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

<strong>Impact</strong> <strong>of</strong> <strong>Hydraulic</strong> <strong>Fracturing</strong> on
Water Resources:
Assessing the broader environmental
footprint <strong>of</strong> shale gas drilling hydraulic
fracturing
Avner Vengosh
icholas School <strong>of</strong> the Environment,
Duke University

The critical role <strong>of</strong> shale gas production
in the U.S.
0.5
Total gas production in U.S.
800
Fraction <strong>of</strong> shale gas out <strong>of</strong>
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 <strong>of</strong> 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;
• <strong>Fracturing</strong> – During this stage, large amounts <strong>of</strong> water and fracturing
fluid are pumped into the well to create fractures for the gas to escape
from the shale;
• A portion <strong>of</strong> the fluid (flowback) is returned into a wastewater
impoundment where it is trucked for disposal/ treatment; once the well
in operation – generation <strong>of</strong> 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 <strong>of</strong> gas and atmospheric venting <strong>of</strong> 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 <strong>of</strong>
drinking water
wells
Fugitive emissions
<strong>of</strong> methane to the
atmosphere
Water use
(3-6 million
gallon per well)
Contamination by
fracturing fluid
(transportation, spills,
disposal)
Disposal <strong>of</strong>
fracturing
fluids/produced
water
Air pollution associated
with different stages <strong>of</strong>
gas production
Health implications,
quality <strong>of</strong> 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 <strong>of</strong> methane in private wells – concentrations, isotopes
4. Analysis <strong>of</strong> the chemistry and isotopes <strong>of</strong> groundwater
associated and not associated with gas wells in PA.
5. Analysis <strong>of</strong> 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 <strong>of</strong> national
Academy <strong>of</strong> Sciences,
May 17, 2011

Duke research in Pennsylvania and ew York

Hydro-geological cross section

Definition <strong>of</strong> active versus non-active wells:
Private wells located

Isotopic fingerprinting <strong>of</strong> 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 <strong>of</strong> 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 <strong>of</strong> produced waters.

The toxicity <strong>of</strong> produced water

How much produced water is generated in
shale gas wells?
• It is estimated that for every million cubic feet <strong>of</strong> gas 5 to
20 barrels ( 28-112 cubic feet) <strong>of</strong> 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) <strong>of</strong> 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 <strong>of</strong> carcinogenic disinfection by-products (e.g.,
trihalomethane) upon chlorination <strong>of</strong> downstream potable
water;
• High concentrations <strong>of</strong> toxic elements (arsenic, selenium,
lead);
• High concentrations <strong>of</strong> 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 <strong>of</strong>
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 <strong>of</strong> groundwater in areas
that are expected to be drilled for shale gas in Lee and
Chatham counties.
1. Characterize the composition <strong>of</strong> formation water in shale gas
in NC.
1. Use the water quality and isotopic fingerprints for a
monitoring system following shale gas drilling and hydr<strong>of</strong>racking.

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