Fracking safe - within limits, says study
The controversial technique for shale gas production known as fracking won't contaminate water sources, say researchers - as long as there's a safe distance between the injection source and water supplies.
Hailed by some as the solution to the world's energy crisis, and seen by others as completely irresponsible, fracking, or hydraulic fracturing, involves injecting a mixture of water, sand and chemicals into shale rocks to force out natural gas.
Objectors claim that the chemicals used can leach out and contaminate ground water.
Hwever, new research from the UK's University of Durham indicates that there's only the tiniest chance of rogue fractures due to shale gas fracking operations extending beyond 0.6 kilometres. The probability of fractures extending beyond 350 metres was found to be just one percent.
The analysis is based on data from thousands of fracking operations in the USA and natural rock fractures in Europe and Africa. Of the thousands of fractures caused by fracking, none exceeded 600 meters, with the vast majority being much less than 250 meters in vertical extent.
"Based on our observations, we believe that it may be prudent to adopt a minimum vertical separation distance for stimulated fracturing in shale reservoirs," says Professor Richard Davies of the Durham Energy Institute.
"Such a distance should be set by regulators; our study shows that for new exploration areas where there is no existing data, it should be significantly in excess of 0.6 km."
The majority of fracking operations are already taking place at between two and three kilometers' depth, indicating that they're perfectly safe - but this could change in future.
"Sediments of different types and ages are potential future drilling targets and minimum separation depths are an important step towards safer fracturing operations worldwide and tapping into what could be a valuable energy resource," says Davies.
"We need to keep collecting new data to monitor how far fractures grow in different geological settings."
Fracking operations are springing up all over the US, and are being tested elsewhere. A recent test well in the UK near Blackpool, Lancashire, was halted after minor earthquakes nearby, but is due to start up again shortly.