Move over fracking: carbon capture and storage schemes (CCS) are more likely to trigger earthquakes, warns the US (NRC). Meanwhile, a separate study warns that quake-fractured rocks could undermine CCS efforts by allowing the trapped gas to leak back into the atmosphere.
Carbon sequestration involves pumping CO2 at high pressure below ground and trapping it in porous rocks at depths of 1 to 4 kilometres. Similar deep injection wells are used to dispose of waste water, but despite the large number of such wells, 鈥渧ery few [seismic] events have been documented over the past several decades鈥�, writes an NRC panel in a new report, .
However, carbon capture and storage could see billions of cubic metres of fluid injected below ground 鈥� potentially enough to trigger more and larger quakes, the report concludes.
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Even if those quakes do not damage property or put lives at risk, they could undermine carbon capture schemes, says , a geophysicist at Stanford University in California. 鈥淚f you trigger an earthquake, you are threatening the seal of the repository,鈥� he says. 鈥淐O2 is buoyant and it wants to rise and get out.鈥�
Although it is possible to find good sites to store CO2 where its added pressure would be unlikely to cause quakes or leaks, too few are available to handle the required volume, Zoback says. Older sedimentary rocks in the central US, where most power plants are located, are brittle and so are more likely to fracture and leak. Large-scale carbon capture and storage 鈥渋s a risky, and likely unsuccessful, strategy鈥� for controlling greenhouse warming, Zoback says. He presented his concerns yesterday to the Senate Energy Committee.
鈥淚t鈥檚 quite possible that quakes may be induced, but that doesn鈥檛 mean that all the CO2 leaks out,鈥� says , a carbon capture and storage researcher at the University of Edinburgh, UK.
Plenty of quakes have been measured in the eastern and central US in the past century, he says, but oil and gas remains to be extracted from wells in the area. 鈥淚f a few per cent leaks out over 10,000 years, it鈥檚 unfortunate, but it鈥檚 not terminal to the future of carbon capture,鈥� he says. 鈥淲e need to work out how to manage it.鈥�
Journal reference: Zoback鈥檚 study is published in the
