Addressing the Environmental Risks from Shale Gas Development

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Addressing the Environmental Risks fromShale Gas DevelopmentMark Zoback a , Saya Kitasei b , Bradford Copithorne cI. Executive SummaryThe rapid development of shale gas resources in the past few years has already dramaticallyaffected U.S. energy markets—lowering energy prices and carbon dioxide emissions—and couldoffer an affordable source of low-carbon energy to reduce dependence on coal and oil. 1 However,the development of shale gas has been linked to a range of local environmental problems,generating a public backlash that threatens to bring production to a halt in some regions. Whilehydraulic fracturing in particular has been the focus of much controversy, our analysis indicatesthat the most significant environmental risks associated with the development of shale gas aresimilar to those associated with conventional onshore gas, including gas migration andgroundwater contamination due to faulty well construction, blowouts, and above-ground leaksand spill of waste water and chemicals used during drilling and hydraulic fracturing.Many technologies and best practices that can minimize the risks associated with shale gasdevelopment are already being used by some companies, and more are being developed. Thenatural gas industry should work with government agencies, environmental organizations, andlocal communities to develop innovative technologies and practices that can reduce theenvironmental risks and impacts associated with shale gas development.Stronger, fully-enforced government regulations are needed in many states to provide sufficientprotection to the environment as shale gas development increases. In addition, continued studyand improved communication of the environmental risks associated with both individual wellsand large scale shale gas development are essential for society to make well-informed decisionsabout its energy future.This briefing paper, part of an on-going series on the role of natural gas in the future energyeconomy, provides an overview of how horizontal drilling and hydraulic fracturing are used toextract shale gas, examines the environmental risks, associated with shale gas development, andCover photo: A drilling rig near Shreveport, Louisiana, by danielfoster437.a Benjamin M. Page Professor of Geophysics, Stanford Universityb MAP Sustainable Energy Fellow, Worldwatch Institutec Finance Specialist, Environmental Defense Fund1
provides an overview of the industry best practices and government regulations that are needed ifshale gas is to contribute its full potential to help build a low-carbon economy in the years ahead.II.Extracting Natural Gas from ShaleGeologists have long been aware that large amounts of natural gas lie trapped in someformations of shale, a sedimentary rock formed from deposits of mud, silt, clay, and organicmatter. Over time, that organic matter breaks down, creating molecules of methane, also knownas natural gas. While some of this natural gas migrates into other formations over millions ofyears, much of it remains trapped in its shale source rock.Although the first producing U.S. natural gas well was drilled into a shale formation in NewYork (in 1821), most commercial drilling during the 19th and 20th centuries targeted gas that hasmigrated out of its source rock and accumulated in permeable reservoirs such as sandstoneformations. 2 Unlike these ―conventional‖ reservoirs, whose relatively high permeability enablesproducers to extract gas using vertical wells, shale is a much ―tighter,‖ less permeable rock. As aresult, methane molecules cannot flow easily through shale and a vertical well is only able todrain gas only from a very small volume of the rock surrounding it, which generally preventsvertical wells from producing sufficient gas to be economical.Over the past decade, however, the application of two techniques, horizontal drilling andhydraulic fracturing, has enabled operators to extract gas economically from shale formationsthousands of feet deep. Although both technologies originally were developed to increaseproduction from conventional wells, their use in the Barnett Shale, near Fort Worth, Texas,revealed that they could be the key to unlocking the trillions of cubic feet of natural gasestimated to exist in shale gas plays throughout the United States. 3 (See Figure 1.) At year-end2009, the five most productive U.S. shale gas fields – the Barnett, Haynesville, Fayetteville,Woodford, and Marcellus shales – were producing some 8.3 billion cubic feet a day, theequivalent of nearly 1.6 million barrels of oil a day, or 30 percent of total U.S. crude oilproduction during 2009. 4Figure 1. Map of Shale Gas Plays, Lower 48 StatesSource: EIA2
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Page 17 and 18: Endnotes1Worldwatch Institute, The
Page 19: Impact Statement, available at www.

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