A mining geologist has called for the suspension of fracking for gas in the main shale areas of northern England because he says the rocks contain high concentrations of toxic heavy metals.

Robin Grayson has written a paper, posted on the website, researchgate.net, about the presence of selenium, arsenic, cadmium and thallium in the Bowland shale.

Cuadrilla, which fracked the Bowland shale at its Preston New Road site near Blackpool before Christmas, said it had been testing for selenium, which was absent or at trace levels. “It was both unhelpful and misleading to local people to suggest otherwise”, a company spokesperson said. (Full statement at the end of this piece)

The Bowland shale is found either side of the Pennines, in parts of Lancashire, Yorkshire, Nottinghamshire and Derbyshire and is the main area licensed by the government for shale gas exploration.

As well as Preston New Road, companies have plans to explore the Bowland shale at Misson Springs in Nottinghamshire, Harthill in south Yorkshire and Bramleymoor Lane in Derbyshire. IGas’s Tinker Lane well, drilled in November 2018, was also looking for the formation but failed to find it.

Mr Grayson said other researchers have reported high levels of selenium in the Bowland shale at the surface, about 11 miles from Preston New Road. It has also been found near Pendle Hill, Walley and Earby in Lancashire and at Edale in Derbyshire, he said.

“It is now realised that the Bowland Shale has remarkably high toxic levels of selenium, everywhere its outcrops have been tested in NW England, Wales, Isle of Man and Ireland. No exceptions.”

He said selenium, while a vital nutrient in tiny quantities, is very toxic in high concentrations. He called for independent tests for selenium and the other heavy metals on rock cuttings taken from several wells drilled recently. These include Cuadrilla’s Lancashire sites at Becconsall, Preston New Road and Preese Hall and the boreholes drilled at Ellesmere Port in Cheshire and Irlam (Barton Moss) in Salford.

He said:

“Until then fracking by Cuadrilla and acidisation by IGas should be suspended with immediate effect. “If, as I suspect, selenium levels in the boreholes are extremely toxic, then the PEDLs [Petroleum Exploration and Development Licences] should be restricted to coalbed methane from the Upper, Middle and Lower Coal Measures.”

He added that flowback waters from the Preston New Road wells should be classed as “highly toxic waste” until proved otherwise.

The paper also warned about the risk of shale gas wells encountering the poisonous and flammable gas, hydrogen sulphide (H2S), known as sour gas.

“Factual evidence shows the risk of encountering H2S is substantial, which is bad news for investors and for the health and safety of local communities, as well as for the workers.”

He said the risk arose from two different sources in the Bowland shale.

Anhydrite rock (calcium sulphate) below the formation – identified in boreholes in the Bowland basin – could produce sulphate waters in huge amounts, he said. If this came into contact with hydrocarbons then hydrogen sulphide could be produced.

He also quoted examples of unconventional shale wells in Texas producing sour gas because of the use of guar gum in fracking. He suggested that guar gum encouraged the growth of anaerobic bacteria, which generated hydrogen sulphide. This may be slowed, but not eliminated, by the use of biocides, he suggested.

DrillOrDrop put Mr Grayson’s concerns to Cuadrilla. A spokesperson for the company said:

“During our operations at Preston New Road we have carried out extensive core sampling, providing us with a unique dataset of the Bowland Shale. “Through this continuous observation we have established that the natural gas in the shale rock contains no hydrogen sulphide, as we would expect in this geology. “We have also been testing for other elements, including selenium, which has been absent or at trace level, with the results independently inspected by the regulator. It is both unhelpful and misleading to local people to suggest otherwise.”

Updated with a comment from Cuadrilla