More than 70 ‘seismic events’ recorded at fracking site this month

Shale gas extraction company Cuadrilla has paused its operations in Blackpool at the Preston New Road fracking site following a tremor that measured 1.55ML on the Richter scale.

The tremor is the largest of more than 70 seismic events at the site this month (August) as recorded by the British Geological Society.

During fracking operations seismic events are generated and the more that occur, the more that are likely to occur, according to Brian Baptie, head of seismology at the British Geological Society.

Baptie told Utility Week: “There are a lot, but they are very, very small – the magnitudes are less than two and most are less than zero, so they are tiny even for a country like the UK.”

Once fracking operations stop the probability of further events returns to normal levels in a few days. There is an initial increased probability of quakes occurring – as happened on Wednesday night at Preston New Road – but this is short term.

These events are caused by motions or small faults in the ground that may be a fraction of a millimetre and not large enough to cause damage to the integrity of the wells.

Following the most recent event Cuadrilla said well integrity was verified and the company is waiting 18 hours before resuming activity.

The company had to pause fracking activity last month because of seismic movements. It is intending to continue extracting shale gas from this site until the end of the year.

Baptie said a particularly large event would have the potential to split the well but this is unlikely. “Vibrations and shakes could cause problems for the structure of the well but it would need to be a very large earthquake to have this impact. The scales of the shakes at the moment are very far off this point.”

A spokesperson for Cuadrilla said: “The Preston New Road exploration site is the most regulated and monitored site in Europe and the systems in place are working as they should.  Minor movements of this level are to be expected and are way below anything that can cause harm or damage to anyone or their property.  All the relevant regulators were informed and we have verified that the well integrity is intact”

Regulatory framework stipulates fracking activity must pause if it triggers any seismic event over 0.5 on the Richter Scale and the company should re-apply for a licence to recommence.

Seismic movement can only be felt at a magnitude above two unless a person is very close to the event.