Methane and Water Contamination Associated with Shale Gas Development and Hydrofracking

transcript

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?

• 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?

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

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)

100.00

1,000.00

10,000.00

Cl (mg/L)

Appalachian (Ordovician Silurian and Devonian) Brines

1 10100

100010000

100000

10000001

100000

Cl (mg/L)

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

10,000

100,000

1,000,000

10,000,000

100,000,000

Cl (mg/L)

Upper Devonian Brines

Marcellus Brines

Mixing Line

1 10 100 1,000 10,000 100,000 1,000,00010

10,000

100,000

1,000,000

10,000,000

Cl (mg/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

• 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.

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.

Methane and Water Contamination Associated with Shale Gas Development and Hydrofracking

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