A study has found that storing carbon dioxide (CO2) deep below the earth's surface could be a safe, long-term solution to one of the planet's major contributors to climate change.
The study, led by Bruce Yardley, Professor in the School of Earth and Environment at the University of Leeds, showed that porous sandstone, drained of oil by the energy giants, could provide a safe reservoir for carbon dioxide.
In the study, data from the Miller oilfield in the North Sea, where BP had been pumping seawater into the oil reservoir to enhance the flow of oil, was looked at.
The study covered samples of water pumped out from the oilfield over a seven-year period. Scientists then compared these with the composition of the water that was there before and the water that was injected.
The comparison showed that minerals had grown and dissolved as the water travelled through the field. The analysis also found that sandstone reacted with injected fluids more quickly than had been predicted; such reactions are essential if the captured CO2 is not to leak back to the surface.
Stephanie Houston, a PhD student at the University found that water pumped out with the oil was especially rich in silica, which showed that silicates usually thought of as very slow to react, had dissolved in the newly injected seawater over less than a year.
"If CO2 is injected underground we hope that it will react with the water and minerals there in order to be stabilized. That way it spreads into its local environment rather than remaining as a giant gas bubble which might ultimately seep to the surface," Yardley said. "It had been thought that reaction might take place over hundreds or thousands of years, but there's a clear implication in this study that if we inject carbon dioxide into rocks, these reactions will happen quite quickly making it far less likely to escape," he said.
The researchers said that this was the type of reaction that would be needed to make carbon dioxide stable in the pore waters, rather like the dissolved carbonate found in still mineral water.
The study indicates that carbon dioxide sequestered deep underground could react quickly with ordinary rocks to become assimilated into the deep formation water.
Although extracting CO2 from power stations and storing it underground has been suggested as a long-term measure for tackling climate change, it has not yet been put to work for this purpose on a large scale.
The study will be published in Geology.