Impact of Hydraulic Fracturing on Water Resources: Assessing the ...

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Impact of Hydraulic Fracturing on Water Resources: Assessing the ...

ong>Impactong> ong>ofong> ong>Hydraulicong> ong>Fracturingong> on

Water Resources:

Assessing the broader environmental

footprint ong>ofong> shale gas drilling hydraulic

fracturing

Avner Vengosh

icholas School ong>ofong> the Environment,

Duke University


The critical role ong>ofong> shale gas production

in the U.S.

0.5

Total gas production in U.S.

800

Fraction ong>ofong> shale gas out ong>ofong>

total gas production

700

0.4

600

500

0.3

400

0.2

20%

Gas production (billion cubic meter)

300

200

0.1

Shale gas

138

100

0

0

1990 2000 2010 2020 2030 2040

Year


The Marcellus Shale, Appalachian Basin


Map ong>ofong> The Marcellus (red) and none-Marcellus (blue)

wells drilled in Pennsylvania in 2010

(PA DEP)

Map

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


Montrose, Susquehanna, Pennsylvania

(June, 2011)


What is hydraulic fracturing (fracking)?


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;

ong>Fracturingong> – During this stage, large amounts ong>ofong> water and fracturing

fluid are pumped into the well to create fractures for the gas to escape

from the shale;

• A portion ong>ofong> the fluid (flowback) is returned into a wastewater

impoundment where it is trucked for disposal/ treatment; once the well

in operation – generation ong>ofong> produced water;

(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 ong>ofong> gas and atmospheric venting ong>ofong> noncombusted

gas;

• Condensate Tanks – Gas pumped from the well may contain brine

and other volatile organic compounds that condense into collection

tanks;

• Compressor stations – Raw gas is piped from wells to compressor

stations where the gas is pre-treated and compressed.

(from PA_DEP report on potential gas emission)


Key environmental risks associated with shale

gas drilling and hydro-fracturing

Methane

contamination ong>ofong>

drinking water

wells

Fugitive emissions

ong>ofong> methane to the

atmosphere

Water use

(3-6 million

gallon per well)

Contamination by

fracturing fluid

(transportation, spills,

disposal)

Disposal ong>ofong>

fracturing

fluids/produced

water

Air pollution associated

with different stages ong>ofong>

gas production

Health implications,

quality ong>ofong> life

(traffic, noise)


The research methods:

Duke Research activities (updated to August 2011):

1.Sampling ~200 shallow private wells in eastern PA, NY;

2. Sampling produced waters from several gas wells in PA and

NY;

3. Analysis ong>ofong> methane in private wells – concentrations, isotopes

4. Analysis ong>ofong> the chemistry and isotopes ong>ofong> groundwater

associated and not associated with gas wells in PA.

5. Analysis ong>ofong> the Marcellus Shale brines

3. Chemical (major and trace elements) and isotopic ( 87 Sr/ 86 Sr,

11

B/ 10 B, 18 O/ 16 O, 2 H/H) measurements.


Proceedings ong>ofong> national

Academy ong>ofong> Sciences,

May 17, 2011


Duke research in Pennsylvania and ew York


Hydro-geological cross section


Definition ong>ofong> active versus non-active wells:

Private wells located


Isotopic fingerprinting ong>ofong> methane source

δ 13 C – 13 C/ 12 C

CH 4

δ 2 H – 2 H/H


Methane source?

Non-active

Active

A distinction between active

wells with thermogenic

isotopic fingerprint and nonactive

wells with a mixed

composition

Non-active

Active


o apparent chemical contamination: no differences between

active to non active wells


Results ong>ofong> the study indicate:

1. High methane concentration in active wells (1 km had lower methane and different

composition;

2. Active wells were not contaminated by chemicals derived

from contamination ong>ofong> produced waters.


The toxicity ong>ofong> produced water


How much produced water is generated in

shale gas wells?

• It is estimated that for every million cubic feet ong>ofong> gas 5 to

20 barrels ( 28-112 cubic feet) ong>ofong> wastewater is generated.

• In 2010 the US produced 4.87 trillion cubic feet (data from

IEA) which would equivalent to 136 to 545 million cubic

feet (about 1 to 4 billion gallon) ong>ofong> produced water

generated for 2010.


What’s in produced water?

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

seawater);

• High bromide, even in diluted brine would enhance the

formation ong>ofong> carcinogenic disinfection by-products (e.g.,

trihalomethane) upon chlorination ong>ofong> downstream potable

water;

• High concentrations ong>ofong> toxic elements (arsenic, selenium,

lead);

• High concentrations ong>ofong> naturally occurring radioactive

materials (NORMs)


What’s in produced water?

Marcellus produced water

226

Ra = 5000 pico-curie per liter

The

Laboratory for

Environmenta

l Analysis ong>ofong>

RadioNuclide

s (LEARN)

Duke

University

(drinking water standard =

5 pico-curie per liter


Research in orth Carolina

1. Work with DENR and USGS (and others) to establish a robust

and systematic baseline for the quality ong>ofong> groundwater in areas

that are expected to be drilled for shale gas in Lee and

Chatham counties.

1. Characterize the composition ong>ofong> formation water in shale gas

in NC.

1. Use the water quality and isotopic fingerprints for a

monitoring system following shale gas drilling and hydrong>ofong>racking.


Can deep gas and brine in northeastern PA flow

to the surface? Is it related to fracking ?

Deep water displacement

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