Shale gas

Shale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s, a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and some analysts expect that shale gas will greatly expand worldwide energy supply.

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. China is estimated to have the world's largest shale gas reserves.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

A 2013 review by the United Kingdom Department of Energy and Climate Change noted that most studies of the subject have estimated that life-cycle greenhouse gas (GHG) emissions from shale gas are similar to those of conventional natural gas, and are much less than those from coal, usually about half the greenhouse gas emissions of coal; the noted exception was a 2011 study by Robert W. Howarth and others of Cornell University, which concluded that shale GHG emissions were as high as those of coal.David J. C. MacKay and Timothy J. Stone, Potential Greenhouse Gas Emissions Associated with Shale Gas Extraction and Use, 9 September 2013. MacKay and Stone wrote (p.3): "The Howarth estimate may be unrealistically high, as discussed in Appendix A, and should be treated with caution." More recent studies have also concluded that life-cycle shale gas GHG emissions are much less than those of coal,Burnham and others, "Life-cycle greenhouse gas emissions of shale gas, natural gas, coal, and petroleum", Environmental Science and Technology, 17 January 2012, v.46 n.2 p.619-627.James Conca, Fugitive Fracking Gets Bum Rap, Forbes, 18 February 2013.Why Every Serious Environmentalist Should Favour Fracking , 2013 report by Richard A. Muller and Elizabeth A. Muller of Berkeley Earth among them, studies by Natural Resources Canada (2012),Natural Resources Canada, Shale gas , 14 December 2012. and a consortium formed by the US National Renewable Energy Laboratory with a number of universities (2012).Jeffrey Logan, Garvin Heath, and Jordan Macknick, Elizabeth Paranhos, William Boyd, and Ken Carlson, Natural Gas and the Transformation of the U.S. Energy Sector: Electricity, Technical Report NREL/TP-6A50-55538, Nov. 2012.

Some 2011 studies pointed to high rates of decline of some shale gas wells as an indication that shale gas production may ultimately be much lower than is currently projected.David Hughes (May 2011). "Will Natural Gas Fuel America in the 21st Century?" Post Carbon Institute, But shale-gas discoveries are also opening up substantial new resources of tight oil, also known as "shale oil".Syed Rashid Husain. "Shale Gas Revolution Changes Geopolitics." Saudi Gazette. 24 February 2013.

History

United States

Shale gas was first extracted as a resource in Fredonia, New York, 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.

Federal price controls on natural gas led to shortages in the 1970s.Zhongmin Wang and Alan Krupnick, A Retrospective Review of Shale Gas Development in the United States , Resources for the Futures, Apr. 2013. Faced with declining natural gas production, the federal government invested in many supply alternatives, including the Eastern Gas Shales Project, which lasted from 1976 to 1992, 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. The DOE program also applied two technologies that had been developed previously by industry, massive hydraulic fracturing and horizontal drilling, to shale gas formations, which led to microseismic imaging.

Although the Eastern Gas Shales Project had increased gas production in the Appalachian and Michigan basins, shale gas was still widely seen as marginal to uneconomic without tax credits, and shale gas provided only 1.6% of US gas production in 2000, when the federal tax credits expired.

George P. Mitchell is regarded as the father of the shale gas industry, since he made it commercially viable in the Barnett Shale by getting costs down to $4 per . Mitchell Energy achieved the first economical shale fracture in 1998 using slick-water fracturing. Since then, natural gas from shale has been the fastest growing contributor to total primary energy 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%.

In 2000 shale gas provided only 1% of U.S. natural gas production; by 2010 it was over 20% and the U.S. Energy Information Administration predicted that by 2035, 46% of the United States' natural gas supply will come from shale gas.

The Obama administration believed that increased shale gas development would help reduce greenhouse gas emissions.

Geology

Because shales ordinarily have insufficient permeability to allow significant fluid flow to a wellbore, 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 playsDan Jarvie, "Worldwide shale resource plays," PDF file, NAPE Forum, 26 August 2008. (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, and 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 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%),US Department of Energy, "Modern shale gas development in the United States," April 2009, p.17. 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 shale matrix. Further, the adsorption of gas is a process of physisorption, exothermic and spontaneous. 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.

Shale gas by country

Although the shale gas potential of many nations is being studied, as of 2013, only the US, Canada, and China produce shale gas in commercial quantities, and only the US and Canada have significant shale gas production.US Energy Information Administration, North America leads the world in production of shale gas, 23 October 2013. While China has ambitious plans to dramatically increase its shale gas production, these efforts have been checked by inadequate access to technology, water, and land.A Comparison between Shale Gas in China and Unconventional Fuel Development in the United States: Water, Environmental Protection, and Sustainable Development, Farah, Paolo Davide; Tremolada, Riccardo in Brooklyn Journal of International Law, Vol. 41, No. 2, 2016, June 2016.China's Coming Decade of Natural Gas?, Damien Ma in Asia's Uncertain LNG Future, The National Bureau of Asian Research, November 2013.

The table below is based on data collected by the Energy Information Administration agency of the United States Department of Energy. Numbers for the estimated amount of "technically recoverable"" Technically recoverable resources represent the volumes of oil and natural gas that could be produced with current technology, regardless of oil and natural gas prices and production costs. Technically recoverable resources are determined by multiplying the risked in-place oil or natural gas by a recovery factor." shale gas resources are provided alongside numbers for proven natural gas reserves.

CountryEstimated technically recoverable shale gasProven natural gas resource estimates of all types Date of report 1 1,115 124 2013 2 802 12 2013 3 707 159 2013 4 665 318 2013 5 573 68 2013 6 545 17 2013 7 485 — 2013 8 437 43 2013 9 285 1,688 2013 10 245 14 2013 11 580 150 2013

The US EIA had made an earlier estimate of total recoverable shale gas in various countries in 2011, which for some countries differed significantly from the 2013 estimates.US Energy Information Administration, World Shale Gas Resources, Apr. 2011. The total recoverable shale gas in the United States, which was estimated at 862 trillion cubic feet in 2011, was revised downward to 665 trillion cubic feet in 2013. Recoverable shale gas in Canada, which was estimated to be 388 TCF in 2011, was revised upward to 573 TCF in 2013.

For the United States, EIA estimated (2013) a total "wet natural gas" resource of 2,431 tcf, including both shale and conventional gas. Shale gas was estimated to be 27% of the total resource. "Wet natural gas" is methane plus natural gas liquids, and is more valuable than dry gas.What Makes Wet Gas Wet?

For the rest of the world (excluding US), EIA estimated (2013) a total wet natural gas resource of . Shale gas was estimated to be 32% of the total resource.

Europe has a shale gas resource estimate of compared with America's reserves , but its geology is more complicated and the oil and gas more expensive to extract, with a well likely to cost as much as three-and-a-half times more than one in the United States. Europe would be the fastest growing region, accounting for the highest CAGR of 59.5%, in terms of volume owing to availability of shale gas resource estimates in more than 14 European countries.

Environment

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 gases 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.

In 2013 the European Parliament agreed that environmental impact assessments will not be mandatory for shale gas exploration activities and shale gas extraction activities will be subject to the same terms as other gas extraction projects.

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