Presentation is loading. Please wait.

Presentation is loading. Please wait.

Fracking – a brief outline from a climate change believer Bruce Yardley School of Earth & Environment, University of Leeds Do we need gas? Is it a competitor.

Similar presentations


Presentation on theme: "Fracking – a brief outline from a climate change believer Bruce Yardley School of Earth & Environment, University of Leeds Do we need gas? Is it a competitor."— Presentation transcript:

1 Fracking – a brief outline from a climate change believer Bruce Yardley School of Earth & Environment, University of Leeds 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?

2 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 CO 2 than coal for the same energy output Gas and coal could be decarbonised through CCS

3 Why Fracking Now? What’s New?

4

5 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.

6 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.

7 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.

8 Does Fracking contaminate Groundwater? What is the composition? 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.

9

10 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.

11 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.

12 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.

13 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.

14 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.

15 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 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.

16 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.

17 About 2000 hydrocarbon wells have been drilled in the UK. The first producing oil well was drilled in 1915 at Tibshelf in Derbyshire.

18 A series of 9 well heads with compressors and storage tanks near Dallas- Fort 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.

19 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.

20 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

21 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?


Download ppt "Fracking – a brief outline from a climate change believer Bruce Yardley School of Earth & Environment, University of Leeds Do we need gas? Is it a competitor."

Similar presentations


Ads by Google