Shale gas is natural gas that is found trapped within shale formations. Shale gas has become an increasingly important source of natural gas in the United States since the start of this century, and interest has spread to potential gas shales in the rest of the world. In 2000 shale gas provided only 1% of U.S. natural gas production; by 2010 it was over 20% and the U.S. government's Energy Information Administration predicts that by 2035, 46% of the United States' natural gas supply will come from shale gas.
Some analysts expect that shale gas will greatly expand worldwide energy supply. China is estimated to have the world's largest shale gas reserves. A study by the Baker Institute of Public Policy at Rice University concluded that increased shale gas production in the US and Canada could help prevent Russia and Persian Gulf countries from dictating higher prices for the gas they export to European countries.
The Obama administration believes that increased shale gas development will help reduce greenhouse gas emissions (in 2012, US carbon dioxide emissions dropped to a 20-year low). Some studies have alleged that the extraction and use of shale gas may result in the release of more greenhouse gases than conventional natural gas. Other recent studies point to high decline rates of some shale gas wells as an indication that shale gas production may ultimately be much lower than is currently projected.
Shale gas was first extracted as a resource in Fredonia, NY in 1821, in shallow, low-pressure fractures. Horizontal drilling began in the 1930s, and in 1947 a well was first fracked in the U.S. Work on industrial-scale shale gas production did not begin until the 1970s, when declining production potential from conventional gas deposits in the United States spurred the federal government to invest in R&D and demonstration projects that ultimately led to directional and horizontal drilling, microseismic imaging, and massive hydraulic fracturing. Up until the public and private R&D and demonstration projects of the 1970s and 1980s, drilling in shale was not considered to be commercially viable.
Faced with declining natural gas reserves, the federal government made investments in many supply alternatives, including shale gas with the Eastern Gas Shales Project in 1976 and the annual FERC-approved research budget of the Gas Research Institute, where the federal government began extensive research funding in 1982, disseminating the results to industry. The federal government also provided tax credits and rules benefiting the industry in the 1980 Energy Act. The Department of Energy later partnered with private gas companies to complete the first successful air-drilled multi-fracture horizontal well in shale in 1986. The federal government further incentivized drilling in shale via the Section 29 tax credit for unconventional gas from 1980-2000. Microseismic imaging, a crucial input to both hydraulic fracturing in shale and offshore oil drilling, originated from coalbeds research at Sandia National Laboratories.
Mitchell Energy utilized all these component technologies and techniques to achieve the first economical shale fracture in 1998 using an innovative process called slick-water fracturing. Since then, natural gas from shale has been the fastest growing contributor to total primary energy (TPE) in the United States, and has led many other countries to pursue shale deposits. According to the IEA, shale gas could increase technically recoverable natural gas resources by almost 50%.
Because shales ordinarily have insufficient permeability to allow significant fluid flow to a well bore, most shales are not commercial sources of natural gas. Shale gas is one of a number of unconventional sources of natural gas; others include coalbed methane, tight sandstones, and methane hydrates. Shale gas areas are often known as resource plays (as opposed to exploration plays). The geological risk of not finding gas is low in resource plays, but the potential profits per successful well are usually also lower.
Shale has low matrix permeability, so gas production in commercial quantities requires fractures to provide permeability. Shale gas has been produced for years from shales with natural fractures; the shale gas boom in recent years has been due to modern technology in hydraulic fracturing (fracking) to create extensive artificial fractures around well bores.
Horizontal drilling is often used with shale gas wells, with lateral lengths up to 10,000 feet (3,000 m) within the shale, to create maximum borehole surface area in contact with the shale.
Shales that host economic quantities of gas have a number of common properties. They are rich in organic material (0.5% to 25%), and are usually mature petroleum source rocks in the thermogenic gas window, where high heat and pressure have converted petroleum to natural gas. They are sufficiently brittle and rigid enough to maintain open fractures.
Some of the gas produced is held in natural fractures, some in pore spaces, and some is adsorbed onto the organic material. The gas in the fractures is produced immediately; the gas adsorbed onto organic material is released as the formation pressure is drawn down by the well.
The extraction and use of shale gas can affect the environment through the leaking of extraction chemicals and waste into water supplies, the leaking of greenhouse gasses during extraction, and the pollution caused by the improper processing of natural gas. A challenge to preventing pollution is that shale gas extractions varies widely in this regard, even between different wells in the same project; the processes that reduce pollution sufficiently in one extraction may not be enough in another.
US President Obama's administration has sometimes promoted shale gas, in part because of their belief that it releases fewer greenhouse gas (GHG) emissions than other fossil fuels, but some scientists have urged caution. In a May 2010 letter to President Obama, the Council of Scientific Society Presidents cautioned against a national policy of developing shale gas without a more certain scientific basis for the policy. This umbrella organization that represents 1.4 million scientists noted that the impact of shale gas on global warming might be substantially stronger than previously estimated.
In late 2010, the U. S. Environmental Protection Agency issued a new report, the first update on emission factors for greenhouse gas emissions by the oil and gas industry by the EPA since 1996. In this new report, the EPA concluded that shale gas emits larger amounts of methane, a potent greenhouse gas, than does conventional gas, but still far less than coal. Methane is a very powerful greenhouse gas, although it stays in the atmosphere for only one tenth as long a period as carbon dioxide. Recent evidence suggests that methane has a global warming potential (GWP) that is 105-fold greater than carbon dioxide when viewed over a 20-year period and 33-fold greater when viewed over a 100-year period, compared mass-to-mass. However, the U.N. Intergovernmental Panel on Climate Change (IPCC), a pre-eminent authority on this issue, ascribes a GWP of only 72 to methane over a 25-year period, and only 25 over a 100-year period. A 2011 study published in Climatic Change Letters controversially claimed that the production of electricity using shale gas may lead to as much or more life-cycle GWP than electricity generated with oil or coal. In that peer-reviewed paper, Cornell University professor Robert W. Howarth, a marine ecologist, and colleagues claimed that once methane leak and venting impacts are included, the life-cycle greenhouse gas footprint of shale gas is far worse than those of coal and fuel oil when viewed for the integrated 20-year period after emission. On the 100-year integrated time frame, this analysis claims shale gas is comparable to coal and worse than fuel oil. However, numerous studies have pointed out critical flaws with that paper and/or come to completely different conclusions, including assessments by experts at the U.S. Department of Energy, peer-reviewed studies by Carnegie Mellon University and the University of Maryland, and even the Natural Resources Defense Council, which concluded that the Howarth et al. paper's use of a 20-year time horizon for global warming potential of methane is "too short a period to be appropriate for policy analysis." In January 2012, Howarth's own colleagues at Cornell University, Lawrence Cathles et al., responded with their own peer-reviewed assessment, noting that the Howarth paper was "seriously flawed" because it "significantly overestimate[s] the fugitive emissions associated with unconventional gas extraction, undervalue[s] the contribution of 'green technologies' to reducing those emissions to a level approaching that of conventional gas, base[s] their comparison between gas and coal on heat rather than electricity generation (almost the sole use of coal), and assume[s] a time interval over which to compute the relative climate impact of gas compared to coal that does not capture the contrast between the long residence time of CO2 and the short residence time of methane in the atmosphere." The author of that response, Lawrence Cathles, concludes that "shale gas has a GHG footprint that is half and perhaps a third that of coal," based upon "more reasonable leakage rates and bases of comparison."
Water and air quality 
Chemicals are added to the water to facilitate the underground fracturing process that releases natural gas. Fracturing fluid is primarily water and approximately 0.5% chemical additives (friction reducer, agents countering rust, agents killing microorganism). Since (depending on the size of the area) millions of liters of water are used, this means that hundreds of thousands liters of chemicals are often injected into the soil. Only about 50% to 70% of the resulting volume of contaminated water is recovered and stored in above-ground ponds to await removal by tanker. The remaining "produced water" is left in the earth where it can lead to contamination of groundwater aquifers, though the industry deems this "highly unlikely". However the wastewater from such operations often lead to foul-smelling odors and heavy metals contaminating the local water supply above-ground.
Besides using water and chemicals however, it is also possible to frack shale gas with only liquified propane gas. This reduces the environmental degradation considerably. The method was invented by GasFrac, of Alberta, Canada.
The 2010 U.S. documentary film Gasland by Josh Fox, which focuses on the impact of hydraulic fracturing, is critical of the industry's assertions of its safety and its exemption from the Safe Drinking Water Act in the Energy Policy Act of 2005.
A study published in May 2011 concluded that fracking has seriously contaminated shallow groundwater supplies in northeastern Pennsylvania with flammable methane. However, the study does not discuss how pervasive such contamination might be in other areas drilled for shale gas.
The United States Environmental Protection Agency (EPA) announced 23 June 2011 that it will examine claims of water pollution related to hydraulic fracturing in Texas, North Dakota, Pennsylvania, Colorado and Louisiana. On 8 December 2011, the EPA issued a draft finding which stated that groundwater contamination in Pavilion, Wyoming may be the result of fracking in the area. The EPA stated that the finding was specific to the Pavilion area, where the fracking techniques differ from those used in other parts of the U.S. Doug Hock, a spokesman for the company which owns the Pavilion gas field, said that it is unclear whether the contamination came from the fracking process. Wyoming's Governor Matt Mead called the EPA draft report "scientifically questionable" and stressed the need for additional testing. The Casper Star-Tribune also reported on 27 December 2011, that the EPA's sampling and testing procedures "didn’t follow their own protocol" according to Mike Purcell, the director of the Wyoming Water Development Commission.
A 2011 study by the Massachusetts Institute of Technology concluded that "The environmental impacts of shale development are challenging but manageable." The study addressed groundwater contamination, noting "There has been concern that these fractures can also penetrate shallow freshwater zones and contaminate them with fracturing ﬂuid, but there is no evidence that this is occurring". This study blames known instances of methane contamination on a small number of sub-standard operations, and encourages the use of industry best practices to prevent such events from recurring.
In a report dated July 25, 2012, the U.S. Environmental Protection Agency announced that it had completed its testing of private drinking water wells in Dimock, Pa. Data previously supplied to the agency by residents, the Pennsylvania Department of Environmental Protection, and Cabot Oil and Gas Exploration had indicated levels of arsenic, barium or manganese in well water at five homes at levels that could present a health concern. In response, water treatment systems that can reduce concentrations of those hazardous substances to acceptable levels at the tap were installed at affected homes. Based on the outcome of sampling after the treatment systems were installed, EPA concluded that additional action by the Agency was not required.
On 26 April 2012, Asahi Shimbun reported that United States Geological Survey scientists have been investigating the recent increase in the number of magnitude 3 and greater earthquake in the midcontinent of the United States. Beginning in 2001, the average number of earthquakes occurring per year of magnitude 3 or greater increased significantly, culminating in a six-fold increase in 2011 over 20th century levels. A researcher in Center for Earthquake Research and Information of University of Memphis assumes water pushed back into the fault tends to cause earthquake by slippage of fault.
On June 19, 2012 The United States Senate Committee on Energy & Natural Resources held a hearing entitled, "Induced Seismicity Potential in Energy Technologies." Dr. Murray Hitzman, the Charles F. Fogarty Professor of Economic Geology in the Department of Geology and Geological Engineering at the Colorado School of Mines in Golden, CO testified that "About 35,000 hydraulically fractured shale gas wells exist in the United States. Only one case of felt seismicity in the United States has been described in which hydraulic fracturing for shale gas development is suspected, but not confirmed. Globally only one case of felt induced seismicity at Blackpool, England has been confirmed as being caused by hydraulic fracturing for shale gas development." 
Although shale gas has been produced for more than 100 years in the Appalachian Basin and the Illinois Basin of the United States, the wells were often marginally economical. Higher natural-gas prices in recent years[when?] and advances in hydraulic fracturing and horizontal completions have made shale-gas wells more profitable. As of June 2011, the validity of the claims of economic viability of these wells has begun to be publicly questioned. Shale gas tends to cost more to produce than gas from conventional wells, because of the expense of the massive hydraulic fracturing treatments required to produce shale gas, and of horizontal drilling.
Total published estimates for UK shale gas resources by companies holding shale gas (Cuadrilla, Igas, Dart, Eden) drilling licenses are approximately 255 trillion cubic feet (7.2 trillion cubic metres). However it is estimated that only around 10-15% of this is recoverable and can therefore be treated as reserves. There are further questions around the proportion which can be economically recovered. This compares to UK gas consumption of 3.5 trillion cubic feet (99 billion cubic metres) per year. However the cost of extracting this gas with existing technology would be probably be more than $200 per barrel of oil equivalent (UK North Sea oil prices were about $120 per barrel in April 2012).
North America has been the leader in developing and producing shale gas. The great economic success of the Barnett Shale play in Texas in particular has spurred the search for other sources of shale gas across the United States and Canada.
Research has calculated the 2011 worth of the global shale-gas market as $26.66 billion.
However, a June 2011 New York Times investigation of industrial emails and internal documents found that the financial benefits of unconventional shale gas extraction may be less than previously thought, due to companies intentionally overstating the productivity of their wells and the size of their reserves. However, no criminal investigations have been made on these serious allegations.
In first quarter 2012, USA imported 840 Bcf (785 from Canada) while exporting 400 Bcf (mostly to Canada); both mainly by pipeline. Almost none is exported by ship as LNG, as that would require expensive facilities. Prices have gone down to $3/MMBtu due to shale gas.
One of the byproducts of shale gas exploration is the opening up of deep underground shale deposits to "tight oil" or shale oil production. By 2035, shale oil production could "boost the world economy by up to $2.7 trillion, a PricewaterhouseCoopers (PwC) report says. It has the potential to reach up to 12 percent of the world’s total oil production — touching 14 million barrels a day — “revolutionizing” the global energy markets over the next few decades." 
Making coal power stations unviable 
Generating electricity by burning natural gas is cheaper than burning coal if the price of gas remains below $3/mmBTU.
See also 
- U.S. Energy Information Administration
- Stevens, Paul (August 2012). "The 'Shale Gas Revolution': Developments and Changes". Chatham House. Retrieved 2012-08-15.
- Clifford Krauss, "New way to tap gas may expand global supplies," New York Times, 9 October 2009.
- Staff (5 April 2011) World Shale Gas Resources: An Initial Assessment of 14 Regions Outside the United States US Energy Information Administration, Analysis and Projections, Retrieved 26 August 2012
- Rice University, News and Media Relations (21 July 2011): Shale Gas and U. S. National Security, accessed 12 November 2012.
- White House, Office of the Press Secretary, Statement on U.S.-China shale gas resource initiative, 17 November 2009.
- Carey, Julie M. (7 December 2012) Surprise Side Effect Of Shale Gas Boom: A Plunge In U.S. Greenhouse Gas Emissions Forbes magazine, Retrieved 21 February 2013
- Howarth RW, Santoro R, and Ingraffea A (2011). Methane and the greenhouse gas footprint of natural gas from shale formations. Climatic Change Letters, doi:10.1007/s10584-011-0061-5, 
- Shindell DT, Faluvegi G, Koch DM, Schmidt GA, Unger N, and Bauer SE. (2009). Improved Attribution of Climate Forcing to Emissions. Science, 326(5953): 716-718, 
- David Hughes (May 2011). "Will Natural Gas Fuel America in the 21st Century?" Post Carbon Institute, 
- Arthur Berman (8 Feb. 2011), "After the gold rush: A perspective on future U.S. natural gas supply and price," The Oil Drum, 
- Name the gas industry birthplace: Fredonia, N.Y.?
- "New York's natural gas history - a long story, but not the final chapter" (pdf). Retrieved 17 May 2012.
- "Proceedings from the 2nd Annual Methane Recovery from Coalbeds Symposium"
- Miller, Rich; Loder, Asjylyn; Polson, Jim (6 February 2012). "Americans Gaining Energy Independence". Bloomberg. Retrieved 1 March 2012.
- The Breakthrough Institute. Interview with Dan Steward, former Mitchell Energy Vice President. December 2011.
- International Energy Agency (IEA). "World Energy Outlook Special Report on Unconventional Gas: Golden Rules for a Golden Age of Gas?"
- Dan Jarvie, "Worldwide shale resource plays," PDF file, NAPE Forum, 26 August 2008.
- US Department of Energy, "Modern shale gas development in the United States," April 2009, p.17.
- Council of Scientific Society Presidents, , letter to President Obama, 4 May 2009.
- Environmental Protection Agency "Greenhouse Gas Emissions Reporting from the Petroleum and Natural Gas Industry, Background Technical Support Document, posted to web 30 November 2010.
- Shindell DT, Faluvegi G, Koch DM, Schmidt GA, Unger N, and Bauer SE (2009). Improved attribution of climate forcing to emissions. Science 326: 716-718.
- Intergovernmental Panel on Climate Change, "Direct Global Warming Potentials," IPCC Fourth Assessment Report, 2007 
- Howarth RW, Santoro R, and Ingraffea A (2011). Climatic Change Letters, doi:10.1007/s10584-011-0061-5, 
- Timothy J. Skone, "Life Cycle Greenhouse Gas Analysis of Natural Gas Extraction & Delivery in the United States." National Energy Technology Laboratory, 12 May 2011 
- Mohan Jiang et al. (2011), "Life cycle greenhouse gas emissions of Marcellus shale gas." Environmental Research Letters, doi:10.1088/1748-9326/6/3/034014, 
- Hultman et al (2011), "The greenhouse impact of unconventional gas for electricity generation." Environmental Research Letters, doi:10.1088/1748-9326/6/4/044008, 
- Dan Lashof, "Natural Gas Needs Tighter Production Practices to Reduce Global Warming Pollution," 12 April 2011 
- Cathles et al. (2011)
- Kijk magazine, 2/2012[verification needed]
- Griswold, Eliza (17 November 2011). "The Fracturing of Pennsylvania". The New York Times.
- Shale gas fracking without water and chemicals
- Richard A. Kerr (13 May 2011). "Study: High-Tech Gas Drilling Is Fouling Drinking Water". Science Now 332: 775. Retrieved 27 June 2011.
- EPA: Natural Gas Drilling May Contaminate Drinking Water
- Gruver, Mead (8 December 2011). "EPA theorizes fracking-pollution link". Associated Press. Retrieved 10 December 2011.
- "Governor Mead: Implications of EPA Data Require Best Science".
- "EPA report: Pavillion water samples improperly tested".
- MIT Energy Initiative (2011). "The Future of Natural Gas: An Interdisciplinary MIT Study". MIT Energy Initiative: 7,8 accessdate = 29 July 2011.
- Terri White. U.S. EPA. "EPA Completes Drinking Water Sampling in Dimock, Pa." .
- "シェールガス採掘、地震誘発？米中部、M3以上6倍" [Magnitude 3 and greater earthquakes 6 fold in the midcontinent of the United States. Beginning in 200. extracted shale gas induce earthquakes ?]. Asahi Shimbun (in Japanese) (Tokyo). 2012-04-26. p. Page 1. Retrieved 2012-04-26.
- Is the Recent Increase in Felt Earthquakes in the Central U.S. Natural or Manmade? United States Geological Survey, 11 April 2012
- Juliette Jowit and Hanna Gersmann in The Guardian. , London, 2-11-2011.
- Matt McGrath , BBC News. , London, 13-12-2012.
- U.S. Senate Committee on Energy, Washington, D.C. 19 June 2012. 
- Simon Mauger, Dana Bozbiciu (2011). "How Changing Gas Supply Cost Leads to Surging Production". Retrieved 10 May 2011.
- Ian Urbina (25 June 2011). "Insiders Sound an Alarm Amid a Natural Gas Rush". The New York Times. Retrieved 26 June 2011.
- Mazur, Karol (3 September 2012) Economics of Shale Gas EnergyPulse, Accessed 26 January 2013
- Gloyston, Henning and Johnstone, Christopher (17 April 2012) Exclusive - UK has vast shale gas reserves, geologists say Reuters Edition UK, Accessed 17 April 2012
- The Shale Gas Market Report 2011-2021  - visiongain
- Urbina, Ian (25 June 2011). "Insiders Sound an Alarm Amid a Natural Gas Rush". New York Times. Retrieved 28 June 2011.; Urbina, Ian (27 June 2011). "S.E.C. Shift Leads to Worries of Overestimation of Reserves". New York Times. Retrieved 28 June 2011.
- Caudillo, Yvonne. "" pp1+19-22. United States Department of Energy. Retrieved: 25 August 2012.
- Philips, Matthew. "Strange Bedfellows Debate Exporting Natural Gas" page 2, BusinessWeek 22 August 2012. Retrieved: 25 August 2012.
- Syed Rashid Husain. "Shale Gas Revolution Changes Geopolitics." Saudi Gazette. 24 Feb 2013. 
- Marcellus Gas Production and Distribution - The Institute for Energy and Environmental Research for Northeastern Pennsylvania.
- Natural Gas for Europe, a website covering shale gas developments in Europe.
- Can Europe join the Shale Gas Revolution?, report on the future of an European Union Shale Gas Policy
- Shale Gas in Poland, a website about shale gas in Poland.
- Unconventional Gas and Implications for the LNG Market by Christopher Gascoyne and Alexis Aik. This is a working paper written for the 2011 Pacific Energy Summit hosted by the National Bureau of Asian Research.
- Haynesville: A Nation's Hunt for an Energy Future, a 2010 documentary which explores the microchasm of a shale gas discovery in Northwest Louisiana (in the Haynesville Shale) and the impact of that discovery along with shale gas as a whole on the United States energy economy
- The Shale Gas Boom: The global implications of the rise of unconventional fossil energy, FIIA Briefing Paper 122, 20 March 2013, The Finnish Institute of International Affairs.