The Barnett Shale is a hydrocarbon-producing geological formation of great economic significance to Texas. It consists of sedimentary rocks and the productive part of the formation is estimated to stretch from the city of Dallas west and south, covering 5,000 square miles and at least 18 counties. (source)

The field name for the productive portion of the Barnett Shale formation has been designated as the Newark, East Field by the Texas Railroad Commission.

The Barnett Shale is a large natural gas reserve encompassing more than 5,000 square miles and including portions of at least 18 counties in North Texas. 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. (source)

The Barnett Shale rock deposit is a rock formation deep below the Texas surface. It was discovered in the 1950's by wildcatters. In 1980, technological advances enabled companies to extract natural gas from the Barnett Shale.  (source)

Over the years the Barnett Shale Natural Gas Field received fame when new drilling technology came into existence.  This technology, which uses various fracturing techniques, is used during horizontal drilling.  The Barnett Shale  was the first major operation to extract gas from shale.  Many companies are using this technology in other shale plays in the United States. (source)

The Barnett Shale is named after John W. Barnett, an early day settler 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. (source)

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. (source)

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, which would have to be broken up to release the gas. After 20 years of research, the introduction of horizontal drilling earlier this decade made it possible to access the gas reserves contained within the Barnett Shale. (source)

The Barnett Shale has acted as an important source and sealing cap rock for conventional oil and gas reservoirs in the area. It was thought that only a few of the thicker sections close to Fort Worth would support economic drilling. It was not until the 1980's with new advances in horizontal drilling and well fracturing technology that the potential of the Barnett Shale was realized. Significant drilling activity did not begin until gas prices increased in the late 1990's. (source)