Abstract
During geological CO 2-sequestration, dissolved CO 2 will diffuse slowly into the lower section of the cap rock where, depending on the cap rock mineralogy, it might trigger geochemical reactions affecting crucial parameters such as porosity (and therefore possibly the sealing capacity). To assess this possibility, reactive transport modelling including reaction kinetics was performed of dissolved CO 2 in the cap rock at Sleipner (37 °C, 101.3×10 5 Pa). Major geochemical reactions between CO 2, the cap rock formation water and the cap rock mineralogy are identified and the impact on the porosity is calculated. After several years of initial carbonate dissolution, feldspar dissolution dominates over the subsequent hundreds and thousands of years, with the reaction rate strongly depending on plagioclase composition. A slight decrease of the porosity is predicted which might improve the sealing capacity of the cap rock, but this porosity change will be restricted to the lower metres, even for the most reactive case. Major uncertainties affecting the accuracy of the modelling are the selection of the primary and secondary mineral assemblages for the cap rock in the model and the poor knowledge of kinetic rate constants. Nevertheless, it is shown that using the local equilibrium hypothesis is inadequate and leads to erroneous results in this case.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.