Is Shale Gas a realistic fossil fuel resource that can be used to help bridge the changeover gap from fossil fuels to renewable technology or are the risks associated with it too great?
What is Shale Gas?
Shale gas is a fossil fuel that is found in gas deposits that have formed over millions of years in tightly bound shale rock formations [1]. It is formed from sedimentary deposits, consisting of clays and silts (formed by the erosion and weathering of rocks), which become compacted [1]. Layers after layers form of these deposits and they eventually break down to form oil or gas [1]. A lot of the oil and gas can migrate if the layers are not too compacted but if they are then shale has formed in tiny pore spaces and the deposits cannot migrate away [1]. This source of gas is known as an unconventional reservoir as it is much harder to access [1]. Some of the largest gas deposits in the world are these kinds of deposits; hence there is great interest within the gas drilling industry at the prospect of being able to extract them.
It was in the 1990s that companies started to develop the technology of fracking, which is used to extract shale gas [1].
Fracking
Fracking is the technology whereby fractures are created in the shale rock to give access to deposits. After drilling vertically down to the deposits, the drill pipe curves into a horizontal position and it continues to drill [1]. This process creates a horizontal well through the shale band [1]. Controlled explosions are then used to open up fractures in the rock [1]. A mixture of water, sand and chemicals are then pumped under high pressure to open up the fractures – this is the actual fracking process – and the gas can be returned to the surface by flowing through the pipe [1].
Although this type of technology has only been developed relatively recently it has led to what has been dubbed the “new gold rush” in America [1]. It has meant that areas that had never been associated with gas drilling have become inundated with drilling sites across the United States, including New York State, Pennsylvania and Arkansas [1].
Uptake has been slower in the UK, but the company Cuadrilla Resources has developed a site near Blackpool and started drilling on 29th March this year [1].
Hazards
While some argue that shale gas is an important find, as gas is much less environmentally harmful than coal and it could help us bridge the gap while transferring to a low carbon economy, there are serious concerns over the process.
One of the main concerns is water pollution and an increase in methane concentration in water around shale gas drilling sites. Both the vertical and horizontal wells have to be lined with alternate layers of sheathing and cement. If these are not completed correctly there is a danger that chemicals that are pumped under high pressure escape [2]. If methane leaks, the dangers are that it could lead to fires or explosions [2]. In 2010, Dimock in Pennsylvania reported water pollution problems in an aquifer that local people used for fresh water [2]. Many people became ill and a water well exploded, with others indicating dangerous levels of methane [2].
Production of gases such as methane, which is a potent greenhouse gas, is not the only concern. The waste water, which is a result of the water that is pumped in under high pressure, has to be dealt with. Some is recycled but most of it has to go to waste water treatment works [1]. There is also a risk that the waste water can contaminate surrounding land and agriculture [2].
Current developments in the UK
There is currently only one shale gas drilling site in the UK, near Blackpool in Lancashire. However, operations were suspended in May following an earthquake measuring 1.5 on the Richter scale [3]. Earlier in the month a quake measuring 2.3 magnitude was recorded by the British Geological Survey (BGS) [3]. There is no definite evidence that the drilling is directly related to the earthquakes, but operations have been halted and the BGS state that, “Any process that injects pressurised water into rocks at depth will cause the rock to fracture and possibly produce earthquakes” [3].
Therefore, it is clear that while there are plenty of deposits of shale gas around the world, enough to be called the “New Gold Rush” [1], there is still a lot of uncertainty surrounding the technology. The transition to a low carbon economy is not going to be easy and shale gas may provide a reasonable and feasible way to ease into that transition, but with such uncertainty there is a risk we are going to create even greater environmental concerns for ourselves.
References
[1] The Environmentalist (May 2011). Institute of Environmental Management and Assessment, Lexis Nexis,
[2] The Guardian (2011) [Online]. Available from http://www.guardian.co.uk/environment/2011/apr/20/shale-gas-fracking-question-answer
[3] The Times (2011) [Online]. Available from http://www.thetimes.co.uk/tto/news/
