UK’s complex geology will pose fracking challenges, developers warned
New underground maps show shale gas deposits overlapping with major drinking water aquifers
The UK’s complex geology will pose challenges for fracking companies wanting to avoid water contamination in some parts of the country, according to the British Geological Survey (BGS).
New maps of underground Britain released by BGS and the Environment Agency show that almost half the area of England and Wales where major drinking water aquifers are located have shale gas deposits below them.
However, the maps also suggest that the vertical distance between the water and the gas is sometimes several kilometres, making water pollution very unlikely.
According to the BGS, the main drinking water aquifers are present across more than 80% of England and Wales, while shales and clays that have the potential for shale gas and oil cover 51% of England and Wales. Areas where the two overlap cover nearly 30% of the total area and are likely to be where development will be most strongly opposed.
The distance between the shale rocks and the water supplies will be critical considerations for the Environment Agency, which will have to assess the likelihood of contamination before giving companies permission to inject chemicals under high pressure to fracture the shale and release gas.
The Bowland shale rock formation in Lancashire, one of the main targets for fracking companies, is nearly 800m below the drinking water aquifer and the chalk aquifer of the South Downs is at least 650m below the uppermost shale oil rocks.
But, says the BGS, in some areas the water and the gas may be much closer. “Even in one region it can vary considerably,” said John Bloomfield, a hydrogeologist with the BGS.
“UK geology is particularly complex. There is enormous diversity on a small island. It’s very different to other places where shale gas has been developed. In the US a lot of the shale is highly continuous; here it is concentrated into tight basins. This offers challenges [in terms of avoiding water contamination] to putative developers,” he said.
Around 27% of the UK population – including London and much of south-east England– gets its drinking water from underground supplies. In the north and west, water supplies come predominantly from surface water.
The BGS also released data showing naturally occurring methane concentrations in UK groundwater. Because methane is many times more powerful as a climate changing gas than carbon dioxide, concerns have been raised about how much could potentially leak in the fracking process, compromising national commitments to reduce emissions.
Concentrations ranged from the practically negligible in southern England to very high in some parts of Lancashire and Cumbria. But, said Bloomfield, the high figures all related to known former landfill sites and other industrial deposits of the gas. “The natural environment is facing many pressures. There was nothing unexpected in the data,” he said.
The data will be used as a reference point by the Environment Agency against which any future changes in groundwater methane concentrations can be measured, he said.