Geopolitics - the clay content of LibDem shales

Given its importance to so much of our everyday lives, geology should be taught to as many people as possible, especially those who might make major political decisions. Sadly, it isn't and current evidence suggests the UK has no intention of remedying this.

A clear example of the problems a lack of geological understanding create is in the controversial topic of shale gas. As fracking stories hit the news on a daily basis, so politicians make variously bold claims about its pitfalls or potentials. Very few use a geological understanding to support their stance.

A global map of major shale basins (from Wikipedia)

It was interesting, therefore, to see this article in the Observer recently. It described a new Liberal Democrat policy document on the topic of 'green growth'. Most of the article's claims about the environmental impacts of shale gas weren't new, but there was one section that caught my eye:

"UK geology is much less favourable than that of the US...[because] the shale contains a much higher proportion of clay, rendering hydraulic fracturing, or 'fracking', techniques, much less viable"

I was amazed. It was great to see sedimentology - the sub-discipline of geology that deals with how sedimentary rocks, such as shale, are formed - making an appearance in this way, but how did the Lib Dems know so much about the clay content of British shales?

How much clay is in this British shale? Answers on a postcard to Nick Clegg please.

To find out more, I consulted the policy papers. There it was in black and white, in section 4.4.3: the UK had 'no realistic prospect' of a shale gas revolution, it claimed, because the shale contained too much clay.

No references were cited, and mention of 'the shale' didn't fill me with confidence. If there's one thing I can tell you about shale, British or otherwise, it's that it is definitely not singular. There are Cambrian shales and Carboniferous shales and Jurassic shales and they are not the same.

I then conducted a quick search for papers on UK shale clay content that the LibDems might have consulted. The most likely source I could find was the DECC paper on UK onshore shale gas prospects, first published in 2011.

That report states that, based on evidence from the USA, one of the criteria for a successful shale gas play is a low percentage of clay minerals. This is in reference to the Barnett Shale, Texas, which as a clay content of around 27%. The report then gives an example of one locality in the UK where shales of a similar age have a clay content of between 56 and 59%.

I don't know if this is the data that the LibDems were relying on, but there aren't many other papers out there that mention the subject.

Why does clay content matter? Well, if you're going to fracture a shale hydraulically to release gas trapped within, you want it to behave brittly. Since clay minerals are ductile (bendy, if you like), shales that contain a lot of clays will not behave brittly. This is the correlation made in the policy document. UK shales cannot be viably fractured by hydraulic stimulation, it argues, because they contain too much clay.

Too much clay.

In principle, this might be true, but there are a number of issues with the claim:

1. No other clay data were presented for UK shales. The clay content of shales of one age from one place isn't much to base an all-encompassing statement on.

2. Within a single shale unit, there can be plenty of variability in the types and quantities of clay present. Good data on this is lacking for many of the UK's possible gas shales.

3. Comparisons with the Barnett Shale may not be very informative. The DECC report notes that its 'low clay content is not typical for many other shale gas plays in the USA'. If they have more clay, but can still be fractured for shale gas, why wouldn't the same be true for shales in the UK?

4. It is not even clear if clay content always correlates well with 'frackability'. I have seen shale successions in which ductile deformation seems to occur in quite clay-poor intervals, and brittle deformation in some with higher clay content. Geochemically inclined colleagues advise me that many other factors (e.g. the amount of organic matter, the presence of other minerals, its salt content) are involved in affecting how a shale breaks.

So, although I am pleased to see our politicians recognizing the importance of geology to critical matters such as Britain's energy future, I do feel that they need to understand the science before using it to make policy decisions. If they don't, boldly erroneous statements may ensue.

Perhaps, if they wanted to make a bigger impact, the LibDems could start petitioning to have geology taught properly in schools?

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