Two small earthquakes in northwest England that occurred earlier this year at some natural gas drilling sites likely were caused by hydraulic fracturing (fracking), according to a report issued on Wednesday by UK-based Cuadrilla Resources Ltd.
According to a report commissioned by Cuadrilla, fracking at the company's Preese Hall-1 site near Blackpool, in Lancashire, England, likely led to the small quakes. Cuadrilla in September said it had discovered a natural gas shale field in the Bowland Basin in Lancashire, which may hold as much as 200 Tcf (see Shale Daily, Sept. 26). Initial testing indicated the basin may be five to 10 times thicker than the Marcellus Shale.
"The 'Geo-Mechanical Study of Bowland Shale Seismicity' confirms that there is little risk in future seismic events reoccurring in the Bowland Basin but proposes a series of mitigation measures in case of any future seismic activity," the producer stated. "This report, which fulfills a commitment made by Cuadrilla to be fully open with the community about all findings, is the most comprehensive scientific study ever undertaken on the geology of the Bowland Basin."
Cuadrilla said it intends to seek a peer review of the report and publish the review.
According to the report, "it is highly likely that the hydraulic fracturing of Cuadrilla's Preese Hall-1 well did trigger a number of minor seismic events." None of the events had any structural impact on the surface above, it said.
"The seismic events were due to an unusual combination of geology at the well site coupled with the pressure exerted by water injection as part of operations. This combination of geological factors was extremely rare and would be unlikely to occur together again at future well sites."
If the 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 suggests that Cuadrilla install an early detection system to monitor seismic activity and to implement a series of steps to prevent activity escalating. Similar systems are in place in the Netherlands and Germany, the report said.
CEO Mark Miller said Cuadrilla "unequivocally" accepted the findings of the independent report was glad the report concluded that "there is no threat to people or property in the local area from our operations. We are ready to put in place the early detection system that has been proposed in the report so that we can provide additional confidence and security to the local community."
The company is working with local and national authorities to implement the report's recommendations so that it could safely resume it operations.
The report, which was commissioned by Cuadrilla and carried out by a European team of independent seismic experts, has been submitted to the England's Department of Energy and Climate Change and the British Geological Survey.
In a statement Wednesday the company said there were five protesters at the Blackpool drilling site, "four of whom are attached to the machinery. The police are present on site and we are working with them to bring the protest to a peaceful end. Our priority is safety of both the protesters and our own staff on site."
Since it began working at the drilling site, "we have been very open, inviting local people, stakeholders and media around the site," the company stated. "Over 50 local people and their elected representatives have been show 'round the Banks site and we would have been delighted to show these protesters around rather than them need to carry out this potentially dangerous occupation of the drilling rig."