Drilling has been suspended at the UK's first shale gas extraction site following two local earthquakes since operations began in March.
Shale gas exploration firm Cuadrilla, which runs the Preese Hall test site near Blackpool, has confirmed work has been halted while it examines information on the 1.5 magnitude tremor felt in the early hours of Friday morning (27 May 2011).
Drilling for shale gas involves hydraulic fracturing, or “fracking”, which forces millions of gallons of water, sand and chemicals into shale, opening fractures and releasing gas trapped in the rock.
In a report following a similar tremor on 1 April, the British Geological Survey (BGS) concluded it couldn’t confirm conclusively that fracking had caused the earthquake but argued that it was “well known that injection of water or other fluids during the oil extraction and geothermal engineering processes can result in earthquake activity.”
Dr Brian Baptie, head of seismology at the BGS, told the BBC that available data indicated the earthquakes were of a similar type and in close proximity.
Announcing the halt in work, Mark Miller, CEO of Cuadrilla Resources, said: “We take our responsibilities very seriously and that is why we have stopped fracking operations to share information and consult with the relevant authorities and other experts.”
“We expect that this analysis and subsequent consultation will take a number of weeks to conclude and we will decide on appropriate actions after that.”
The second tremor came less than a week after the UK’s Energy Select Committee refused environment groups’ request for a moratorium on shale gas in the UK.
The committee had investigated threat of groundwater pollution from fracking, after a number of high-profile cases in the US, and concluded there was no evidence it posed a direct risk to underground water supplies. It did not, however, investigate the possibility of increased seismic activity.
Shale gas has also been the subject of debate as to the amount of carbon dioxide it releases into the atmosphere, with one group of researchers claiming it has a larger carbon footprint than coal.
