A UK energy company has admitted that their hydraulic fracturing project (commonly known as ‘fracking’) probably caused a few surprisingly large earthquakes in Lancashire this spring. But, their report into the events concludes, it should be safe to continue operations in the area. Protesters disagree.
Fracking involves pumping millions of litres of water underground to fracture shale rock, allowing natural gas trapped inside to flow up the well. Concerns have been raised about whether this technique is safe (see Should fracking stop? and United States investigates fracking safety).
Two quakes of magnitude 2.3 and 1.4 in April and May, along with a cluster of 48 much smaller events, struck near the fracking project of Lichfield-based company Cuadrilla Resources. Cuadrilla stopped operations, and commissioned independent reports from a handful of consultants, including a Czech Republic seismic company and a British geomechanical services company, to investigate whether the drilling had triggered a nearby fault. Their synthesis report is now out.
It is extremely rare for fracking itself to cause detectable earthquakes — so rare that geologist Scott Ausbrooks of the Arkansas Geological Survey in Little Rock told this reporter in May that it never happens. The Cuadrilla report acknowledges, however, two previous reported cases of small quakes (of magnitudes 1.9 and 2.8) being spurred by massive fracking projects in Oklahoma. More often, tremblors are caused by the disposal of the fracking fluids after they have been used for mining, which triggered quakes up to magnitude 5 in Colorado in the 1960s.
The report concludes that there are a couple of reasons for the unusual quake activity in the Bowland Shale, including the fact that the stress in the rock was about 10 times higher than usual in US fracking operations. The report concludes that even if all the same conditions are met again in another well, the maximum shaking it could cause is a magnitude 3. They point out that straightforward mining in Lancashire has caused quakes of up to magnitude 3.1 in the past, causing only “slight damage”.
The company is working with authorities to put safety steps in place and resume drilling. But the ‘Frack off’ protest group said the report “did not inspire confidence” and are pressing for the project to end.
Photo: Blackpool, Lancashire, by Paolo Camera