Shale gas

48 Shale basins in 38 nations, per the EIA

Shale gas is natural gas formed from being trapped within shale formations.[1] Shale gas has become an increasingly important source of natural gas in the United States over the past decade, and interest has spread to potential gas shales in the rest of the world. One analyst expects shale gas to supply as much as half the natural gas production in North America by 2020.[2]

Some analysts expect that shale gas will greatly expand worldwide energy supply.[3] 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 it exports to European countries.[4] The Obama administration believes that increased shale gas development will help reduce greenhouse gas emissions.[5] 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,[6][7] although other studies[8] have criticized one of these for relying on implausibly high leakage rates and misstating the global warming potential of methane.[9] 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.[10][11]

History

Shale gas was first extracted as a resource in Fredonia, NY in 1821,[12][13] in shallow, low-pressure fractures. 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[14] 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.

Early federal government investments in shale gas began with the Eastern Gas Shales Project in 1976 and the annual FERC-approved research budget of the Gas Research Institute. 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. In 1991 the Department of Energy subsidized Texas gas company Mitchell Energy's first horizontal drill in the Barnett Shale in north Texas.[citation needed]

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.[15][16] 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, the economical extraction of shale gas more than doubles the projected production potential of natural gas, from 125 years to over 250 years.[17]

Geology

Illustration of shale gas compared to other types of gas deposits.

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; other unconventional sources of natural gas include coalbed methane, tight sandstones, and methane hydrates. Shale gas areas are often known as resource plays[18] (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.[citation needed]

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.[citation needed]

Horizontal drilling is often used with shale gas wells, with lateral lengths up to 10,000 feet ({{#invoke:Math|precision_format| 3,048 | 1-3 }} m) within the shale, to create maximum borehole surface area in contact with the shale.[citation needed]

Shales that host economic quantities of gas have a number of common properties. They are rich in organic material (0.5% to 25%),[19] 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. In some areas, shale intervals with high natural gamma radiation are the most productive, as high gamma radiation is often correlated with high organic carbon content.[citation needed]

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.[citation needed]

Environment

Climate

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[20] 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 shale gas might actually aggravate global warming, rather than help mitigate it.[citation needed]

In late 2010, the U. S. Environmental Protection Agency[21] 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, 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.[22] However, the U.N. Intergovernmental Panel on Climate Change (IPCC), a preeminent authority on this issue, ascribes a GWP of only 25 to methane over a 100-year period, and only 72 over a 20-year period.[23] A 2011 study published in Climatic Change Letters controversially claimed that the extraction of shale gas may lead to the emission of as much or more greenhouse gas emissions than oil or coal.[24] 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,[25] peer-reviewed studies by Carnegie Mellon University[26] and the University of Maryland,[27] 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."[28] 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."[29] 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."[citation needed]

Water and air quality

Chemicals are added to the water to facilitate the underground fracturing process that releases natural gas. Some 0.5% chemicals (friction reducer, agents countering rust, agents killing microorganisms) need to be added to the water. Since (depending on the size of the area) millions of liters of water are used, this means that hundreds of thousands liter of chemicals are often injected into the soil.[30] 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.[31]

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.[32]

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.[citation needed]

A study published in May 2011 concluded that fracking has seriously contaminated shallow groundwater supplies in northeast Pennsylvania with flammable methane. However the study does not discuss how pervasive such contamination might be in other areas where drilling for shale gas has taken place.[33]

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.[34] 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.[35] Wyoming's Governor Matt Mead called the EPA draft report "scientifically questionable" and stressed the need for additional testing.[36] 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.[37]

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.[38]

Landscape

The extraction of shale gas often temporarily damages the landscape. This is due to the large number of drilling towers erected for the weeks or months each while the wells are drilled. Using "directional drilling", the tower density in the landscape needs to be very high. Omnidirectional drilling requires fewer towers.[citation needed]

Earthquakes

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.[39][40]

Economics

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.[41] As of June 2011, the validity of the claims of economic viability of these wells has begun to be publicly questioned.[42] 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. However, this is often offset by the low risk of shale-gas wells.[citation needed] A 2012 article estimated that the UK may have offshore shale gas reserves of 1,000 trillion cubic feet ({{#invoke:Math|precision_format| ( 1,000 )*28,316,846,592/1,000,000,000,000 | 1-1 }} trillion {{convert/engout/nExpression error: Unrecognised punctuation character "["|empty/Loff|#32||{{{n}}}|cubic metres}}) compared to UK gas consumption of 3.5 trillion cubic feet ({{#invoke:Math|precision_format| ( 3.5 )*28,316,846,592/1,000,000,000 | 1-1 }} billion {{convert/engout/nExpression error: Unrecognised punctuation character "["|empty/Loff|#32||{{{n}}}|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).[43]

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.[citation needed]

Research has calculated the 2011 worth of the global shale-gas market as \$26.66bn.[44]

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.[45]

References

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