There was a ripple of fear in Britain when test-drilling for shale gas in north-west England set off small earth tremors, but the evidence so far suggests that earthquakes should not be a worry. Fracking has been used in conventional wells for at least 50 years. A report from America’s National Research Council on energy and seismic activity, due to be published later this year, records only two incidents of minor tremors associated with fracking—the one in Britain and just one in America, depite the scale of activity there.
Water is a more serious problem, both because a lot of it is needed to frack wells and because local groundwater is seen to be at risk of pollution. A recent report from MIT says that in America shale gas has a good environmental record. With over 20,000 wells drilled in the past decade there have been only a few instances of groundwater contamination, all of them due to breaches of existing regulations. There does not appear to be any systemic risk. Fracking takes place thousands of feet below the water table, and fracking zones are typically separated from groundwater by fairly impermeable rocks.
A shale well does use a lot of water—an average of up to 22m litres (5m gallons) over its lifetime—but this is no more than a golf course in Florida consumes in three weeks, according to one estimate. Most of that water stays in the well, but 20% returns to the surface as flow-back in the days and weeks after fracking. This must be stored and disposed of or recycled safely. Still, the MIT report points out that shale-gas extraction uses less water than other industries, and indeed than other sources of energy. In America’s big shale fields it gets through much less water than local mines or local livestock.