Methane and Water Contamination Associated with Shale Gas Development and Hydrofracking
Methane and Water ContaminationAssociated 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?
Does shale gas drilling and hydro-fracking cause contamination of drinking water wells?Figure from Scientific American Magazine, November 2011
Possible mechanisms for leakage of stay gas to water resources Leakage of pressurized gas through uncompleted casing to shallow fracture systems Migration from target formation via fracture system (could be enhanced by fracturing) Figure from Scientific American Magazine, Nov 2011
Possible mechanisms for leakage of stay gas to water resourcesFrom Penoyer, (2011), Natural Resource Stewardship & Science
No apparent chemical contamination: no differences betweenactive to non active wells
No apparent isotopic differences between active to non activewells
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 aquifersWarner, et al., Geochemical evidence for natural migration of Marcellus-like brine to shallowdrinking water in Pennsylvania, submitted to PNAS)
100000 10,000.00 Appalachian Brines Appalachian (Ordovician (Ordovician Silurian and Silurian and Devonian) 1,000.00 10000 Devonian) Brines 100.00 Type D Water 1000 Na (mg/L) Br (mg/L) 10.00 Mixing Line Mixing Line 1.00 100 0.10 10 0.01 Type C Water 1 0.00 1 10 100 1000 10000 1000001000000 1 10 100 1,000 10,000 100,000 1,000,000 Cl (mg/L) Cl (mg/L) 100,000,000 10,000,000 Marcellus Marcellus 10,000,000 Brines 1,000,000 Brines 1,000,000 Mixing Line 100,000 100,000 Mixing LineBa (ug/L) Sr (ug/L) 10,000 10,000 Upper Upper 1,000 Devonian 1,000 Devonian Brines Brines 100 100 10 10 1 1 1 10 100 1,000 10,000 100,000 1,000,000 1 10 100 1,000 10,000 100,000 1,000,000 Cl (mg/L) Cl (mg/L)
The strontium isotope fingerprint of the Appalachian brines
The strontium isotope fingerprint of the Marcellus brines
Hydrological connectivity between shallow aquifers and deep Marcellus brine Deep water displacement
Does produced water disposal cause long- term ecological effects and health risks ?
Flowback from the Marcellus gas well: formation water Frack water Frack water Days (after fracking)
Management of produced 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.
Deep well injectionIn 2009 about 140 million gallon were injected in Ohio;In 2011 a significant increase; nearly 50% is coming from PAwhere PA last May banned shipment of drilling waste to its sewagetreatment plants. Ohio 181 injection wells were in full capacity.Trigger for earthquakes ? (Oklahoma, 5.6R; Arkansas4.7R;Youngstown, Ohio 2.7R; 4.0R (12/31/2011)
The effects of brine disposal: (preliminary results) High salinity in the river water (up to 500m downstream) background background
The effects of brine disposal: (preliminary results) High bromide in the river water (up to 500 m downstream) •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, bromodichloromethan e) in potable water. background background
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) Accumulation of radionuclides in river sediments (up to 300m downstream); implications for long- term radium bioaccumulation. background
The take-home messages of this talk:• Shale gas exploitation through hydro-fracturing may save Americafrom foreign oil but seems to cause methane contamination in shallowdrinking water wells in the Appalachian Basin.•No evidence has shown, so far, for direct groundwater contaminationfrom produced/flowback water; yet new data show possible hydraulicconnectivity between the Marcellus and shallow aquifers in PA.• Disposal of produced water from gas exploration directly into surfacewater poses a significant risks to the ecological systems and waterwaysin Pennsylvania.• Sustainable and long-term shale gas developments will need toaccommodate the environmental issues associated with shale gasdrilling and hydro-fracturing.
Further reading:Osborn, S., Vengosh, A. Warner, N. Jackson, R. (2011). Methanecontamination of drinking water accompanying gas drilling andhydro-fracking. Proceedings of the National Academy ofSciences, 108, 8172-8176.Acknowledgements:• FrankStanback, North Carolina• National Science Foundation, Geobiology & Low-TemperatureGeochemistry Program• Nicholas School of Environment, Duke University
Further information: http://sites.nicholas.duke.edu/avnervengosh/NSF Workshop at Duke (January 9, 2011): Environmentaland Social Implications of Hydraulic Fracturing and GasDrilling in the United States: An Integrative Workshop for theEvaluation of the State of Science and Policyhttp://www.nicholas.duke.edu/hydrofrackingworkshop2012/workshop