“Most geologists think this is a pretty safe activity,” Mike Stephenson, head of energy science at the British Geological Survey, told the event organized by the city’s Science Media Centre, Bloomberg reported.

“We think the risk is pretty low and we have the scientific tools to tell if there is a problem”, he said.

Hydraulic fracturing has made the US the world’s largest natural-gas producer, but it has also raised concerns the technique pollutes drinking water and causes earthquakes.

Cuadrilla suspended its use of hydraulic fracturing in northwest England last year after two tremors occurred. The first tremor on April 1 measured 2.3 in magnitude on the Richter scale. A weaker quake of 1.5 was recorded in May.

An independent report (pdf download) subsequently commissioned by the explorer found it was "highly probable" that hydraulic fracturing by Cuadrilla was reponsible for the tremors.

Fracking, as the process has become known, is unlikely to start earthquakes stronger than magnitude 3.3 on the Richter scale, a level that typically causes no damage to property, and most will be around magnitude 2, said Peter Styles, a professor of applied and environmental geophysics at Keele University.

Styles said he has examined seismic data from thirty years of coal mining in the English midlands to assess the threat from fracking. The research suggests there is a “low” probability of unconventional gas drilling operations causing major earthquakes, he said

The rock drilled by Cuadrilla, the company that caused last year’s earthquakes, is similar to that found at the country’s major coal-mining sites, suggesting potential tremors will be of a similar or lesser magnitude, he said.

“There’s not an exact analogy to coal mining, but the seismicity is remarkably similar,” Styles said. “If there are going to be others, they will be about this magnitude and because they’re of that magnitude they’re very unlikely to cause damage.”

'More gas than Iraq'

Stephenson also told the briefing meanwhile that the UK could have more shale gas the previously thought. The British Geological Survey is reviewing its estimates for UK onshore shale gas resources. The survey originally estimated that there is about 150 billion cubic meters of shale gas onshore, compared with about 300 billion cubic meters of conventional gas resources.

Cuadrilla Resources says it has found more natural gas trapped in the shale rock around Blackpool in northwest England than Iraq has in its entire reserves.

“There is much more shale than we thought under Blackpool,” the British Geological Survey’s Stephenson said at the briefing, adding more research remains to be done on the impact of fracking.

The debate over shale drilling in the US and Europe has intensified in recent months following tremors near wastewater disposal sites in Ohio and concerns about water pollution in Pennsylvania. The US Environmental Protection Agency is studying the effects of fracking on drinking water with an eye on possible nationwide regulations.

Published: 11 January 2012 10:44 GMT | Last updated: 11 January 2012 15:56 GMT

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