered natural gas resources in the Barnett Shale have been estimated at 26.2 tcf (Pollastro et al. 2004), and currently there are over 3,500 producing wells.
Initially developed by Mitchell Energy, the Barnett play has continued to grow outside the initial "core area" as a result of improved completion and fracturing practices, horizontal drilling and successful refracing of existing wells.
Devon, the biggest operator, has drilled over 800 wells since taking over Mitchell Energy in 2001 and now operates over 1,700 Barnett wells. In August 2004, Devon announced the drilling of its 100th horizontal hole with rates up to 4 mmcfgd.
In the last several years Devon has been joined in the Barnett play by other gas players, including Burlington, Chief Oil and Gas, EOG, Quicksilver and EnCana.
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