Geoscience Reference
In-Depth Information
VISUAL CONCEPT CHECK
20.3
Believe it or not, this glob of Earth held in this
gloved hand can be refined to power your au-
tomobile. What is this material called, where
is it found, and what are two ways it can be
extracted from the ground?
Enhanced energy security is desirable for many reasons; in par-
ticular, it may keep us out of costly conflicts in unfriendly places.
On the other hand, concerns abound that extracting these uncon-
ventional oil deposits may have a huge negative impact on the
environment. You may have heard about some of these issues.
The environmental impacts of open-pit mining in the Atha-
basca oil sands are pretty straightforward. As you can clearly
see in Figure 20.28, such mining operations play havoc with the
landscape. Giant earthmovers excavate hundreds of thousands
of metric tonnes of Earth each day, which is then hauled to ore
crushers where the extraction of bitumen begins. A number of
roads have been carved out of the wilderness to facilitate the
process, which has certainly impacted wildlife in the area. The
visible tailing pond may also leach pollutants into the nearby
Athabasca River, such as mercury and naphthenic acid, that
are harmful to fish and wildlife. In the places where bitumen at
depth is liquefied by steam, a tremendous amount of water from
the river is required in the process; estimates are that 2 to 4.5 m
3
of water is needed to produce 1 m
3
of oil. Yet another environ-
mental impact is related to the fact that extraction of bitumen
requires energy generated by burning natural gas. It is estimated
that mining these unconventional resources contributes 5% to
15% more carbon emissions into that atmosphere than conven-
tional mining operations. These higher carbon emissions make
future climate change more likely.
Several of the environmental problems associated with
fracking are similar to those observed in the Canadian oil
sands. For example, some have argued that the fracking process
releases greenhouse gases into the atmosphere in the form of
methane from equipment and from the well through leaks and
venting. Fracking also requires a lot of water. A typical well re-
quires 11,000 to 19,000 m
3
(3 to 5 million gallons) of water for
the initial injection and potential restimulation at a later date.
Such usage can be a problem for streams in semi-arid to arid
zones because it reduces discharge.
The primary environmental issue associated with frack-
ing revolves around the possibility of groundwater con-
tamination. As you can see in the geological layers shown
in Figure 20.29a, a stratum containing groundwater overlies
the oil-bearing shale below. This groundwater zone was pen-
etrated by the well as it proceeded through to the underly-
ing shale bed. Mining firms are required to line the well hole
with steel casing, which is cemented into place, to protect
groundwater layers from contamination by methane released
in the fracking process or the chemicals (such as sodium
chloride, ethylene glycol, borate salts) used to improve flow.
It is conceivable, however, that such casings can leak, caus-
ing groundwater contamination. Yet another way that ground-
water can theoretically be contaminated is by the release of
methane (or chemicals) from the fracked shale into an overly-
ing groundwater zone.
At this point, it seems safe to say that uncertainty pre-
vails with respect to the degree of groundwater contamination
caused by fracking. Environmentalists argue that the process is
woefully unsafe and that groundwater contamination is com-
mon. Unacceptable levels of methane and chemicals such as
arsenic, barium, and glycol compounds have certainly been
measured in some areas where fracking is commonplace. In a
similar vein, people living in and around places heavily fracked
have reported that water tastes odd and that their livestock have
become ill by drinking the local water. In 2011 the U.S. Envi-
ronmental Protection Agency reported for the first time that
groundwater contamination from fracking likely occurred in
Wyoming. The industry maintains, however, that the process
is safe and that pollutants can come from a number of places
unrelated to fracking. For example, the industry argues that
it is possible that personal water wells and municipal wells,
which may be less well designed than industrial systems, can
penetrate methane-rich deposits that contaminate groundwa-
ter. As a result of these conflicting points of view, states are
grappling with how to regulate the industry to ensure environ-
mental safety. Meanwhile, the growth of fracking operations
continues to grow at a frenetic pace.
This case study focused on an issue that is important
to everyone—oil resources. Given that our industrial soci-
ety currently depends so much on reliable oil supplies, it is
important to understand the factors involved in maintaining
them. As you can see, this issue is directly related to geology
