It is estimated that the total available supply of natural gas in the US is about 2,000 trillion cubic feet, equivalent to about 100 years of supply at current rates of consumption.
Incredibly in 2009 there were about half a million producing natural gas wells in the US. Several factors have contributed to the rapid development of the shale gas industry in the US, a benign regulatory environment which has kept the price low and encouraged entrepreneurs, and the fact that in the US landowners own the hydrocarbons under their land. These factors are not typical in other jurisdictions, so there is doubt whether what has happened in the US can be replicated in other jurisdictions.
The impact of shale gas on the US economy is hard to underestimate. Recently FERC Commissioner Philip Moeller said that the biggest recent trend in the energy industry is the huge impact that shale gas has had on the energy industry by pushing gas prices down and keeping them there. The drop in gas prices has affected wholesale power markets and resulted in lower energy prices for consumers. But the price drop may not help developers of new renewables, nuclear, clean coal, or new gas pipelines. The question now is whether the benign regulatory environment can continue given the environmental impact (GHG emissions and water quality) of the shale gas industry that is now just coming to light.
Most of the natural gas wells in the US are shale gas wells which involves a process called hydraulic fracture or fracking in which a hydraulic fracture is formed by pumping a fracturing fluid into the well at a high enough rate that the pressure causes the shale to crack. To keep the fracture open, a solid material, typically sand, is added to the fracture fluid. The result is a permeable conduit that allows natural gas and other fluids to flow to the well. About 90% of the natural gas wells in the US use hydraulic fracturing to produce gas at economic rates. The injected fluid mixture is approximately 99% water and sand but with additives that can include any of up to 600 chemicals (Gasland, available on iTunes). A typical frac will utilize approximately 15,000m3 (4 million US gallons) of water per well and it is typical for a well to be fracked up to 18 times.
In 2005 Congress passed the Energy Policy Act of 2005, which was an omnibus energy bill (that among many other things changed daylight savings time in the US). Among the provisions of the bill was one (the so-called "Halliburton loophole") that exempted hydraulic fracturing from protections under the Clean Air Act, Clean Water Act, Safe Drinking Water Act, and CERCLA, which means that fracking is not regulated at the federal level. It has been argued that state regulation is not effective for a variety of reasons. (In 2009 an attempt was made to regulate the industry federally when a Fracturing Responsibility and Awareness of Chemicals Bill was introduced in Congress and sponsored by Rep. Diana DeGette, Colorado, and Rep. Maurice Hinchey, New York, that would have repealed these exemptions.)
Emissions Associated with Electric Power Production
It has been asserted that natural gas power plants, which are responsible for 21% of power generation in the US, produce 50% less emissions than coal-fired plants. However, in the past the amount of methane gas that leaks from pipes and is vented from gas wells has not been included in the calculation. Now a new EPA analysis doubles its previous estimates for the amount of methane gas that leaks from pipes and is vented from gas wells, which significantly changes the emissions picture. Methane (CH4) levels from hydraulic fracturing of shale gas were found to be 9,000 times higher than previously reported. Based on the new numbers, the median gas-powered plant in the United States is estimated to be 40 % cleaner than coal-fired plants, according to calculations ProPublica has made. In addition about half of the 1,600 gas-fired power plants in the US operate relatively inefficiently. In the past these plants were estimated to be 32 % cleaner than coal, but now with the new EPA estimates, these ~800 inefficient plants are estimated to produce 25 percent less emissions than coal.
But there is another issue. Methane is one of the more potent greenhouse gases for global warming, but it is not clear just how much more potent methane is than CO2. The EPA has estimated a factor of 21 times compared to carbon dioxide. But Robert Howarth, an environmental biology professor at Cornell University, has suggested that it is actually 72 times as powerful as carbon dioxide in terms of its warming potential. This is critical, because if the climate effect of methane from natural gas is 72 rather than 21 times that of carbon dioxide from burning coal, natural gas may even turn out to be worse than coal in terms of global warming. Recently Howarth said that the type of shale gas drilling taking place in Texas, New York and Pennsylvania generates particularly high emissions of methane and could be as dirty as coal.
Water Usage and Pollution
A series of ProPublica reports has identified instances where ground water has been contaminated in drilling areas across the country and Gasland has shown examples of burning tap water and other effects attributed to fracking. The serious concerns about hydraulic fracturing’s potential impact on drinking water, human health and the environment is serious enough that Congress has appropriated funding for the EPA to undertake a major study of hydraulic fracturing and its impact on drinking water. In Canada the Quebec government has raised concerns about the shale gas industry, even hinting at a ban, because of reported leaks that the Quebec Ministry of Natural Resources said it had found in 19 of 31 shale gas wells it inspected.