Long-term performance of a mudrock seal in natural CO2 storage
- 1School of GeoSciences, The University of Edinburgh, Edinburgh EH9 3JW, Scotland
- 2Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, Scotland
Abstract
The ability of mudrock seals to prevent CO2 leakage is a major concern for geological storage of anthropogenic CO2. The long-term performance of a mudrock seal, which provides a natural analogue, in the North Sea Miller oil field has been evaluated. This mudrock seal is immediately above a natural CO2-rich reservoir. The paper reports the stable isotopes of carbon from carbonate minerals in the mudrock that have precipitated in contact with CO2 during 4 km of burial. A well-defined linear trend of upward-decreasing δ13C traces the progressive penetration of free-phase CO2 causing dissolution and reprecipitation of carbonate minerals. The CO2 was emplaced ca. 70–80 Ma, and has only penetrated 12 m vertically in this case. The infiltration rate is estimated as ~9.8 × 10−7g cm−2 yr−1. Engineered CO2 storage under this type of mudrock seal will have a considerable safety margin.
Footnotes
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↵*Current address: Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758, USA; E-mail: jiemin.lu{at}beg.utexas.edu
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↵GSA Data Repository item 2009009, isotope data tables and modeling details, is available online at www.geosociety.org/pubs/ft2009.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Received 21 May 2008.
- Revision received 4 September 2008.
- Accepted 8 September 2008.
- © 2009 Geological Society of America
