Carbon Briefing: what does extracting shale gas mean for the local environment?
- 15 May 2013, 16:50
- Robin Webster
As the energy minister Michael Fallon encourages companies to
explore for shale gas, concerns remain that the extraction process
is safe. We asked at what so-called fracking will do to the local
environment, and what regulation is needed.
Several official reports - from Parliament's
Energy and Climate Change (ECC) Committee, the
International Energy Agency (IEA) and the
Department for Energy and Climate Change (DECC) appear to agree
that the local impacts of shale gas extraction are manageable.
And the government's now on the same page. In front of a
Parliamentary Committee today, new energy minister Michael Fallon
said the government is "creating the right framework to accelerate
shale gas development in a responsible way", adding that it is now
up to oil and gas companies to come forward with plans to explore
the country's shale gas potential.
Despite the reassurances, many communities are worried. Here's a
quick and dirty run down of the main issues, with a few of the
How to frack
Shale is a sedimentary rock formed from deposits of mud, silt,
clay and organic matter. It's very common. According to the British
Geological Survey, it makes up 35 per cent of the world's
surface rocks - but until recently it wasn't that easy to extract
gas from it. That's because shale gas is very fine-grained,
so the gas sticks to the rock.
Hydraulic fracturing involves pumping a fluid made of water
mixed with chemicals at high pressure into a well that has been
drilled. The fluid creates fractures in the rock, making it
possible to get the gas out. According to oil and gas company
Cuadrilla, the fracking process may take a couple of hours, and
be repeated several times over a period of weeks in order to create
In this country, initial fears focused on the possibility that
fracking could cause earthquakes. In 2011, exploratory fracking by
two earth tremors, measuring 2.3 and 1.5 on the Richter
But a subsequent study commissioned by DECC from the
Royal Academy of Engineering pointed out that the quakes are
unlikely to pose a threat. In comparison, coal mining has been
causing earthquakes for years - up to about 4 on the Richter scale.
"the magnitude of seismicity induced by
hydraulic fracturing would be not greater than 3ML [on the Richter
scale]...felt by few people and resulting in negligible, of any,
A more recent study
from the Durham Energy Institute published in April agrees,
concluding that fracking causes earthquakes - but not
Pollution of drinking water
In its 2011 report '
Are we entering a golden age of gas?', the IEA illustrated some
of the key environmental concerns connected to shale gas
In any circumstances, drilling for gas is a risky process -
opening the possibility of accidental spills and water
contamination. Particular concerns have been raised about fracking,
- the chemical additives used in the process could leak into
groundwater underground; or alternatively by accidentally spilling
on the surface;
- the gas itself could leak into drinking water. The campaign
highlighted this possibility.
The reports are pretty dismissive of the possibility that
groundwater leakage could occur, because the gas is usually
situated far below the water table. The IEA says:
"For example the deepest potential
underground sources of drinking water in the Barnett shale [in
Texas] are at a depth of 350 metres, whereas the shale layer is at
2000 to 2300 meters".
There appears to be
some evidence that leakage of gas into drinking water has
taken place in the USA - although this is
contested - and research led by Durham's Energy Institute
indicates that the risk is extremely
low. DECC told the
ECC committee that this was "incompetent" operators'
fault, and would not happen in the UK.
Davies from Durham recently told BBC News that worries
about the fracking process are a distraction and that cracks in the
well or accidental surface spills are far more significant risks.
This means that well design - keeping it intact and safe over a
possible thirty year lifespan - is an
important part of regulation.
Water use and storage of wastewater
The process of opening up the rock by fracking uses a lot of
water. According to the IEA, each well might require anything from
a few thousand to 20 million litres of water. The Tyndall Centre
for climate change research has calculated the figure at
nine to 29 million litres per well.
It may be possible to
recycle the water, reducing the amount needed. The ECC
committee concludes, "there is only a small risk that the large
volumes of water required for hydraulic fracturing will place undue
stress on the water supply" - but that the risk could be more
significant during times of drought.
After it's been used for fracking, the wastewater - now
contaminated by chemicals, hydrocarbons and naturally occurring
radioactive material - must either be cleaned up or
stored safely. The
IEA says the technology exists to treat the water
appropriately, or to store it, depending on location.
Disruption - noise and number of wells
The disruption and industrialisation of rural areas associated
with shale gas extraction may in the end prompt more
objections to fracking than any other factor.
In a blog post, Michael Liebreich from
Bloomberg New Energy Finance calculates that, in the
hypothetical situation where the decline in
North Sea gas is replaced entirely with UK-produced shale gas
up to 2030, the country would need to construct 2,500 new
Drilling the well in the first place is the most intensive - and
disruptive - part of the process. According to the IEA it could
involve "between 100 and 200 truck movements to deliver all the
equipment" - and once it starts, will operate for 24 hours a
But the extracting the gas is by far the longest part of the
process and may go on for up to thirty years. During this time, the
well is less visually intrusive - it uses what the IEA calls a
"Christmas tree" of valves, typically about one metre high, sitting
on top of the well.
Regulation, regulation, regulation
Two years ago the
ECC Committee concluded that there is "nothing inherently
dangerous" about fracking, provided there is a robust regulatory
regime. Reports by the IEA and Institute of Mechanical Engineers
agree that it can be done - so long as laws are put in place to
make it happen safely.
Since then, the government has
lifted a temporary moratorium on fracking. Despite concern from
government advisers the
Committee on Climate Change that expanding a domestic gas
industry will undermine the UK's carbon targets, the chancellor
George Osborne appears strongly supportive of the technology and
tax breaks to encourage its development.
As UK fracking moves from theoretical debate in the media and
between politicians to drilling on the ground, it will become
clearer whether the government's regulatory regime can keep shale
gas drilling safe.