The Barnett Shale is more than 7,000 feet below the surface and is comprised of dense non-permeable rock. According to Dr. Ken Morgan, a geologist at Texas Christian University, “Solid hard rocks that are 7000 feet down don’t subside. You have more than a mile of solid rock that holds it all up. Subsidence occurs when you have loose, soft materials like in Houston (sands, clays, etc.) but not in cemented hard rocks like the Barnett Shale.”
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Facts About Barnett Shale
The Barnett Shale is a large natural gas reserve encompassing more than 5,000 square miles and stretching across 20 counties in North Central Texas. Many experts believe the Barnett Shale may be the largest onshore natural gas field in the United States, containing more than an estimated 40 trillion cubic feet of natural gas. In recent years, advances in drilling technology have made it possible for energy companies to extract large amounts of natural gas from the Barnett Shale.
Contrary to popular belief, urban drilling is not new and has occurred at various places throughout the United States. However, the concentrated number of gas wells being drilled in a large metropolitan area, like around Fort Worth and surrounding cities, has created more awareness about urban drilling. The high activity levels of urban drilling in North Texas are a direct result of three things:
- The Barnett Shale may be the largest and most active natural gas reserve field in the United States, making it an integral part of America’s energy sources.
- The most populated areas of North Texas happen to sit atop the Barnett Shale. (The major part of potential development lies beneath Tarrant, Johnson, and western Dallas counties, about one mile and a half underground.
- Advances in drilling techniques enable producers to extract this gas efficiently and economically.
The Barnett Shale has already provided an economic boost to many North Texas cities, counties and residents and has already produced more than 4.8 trillion cubic feet of natural gas.
How did the Barnett Shale form?
More than 100 million years ago, North Texas was under an ocean. Over the course of millions of years, the oceans dried up and sea creatures died. The mud hardened into rock and the organic matter decomposed and produced methane, the predominant component of natural gas. The methane deposits then became trapped in the porous rocks in the shale’s layers.
Why has drilling started recently in the Barnett Shale?
Mitchell Energy drilled the first gas well in the Barnett Shale in 1981. After studying the Barnett Shale, the company could see its potential, but knew drilling would be difficult because the natural gas was literally hiding in the source rock layers. The industry calls this kind of deposit “unconventional” (also known as “nonconventional”) because the gas is not located in relatively shallow, highly porous rock formations which create pockets of gas (known as “conventional” deposits). Conventional deposit formations are much easier to produce.
In the Barnett Shale, the source rock has to be fractured to release the gas, a technique that at the time wasn’t netting the company with large enough gas reserves to be truly profitable.
For the next 20 years, Mitchell Energy continued to work at inventing the technology to unlock the key to the Barnett Shale. By the late 1990s, Mitchell Energy increased the economic efficiency of Barnett Shale gas wells by using hydraulic fracturing methods, which is the use of water and sand under high pressure, to fracture the rock and release the gas. Since Mitchell Energy’s pioneering efforts, many gas companies have continued to develop methods and technologies to improve production. The final piece of the puzzle was the introduction of horizontal drilling in 2002.
According to the Texas Drilling Observer, “The development of the Barnett Shale can truly be considered a function of technology, as modern, much larger fracture stimulation methods have led to greater investments.”
Where is the Barnett Shale located?
The Barnett Shale covers over 5,000 square miles in North Texas. It is geologically defined by a number of faults, arches and uplifts. The productivity of the shale varies with its thickness and there are currently wells or permitted wells in 20 counties. The most productive part of the Barnett Shale is in Tarrant, Wise, Denton and Johnson counties. Download the PDF.
What is the economic impact of the Barnett Shale?
A study released by The Perryman Group in March 2009 estimated that natural gas activity in the Barnett Shale would lead to about 70,000 jobs and $6.5 billion in annual output to the Texas economy in 2009.
City officials in Fort Worth estimate that the city has already received over $100 million in lease bonuses and royalties and expects to receive more than $1 billion in natural gas revenues over the next 20 years. Also, many school districts have benefited from leasing their mineral rights. As an example, the Birdville Independent School District north of Fort Worth used their gas well revenues to fund a scholarship program which provides two full years of college at Tarrant County College. As of January, 2010, there were just under 14,000 wells in the Barnett Shale producing over 4.8 Bcf per day.
Who oversees regulations regarding sound around natural gas drilling?
Cities/municipalities have jurisdiction over sound.
