Fracking – a brief outline from a
climate change believer
Bruce Yardley
School of Earth & Environment, University of Leeds
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Do we need gas?
Is it a competitor to renewables or an essential complement?
What does fracking involve?
Does it contaminate water?
Does it cause earthquakes?
Does it result in methane emissions?
Does it use too much water?
What is the operational impact?
Will it reduce the price of energy?
Are opponents saving the planet or preserving their backyards?
Where does gas fit in the energy spectrum?
Gas is an important fuel in its own right, and is also used to generate
electricity.
We have 3 types of electricity supply:
Baseload supplies do not fluctuate and cannot reflect changes in demand
through the day (mainly nuclear)
Most renewable energy supplies fluctuate in an unpredictable manner
(wind) or in an unhelpful manner (solar)
Fossil fuel power stations can provide a supply to match demand, although
having to cope with large fluctuations reduces efficiency
As a result fossil fuels are an essential complement to renewables; we must
have enough spare capacity to cover for the absence of wind energy in
calm, cold weather
Gas produces significantly less CO2 than coal for the same energy output
Gas and coal could be decarbonised through CCS
Why Fracking Now? What’s New?
Why Fracking Now? What’s New?
Why Fracking Now? What’s New?
Fracking has been around for 60 years, applied to vertical wells in rocks
that were not very permeable.
Horizontal drilling technology IS new, especially the ability to steer the drill
along specific rock layers.
The price of gas is consistently much higher than it used to be, making it
worth extracting gas from more difficult reservoirs than in the past.
The overall result is that, by a combination of horizontal drilling and
fracking, gas can be extracted from rocks which previously held on to their
gas too tightly for extraction to be viable.
Whether this will be economic in the UK is not yet known.
How to Frack for Shale Gas
The shale gas reservoir must be deep – fracking does not work much less than about
2km because the stress regime in shallow rocks is wrong.
The vertical hole is cased and cemented in to isolate it from the surrounding rocks.
In the reservoir, the hole is deviated so that it runs horizontally through the shale.
Fracking itself involves pumping water under pressure into the shale to make it
fracture. A long horizontal well will be fractured in sections.
The fracking operation takes weeks to months at a single site, but wells will not need to
be fracked again for many years, if at all.
After fracking there is flowback of excess water, and this will be contaminated with the
deep natural groundwater.
The additives are basically detergent and sand with a bit of acid – sand grains lodge in
the fractures and prop them open.
On the left is a true scale image of a
well with fracking. In contrast pictures
like the one above make it look as
though fracking takes place very close
to aquifers that supply our water.
Does Fracking contaminate Groundwater?
What is the composition?
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Fracking fluid is water with additives, but water returning from depth (flowback) is
contaminated by the deep groundwater which is usually saline. This contains traces
of NORM (Naturally Occurring Radioactive Elements), notably potassium, which is
slightly radioactive, and can carry small amounts of radon. Fracking fluid is denser
than freshwater and so is not buoyant, however gas will rise spontaneously.
There are a series of ways in which fracking might contaminate groundwater.
• The fractures might propagate upwards and meet aquifers
• The drilling might intersect faults which could provide pathways for water to move
upwards and encounter aquifers
• The protective casings surrounding the hole where it passes through shallow rocks
might experience total failure
• Operators could spill contaminated water on site
The first 2 of these are unique to fracking but have NEVER been demonstrated.
Total casing failure allowing gas or fluid to leak is extremely rare (1 case from
2000 UK conventional wells). Most cases of contamination in the US are due to
surface spills.
Does Fracking cause Earthquakes?
Fracking causes microseismic event much too small to be detected by people,
but these can be monitored to show where the fractures are. Very rarely (less
than one in a thousand wells), fracking lubricates a fault plane which is under
stress and makes it fail earlier than would otherwise be the case.
Does Fracking cause Earthquakes?
Fracking causes microseismic event much too small to be detected by people,
but these can be monitored to show where the fractures are. Very rarely (less
than one in a thousand wells), fracking lubricates a fault plane which is under
stress and makes it fail earlier than would otherwise be the case.
Does Fracking cause Earthquakes?
Fracking causes microseismic event much too small to be detected by people,
but these can be monitored to show where the fractures are. Very rarely (less
than one in a thousand wells), fracking lubricates a fault plane which is under
stress and makes it fail earlier than would otherwise be the case.
Does Fracking Cause Methane Emissions?
Methane is a powerful greenhouse gas, and if fracking resulted in methane releases,
then this could counter the benefits of using gas rather than coal.
The isotopic composition of methane derived from depth is quite distinct from that of
methane produced by biological processes in soils, marshes etc. Methane derived from
depth will also have distinctive associated gases. On this basis, leakage of methane
from faulty wells can be detected, but is very rare.
There has been one study that reported apparently high emissions from a single site,
but many other studies that attempted to duplicate this result have failed to detect
significant emissions.
Maps of atmospheric methane concentrations over the USA over the past decade
appear to show a increase in methane in some areas where there is now fracking, but
other areas show no increase, while some areas with no fracking activity also record
increases. So the origin of the trends in the data is far from clear.
Does Fracking Cause Methane Emissions?
Methane is a powerful greenhouse gas, and if fracking resulted in methane releases,
then this could counter the benefits of using gas rather than coal.
The isotopic composition of methane derived from depth is quite distinct from that of
methane produced by biological processes in soils, marshes etc. Methane derived from
depth will also have distinctive associated gases. On this basis, leakage of methane
from faulty wells can be detected, but is very rare.
There has been one study that reported apparently high emissions from a single site,
but many other studies that attempted to duplicate this result have failed to detect
significant emissions.
Maps of atmospheric methane concentrations over the USA over the past decade
appear to show a increase in methane in some areas where there is now fracking, but
other areas show no increase, while some areas with no fracking activity also record
increases. So the origin of the trends in the data is far from clear.
How much Water does it take to Frack a Well?
In some parts of the USA, water resources are limited and there is a conflict between
water requirements for fracking and for agriculture.
Each fracking operation uses 10-30000 cubic metres of water (2-6 million gallons) and
takes around a week – this is a one-off demand. Water extraction is licenced by the
Environment Agency who also regulate treatment of flowback and produced water.
This is a tiny percentage of the amount of treated water lost to leaky pipes in the UK.
Water companies are legally required to maintain contingency plans in case of drought
and must assess demands before permitting use for fracking.
To date, one shale gas well has been fracked in the UK. The water was purchased from
the local water company (rather than abstracted under licence) and the flowback was
taken to a conventional licenced water treatment works.
What is the operational impact?
There are large numbers of oil and gas wells in the UK, but normally we never notice
them. However for fracking to go ahead, drilling platforms would have to be
constructed and there would be of months of activity, including truck movements. As
horizontal drilling gets better, the spacing between platforms will increase, but at the
moment it would be a few kilometres. Areas of shale gas production would have road
movements and quite possibly road building, and although relatively unobtrusive there
would be many drilling pads.
About 2000
hydrocarbon wells
have been drilled in
the UK. The first
producing oil well
was drilled in 1915 at
Tibshelf in
Derbyshire.
A series of 9 well heads with compressors and storage tanks near DallasFort Worth airport.
After the group of wells around a single pad are operational, there is very
little infrastructure remaining. Compressors pressurise the gas so that it
flows down a pipeline. Because of the very high energy content of natural
gas, the impact on the ground is tiny compared to wind farms.
A part of Scout Moor
wind farm above
Manchester. On a
windy day this
produces about the
same amount of
energy as the wells
above.
Will fracking reduce the price of energy?
Probably not by a lot – it is partly becoming viable because the price is high
Quite possibly it will turn out to be completely uneconomic over much of the UK
But until more wells are fracked and tested there is no way of knowing for sure
Some Questions
Are you happy to do without gas central heating/cooking and without electricity when
there is no wind?
Fracking is not fundamentally different from other methods of extracting gas by
drilling, so are opponents just reluctant to see the environmental impact of the
hydrocarbon industry, even though their lives depend on it?
Is it time to draw a line in the sand and insist on no more use of gas, even though the
next generation of technologies to provide heating and fill the renewables gap in
electricity production will not be ready for many years?
If we oppose fracking over issues which are unsupported by evidence, is there a risk
we will also oppose other technologies to reduce carbon emissions, such as carbon
capture and storage or the use of geological reservoirs to store energy from
renewables for times when the wind does not blow?