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| Titel |
A coupling alternative to reactive transport simulations for long-term prediction of chemical reactions in heterogeneous CO2 storage systems |
| VerfasserIn |
M. Lucia, T. Kempka, M. Kuhn |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 2 ; Nr. 8, no. 2 (2015-02-11), S.279-294 |
| Datensatznummer |
250116110
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| Publikation (Nr.) |
 copernicus.org/gmd-8-279-2015.pdf |
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| Zusammenfassung |
| Fully coupled, multi-phase reactive transport simulations of
CO2 storage systems can be approximated by a simplified one-way
coupling of hydrodynamics and reactive chemistry. The main
characteristics of such systems, and hypotheses underlying the
proposed alternative coupling, are (i) that the presence of CO2
is the only driving force for chemical reactions and (ii) that its
migration in the reservoir is only marginally affected by
immobilisation due to chemical reactions. In the simplified
coupling, the exposure time to CO2 of each element of the
hydrodynamic grid is estimated by non-reactive simulations and the
reaction path of one single batch geochemical model is applied to
each grid element during its exposure time. In heterogeneous
settings, analytical scaling relationships provide the dependency of
velocity and amount of reactions to porosity and gas saturation. The
analysis of TOUGHREACT fully coupled reactive transport simulations
of CO2 injection in saline aquifer, inspired to the Ketzin
pilot site (Germany), both in homogeneous and heterogeneous
settings, confirms that the reaction paths predicted by fully
coupled simulations in every element of the grid show a high degree
of self-similarity. A threshold value for the minimum concentration
of dissolved CO2 considered chemically active is shown to
mitigate the effects of the discrepancy between dissolved CO2
migration in non-reactive and fully coupled simulations. In real
life, the optimal threshold value is unknown and has to be
estimated, e.g. by means of 1-D or 2-D simulations, resulting in an
uncertainty ultimately due to the process de-coupling. However, such
uncertainty is more than acceptable given that the alternative
coupling enables using grids of the order of millions of elements,
profiting from much better description of heterogeneous reservoirs
at a fraction of the calculation time of fully coupled models. |
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