Environmental Engineering Reference
In-Depth Information
2.2.2 Environmental Issues. There are a number of environmental con-
cerns, both real and imaginary, relating to the exploitation of shale gas in
the UK, which, due to the fact that we live on a relatively small island
which is heavily populated, means that the development of shale gas is in-
variably going to impact one community or another.
This could be in the exploration and production phase of the work or in
the need to lay gas pipelines to access the existing gas distribution network.
It is these issues and how the shale gas industry and the Government ad-
dress them that will play a key role in allaying public concerns and con-
vincing the public that the resources can be developed in a safe and ecient
manner.
2.2.2.1 Hydraulic Fracturing can have Adverse Effects on Drinking Water
Vertical drilling is a well-established practice that has been carried out over
many years and millions of wells have been drilled through aquifers with no
significant issues. Drinking water aquifers are normally at depths of 300 m
or less while the natural-gas-producing shale formations are typically at
3000-4000 m. Wells have metal casings between the rock and the bore,
which extend well below the levels of the aquifers, and the gaps between the
rock and the casings are filled with cement. The design of the casings is
required to take account of the geology of the site and any fluids within them
and, if necessary, there can be multiple casings extending below the drink-
ing water aquifers to reduce the possibility of contamination. In the ex-
tremely rare cases where groundwater has been contaminated it was found
to be as a result of faulty well casing installations.
There are a number of precautions that can be taken to minimise the risk
to groundwater, in addition to the design and construction of the well. These
include monitoring the water quality before and during the operation,
having a quality assurance programme to ensure that the equipment and
materials are to the correct specification and maintaining close supervision
while the work is carried out. A minimum well depth can also be set to
ensure adequate separation of the aquifer and the shale to be hydraulically
fractured.
2.2.2.2 Water Volumes used for Hydraulic Fracturing
Concerns have been raised at the large quantities of water that are used in
the process of hydraulic fracturing, particularly in areas such as the South
East of England where the existing water infrastructure is under stress. The
volumes required for hydraulically fracturing a single well are in the region
of 10-20 million litres of water, depending on well depth, length and geol-
ogy. For a typical drill pad consisting of 10 wells, this will require 100-200
million litres of water per pad. In reality, compared to the daily usage of
water in the UK of 15 000 million litres per day,
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this represents a relatively
small volume. Sourcing and use of water is heavily regulated and therefore
the amount that can be abstracted at any time will be closely monitored and
