Shale gas extraction company Caudrilla has temporarily ceased work at its Preston New Road extraction exploration site near Blackpool, following a 1.5-magnitude quake. Hydraulic fracturing operations on the site were resumed by Caudrilla in October, for the first time since 2011 when earthquakes of magnitude 2.3 and 1.5 caused work to be halted.
The site’s regulator is the Oil and Gas Authority, operating to a Hydraulic Fracture Plan (HFP) agreed with the Environment Agency (EA). Under the OGS’s traffic light system, tremors of 0 to 0.5 lead to operators "proceeding with caution" and intensifying monitoring. If a tremor occurs at 0.5 or greater, the operator must suspend injection, reduce pressure and monitor seismicity for future events, before resuming fracking. Work must be stopped for a minimum of 18 hours.
A statement from the OGA confirmed that a number of minor seismic events were recorded in the Preston New Road area, including one of magnitude 1.5 on 11th of December. Tom Wheeler, OGA director of regulation, said: "This is the largest seismic event triggered by the Preston New Road operations to date and it may have been felt by some people close to the site."
He compared the vibrations of an event like this as "similar those caused by a lorry or a coach passing on a nearby road". He added: "The event would have needed to be more than 30 times greater for there to be even the possibility of superficial damage to property." The OGA statement says that, to date, five seismic events at Preston New Road have exceeded the magnitude 0.5 limit for caution.
In October 2016, a previous decision by Lancashire county council was overturned by the government, giving Cuadrilla consent to construct two shale wells on the Preston Road site. This September, two protestors, Simon Bevins and Richard Robins, received prison sentences for causing public nuisance, for blocking a convoy of lorries delivering equipment.
In November, the company reported that the first natural gas was flowing to the surface at Preston Road. Cuadrilla has eight sites in its Bowland shale gas exploration licence area, of which only Preston Road is operational. It has 18 site exploration licences in Yorkshire and three sites in the south of England.
A report from the company states: "We believe that at least 200 tr/ft3 of natural gas is trapped in the shale rock in our [Bowland] licence area which could be of great importance to the UK’s natural gas requirement as the country currently uses approximately 3 tr/ft3 annually over half of which is currently imported." Caudrilla plans to continue test flow rates at Preston Road until the end of December, before deciding the future of the site.
Responding to the latest tremor at the Preston Road site, Tony Bosworth, Friends of the Earth campaigner, said that fracking poses risks for climate and the environment and called for all fracking to be halted in England. He added: "It appears that they cannot frack without triggering tremors. And instead of acknowledging that fracking needs to end, Cuadrilla is instead urging for regulations around earthquakes to be relaxed.
A report commissioned from Liverpool University by BEIS, Seismic Context Measurements for Induced Seismicity, compares seismic activity levels to a range of scenarios, such as dropping objects onto the floor, or operating equipment such as fans and computers. The report likens 0.5 threshold at which fracking must stop to vibrations from mixed traffic on a busy road or a door slamming. A 1.1 tremor is compared to 1kg bag of flour dropping to the floor.