93
Table 6: Water Intensity
212
Energy Source
Range in Water Intensity
(gallons/mmBtu)
Conventional Natural Gas
~0
Shale Gas
0.6 – 1.8
Coal (no slurry transport)
2 – 8
Nuclear (uranium at plant)
8 – 14
Conventional oil
1.4 – 62
Oil Shale Petroleum (mining)
7.2 – 38
Oil Sands Petroleum (
in situ)
9.4 – 16
Synfuel (coal gasification)
11 – 26
Coal (slurry transport)
13 – 32
Oil Sands Petroleum (mining)
14 – 33
Syn Fuel (coal Fischer-Tropsch)
41 – 60
Enhanced Oil Recovery
21 – 2,500
Fuel ethanol (irrigated corn)
2,500 – 29,000
Biodiesel (irrigated soy)
13,800 – 60,000
The Addendum also explains that, despite its relatively low long-term water intensity, shale gas
production could impact water supply in
specific areas, particularly arid regions such as the Eagle
Ford Shale play in Texas. The Addendum notes that the relationship between shale gas
production and water quantity is principally a local issue, and that the degree of impact depends on
“the local climate, recent weather patterns, existing water use rates, seasonal fluctuations, and
other factors.”
213
The following Table 7 shows the variation in the proportion of water usage by
activity in shale gas regions:
212
Id. at 11 (Table 2).
213
Id. at 12.
94
Table 7: Water Usage in Shale Gas Regions
214
Play
Public
Suppl
y (%)
Industr
y &
Mining
(%)
Power
Generatio
n (%)
Irrigatio
n (%)
Livestoc
k (%)
Shal
e
Gas
(%)
Total
Water Use
(Bgals/yr)
*
Barnett 1
82.7
4.5
3.7
6.3
2.3
0.4
133.8
Eagle Ford
2
17
4
5
66
4
3 – 6
64.8
Fayetteville
1
2.3
1.1
33.3
62.9
0.3
0.1
378
Haynesville
1
45.9
27.2
13.5
8.5
4.0
0.8
90.3
Marcellus
1
12.0
16.1
71.7
0.1
0.01
0.06
3,570
Niobrara
3
8
4
6
82
0.01
1,280
[*Bgal/yr = billion gallons per year]
2.
Water Quality
Observing that water quality concerns may have received more
attention than any other
aspect of unconventional natural gas production, the Addendum addresses water quality issues
arising from four aspects of unconventional natural gas production: construction, drilling, use of
hydraulic fracturing fluids, and handling of flowback and produced waters.
Runoff from the construction of access roads and other earth-disturbing activities can lead
to temporary increases in turbidity and sedimentation in surface waters when well sites are being
developed. However, the Addendum states that “when standard
industry practices and
preventative measures are deployed, only minor impacts are likely to result.”
215
Drilling in unconventional natural gas production requires penetrating shallower fresh
water aquifers. Referring to NETL’s
Modern Shale Gas Development in the United States: A
Primer, the Addendum briefly explains the manner in which such drilling can be undertaken to
protect fresh water aquifers.
216
The Addendum acknowledges, however, that while
214
Id. at 12 (Table 3) (citations omitted).
215
Id. at 13.
216
Addendum at 13-14 (citing GWPC and ALL Consulting. 2009.
Modern Shale Gas Develop. In the United
States: A Primer. Nat’l Energy Tech. Lab.;
available at: http://www.netl.doe.gov/File%20Library/Research/Oil-
Gas/Shale_Gas_Primer_2009.pdf).
95
unconventional natural gas formations are thousands of feet below aquifers associated
with public
water supply or surface hydrological connection, poor construction practices may cause failure of
a casing or cement bond. This failure, in turn, could lead to potential contamination of an aquifer.
The Addendum also observes that drilling may create connections with existing fractures or faults,
or improperly plugged or abandoned wells, allowing contaminants to migrate through the
subsurface.
217
The fluid used for hydraulic fracturing consists of over 98 percent water, but also may
include several different chemical compounds.
218
These compounds can
vary from well to well
based on site specific geological information. The Addendum describes federal and state efforts to
gather information and require disclosure of the types of chemical additives being used in
hydraulic fracturing. The risks posed by the use of these fluids may come from spills and leakages
during transport to the well,
storage on the well pad, or during the chemical mixing process.
219
Further, chemical additives may contaminate groundwater should the integrity of the casing or
cement seal of the well be compromised.
220
The Addendum considers the potential environmental impacts associated with produced
water recovered during flowback operations. Produced water may contain elevated levels of total
dissolved solids, salts, metals, organics, and natural occurring radioactive materials, as well as the
chemicals included in the fracturing fluid noted above. The Addendum discusses the three
principal ways of mitigating the impacts associated with produced water: minimization of the
quantity of water used, recycling and
re-use of produced water, and disposal.
217
Id. at 14.
218
Id. at 14-15.
219
Id. at 18.
220
Id.