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| Titel |
The effect of caprock topography on long-term CO2 migration |
| VerfasserIn |
Paulo Herrera, Helge Dahle |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053921
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| Zusammenfassung |
| The mathematical modeling of long-term CO2 migration in deep saline aquifers is
challenging because of the large spatial and temporal scales that must be considered.
Consequently, full-scale numerical simulations can be too expensive to perform detailed risks
assessment of potential storage sites. The use of simplified mathematical models that can be
solved with analytical methods has been proposed as an alternative to reduce the
computational overhead. Yet, it is difficult to develop simplified models that are
able to capture the most important aspects of the CO2 plume dynamics. Our main
objectives are: i) to demonstrate that current analytical models fail to estimate key
parameters such as plume speed and maximum migration distance for realistic
scenarios and ii) to propose improvements to those models to obtain more accurate
results.
First, we discuss how measurements performed in real storage sites indicate that the shape
of the aquifer caprock controls the direction and speed of the CO2 plume. Second, we
use full-scale numerical simulations to demonstrate how variations of the aquifer
caprock can result in important differences in migration distance and plume speed in
comparison with results predicted by simple analytical models that approximate
the aquifer caprock as a flat sloping surface. Third, we explain why it is crucial to
account for the volume of CO2 that can be potentially trapped underneath the aquifer
caprock to get realistic estimates of the maximum migration distance of the plume.
Based on theses observations, we conclude that mathematical models of long-term
CO2 migration should always include the effects of the topography of the aquifer
caprock.
Since including a high-resolution description of the caprock elevation is difficult in
large-scale models, we discuss alternative modeling approaches to take into account the
effects of the small-scale fluctuations of the aquifer boundaries. We propose an alternative
modeling approach based on an upscaled transport equation with effective parameters that
capture the effect of the caprock variability on the plume speed and trapped CO2 volume.
Finally, we discuss the advantages of the proposed effective model versus existent analytical
and numerical approaches. |
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