14-1190b-innovation-managing-risk-evidence

THE SCIENCE AND ENGINEERING PERSPECTIVE
Robert Mair (University of Cambridge)
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In 2012, the Royal Society (RS) and the Royal Academy of
Engineering (RAEng) published a joint report — Shale gas
extraction in the UK: a review of hydraulic fracturing 1 — that
had been commissioned by the UK government.
The report independently reviewed the scientific and
engineering evidence associated with hydraulic fracturing
(often termed ‘fracking’). The report addressed two key
questions in connection with fracking: (i) what are the
risks of earthquakes? (ii) what are the environmental
risks, particularly in relation to possible groundwater
contamination? It concluded that these risks can be managed
effectively in the United Kingdom so long as operational best
practices are implemented and enforced through effective
regulation. The report’s principal conclusions regarding these
risks can be summarized as follows.
Fracking is unlikely to contaminate drinking water. The
available evidence shows that fractures can be constrained
within shale formations effectively. To reach overlying
freshwater aquifers, the fractures in the shale would have to
propagate upwards towards the surface for many hundreds
of metres. The risk of this happening is very low, provided
that fracking takes place at great depths (operations are
typically at depths of several kilometres).
But it is important not to conflate fracking itself with shalegas
well operations. Groundwater contamination is much less
likely to be due to the fracking process than to faulty well
construction. The only realistic way that any contamination of
groundwater may occur is if operations are poorly regulated
and faulty wells are constructed as a result — consequently,
the bigger risk to drinking water would be leakage from a
faulty well. The report therefore recommended that well
integrity should be a top priority if the risk of contamination
is to be kept to an absolute minimum.
All wells are lined with steel casing, which is sealed into
the ground by cement. If wells are properly constructed,
sealed and managed, the risk of contamination is very low.
Also, the Environment Agency does not currently permit any
hydraulic fracturing near freshwater aquifers based on a risk
assessment, taking into account the geology and depth at
which fracking is proposed at the particular site.
The other main potential causes of environmental
contamination are poor site construction, or control
measures at the surface that include treatment and disposal
of wastewaters. However, any risks can again be minimized
by best practice and good regulation, which the United
Kingdom has a good track record of upholding.
The report also recommended that robust monitoring of
groundwater should be conducted across the entire shale
gas lifecycle: before, during and after operations. This is an
important lesson to learn from the US shale gas experience:
it has proved difficult to verify allegations of water
contamination caused by fracking in the United States due to
a lack of baseline monitoring.
Earth tremors resulting from fracking are smaller than
those caused by coal mining, and in this context ‘earth
tremor’ is a much more appropriate term than ‘earthquake’.
There are thousands of seismic events in the United
Kingdom every year — those with a Richter magnitude
of 1–2 are rarely felt. There are around 25 per year with
magnitude 2 and about three per year at magnitude 3.
Fracking can cause earth tremors, but these are likely to be
small because shale is weaker than other rocks and yields
before larger seismic events can occur.
The United Kingdom has a history of induced seismicity
from coal mining and the settlement of abandoned coal
mines (up to magnitude 4). British Geological Survey records
indicate that this mining-related seismicity is of smaller
magnitude than natural seismicity; any seismicity induced
by hydraulic fracturing is likely to be smaller still. To put
fracking-related earth tremors in context, the two induced
by hydraulic fracturing near Blackpool in 2011 had a Richter
magnitude of 2.3 and 1.5. The RS/RAEng report concluded
that these two minor earth tremors were due to the
reactivation of a pre-stressed existing fault, and that it was
very unlikely that future earth tremors caused by fracking
would ever exceed magnitude 3 – and the effects felt would
be no worse than a passing lorry. In other words, the risk of
earth tremors of any real significance is very low.
The RS/RAEng report concluded that UK fracking and
shale gas extraction can be adequately controlled with its
existing strong regulatory system, combined with 60 years’
experience of regulating onshore and offshore oil and gas
industries. Fracking is an established technology that has
been used in the oil and gas industries for many decades, and
the United Kingdom has considerable experience of fracking
and horizontal drilling for non-shale gas applications. Over
the past 30 years, more than 2,000 wells have been drilled
onshore in the United Kingdom, approximately 200 of which
have been fracked. There is nevertheless a need to ensure
that the UK regulatory system is constantly reviewed and
fit for purpose if shale gas extraction is to continue in this
country with acceptably low risks.
Fracking can be done safely in the United Kingdom, but
not without effective regulation, careful management, robust
environmental risk assessments and rigorous monitoring. It
is also essential to build public confidence: local communities
need to be involved and well informed, and to feel that their
concerns are being fully addressed.
Fracking is unlikely to
contaminate drinking water.