Fracking Likely Cause of UK Cuadrilla Well Tremors

Researchers investigating surface-level tremors felt at a well site in the United Kingdom in April and May confirmed Tuesday fracking likely caused the seismic events.

The Geomechanical Study of Bowland Shale Seismicity concluded that it was "highly probable that the fracking at [Cuadrilla Resources'] Preese Hall-1 well triggered the recorded seismic events." Researches suspect the well site's specific geology at the time along with pressure exerted by water injection caused the tremors but believe this was a rare event that is not likely to occur again at future well sites.

Staffordshire-based Cuadrilla pledged to implement an early-warning system and other recommendations from the study to mitigate the risk, but said the report vindicated its stance that its operations pose "no threat to people or property in the local area." Cuadrilla in September announced a big shale gas discovery, but development is now on hold after the company and government agreed in June to stop fracking until its potential consequences were better understood.

The study reported the following findings and proposed recommendations:

  • The cause of seismicity included a pre-existing critically stressed fault that was susceptible to accepting large quantities of fluid; the fault was brittle enough to fail seismically; and the repeated seismicity was most likely induced by repeated direct injection of fluid into the same fault zone.
  • It is unlikely another well in the Bowland basin will encounter a similar fault with the same critical stresses and high permeability; however, in the event another seismic event happens, the maximum magnitude is not likely to exceed a magnitude of 3 on the Richter scale.
  • Experts believe an impermeable formation of rock above the Bowland shale acts as a confinement layer between ground water aquifers (about 300m deep) and the fracking zone (about 3km deep), which greatly limits the potential for fracking fluid to escape.
  • Seismic hazards related to a fault slippage would not present a risk to personal safety or damage at the surface level
  • If an early detection systems shows signs of a magnitude-1.7 tremor or higher, immediately stop water injection and release pressure by withdrawing fluid from the well to reduce pressure.

Following the magnitude-2.3 tremor on April 1 and the magnitude-1.5 tremor on May 27, a small number of nearby of people near Lancashre's Fylde Coast, which sits on the eastern limits of Blackpool, reported the tremors although neither event had any surface-level structures. After receiving reports of the May tremors, Cuadrilla halted activity at the Preese Hall site to begin studying the cause and impact of the seismic events.

The report could complicate efforts by privately-held Cuadrilla to progress hydraulic fracturing plans that were halted after the two seismic incidents, which came in at well below the levels that would threaten human activity. The U.K. has become the latest venue in Europe to see shale gas spur major debate because of controversy surrounding "fracking," which has been heavily criticized by environmental groups.

U.K. regulators vowed to carefully review the findings before shifting policy. Leading environmental groups and local government officials also called for continued caution on the U.K.'s use of fracking, which has been a key component of the rise of shale gas in the U.S. and some other areas.

The Department of Energy and Climate Change will "carefully" study the implications of the report, a department spokesman said.

"The implications of this report will be reviewed very carefully - in consultation with the British Geological Survey, independent experts, and the other key regulators, HSE and the Environment Agency," said the DECC spokesman.

Cuadrilla said the report was overseen by an independent team of seismic experts and was prepared in consultation with the DECC. A DECC spokesman said that the report was commissioned by the company and that it would study its findings before commenting on the substance of its conclusions.

Nick Molho, head of energy policy at WWF-UK, said the findings "are worrying, and are likely to add to the very real concerns that people have about fracking and shale gas."

And local Liberal Democrat Councillor Sue McGuire, who also leads a residents group opposed to fracking, said that if Cuadrilla drilled the 400 to 800 wells proposed than "we could be looking at significant seismic activity in the area, which could have major impact on peoples' homes and businesses in the area, not to mention the impact on the environment."

"A moratorium would give the government time to ensure that industry specific legislation can be put in place," said McGuire.

Dow Jones Newswires' Alexis Flynn contributed to this report.


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