Environmental implications of hydraulic fracturing and shale gas drilling in the United States Avner...

transcript

Environmental implications of hydraulicfracturing and shale gas drilling in the

United States

Avner Vengosh

Nicholas School of the Environment, Duke University

Rob B. JacksonNathaniel R. Warner*Stephen Osborn,Adrian Down

Nicholas School of EnvironmentDuke University

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, so far, for groundwater contamination from produced/flowback water.

• Disposal of produced water from shale gas wells 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.

Energy production in the USA (2009)

EIA- US Energy Information Administration

Total production= 73 quadrillion Btu

What is hydraulic fracturing (fracking)?

The critical role of shale gas production in the U.S.

Estimates of undeveloped technically recoverable shale gas and shale oil resources (total 750 trillion cubic feet)

Source: IEA (2011)

Global shale gas basins

North America*

Europe OECD

Asia Pacific

Latin America

Africa

Middle East

1000 TCF

Conventional

Unconventional

Global Gas Resource

Source: IEA; * Includes Europe Non OECD

•World: ~250 years coverage at current demand•Large unconventional gains anticipated

Russia/Caspian*

Montrose, Susquehanna, Pennsylvania(June, 2011)

Shale-gas drilling and hydro-fracturing

The Marcellus Shale, Appalachian Basin

Map of The Marcellus (red) and none-Marcellus (blue) wells drilled in Pennsylvania in 2010(PA DEP)

1,386 gas and oil wells were drilled in PA in 2010

Major stages in shale gas production:

• Pad, impoundment and road construction; heavy truck traffic and heavy equipment;

• Drilling – drilling rigs require power from diesel engines; noise…

• Fracturing – during this stage, large amounts of water and fracturing fluid are pumped into the well to create fractures for the gas to escape from the shale;

• A portion of the fluid (30-40%; flowback) is returned into a wastewater impoundment where it is trucked for disposal/ treatment; once the well in operation – generation of produced water that need to be disposed;

(from PA_DEP report on potential gas emission)

Major stages in shale gas production:

• Flaring –testing the gas well before production. Emissions are created from the burning of gas and atmospheric venting of non-combusted gas;

• Condensate Tanks – gas pumped from the well may contain brine and other volatile organic compounds that condense into collection tanks;

• Compressor stations – waw gas is piped from wells to compressor stations where the gas is pre-treated and compressed; building a network of gas pipes through the region.

(from PA_DEP report on potential gas emission)

Key environmental risks associated with shale gas drilling and hydro-fracturing

Methane contamination of drinking water

Fugitive emissions of methane to the

atmosphere

Contamination by fracturing fluid

(transportation, spills, disposal)

Air pollution associated with different stages of

gas production

Disposal of fracturing

fluids/produced water

Health implications, quality of life (traffic, noise)

Water use, lost(7-15 million liter per well)

Release of of fracturing fluid chemicals (spills,

transportation)

What are the environmental risks associated with shale gas drilling and

hydro-fracturing?

• Do we have enough 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?

Do we have enough water?

• Drilling – 230,000 to 3,780,000 liter per well;

• Fracking – 7.6 to 15.1 million liter per well 1400 wells per year, like in the Marcellus Shale, means 10-20 million cubic meter per year

• (Durham, NC consumes 27-34 MCM/year)

Figure from Scientific American Magazine, November 2011

Does shale gas drilling and hydro-fracking cause contamination of drinking water wells?

Duke Research activities (updated to August 2011):

1. Sampling over 200 shallow private wells in eastern PA, NY;2. Sampling produced waters from several gas wells in PA and NY;3. Analysis of methane in private wells – concentrations, isotopes (d13CCH4, d2HCH4)4. Analysis of the chemistry and isotopes of groundwater associated and not associated with gas wells in PA.5. Analysis of the Marcellus Shale brines6. Chemical (major and trace elements) and isotopic (87Sr/86Sr, 11B/10B, 18O/16O, 2H/H) measurements.7. Measurements of naturally occurring radium (226Ra, 228Ra) nuclides

The research methods:

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

Hydro-geological cross section

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 <1km from a shale gas had typically higher methane

(based on 91 wells)

Lockheaven FmCatskill Fm

Methane sources?

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 ?

Biogenic

Dry thermogenic

Methane sources ?

Possible mechanisms for leakage of stay gas to water resources

Figure from Scientific American Magazine, Nov 2011

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

Strontium isotopes: a sensitive tracer for mixing with produced/flowback water

A lower 87Sr/87Sr for non-mixed fracturing fluids

The sensitivity of strontium isotopes to mixing with fracturing fluids and backflow brines

Fracturing fluids-formation water mix

Boron isotopes: differentiation from other contaminant sources

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)

Possible hydraulic connectivity between deep Marcellus-like brine to shallow aquifers

Deep water displacement

Can deep gas and brine in northeastern PA flow to the surface? Is it related to fracking ?

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.

Does produced water disposal cause long-term ecological effects and health risks ?

What’s in produced water?

• Salinity (Marcellus brine – 250,000 mg/L (10 fold seawater);

• High bromide, bromide presence in water enhances the formation of carcinogenic disinfection by-products (e.g., trihalomethane) upon chlorination of downstream potable water;

• High concentrations of toxic elements (barium, arsenic, selenium, lead);

• High concentrations of naturally occurring radioactive materials (NORMs); (5000 pCi/L, drinking water standard=5 pCi/L)

• Hydrocarbon residuals, oil, organics

• 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

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.

High barium in the river water (up to 500 m downstream)

background

Accumulation of radionuclides in river sediments (up to 300m downstream); implications for long-term radium bioaccumulation.

A roadmap to clean energy

Mountaintop coal mining streams contamination

Installation of scrubbers to prevent air pollution (“clean coal”) enhances contaminants’ accumulation in coal combustion products water contamination

Shale gas drilling and hydro-fracturing stray gas emission, methane contamination of shallow aquifers, produced water disposal

Environmental implications of hydraulic fracturing and shale gas drilling in the United States Avner...

Documents