Scholarly article on topic 'The Effects of Shale Gas Exploration and Hydraulic Fracturing on the Quality of Water Resources in the United States'

The Effects of Shale Gas Exploration and Hydraulic Fracturing on the Quality of Water Resources in the United States Academic research paper on "Earth and related environmental sciences"

CC BY-NC-ND
0
0
Share paper
Keywords
{"Shale gas" / "Hydraulic fracturing" / "Stray gas" / Salinity / "Water contamination" / "Produced water"}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — Avner Vengosh, Nathaniel Warner, Rob Jackson, Tom Darrah

Abstract Advances in drilling technologies and production strategies such as horizontal drilling and hydraulic fracturing have significantly improved the production of natural gas by stimulating fluid flow from wells. Since 2008, these technological developments have spurred exponential growth of gas well drilling across the U.S. While the new drilling for shale gas and hydraulic fracturing technologies have dramatically changed the energy landscape in the U.S., recent scientific findings show evidence for contamination of water resources. This paper provides key observations for the potential risks of shale gas drilling and hydraulic fracturing on the quality of water resources and include: (1) stray gas contamination of shallow groundwater overlying shale gas basins; (2) pathways and hydraulic connectivity between the deep shale gas formations and the overlying shallow drinking water aquifers; and (3) inadequate disposal of produced and flowback waters associated with shale gas exploration that causes contamination of surface waters and long-term ecological effects. By using geochemical (e.g., Br/Cl) integrated with oxygen, hydrogen, strontium, radium, and boron isotopic tracers, we have characterized the geochemical fingerprints of brines from several shale gas basins in the USA, including the Utica and Marcellus brines in the Appalachian Basin and the Fayetteville brines in Arkansas. We use these geochemical fingerprints to delineate the impact of shale gas associated fluids on the environment.

Academic research paper on topic "The Effects of Shale Gas Exploration and Hydraulic Fracturing on the Quality of Water Resources in the United States"

Available online at www.sciencedirect.com

SciVerse ScienceDirect

Procedia Earth and Planetary Science 7 (2013) 863 - 866

Water Rock Interaction [WRI 14]

The effects of shale gas exploration and hydraulic fracturing on the quality of water resources in the United States

Avner Vengosha*, Nathaniel Warnera, Rob Jacksona, Tom Darraha,

a Nicholas School of Environment, Duke University, Box 90227, Durham, North Carolina 27708, United States

Abstract

Advances in drilling technologies and production strategies such as horizontal drilling and hydraulic fracturing have significantly improved the production of natural gas by stimulating fluid flow from wells. Since 2008, these technological developments have spurred exponential growth of gas well drilling across the U.S. While the new drilling for shale gas and hydraulic fracturing technologies have dramatically changed the energy landscape in the U.S., recent scientific findings show evidence for contamination of water resources. This paper provides key observations for the potential risks of shale gas drilling and hydraulic fracturing on the quality of water resources and include: (1) stray gas contamination of shallow groundwater overlying shale gas basins; (2) pathways and hydraulic connectivity between the deep shale gas formations and the overlying shallow drinking water aquifers; and (3) inadequate disposal of produced and flowback waters associated with shale gas exploration that causes contamination of surface waters and long-term ecological effects. By using geochemical (e.g., Br/Cl) integrated with oxygen, hydrogen, strontium, radium, and boron isotopic tracers, we have characterized the geochemical fingerprints of brines from several shale gas basins in the USA, including the Utica and Marcellus brines in the Appalachian Basin and the Fayetteville brines in Arkansas. We use these geochemical fingerprints to delineate the impact of shale gas associated fluids on the environment.

© 2013TheAuthors.Publishedby ElsevierB.V.

Selection and/or peer-reviewunder responsibilityof theOrganizingandScientific Committeeof WRI14- 2013 Keywords: shale gas; hydraulic fracturing, stray gas; salinity; water contamination; produced water.

1. Introduction

Recent advances in drilling technologies and production strategies such as horizontal drilling and hydraulic fracturing have significantly improved the production of hydrocarbons by stimulating the flow of gas and liquids from impermeable geologic formations [1-3]. These technological improvements have increased oil and gas exploration in numerous unconventional fields across the U.S., particularly in the

* Corresponding author. Tel.: +1-919-681-8050; fax: +1-919-684-5833. E-mail address: vengosh@duke.edu

1878-5220 © 2013 The Authors. Published by Elsevier B.V.

Selection and/or peer-review under responsibility of the Organizing and Scientific Committee of WRI 14 -doi:10.1016/j.proeps.2013.03.213

Barnett, Haynesville, Bakken, Fayetteville, Woodford, Utica, and Marcellus shale formations (Figure 1). The U.S. Department of Energy Energy Information Agency (EIA) projects that by 2035 shale gas production will increase to 340 billion cubic meters per year, about 50% of the total projected gas production in the U.S [4].

I—I—I—I—I—I—I—I—I 0 400 800 1,600 km

_egend

Basin ^ Shale Play

Shallowest/youngest Intermediate deptlvage Deepesttoldest

Fig. 1. Map of shale gas basins in the USA. Map was prepared by Cidney Christie (Duke University), based on data from U.S. Energy Information Administration (EIA).

The increased extraction of natural gas resources from the shale gas basins in the U.S. has increased awareness for possible environmental consequences, particularly contamination of shallower drinking water aquifers. The debate surrounding the safety of shale gas extraction and hydraulic fracturing [5] has focused on stray gas migration to shallow groundwater [6] and to the atmosphere [5], possible hydraulic connectivity between deep shale formations and shallow aquifers [7], water use [8], air quality [9]as well as the potential for contamination from hydraulic fracturing fluid and/or produced brines containing toxic substances during drilling, transport, and disposal [10-12]. As shale gas exploration is expected to become global, with new initiatives and explorations in China, Germany, Poland, Australia, and New Zealand, the results that are emerging from field-based studies in the U.S. are vital for a global assessment of the environmental risks of shale gas drilling and hydraulic fracturing. This paper provides an overview on three major possible impacts on water quality induced from shale gas exploration and hydraulic

fracturing: (1) shallow groundwater contamination; (2) possible hydraulic pathways between deep and shallow formations; and (3) disposal of produced and flowback waters.

2. Shallow groundwater contamination

One of the most intensive debates on the environmental safety of shale gas exploration and hydraulic fracturing is the possible contamination of drinking water wells in areas of extensive shale gas operation. Our previous study in northeastern Pennsylvania has shown elevated levels of methane in wells located near (<1 km) shale gas drilling sites, whereas wells located away (>1 km) from these areas had much lower methane concentrations [6]. In contrast, it was argued that relatively high methane in this part of the Appalachian Basin is due to natural flux of methane and is not linked to the shale gas drilling [13]. The ability to delineate methane sources and thus the distinction between natural flux and anthropogenic contamination is based on the different isotopic (S13C-CH4; S2H-CH4) and geochemical (propane/methane ratios) compositions of thermogenic relative to biogenic methane sources. It was shown that the elevated methane in drinking water wells near the shale gas wells had a thermogenic composition (e.g., heavier 13C-CH4) than wells located 1 km away from shale gas sites with an apparent mixed thermogenic-biogenic composition. New emerging noble gas data [14] reinforce the carbon isotopes and hydrocarbon ratios data and indicate that the high levels of methane exceeding the hazard level of 10 mg/L are indeed related to stray gas contamination directly linked to shale gas operation. The most probable mechanism for stray gas contamination is leaking through inadequate cement on casing or through well annulus from intermediate formations [6, 14].

In contrast to stray gas contamination, our previous work has not shown evidence for actual contamination of dissolved constituents in shallow aquifers in northeastern Pennsylvania, even for wells with high methane contents [6,7]. New data from 236 domestic wells from Pennsylvania and New York states show no systematic difference in chloride, barium, chromium, boron, and arsenic contents in wells located in "active" zones (<1 km) and "non-active" areas (>1 km). In contrast, an EPA study reported the presence of synthetic organic compounds (e.g., diethylene glycol) as well as elevated chloride and potassium in two high-pH deep wells near extensive shale gas operation in Pavillion, Wyoming[15].

2. Hydraulic connectivity between deep and shallow formations

The fragility of shallow aquifer systems to possible contamination of fugitive gas, fracking fluids, and/or formation water depends primarily on the hydraulic connectivity between deep shale gas formations and the overlying shallow aquifers. In the Appalachian Basin, the depth of the Marcellus Shale is about one to two km, yet an intensive fracture network system provides a possible conduit for gas and fluids migration [16]. Evidence for natural pathways from deep formations to shallow aquifers in northeastern Pennsylvania is shown by the distinctive geochemical (elevated Br/Cl) and isotopic (87Sr/86Sr ratios) compositions of saline groundwater identified in shallow aquifers [7]. The Na-Ca-Cl composition of the saline shallow groundwater mimics the composition of the Marcellus brines and different from the Ca-HCO3 and Na-HCO3compositions that characterize local groundwater. In addition, the 87Sr/86Sr ratios of the saline groundwater overlap the 87Sr/86Sr ratios measured in the Marcellus brines, inferring mixing between the deep Marcellus brines and shallow groundwater [7].

3. Disposal of produced and flowback waters

The high levels of salinity (TDS up to 300,000 mg/L), toxic elements (e.g., barium), and radioactivity of produced and flowback waters from the Marcellus Shale [7, 10-12, 17-18] and other shale gas basins

present new challenges for handling the wastewater that is generated together with the natural gas. Our data show that disposal of the hypersaline wastewaters to waterways in western Pennsylvania, even through a brine treatment facility, generates a highly saline plume (TDS up to 100,000 mg/L) and radioactivity in both downstream surface waters and river sediments. We use the strontium isotopes to determine the source of the wastewater and to distinguish produced waters originated from shale gas from conventional oil and gas production. Alternative disposal of wastewaters through deep-well injection could induce seismic events, as shown in different sites in the U.S. [19]. Overall, one of the direct unquestioned impacts of shale gas exploration on water quality is the issue of management and disposal of wastewater associated with the gas production. The increase use of hydraulic fracturing technology for enhancement and tapping of also conventional oil and gas wells is expected to increase the volume of these types of wastewaters in the U.S.

References

[1] Pacala S, and Socolow R. Stabilization wedges: Solving the climate problem for the next 50 years with current technologies. Science 2004; 305: 968-972.

[2] Kargbo DM, Wilhelm RG, Campbell DJ. Natural Gas Plays in the Marcellus Shale: Challenges and Potential Opportunities. Env

Sci Technol 2010; 44: 5679-5684.

[3] Kerr RA.Natural Gas From Shale Bursts Onto the Scene.Science2010; 328; 1624-1626.

[4] US Energy Information Agency. Annual Energy Outlook 2011 with Projections to 2035. Washington, D.C.

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

[6] Osborn SG, Vengosh A, Warner NR, Jackson RB. Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. PNAS 2011; 108: 8172-8176.

[7] Warner NR, Jackson, RB, Darrah, TH, Osborn, SG, Down A, Zhao K, White A, Vengosh A. Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. PNAS 2012 (doi: 10.1073/pnas.1121181109).

[8] NicotJP, Scanlon, BR. Water Use for Shale-Gas Production in Texas, U.S.. Env Sci Technol 2012; 46: 3580-3586.

[9] Colborn, T, Schultz, K, Herrick L, Kwiatkowski C. An Exploratory Study of Air Quality near Natural Gas Operations; Human Ecological Risk Assessment 2012 (in press).

[10] Dresel P, Rose A. Chemistry and origin of oil and gas well brines in Western Pennsylvania. Pennsylvania Geological Survey. 4th series Open-File Report OFOG 10-01.0; 2010, p 48.

[11] Rowan E, EngleM, Kirby C, Kraemer T. Radium content of oil- and gas-field produced waters in the northern Appalachian Basin (USA)-Summary and discussion of data. U.S. Geological Survey Scientific Investigations Report 2011; 513: 31 pp.

[12] Gregory KB, Vidic RD, Dzombak DA. Water management challenges associated with the production of shale gas by hydraulic fracturing. Elements2011; 7: 181-186.

[13] Molofsky LJ, Connor JA, Farhat SK, Wylie AS, Jr, Wagner T. Methane in Pennsylvania water wells unrelated to Marcellus shale fracturing. Oil Gas J 2011; 109: 54-67.

[14] DarrahT, Vengosh A, Jackson RB, Warner N. Constraining the source and migration of natural gas in shallow aquifers within active shale gas production zone: insights from integrating noble gas and hydrocarbon isotope geochemistry. GSA meeting, 4-7Nov 2012, Charlotte, NC, USA.

[15] Di Giulio DC, Wilkin RT, Miller C, Oberley G. Investigation of Ground Water Contamination near Pavillion, Wyoming. U.S. Environmental Protection Agency Report 2011 (http://www.epa.gov/region8/superfund/wy/pavillion/).

[16] Warner NR, Jackson, RB, Darrah, TH, Osborn, SG, Down A, Zhao K, White A, Vengosh A. Reply to Terry Engelder: Potential for fluid migration from the Marcellus Formation remains possible. PNAS 2012 (in press).

[17] Chapman EC, Capo R, Stewart BW, Kirby C, Hammack RW, Schroeder K, Edenborn HM. Geochemical and strontium isotope characterization of produced waters from Marcellus Shale natural gas extraction. Environ Sci Technol. 2012; 46: 3545-3553

[18] Haluszczak LO, Rose RW, Kump LR. Geochemical evaluation of flowback brine from Marcellus gas wells in Pennsylvania, USA. App Geoch 2012 (in press).

[19] Hitzman MW. Induced seismicity potential and energy technologies. GSA meeting, 4-7Nov 2012, Charlotte, NC, USA 2012.