Hydraulic fracturing, commonly known as fracking, is a
process that blasts bedrock to create fractures for natural gas to escape form
the bedrock. Fracking is used in unconventional wells that are extended
horizontally from an initial vertical borehole. The process is used in
Pennsylvania to extract natural gas from the Marcellus Shale Formation, which
is encountered as depths as great as 8,000 to 10,000 feet below ground in the
northern and western parts of the state.
Hydraulic fracturing of an unconventional gas well.
( http://www.nt.gov.au/d/Minerals_Energy/?header=How%20do%20we%20access%20Unconventional%20Gas)
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I am not anti-fracking. As a geologist, I understand how fracking
is supposed to work, and I think it’s a viable means of extracting natural gas
from deep formations in which conventional drilling is not practicable. But I
also think that Pennsylvania has done a horrendous job of overseeing how the energy
companies operating in PA drill for natural gas and manage their drilling
wastes.
The Pittsburgh Post-Gazette does a great job covering
Marcellus Shale gas drilling issues in PA, including reporting on negative
environmental aspects of bringing this natural resource to market. Last week
the Post-Gazette
ran a great editorial piece that cited data they obtained from the Pennsylvania
Department of Environmental Protection (PADEP) about compromised water supplies
related to oil and gas operations. The editorial also criticized PADEP for
issues with public access to information related to water supplies contaminated
by oil or gas drilling activities. Many of the chemicals used in the fracking
process are claimed by drillers to be trade secrets. And PADEP will not release
information about those chemicals. So the public and their advocates have no
opportunity to evaluate the risks they may be facing from fracking fluid
contamination.
When the reports about methane in residential water wells near
Marcellus gas wells in northern PA first started hitting the media five or
six years ago, the red flags should have been clear to anyone familiar with
drilling. The drillers were swearing that there was no way methane from
their target formation at 8,000 feet below ground could have contaminated the
shallow aquifer only 100 to 150 feet bellow ground where most domestic wells
are built. And, if the wells were constructed properly, that should be true. But
the drilling boom came upon PADEP too quickly. The DEP had neither the field
inspectors nor the funding to hire enough field inspectors to be able to ensure
that gas wells were being constructed properly.
Steel casing is supposed to be cemented into the surrounding bedrock to
a depth far below the drinking water aquifer. The cement slurry, a mixture of
cement and bentonite clay, effectively seals the annular space around the
outside of the steel casing to prevent any drilling fluids or gas from leaking
around the casing and getting into the aquifer. And a good annular seal also
prevents surface runoff water from seeping down along the outside of the casing
and tainting the underlying drinking water aquifer. That is assuming the wells
are being properly sealed.
In my job, I have overseen drillers installing hundreds of groundwater
monitoring wells or remediation wells designed to delineate or treat petroleum,
solvents or metals contamination in groundwater. There have been many times I
have given the driller my construction specifications and, when they thought I
wasn’t looking, caught them cutting corners. Most often the corner getting cut involved
how they were grouting the well materials in the borehole. And that's exactly
what I think happened in the majority of instances in which methane was documented in domestic wells in close proximity to an unconventional gas well.
If the cement used to seal the steel casing into the
borehole is mixed with too much water, the cement will shrink as it cures and
will pull away from the borehole walls. If not enough bentonite is mixed with
the concrete, if it is not mixed uniformly or if it is pumped too quickly down
the borehole, there may be pockets of concrete that do not seal completely
to the borehole walls. These are the conditions that PADEP inspectors should have been on hand to look for during well drilling. Presumably, at this point in
the drilling boom, something as basic as proper well grouting has been rectified
between drillers and PADEP.
Fracking fluid impoundment in western PA.
(photo credit: Observer-Reporter.com)
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Assuming that gas wells are now being properly constructed,
spills of drilling fluid are probably the biggest on-going concern for public
health. Spills of drilling fluids are a
largely preventable threat to groundwater and surface water resources. A
different Post-Gazette editorial published earlier this week cited the
disturbing frequency of drilling companies failing to detect or report spills
on their drilling sites. Half of the drilling fluid spills for which PADEP
fined drillers through 2012 were not reported to PADEP by drillers as required
by law. Instead, they were reported by drilling site land owners or neighboring
property owners or observed by PADEP inspectors or other officials.
PADEP needs to be better funded to better police Marcellus
drilling sites so that drillers will be less likely to carelessly allow
preventable spills to happen and will be more diligent in policing their sites to promptly discover and act on truly accidental spills. PA’s groundwater and
surface water resources depend on it.