Shale gas risks and rewards need to be balanced says BGS chief scientist

Professor Michael Stephenson is chief scientist at the British Geological Survey. This month he published his book "Shale gas and fracking: The science behind the controversy". Bernadette Ballantyne asked him to outline the key findings.

Bernadette Ballantyne
12 March 2015

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"Much of the discussion surrounding shale gas and hydraulic fracturing is a combustible mixture of fact and conjecture, with agendas thinly disguised on the side that wants to exploit shale and those that want to stop it at all costs. I wanted to try to get to the bottom of this argument and to the shale itself, examining its geology and its potential, if indeed it has any outside the US.

"Recent work from shale gas drilling sites suggests that the leakage rate is about half of one percent of gas production but precise leakage rates are unknown outside the United States. Earthquakes relating directly to fracking are extremely rare but those that relate to deep geological disposal of frack fluid and other produced water appear to be on the increase."

What I found was that there are risks and rewards to be had from a shale gas industry and that regulation is the key to balancing the two. This is perhaps one of the most important lessons coming from the US where research shows that in the 31 states that conduct hydraulic fracturing, the regulations vary extensively.

For those that don’t know, shale is a fine grained dark coloured sedimentary rock that is actually very common. Geologists always knew that it contained gas and oil in microscopic pores between the particles but weren’t sure how to get them out - until hydraulic fracturing came along.

But hydraulic fracturing has raised concerns over degradation of the environment: groundwater contamination by stray methane, uncontrolled emissions of methane to the atmosphere (fugitive emissions), and earthquakes directly or indirectly related to hydraulic fracturing.

Perhaps the area that has caused most concern has been the first. At least two peer-reviewed papers representing studies of groundwater in Pennsylvania close to hydraulic fracturing of shale have reported contamination of shallow water wells (Osborn et al., 2011; Jackson et al. 2013), probably due to poorly sealed wells rather than directly due to fracking.

Methane emissions from the surface installations of shale gas wells are also cause for concern since very high emissions would cast doubt on the claims that shale gas could be a low carbon fuel, for example in comparison with coal.

Recent work from shale gas drilling sites suggests that the leakage rate is about half of one percent of gas production but precise leakage rates are unknown outside the United States. Earthquakes relating directly to fracking are extremely rare but those that relate to deep geological disposal of frack fluid and other produced water appear to be on the increase.

In the US gas extraction is sometimes referred to as the shale gas factory. Not only is shale gas unlike conventional natural gas geologically in that you have to frack to get it out, but its systematic extraction is different also. To get the gas out and make money, the companies drill across swathes of land dividing it into a grid, and advancing across the grid hoping to maintain their rates of production.

A single well might drain a square mile of shale of its gas, but the next square mile will need to be drained too.  One of the issues of this very intense development is noise and truck traffic which can be very significant, though it’s unlikely that this kind of dense development would be permitted in Britain.

There is no doubt lots of shale in Britain but no one knows at the moment whether a commercial business could be developed here. Britain is a densely populated country, unlike the places were shale gas was proved in the wide open spaces of Texas. We’ll have to wait and see.

"Shale gas and fracking: The science behind the controversy" was published this month and is available from Elsevier