Fractured sea floor could leak sequestered carbon dioxide

Nature : The floor below the North Sea is more fractured and scarred than previously thought, say researchers working on the ECO₂ project funded by the European Commission. The project assesses the risks associated with carbon dioxide emissions that are captured from power plants and other industries and pumped into underground rock formations in the ocean to keep them out of the atmosphere and reduce global warming. The ECO₂ researchers use sonar to send acoustic pulses below the sea floor to study its geological structures. They found that at one site—used by a company in Norway to sequester CO₂ since 1996—the overlying sedimentary layer appears to be heavily scarred and to contain vertical chimneys and pipes through which the stored CO₂ could escape. However, no leakage has been recorded so far, and any CO₂ that managed to escape would probably dissolve and disperse in the lower few meters of water, with very little reaching the atmosphere, according to Klaus Wallmann, ECO₂ coordinator. Also, because of the difficulty involved, pumping CO₂ offshore remains prohibitively expensive for most countries.