Storing tiny bubbles of CO2 underground could prevent pollution above, say researchers

Bubbles

International team of scientists research capture of CO2 - <em>News</em>

By Naomi Weston
Thursday 8 February 2007

Storing tiny bubbles of carbon dioxide underground could substantially reduce the emission of harmful greenhouse gases says an international team of scientists from Imperial College London, MIT, and Stanford.

In a paper published in a recent issue of Water Resources Research, the scientists describe a mechanism for capturing carbon dioxide emissions from a power plant and injecting the CO2 into the ground. From there it will be trapped naturally as tiny bubbles and safely stored in briny porous rock.

This means, according to the team, that a power plant could have all its CO2 emissions captured and injected underground throughout the life of the plant, and then safely stored over centuries and even millennia. The carbon dioxide eventually would dissolve in the brine and a fraction would adhere to the rock in the form of minerals such as iron and magnesium carbonates.

The researchers consider the possibility of storing CO2 beneath the Earth’s surface in at least three types of geologic formations: depleted oil and gas fields, unminable coal seams, and deep saline aquifers.

CO2 could be injected underground through everal layers of the Earth's substrata into the briny porous rock belowTheir study shows that CO2 gas could be compressed as it leaves the power plant and injected through a well deep underground into a natural sublayer consisting of porous rock, such as sandstone or limestone, saturated with saltwater. The injected gas will then form a plume and begin to rise through the permeable rock.

Once the injection stops, for example after the power plant has operated for decades, the plume of gas will continue to rise, but saltwater would close around the back of the gas plume. The saltwater and carbon dioxide would begin to juggle for position while flowing through the tiny pores in the rock and, because rock’s surface attracts water, the water would cling to the inner surface of the pores.

These wet layers would swell and constrict the flow of carbon dioxide until the once-continuous plume of CO2 breaks into small bubbles or blobs, which will remain trapped in the pore space.

Professor Martin Blunt , from the Department of Earth Science and Engineering at Imperial, explains: "This process has the potential to play a crucial part in the fight against global warming. Previously some researchers have been concerned about the danger of the CO2 escaping back into the atmosphere in some way but we have demonstrated that this is extremely unlikely."

The co-authors of the research are Martin Blunt of Imperial College London, Ruben Juanes from MIT, Elizabeth Spiteri, an MSc student supervised by Juanes at MIT and now at Chevron, and Franklin Orr Jr., of Stanford University.

Researchers at Imperial are now continuing work on the design of CO2 injection and improving simulation methods to predict the long-term fate of CO2 underground. This is part of the UKCCSC - UK Carbon Capture and Storage Consortium that is led by Imperial and involves 14 other institutions in the UK.

Notes to editors:

Impact of relative permeability hysteresis on geological CO2 storage, Water Resources Research, 23 December, 2006

R. Juanes, E. J. Spiteri, F. M. Orr Jr., and M. J. Blunt.

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