Experimentally Produced Increase in the Permeability of Caprock by Flow of Carbon Dioxide Saturated Water

Armitage, Peter; Faulkner, Dan; Worden, Richard H.; Blake, Oshaine

The long-term storage of industrial carbon dioxide in depleted oil reservoirs is viewed as an essential component of the strategy to combat the build-up of greenhouses gases in the atmosphere. The success of these projects relies on the integrity of low-permeability caprocks that must seal the carbon dioxide within the reservoir formation over significant periods of time. Here we show that flowing carbon dioxide-saturated aqueous fluids through siltstone caprock from one of the world's largest current carbon storage projects at In Salah, Algeria, under simulated reservoir conditions increases the permeability by one order of magnitude. In contrast flowing gas phase carbon dioxide, inert gas or water through the caprock has no effect on permeability. The increase in permeability is due to the dissolution of chlorite and siderite in pore throats in the siltstone. The results show that the chemistry of these systems can significantly alter the physical properties of the caprock and this must be taken into account when modelling their long-term behaviour. A localised increase in permeability due to dissolution close to carbon dioxide injector wells at In Salah might be ameliorated by the precipitation of the dissolved phases at some distance along the flow path where the carbon dioxide concentration is less and fluid pressure is lower.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013