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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