Shale gas is the term used to describe natural gas found in shale rock.
Although it’s considered an unconventional source of natural gas because of the difficulty involved in extracting it, shale gas in the last decade has gained prominence as technological advances have made it more easily accessible. It’s considered a cleaner fuel than coal because it emits fewer greenhouse gases during combustion. However, hydraulic fracturing or 'fracking' is a technique to extract shale gas that has come under fire for environmental and public health concerns.
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The recent success of shale gas production in the United States has led to similar projects starting in Canada, Europe, Asia and Australia. In November 2009, the Obama Administration announced the launch of a new U.S.-China partnership whereby American expertise would be tapped to help China access its shale gas resources.
According to a 2010 study by IHS CERA, an energy research center in Cambridge, Mass., shale gas accounted for only one percent of the natural gas supply in the United States in 2000. A decade later, the percentage had increased to 20 percent and by 2035 it could be as high as 50 percent, according to the study.
From 2007 to 2010, more than 1,800 trillion cubic feet of natural gas reserves have been discovered in North America, bringing the total untapped natural gas reserves to 3,000 trillion cubic feet in North America. According to the IHS CERA study, that’s enough to supply current U.S. consumption for more than 100 years.
There are environmental concerns about shale gas extraction. The extraction process involves digging a well an average of one-and-a-half miles into the ground to reach the gas-bearing rock. Once the well is dug vertically, oftentimes the next step is to drill horizontally into the shale rock. After drilling horizontally for close to a mile, water, sand and chemicals are pumped into the well at high pressure to fracture the shale rock and release the gas, which in turn rises back up the well to the surface.
That’s the concern comes in: if the well’s casing should leak any of the gas or drilling fluids, it could contaminate the local water supply.
The first commercial gas well drilled in the United States was a shale gas well dug in 1821 in Fredonia, New York. Because of natural gas prices and the expense of horizontal drilling, shale gas wells were not considered economically viable until the recent advances in technology.