Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks

N. Kapman
A. Busch
P. Bertier
J. Snippe
S. Hangx
V. Pipich
Z. Di
G. Rother
J. F. Harrington
James P. Evans, Utah State University
A. Maskell
H. J. Chapman
M. J. Bickle

Publishers version can be found at http://www.nature.com/ncomms/2016/160728/ncomms12268/full/ncomms12268.html


Storage of anthropogenic CO2 in geological formations relies on a caprock as the primary seal preventing buoyant super-critical CO2 escaping. Although natural CO2 reservoirs demonstrate that CO2 may be stored safely for millions of years, uncertainty remains in predicting how caprocks will react with CO2-bearing brines. This uncertainty poses a significant challenge to the risk assessment of geological carbon storage. Here we describe mineral reaction fronts in a CO2 reservoir-caprock system exposed to CO2 over a timescale comparable with that needed for geological carbon storage. The propagation of the reaction front is retarded by redox-sensitive mineral dissolution reactions and carbonate precipitation, which reduces its penetration into the caprock to ~7 cm in ~105 years. This distance is an order-of-magnitude smaller than previous predictions. The result attest to the significance of transport-limited reactions to the long-term integrity of sealing behaviour in caprocks exposed to CO2