The Barnett Shale is a rich source of natural gas that spans 5,000 miles beneath at least 18 North Texas counties, stretching west from Dallas to Wichita Falls and south to Waco. Shale is a sedimentary rock made mostly of clay and very fine grains of quartz. The Barnett Shale is an impermeable and nonporous shale that did not yield enough gas for commercial use until the 1980s, when technological advances in horizontal drilling and hydraulic fracturing, or "fracking," allowed wells to tap into gas from the shale.
The Barnett Shale is the largest source of natural gas in Texas and has the potential to be the largest in the country, according to the Barnett Shale Energy Education Council, an industry group. Natural gas currently accounts for 42 percent of Texas’ electricity production and 23 percent of electricity use in the rest of the country.
Thousands of natural gas wells tapped into the Barnett Shale’s gas reservoir dot the North Central Texas landscape. But a unique and controversial aspect of extracting natural gas from the Barnett Shale, as opposed to other shales around the country, is the presence of wells in urban areas. Urban drilling is increasingly common in the Fort Worth-Arlington metropolitan area, which has about 80 percent of the core production, according to a 2007 report by the Perryman Group. Some citizens have raised concerns about the high level of water use for fracking, as well as possible contamination of groundwater and increases in truck traffic and noise.
North Texans are struggling to square their environmental and health concerns with the economic boom created by tapping into a homegrown energy source that is cleaner than other fossil fuels. Drilling natural gas from the Barnett Shale could create more than 108,000 jobs and be responsible for $10.4 billion of output by 2015, according to the Perryman Group. Environmental groups and North Texas communities that host natural gas wells have expressed concern that local water and air quality may be compromised by continued drilling that is not heavily regulated. The Texas Commission on Environmental Quality has four air quality monitors that record and stream hourly online reports on the levels of 46 volatile organic compounds. Nonetheless, there have been concerns in some drilling areas over high levels of benzene.