Water Contamination Concerns Linger For Shale Gas
Horizontal Drilling And Water Fracturing: The Keys To Shale Gas
Production
National Public Radio
23 September 2009
by Tom Gjelten
Advances in technology have helped boost the growth of shale drilling
in the United States over the past few years. But as the practice of
harvesting natural gas embedded in shale rock deep below the Earth's
surface has expanded, it has raised concerns about the impact this type
of drilling has on the environment — especially on groundwater.
At issue is the practice of "hydraulic fracturing," which in
combination with horizontal drilling is an essential part of the shale
gas production process. The shale rock in which the gas is trapped is
so tight that it has to be broken in order for the gas to escape. A
combination of sand and water laced with chemicals — including benzene
— is pumped into the well bore at high pressure, shattering the rock
and opening millions of tiny fissures, enabling the shale gas to seep
into the pipeline.
This fracturing technique has been in use since 1948, and industry
sources say the procedure has been used in a million gas wells in the
years since. But the practice has expanded in the past few years as
energy companies began exploring shale formations.
The results have been so successful that energy analysts now see the
development of shale gas reservoirs as a key step toward U.S. energy
independence and a cleaner environment. When burned, natural gas
produces about 25 percent less carbon dioxide than coal.
Benzene Contamination And Other Environmental Risks
Some landowners in shale gas areas, however, say the energy and
environmental benefits of this new production are outweighed by the
environmental risks it raises. NPR's Jeff Brady documented these issues
in a report earlier this year.
Steve Harris, who resides near Dallas, told Brady that he noticed a
foul odor coming from his tap water shortly after a gas company used
hydraulic fracturing in a natural gas well near his house. Harris said
he complained to the drilling company and to state authorities but
without result.
"Basically, you get to the point where you think maybe everybody's
working with the gas people and against the little guy," Harris said.
In 2008, a hydrologist found evidence of benzene contamination in a
water well in Wyoming, in the vicinity of a large gas field. Residents
near Dimock, Pa., have also complained of contamination of their water
supply as a result of gas well drilling in their area. Dimock is in an
area of Pennsylvania that sits atop the Marcellus shale formation, one
of the largest in the country, and natural gas companies have been
active there.
Critics of hydraulic fracturing suspect that the chemicals used in the
process have somehow leaked into the groundwater supply. It has been
difficult, however, to demonstrate a direct connection between these
apparent instances of water pollution and the hydraulic fracturing
procedures that have taken place nearby. Industry sources point out
that the shale rock subjected to the fracturing is thousands of feet
below the surface of the Earth, far below the aquifers that supply
drinking water. Many layers of rock are in between. The well bores
themselves are shielded from the surrounding earth by steel and cement
casing.
Checking For Groundwater Contamination
Gas producers cite investigations by the Ground Water Protection
Council, a national association of state agencies responsible for
maintaining safe water supplies. To date, the GWPC has uncovered no
documented instance of groundwater contamination clearly due to
hydraulic fracturing.
"We have gone to the state regulators on this, but we don't have any
good evidence right now," says Mike Paque, the GWPC's executive
director. "A lot of it is anecdotal."
It is also true, however, that state regulators have not been able to
disprove a connection between hydraulic fracturing and water
contamination. Some problems loosely associated with gas wells seem to
have been a result of preventable accidents. Gas well pipes have
broken, resulting in leakage of contaminants into the surrounding
ground.
There have also been cases of improper disposal of potentially toxic
wastewater from a fracturing operation. In addition, the process of
drilling a well has on at least one occasion disrupted a layer of
limestone containing methane, which subsequently escaped.
Such instances argue for closer monitoring of shale gas drilling
operations.
The GWPC has recently contracted with the U.S. Department of Energy to
develop an environmental risk assessment for hydraulic fracturing. The
assessment would create a database of fracturing operations so that it
would be easier to identify any possible connection to subsequent
contamination problems.
Just last week, the GWPC board approved a resolution encouraging
Congress, federal agencies and state regulators to work with the GWPC
"to evaluate the risks posed by [hydraulic fracturing]."
Still Identifying Potential Risks
The rapidly expanding development of shale gas reservoirs has left
regulatory agencies and legislatures scrambling to keep up with the new
environmental issues raised by the operations. In June, several members
of Congress introduced the "Fracturing Responsibility and Awareness of
Chemicals Act." The "FRAC Act" would amend the federal Safe Water
Drinking Act to bring hydraulic fracturing under federal rather than
state regulation.
In the resolution approved last week, however, the GWPC expressed
concern that additional federal regulation of hydraulic fracturing
"will divert compliance and enforcement resources from higher priority
issues that pose significant threats of endangerment to underground
sources of drinking water." GWPC's Paque says his organization, at this
point, is more concerned about water contamination from agricultural
practices and groundwater runoff than from hydraulic fracturing.
The "FRAC Act" would also require natural gas producers to disclose the
chemicals they are using during hydraulic fracturing operations. The
producers have been reluctant to reveal the chemical formulas used in
their fracturing operations, for fear of disclosing proprietary
information to their competitors.
In a statement accompanying the introduction of the bill, the sponsors
said they do not oppose hydraulic fracturing but want "to ensure that
the practices are done safely and do not threaten the health of the
public."