Rock breaking research offers insight into fracking

In a ground breaking discovery, geologists have discovered what else escapes from fractured shale other than methane.

The finding, published in Environmental Science and Technology could have important implications for fracking, as other hydrocarbons of commercial interest may now also be extracted from shale.

Samples from the Bowland- Hodder formation in Lancashire, England, revealed a wide range of Non-Methane Hydrocarbons (NMHC) – including alkanes, cycloalkanes, aromatics and bicyclic hydrocarbons – are also released during the fracking process.

“What we have done is to study how hydrocarbons are released from shale when it is crushed,” Roberto Sommariva from the University of Leicester told Laboratory News. “We wanted to understand the mode of release, rather than quantify the total amount of gas in the rock (in the paper there is an estimate of gas released per gram of crushed shale, but it comes with several caveats).”

The samples were analysed under different conditions of temperature, fracking and humidity, with mass spectrometry providing an understanding of the dynamic processes of gas release upon fracturing shale.

“We found that the release rate when the shale is crushed occurs on two timescales – "fast" and "slow", which we think depends on how the gas is stored inside the rock – and is controlled by several parameters, like temperature and humidity, as well as the extent of fracturing of the rock,” said Sommariva.

“Our results indicate that higher energy inputs (i.e. temperatures) significantly increase the amount of NMHC released from shale, while humidity tends to suppress it; additionally, a large fraction of the gas is released within the first hour after the shale has been fractured,” said Professor Paul Monks.

“These findings suggest that other hydrocarbons of commercial interest may be extracted from shale and open the possibility to optimise the ‘fracking’ process, improving gas yields and reducing environmental impacts.”

Professor Mike Stephenson, Director of Science and Technology at the British Geological Survey said: “These results show that it might be possible to influence the outcome of fracking to improve the amount of gas we get and the kind of gas. Gases like ethane are useful in industrial manufacturing, beyond their use for energy.”

“With more detailed information on how different gases are stored, how they are released when the rock is fractured and which parameters control these processes it might be possible to tweak the fracking process, reducing the environmental impact and/or increasing its efficiency,” Sommavaria added.

Observations of the Release of Non-methane Hydrocarbons from Fractured Shale