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Methane and Water Contamination Associated with Shale Gas Development
and Hydrofracking
Avner Vengosh
Nicholas School of the Environment, Duke University
What are the environmental risks associated with shale gas drilling and
hydro-fracturing?
Water
• Does shale gas drilling and hydro-fracking cause contamination of drinking water wells?
• Does produced water disposal cause long-term ecological effects and health risks?
Figure from Scientific American Magazine, November 2011
Does shale gas drilling and hydro-fracking cause contamination of drinking water wells?
CH4
d13C – 13C/12C
d2H – 2H/H
Isotopic fingerprinting of methane source
Proceedings of National Academy of Sciences, May 17, 2011
Duke research in Pennsylvania and New York
Definition of active versus non-active wells: Private wells located <1km from a shale gas had typically higher methane
(based on about 60 wells)
Definition of active versus non-active wells: Private wells located <1 km from a shale gas had typically higher methane
(based on 91 wells)
Lockheaven FmCatskill Fm
Methane sources?
Active
Active
Non-active
Non-active
A distinction between active wells with a thermogenic isotopic fingerprint and non-active wells with a mixed composition
Thermogenic
Biogenic
Methane sources ?
Methane sources?
Thermogenic source
Possible mechanisms for leakage of stay gas to water resources
Figure from Scientific American Magazine, Nov 2011
Leakage of pressurized gas through uncompleted casing to shallow fracture systems
Migration from target formation via fracture system (could be enhanced by fracturing)
From Penoyer, (2011), Natural Resource Stewardship & Science
Possible mechanisms for leakage of stay gas to water resources
No apparent chemical contamination: no differences between active to non active wells
No apparent isotopic differences between active to non active wells
Results of the study indicate:
1. High methane concentration in active wells (<1 km from gas well) are associated with a distinguish chemical and isotopic composition identical to the Marcellus gas in production wells while wells located >1 km had lower methane and different composition;
2. Active wells were not contaminated by chemicals derived from contamination of produced waters.
Occurrence of saline groundwater enriched in barium in shallow aquifers
Warner, et al., Geochemical evidence for natural migration of Marcellus-like brine to shallow drinking water in Pennsylvania, submitted to PNAS)
1.00
10.00
100.00
1,000.00
10,000.00
Cl (mg/L)
Br (m
g/L)
Appalachian (Ordovician Silurian and Devonian) Brines
1 10100
100010000
100000
10000001
10
100
1000
10000
100000
Cl (mg/L)
Na
(mg/
L)Appalachian Brines(Ordovician Silurian and Devonian)
Mixing Line
Type D Water
Type C Water
Mixing Line
Upper Devonian Brines
Marcellus Brines
Mixing Line
1 10 100 1,000 10,000 100,000 1,000,00010
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
Cl (mg/L)
Ba (u
g/L)
Upper Devonian Brines
Marcellus Brines
Mixing Line
1 10 100 1,000 10,000 100,000 1,000,00010
100
1,000
10,000
100,000
1,000,000
10,000,000
Cl (mg/L)
Sr (u
g/L)
The strontium isotope fingerprint of the Appalachian brines
The strontium isotope fingerprint of the Marcellus brines
Deep water displacement
Hydrological connectivity between shallow aquifers and deep Marcellus brine
Does produced water disposal cause long-term ecological effects and health risks ?
Flowback from the Marcellus gas well: formation water
Days (after fracking)
Frack water
Frack water
• Inject underground through a disposal well (onsite or offsite),
• Discharge to a nearby surface water body,
• Haul to a municipal wastewater treatment plant,
• Haul to a commercial industrial wastewater treatment facility,
• Reuse for a future fracking job either with or without treatment.
Management of produced water
In 2009 about 140 million gallon were injected in Ohio;In 2011 a significant increase; nearly 50% is coming from PA where PA last May banned shipment of drilling waste to its sewage treatment plants. Ohio 181 injection wells were in full capacity.
Trigger for earthquakes ? (Oklahoma, 5.6R; Arkansas 4.7R;Youngstown, Ohio 2.7R; 4.0R (12/31/2011)
Deep well injection
Source: Cidney Christie, Duke
background
High salinity in the river water (up to 500m downstream)
The effects of brine disposal: (preliminary results)
background
background
The effects of brine disposal: (preliminary results)
High bromide in the river water (up to 500 m downstream)
background
• Long-term salinization of fresh water resources: high chloride and bromide in surface water enhance the formation of carcinogenic disinfection by-products (e.g., trihalomethane, bromodichloromethane) in potable water.
The effects of brine disposal: (preliminary results)
High barium in the river water (up to 500 m downstream)
background
The effects of brine disposal: (preliminary results)
background
Accumulation of radionuclides in river sediments (up to 300m downstream); implications for long-term radium bioaccumulation.
The take-home messages of this talk:
• Shale gas exploitation through hydro-fracturing may save America from foreign oil but seems to cause methane contamination in shallow drinking water wells in the Appalachian Basin.
• No evidence has shown, so far, for direct groundwater contamination from produced/flowback water; yet new data show possible hydraulic connectivity between the Marcellus and shallow aquifers in PA.
• Disposal of produced water from gas exploration directly into surface water poses a significant risks to the ecological systems and waterways in Pennsylvania.
• Sustainable and long-term shale gas developments will need to accommodate the environmental issues associated with shale gas drilling and hydro-fracturing.
Further reading:
Osborn, S., Vengosh, A. Warner, N. Jackson, R. (2011). Methane contamination of drinking water accompanying gas drilling and hydro-fracking. Proceedings of the National Academy of Sciences, 108, 8172-8176.
Acknowledgements:• Frank Stanback, North Carolina • National Science Foundation, Geobiology & Low-Temperature
Geochemistry Program • Nicholas School of Environment, Duke University
Further information:
http://sites.nicholas.duke.edu/avnervengosh/
NSF Workshop at Duke (January 9, 2011): Environmental and Social Implications of Hydraulic Fracturing and Gas Drilling in the United States: An Integrative Workshop for the Evaluation of the State of Science and Policy
http://www.nicholas.duke.edu/hydrofrackingworkshop2012/workshop