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Shale gas: mining the data

In the early 1990s the oil and gas industry in Texas started to produce gas by drilling into deeply-buried shale layers. They found that creating underground fractures in the layers, later coined 'fracking', increased the rates of gas production and their investments started to make money. The shale gas revolution had started and may now become global.

Hydraulic fracturing is not a new technology; it's been carried out in many wells since the 1940s, but is now controversial. Fuelled by the media frenzy the word 'fracking' has turned into a catch-all term covering all shale gas operations. A tipping point may have been in the USA when the filmmaker Josh Fox was asked to lease his land for drilling, it resulted in him making the documentary 'Gaslands' (2010), with footage of gas coming out of taps being ignited. The potential link between fracturing and the contamination of water supplies with methane was thus made. Then in 2011 the UK's first shale gas exploratory well, drilled near Blackpool in northwest England triggered earthquakes up to 2.3 in magnitude.

Hydraulic fractures occur naturally and can be formed artificially by pumping granular material such as sand in a water-based fracturing fluid into rock layers. The direction of growth of the fractures is known but the exact pattern of fractures cannot yet be predicted and some can extend beyond the target layer. If pumping occurs into a geological fault, it could lubricate it helping it to slip. All forms of energy production have associated risk - and shale gas is no different - so there are good reasons to be cautious.

But we do have data - and lots of it. There has already been 20 years of shale gas exploration and production. Thousands of fracturing operations have already been completed in the USA. The dimensions of these fractures have been recorded and we can calculate the chances of a rogue fracture extending much further than the target rock layer. Over the last 80 years there have been hundreds of documented examples of 'induced' earthquakes caused by activities other than hydraulic fracturing: the filling of dams, injected military waste underground, fracturing for geothermal energy, injecting water to maintain oil field pressure and because of subsidence triggered by mining or oil and gas extraction. The phenomena are far from being new.

There are hundreds of research papers on shale gas activities - I've spent months pouring over them for a forthcoming peer-reviewed paper. I've been surprised - much of the basic information has yet to be mined. Some thorough peer-reviewed research based on the existing data archive would go a long way to inform regulators, non government organisations and the public about safe shale gas operations in a hyperbole-free way.

Richard Davies is Director of Durham Energy Institute, Durham University