Posted on behalf of Leila Haghighat.
A report published today by the UK Department of Energy and Climate Change (DECC) says that hydraulic fracturing, or fracking, should continue in the country, despite the minor earthquakes it may cause. The report gives recommendations for mitigating the risks of such earthquakes and invites the public to share their comments.
The report arrives at similar conclusions to one published last November by the UK energy company Cuadrilla, but provides stricter recommendations for future fracking procedures.
Both investigations were prompted by earthquakes in April and May 2011, of magnitude 2.3 and 1.5, respectively, near one of Cuadrilla’s shale fracking wells in Lancashire, UK. Fracking taps natural-gas reserves by pumping several million litres of fluid beneath the Earth’s surface, fracturing the rock and creating channels for trapped gas to flow into the well.
The independent consultants who authored today’s report advise the DECC to inject a smaller volume of fluid into the shale rock and allow it to flow back to relieve pressure during preliminary tests. They also suggest monitoring seismic activity in as close to real-time as current technology allows and using a ‘traffic-light’ system to determine when operations should be stopped.
The report recommends halting fracking following an earthquake of local magnitude 0.5 or greater. Cuadrilla proposed a threshold of 1.7.
The lower limit is a sensible choice, says geologist Stuart Haszeldine at the University of Edinburgh, UK. “Even if an earthquake 200 times larger occurs, of 3.0, the effects at surface will just make the pictures rattle on the wall in your living room.”
The new report’s authors caution that their recommendation is based only on data from Cuadrilla’s Preese Hall well. This threshold needs to be refined as more data become available, and optimized for each fracking site. “No two shale planes are the same,” said seismologist Christopher Green, director of Wigan-based consultancy G Frac Technologies and one of the report’s three authors, at a press briefing in London today.
Cuadrilla’s report attributed last year’s earthquakes to an “unusual combination of factors” that are “unlikely to occur together again”. The authors of the DECC report conclude that earthquakes will recur, but will pose minimal risks.
Peter Styles, a geophysicist at Keele University in Newcastle, UK, and a co-author of the report, said the different layers of the Earth’s surface get less pliable towards the core and more dangerous if perturbed by seismic activity. But, he said, current technologies are incapable of triggering an earthquake at a depth that would pose danger at the surface.
The DECC is accepting comments on the report for the next six weeks. It will take these into consideration before making any decision on the future of fracking for shale gas.