The Barnett Shale Formation of
North Texas and Oklahoma
Oilfield Books, Geology & Petroleum Engineering Books
Map Of The Barnett Shale
Oilfield Jobs In Texas
Frac Tanks Used For?
Rig site near
Working on Barnett Shale Rig
Horizontal or Directional Drilling For Gas In the Barnett Shale
In part due to the worldwide demand
for energy and decreasing oil and natural gas supplies, oil and gas
companies are exploring areas previously passed over because they were believed to be
unproductive. One such area that has been known about for years is the Barnett
shale formation of North Texas and Oklahoma.
What is The Barnett Shale?
The Barnett Shale is named after
early day settler John W. Barnett who homesteaded in San Saba County Texas where
he named a local creek the Barnett Creek. During the early 20th century
during a geological mapping expedition a geologist noticed the black shale
outcropping in Barnett Creek and named it the Barnett shale after the creek. In
that area of the state the formation outcrops or touches the surface. It is in
the seven to eight thousand foot deep range near Dallas.
What creates gas and condensate in
the Barnett Shale is organic matter called kerogen that lies embedded in the
shale. Through biogenic and thermogenic action, natural gas is given off. The
Barnett Shale is rich in organic matter and some believe that biogenic action is
still producing natural gas even now. The Barnett Shale is known as a
"tight" gas reservoir meaning that the gas is not easily extracted. The
formation is a very hard shale and it was virtually impossible to produce gas in
commercial quantities from this formation until recent improvements were made in
fracturing technology and directional drilling. Large quantities of fresh water
are used to frac the Barnett Shale. Surface water supplies may be depleted
during this process.
How Old Is The Barnett Shale and
How Large Is It?
It consists of Mississippian age (354-323
million years ago) sedimentary shale rocks and stretches from Dallas to
west of Fort Worth and southward, covering at least 5,000 square miles in
the Fort Worth Basin. The Barnett shale is also found as far West as Pecos
County in West Texas. There have been exploratory wells drilled in Reeves County
in the Barnett shale with mixed results but exploration continues there. (See
map of Barnett Shale below)
How Much Gas Does The Barnett Shale Contain?
Oil and Gas Experts have suggested that it may
be the largest onshore natural gas field in the US although new estimates from
the newly discovered Marcellus Formation in Appalachia may equal the Barnett.
The field is proven to have 2.5 trillion cu. ft of natural gas and the
figure could be higher as the boundaries of the Barnett Shale are pushed. Besides
natural gas condensate and light oil has been found in lesser quantities and sufficient enough
at today's prices to be commercially viable. Below is a chart showing the amount
of natural gas production from the Barnett Shale.
Illustration of how much gas was produced since horizontal
drilling in the Barnett Shale Began. (It is over 800 billion cu/ft per year
What Is Horizontal Drilling?
Horizontal drilling is a technology whereby oil
and gas companies can drill "sideways" at ninety degrees across a zone of rock
such as the Barnett shale, allowing for hundreds of feet of profile to be
exposed. After the horizontal well bore is drilled it is cased, perforated
and then "fraced". A frac job involves the pumping of super high pressure
fluids into the formation to open up more fissures for gas to escape from. See
the photo below of a Halliburton frac job in progress. Many high pressure pumps
are used in stages to pump thousands of gallons of fluid into the formation,
often along with a "proppant" or spherical type of glass or polymer bead to keep
the fissures open.
How Does Horizontal Drilling Apply To The Barnett Shale?
The Barnett shale has been known to geologists
and oil men for decades. When it was drilled through a small amount of natural
gas would be encountered but because it was shale, a low porosity rock, it was
never considered a reservoir of natural gas. When horizontal drilling was
perfected a couple of decades, oil and gas companies such as Chesapeake, Devon, EOG and others, began taking a look at shale formations such as the Barnett
shale. In 1981 Mitchell Energy, later acquired by Devon Energy, drilled the
first well in the Barnett Shale and decided to try and produce it because of the
amount of gas detected by the mudloggers. They set casing and did a small frac
job and were able to produce a fair amount of vas for a vertical well. Although
that well was not economically viable it focused attention on the Barnett shale.
Over the years hydraulic fracturing techniques were perfected, as was horizontal
drilling, and the gas boom was on. Now there are dozens of rigs drilling
horizontal wells in the Barnett Shale for a variety of oil and gas companies.
See the You Tube Video below for an illustration of how horizontal drilling in
the Barnett Shale is done.
The Economic Impact Of The Barnett Shale
The Barnett Shale Formation Of North Texas
Is possibly the biggest economic boost to that area in history. It has
been estimated by the Fort Worth Chamber Of Commerce, that the impact of the Barnett shale on the economy
of a five county area, including Tarrant, Johnson, Hood, Palo Pinto and Erath
counties is equal to five Boeing jet manufacturing plants opening up. The
Barnett shale is productive in at least 17 counties. Far from
a drop in the bucket, the natural gas contained in the Barnett shale will go a
long way to powering America's future. Advocates of a natural gas powered United
States, such as T. Boone Pickens, believe that there is enough natural gas in
shale formations like the Barnett to last over 100 years.
Formerly economically depressed
areas such as Cleberne, Texas and Weatherford, Texas are now boom
towns. Thanks to high paying oilfield jobs and landowners spending gas royalties,
the local economies and tax base have drastically improved in counties where the
Barnett shale is productive. In 2006, the Barnett Shale was
responsible for creating 55,385 permanent new jobs, and is estimated to
have contributed $491 million in revenues to the state of Texas, and $228
million to local governments. Economists estimate that by 2015 the Barnett
Shale may be responsible for more than 108,000 total jobs in the areas where it
is being heavily exploited. One drilling rig provides good paying jobs directly
and indirectly for over 130 persons.
Impediments to Development
From the Comic Strip "BC"
The development of the full potential of the
Barnett shale has come up headlong against the dense urban areas of the growing
Dallas - Fort Worth Metroplex and protests are growing from homeowners and city governments
worried about eyesores and noise from drilling rigs and pipeline construction.
Lawsuits from neighborhood groups and individuals abound, especially ones from
do not own the mineral rights under their property.
Environmental Concerns. Due to the fact that it is a
low porosity, low pressure gas formation it requires a serious "frac job" or
fracturing of the rock formation, by a
company such as Halliburton to produce gas.
process requires massive amounts of water, which is injected under extreme pressure
to fracture the rock and allow it to release gas. This need for large
amounts of water has put a strain on surface water
supplies in the areas where Barnett shale directional drilling is
concentrated. Despite these impediments rigs are working night and day at present and there
is no end in sight to the wells being drilled despite the economic downturn and
the resulting lower price of natural gas. Drilling throughout this area has been intense, with directional
drilling programs by companies such as Chesapeake running at full steam ahead and landmen rushing to grab up mineral rights
in areas that were previously overlooked.
Devon, EOG, XTO, Chief, Williams, Chesapeake
and Quicksilver are all major players. The maps below show the heart of the Barnett shale in Parker, Tarrant,
Johnson, Hood, Palo Pinto and Erath counties and top leaseholds.
Map Of The Barnett Shale.
Click Here For Full
Sized Map Of The Barnett Shale
How Long Will Drilling In The
Barnett Shale Last?
In an interview with the American
Association of Petroleum Geologists, Larry Brogdon, exploration manager for Four
Sevens Oil Company, had this to say; "We will all be dead
and folks will still be drilling Barnett wells," he said. "There are literally
thousands of infill wells to be drilled in the core areas and operators will
continue to push its limits."
Update: Depressed natural gas prices have led to
a reduction in overall drilling in the Barnett Shale. Despite this, drilling
continues in some parts of the play, especially the "Barnett Combo" which
centers around Montague county, and which contains valuable liquids such as oil
Helpful Links about shale gas
Oil Patch Bookstore
Marcellus Shale Formation
In an interesting
side note, another shale formation, the Eagle Ford shale in South Texas, is
proving to hold even more natural gas than the Barnett shale. For more about the newly discovered
Eagle Ford Shale click here:
The Eagle Ford Shale Formation, Map and Info.
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