In This Issue
Summer Issue of The Bridge on Shale Gas: Promises and Challenges
June 15, 2014 Volume 44 Issue 2

NAE Topical Meeting: “Shale Gas: Promises and Challenges”

Monday, June 23, 2014

Author: John C. Angus, Steven W. Percy and Beverly Z. Saylor

Editors’ Note

The recent revolution in methods for extracting natural gas and liquid hydrocarbons from shale formations presents the nation with unprecedented opportunities and challenges. Policy decisions concerning a host of technical, economic, and environmental questions will have to be made. To enhance public understanding of the issues related to shale gas development, Cleveland members of the NAE and others from local universities and groups organized a Topical Meeting, “Shale Gas: Promises and Challenges,” covering

  • impacts on the economy,
  • science and technology challenges,
  • energy security and independence, and
  • environmental, health, and safety implications.

The meeting, held in Cleveland June 18–19, 2013, was hosted by Case Western Reserve University and cosponsored by Kent State and Cleveland State Universities. There were 25 speakers and over 900 attendees from business, academia, local, state, and regional government, and the public. Financial support was provided by 28 individuals, local foundations, and corporations. The organizing committee and staff were

Hunter Peckham (NAE), general chair
Steven Percy, cochair
Trevor Jones (NAE), development chair
John Angus (NAE)
Arthur Heuer (NAE)
Karen Mulloy
Vikas Prakash
Gary Previts
Beverly Saylor
David Zeng
Tom Barnish
Regina Loiko, conference administrator
Sharon Floyd, staff writer

The papers in this issue, drawn from the talks presented at the meeting, provide insight into some of the major issues surrounding shale gas development.

It should be recognized that the field is rapidly evolving and the level of understanding of these issues is changing. Interested readers are encouraged to explore the literature sources referenced in this issue; of particular note are reviews by Kell (2011), King (2012), King and King (2013), Vidic et al. (2013), and Zoback and Arent (2014). Useful information is also available from interest groups such as Resources for the Future (Krupnick et al. 2013, 2014) and the Environmental Defense Fund as well as government sources such as the Energy Information Agency, US Geological Survey, Department of Energy, and Environmental Protection Agency.

Background: Shale Gas, Horizontal Drilling, and Hydraulic Fracturing

Natural gas is found in conventional gas reservoirs, in coal beds, and in “tight gas” formations such as shale (Figure 11). Shale gas may represent 32 percent of global and 27 percent of US natural gas resources (EIA 2013). However, until relatively recently it was not possible to economically recover this gas because of the extremely low permeability of shale. The use of hydraulic fracturing to increase the permeability, together with horizontal drilling, has enabled the development of this resource.

Figure 1

To access shale gas a well is first drilled vertically then directed in a relatively horizontal direction to follow the shale formation. Depending on the local conditions the vertical portion of the well is typically several kilometers deep, and the horizontal section two kilometers or more in length. The vertical and horizontal sections of the well are cased with steel and cement during drilling.

To liberate the natural gas, the casing of the horizontal section is perforated with a series of explosive charges along its length. Fractures in the shale caused by these explosions are expanded and extended using water under high pressure (the hydraulic fracturing). The water used for hydraulic fracturing contains a proppant, typically sand, which keeps the fractures propped open after the pressure is reduced. Small concentrations of additives for surface tension and viscosity control, corrosion inhibition, and biocides for suppression of biological growth are used as well. Over time, after the pressure is reduced, this water flows back out of the well. In addition to this flowback water, additional water is produced during the lifetime of the well.

An excellent overview of horizontal drilling and hydraulic fracturing was provided by Zoback and Arent (2014) in the previous issue of the Bridge.

Some Perspective

The application of horizontal drilling and hydraulic fracturing is bringing about a sea change in the nation’s energy posture. Figure 2 shows the dramatic projected increase in US production of natural gas from shale. Natural gas is the largest single component of the country’s total energy production: in 2012 it accounted for 31 percent of the total energy produced in the United States (EIA 2014). However, petroleum and other liquid fuels remain the largest component in US energy consumption; in 2012 they accounted for 37 percent compared to 27 percent for natural gas (EIA 2014).

Figure 2

The changes brought about by production of shale gas are likely to have a significant impact on the global energy picture, as discussed in this issue by Finley and Rühl (2014), as well as a positive influence on the competitiveness of US industry. Swift (2014) in this issue describes how these changes will particularly affect the US chemical industry, which relies on natural gas not only as fuel but also as a primary feedstock for the production of basic chemicals. Furthermore, shale gas is projected to appreciably reduce US net energy imports (Figure 3). Recent events in Eastern Europe are likely to enhance the strategic importance of alternative supplies of natural gas.

Figure 3

Unresolved Issues

Public Concerns

Several major points became clear from the presentations and the public response to the meeting. There is a very strong public desire for unbiased information on the potential benefits and downsides of natural gas development. Many fear that the individuals and communities most impacted by development will not share appropriately in the benefits, a point made in this issue by Lendel (2014). Air quality and worker health and safety are other significant concerns; they are discussed in this issue by Pétron (2014) and Mulloy (2014), respectively.

Water Resources

The impact of shale gas development on water resources is perhaps the most serious concern expressed by the general public. Hydraulic fracturing in vertical wells has been used in the oil and gas industry for decades. However, the recent major expansion of hydraulic fracturing to horizontal wells has increased both the demand for water and the potential impact on water resources. Careful handling of the large volumes of water generated from well operations is required. Contamination can occur from surface operations—for example, through a breach of containment ponds, operator error, equipment failure, truck accidents, and illegal dumping. All of these risks can be reduced through the use of best management practices and appropriate regulations.

A related public concern is the lack of complete disclosure in all cases of the chemicals added to the water used in hydraulic fracturing. The migration, decomposition, and fate of these additives are areas of active research.

Reclamation and recycling of the water from well operations can significantly reduce both the demand for groundwater resources and the amount of water that must be disposed of in injection wells, thus diminishing the potential for induced seismicity. The technology and tradeoffs of water recovery are reviewed in this issue by Silva and colleagues (2014).

A separate problem is the potential contamination of groundwater by methane. Dramatic examples of methane contamination of well water have been cited, but careful studies to understand the source and magnitude of this problem are still ongoing. In this issue Bachu and Valencia (2014) discuss the potential for methane contamination by loss of well integrity. The available data indicate that surface operations involving handling and storage of wastewater are a more likely source of contamination than underground activities. With a few exceptions (e.g., Heisig and Scott 2013), baseline data on hydrocarbon contamination before oil and gas operations take place are often not available. This highly contentious issue of groundwater contamination by methane is being played out in a series of articles in the Proceedings of the National Academy of Sciences and elsewhere (e.g., Davies 2011; Fontenot et al. 2013; Jackson et al. 2011, 2012, 2013; Li and Carlson 2014; Molofsky et al. 2013; Olmstead et al. 2013; Osborn et al. 2011a, 2011b; Saba and Orzechowski 2011; Schon 2011; Vidic et al. 2013; Warner et al. 2012, 2013).

A major report from the Environmental Protection Agency on the potential impacts of hydraulic fracturing on drinking water resources is in preparation. A progress report has been released (EPA 2012) and a draft report for public comment and peer review is expected this year (EPA 2014).

Air Quality and Carbon Balance

Replacement of coal by methane for power generation and other uses will result in an overall reduction in particulates, sulfur dioxide, nitrogen oxides, and mercury. Furthermore, if losses during production and distribution are sufficiently low, replacement of coal by natural gas will help the overall atmospheric carbon balance, partially mitigating the potential for global warming.

However, there is still uncertainty about the magnitude of fugitive gas emissions from the natural gas production and distribution system. One study (Howarth et al. 2011) suggested that up to 8 percent of the methane from shale gas production escapes to the atmosphere, offsetting any potential mitigation effect. In contrast, other studies (Burnham et al. 2012; Jiang et al. 2011; Laurenzi and Jersey 2013), using lower estimated emissions and a life cycle approach to account for all offsets, found an overall reduction of carbon emission through the use of natural gas. This debate continues. A recent major study indicated that current EPA estimates of methane leakage are low (Brandt et al. 2014). In this issue one of the coauthors of that study discusses various types of measurements of hydrocarbon emissions and the effect of emissions on air quality (Pétron 2014).

In Summary

Much more comprehensive data and analyses are needed to support sound engineering and policy decisions for natural gas development. Many competing near- and long-term interests must be balanced to avoid nonoptimal, short-term consumption of these major hydrocarbon deposits. With wise decisions this resource has the potential to provide a bridge to a renewable and sustainable energy future; unwise decisions can leave the global community with a continuing unsustainable reliance on fossil fuels.


Bachu S, Valencia RL. 2014. Well integrity and risk assessment. The Bridge 44(2):28–33.

Brandt AR, Heath GA, Kort EA, O’Sullivan F, Pétron G, Jordaan SM, Tans P, Wilcox J, Gopstein AM, Arent D, Wofsy S, Brown NJ, Bradley R, Stucky GD, Eardley D, Harriss R. 2014. Methane leaks from North American natural gas systems. Science 343:733–735.

Burnham A, Han J, Clark CE, Wang M, Dunn JB, Palou-Rivera I. 2012. Life-cycle greenhouse gas emissions of shale gas, natural gas, coal, and petroleum. Environmental Science and Technology 46:619−627.

Davies RJ. 2011. Methane contamination of drinking water caused by hydraulic fracturing remains unproven. Proceedings of the National Academy of Sciences 108:E871.

EIA [US Energy Information Administration]. 2013. Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States. Washington. Available at

EIA. 2014. Annual Energy Outlook 2014: Early Release Overview. Washington. Available at

EPA [US Environmental Protection Agency]. 2012. Study of the potential impacts of hydraulic fracturing on drinking water resources: Progress report. Washington: US EPA Office of Research and Development, December. EPA/601/R-12/011; available at fracturing-drinking-water-resources-progress-report-0.

EPA. 2014. Study of the potential impact of hydraulic fracturing on drinking water resources. Draft report, publication pending. Washington.

Finley M, Rühl C. 2014. Trends in the world energy balance. The Bridge 44(2):9–14.

Fontenot BE, Hunt LR, Hildenbrand ZL, Carlton DD, Hyppolite O, Walton JL, Hopkins D, Osorio A, Bjorndal B, Oinhong HH, Schug KA. 2013. An evaluation of water quality in private drinking water wells near natural gas extraction sites in the Barnett shale formation. Environmental Science and Technology 47:10032–10040.

Heisig PM, Scott T-M. 2013. Occurrence of methane in groundwater of south-central New York State, 2012: Systematic evaluation of a glaciated region by hydrogeologic setting. Scientific Investigations Report 2013-5190. Washington: US Geological Survey.

Howarth RW, Santoro R, Ingraffea A. 2011. Methane and the greenhouse-gas footprint of natural gas from shale formations. Climatic Change 106:679–690.

Jackson RB, Osborn SG, Vengosh A, Warner NR. 2011. Reply to Davies: Hydraulic fracturing remains a possible mechanism for observed methane contamination of drinking water. Proceedings of the National Academy of Sciences 108:E872.

Jackson RB, Vengosh A, Darrah TH, Warner NR, Down A, Poreda RJ, Osborn SG, Zhao K, Karr JD. 2012. Increased stray gas abundance in a subset of drinking water wells near the Marcellus shale gas extraction. Proceedings of the National Academy of Sciences 110:11213–11214.

Jackson RE, Gorody AW, Mayer B, Roy JW, Ryan MC, Van Stempvoort DR. 2013. Ground water protection and unconventional gas extraction: The critical need for field-based hydrogeological research. Ground Water 51:488–510.

Jiang M, Griffin MW, Hendrickson C, Jaramillo P, VanBriesen J, Venkatesh A. 2011. Life cycle greenhouse gas emissions of Marcellus shale gas. Environmental Research Letters 6: article no. 034014.

Kell S. 2011. State oil and gas agency groundwater investigations and their role in advancing regulatory reforms. A two state review: Ohio and Texas. Presentation to Ground Water Protection Council, Oklahoma City, August.

King GE. 2012. Hydraulic fracturing 101: What every representative, environmentalist, regulator, reporter, investor, university researcher, neighbor, and engineer should know about estimating frac risk and improving frac performance in unconventional gas and oil wells. Society of Petroleum Engineers Report, SPE 152596.

King GE, King DE. 2013. Environmental risk arising from well construction failure: Difference between barrier and well failure, and estimates of failure frequency across common well types, locations and well age. Society of Petroleum Engineers Report, SPE 166142, Production and Operations 28:323–344.

Krupnick A, Gordon H, Olmstead S. 2013. Pathways to Dialogue: What the Experts Say about the Risks of Shale Gas Development. Washington: Resources for the Future.

Krupnick AJ, Kopp RJ, Hayes K, Roeshot S. 2014. The Natural Gas Revolution: Critical questions for a Sustainable Energy Future. Washington: Resources for the Future.

Laurenzi IJ, Jersey GR. 2013. Life cycle greenhouse gas emissions and freshwater consumption of Marcellus shale gas. Environmental Science and Technology 47:4896–4903.

Lendel I. 2014. Social impact of shale development on municipalities. The Bridge 44(2):47–51.

Li H, Carlson KH. 2014. Distribution and origin of groundwater methane in the Wattenberg oil and gas field of northern Colorado. Environmental Science and Technology 48:1484–1491.

Molofsky LJ, Connor JA, Wylie AS, Wagner T, Farhat SK. 2013. Evaluation of methane sources in groundwater in Northeastern Pennsylvania. Ground Water 51:333–349.

Mulloy KB. 2014. Occupational health and safety considerations in oil and gas extraction operations. The Bridge 44(2):41–46.

Olmstead SM, Muehlenbachs LA, Shih J-S, Chu Z, Krupnick AJ. 2013. Shale gas development impacts on surface water quality in Pennsylvania. Proceedings of the National Academy of Sciences 110:4962–4967.

Osborn SG, Vengosh A, Warner NR, Jackson RB. 2011a. Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proceedings of the National Academy of Sciences 108:8172–8176.

Osborn SG, Vengosh A, Warner NR, Jackson RB. 2011b. Reply to Saba and Orzechowski and Schon: Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proceedings of the National Academy of Sciences 108:E665–E666.

Pétron G. 2014. Air pollution issues associated with shale gas production. The Bridge 44(2):19–27.

Saba T, Orzechowski M. 2011. Lack of data to support a relationship between methane contamination of drinking water wells and hydraulic fracturing. Proceedings of the National Academy of Sciences 108:E663.

Schon SC. 2011. Hydraulic fracturing not responsible for methane migration. Proceedings of the National Academy of Sciences 108:E664.

Silva JM, Gettings RM, Kostedt WL, Watkins VH. 2014. Produced water from hydrofracturing: Challenges and opportunities for reuse and recovery. The Bridge 44(2):34–40.

Swift TK. 2014. Shale gas production: Effects on investment and competitiveness in the US chemical industry. The Bridge 44(2):15–18.

Vidic RD, Brantley SL, Vandenbossche JM, Yoxtheimer D, Abad JD. 2013. Impact of shale gas development on regional water quality. Science 340(6134), doi:10.1126/science.1235009.

Warner NR, Jackson RB, Darrah TH, Osborn SG, Down A, Zhao KG, White A, Vengosh A. 2012. Geochemical
evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. Proceedings of the National Academy of Sciences 109:11961–11966.

Warner NR, Kresse TM, Hays PD, Down A, Karr JD, Jackson RB, Vengosh A. 2013. Geochemical and isotopic variations in shallow groundwater in areas of the Fayetteville Shale development, north-central Arkansas. Applied Geochemistry 35:207–220.

Zoback MD, Arent DJ. 2014. Shale gas development: Opportunities and challenges. The Bridge 44(1):16–23.



1 Managing Editor’s note: Color images are printed in this issue thanks to a special contribution from the editors and their colleagues involved in the Cleveland NAE Topical Meeting on which this issue is based.


About the Author:John C. Angus (NAE) is Kent Hale Smith professor emeritus of chemical engineering, Case Western Reserve University. Steven W. Percy is retired chief executive officer, BPAmerica, and former interim dean, Cleveland State University College of Business. Beverly Z. Saylor is associate professor of geology, Department of Earth, Environmental, and Planetary Systems, Case Western Reserve University.