A controversial “fracking” technique to extract gas from the ground was the “highly probable” cause of earth tremors which hit Britain’s Fylde coast in Lancashire earlier this year, a report concluded today.
One tremor of magnitude 2.3 on the Richter scale hit the area on April 1st followed by a second of magnitude 1.4 on May 27th, prompting locals and environmental campaigners to blame the fracking technique being used locally by oil and gas firm Cuadrilla.
Fracking involves extracting gas reserves from underground by a process of hydraulic fracturing of shale rock using high pressure liquid to release gas - a process green groups claims is damaging the environment.
The firm commissioned a report by independent experts to investigate any links between the tremors and fracking work at their Preese Hall-1 well in Lancashire.
Today a summary published by the company said it is probable the fracking caused the tremors.
It said: “The report concludes that it is highly probable that the fracking at Preese Hall-1 well triggered the recorded seismic events.
“This was due to an unusual combination of factors including the specific geology of the well site, coupled with the pressure exerted by water injection.
“This combination of geological factors was rare and would be unlikely to occur together again at future well sites.
“If these factors were to combine again in the future, local geology limits seismic events to around magnitude 3 on the Richter scale as a worst-case scenario.”
The report said a “number of factors coincided to cause the seismic events”.
First, the gas well encountered a “pre-existing critically stressed fault” which “accepted large quantities of fluid”, and the fault was “brittle enough to fail seismically”.
The two tremors were “most likely” induced by “repeated direct injection of fluid into the same fault zone”, the report states.
But it goes on to say the probability of a repeat occurrence of a “fracture-induced seismic event” with similar magnitude is “very low”.
The report, titled Geo-mechanical Study Of Bowland Shale Seismicity, was commissioned by Cuadrilla Resources and carried out by a team of independent experts from across Europe, according to the company.
Fracking has also been blamed on spoiling water supplies by fluid used in the process seeping into underground waterways.
PA