Horizontal drilling and continuing advances in hydraulic fracturing have made the Barnett Shale formation of north Texas one of the great recent success stories in gas production and
a showcase for tight-reservoir development technologies. Yearly production from the north-Texas Barnett Shale, officially called the Newark East field by the Texas Railroad Commission,
grew to 1.1 Tcf of gas equivalent in 2007, making it second in size only to the Panhandle-Hugoton field among US producing gas fields. Cumulative Barnett production from 2000 onward
now exceeds 4 Tcf.
The north-Texas Barnett Shale extends over 5,000 square miles and at least 17 counties, with the core areas lying within Denton, Tarrant, and Wise counties. While the formation can be
found at depths as shallow as 3,000 ft in some areas, it primarily appears between 7,000- and 9,000-ft depths. Pay-zone thickness ranges from 100 to 1,000 ft and averages 300–500 ft.
Notably, shales like the Barnett once were seen mainly for their role as barriers that trapped hydrocarbons in other rock or were useful for containing secondary-recovery repressurization
or fracturing operations. They were seldom considered producible formations because of shale’s low permeability, making it difficult for fluids to move within the rock and, thus, for hydrocarbons to flow to the wellbore. Matrix permeability in the Barnett is extremely low, ranging generally between 10–7 and 10–9 darcies.
Partially improving the permeability is the presence of interbedded silt- and sand-sized particles.
The Barnett Shale was believed to be hydrocarbon-rich even before a discovery well was drilled by Mitchell Energy....
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