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| Titel |
The CO2 Vadose Project - Buffering capacity of a carbonate vadose zone on induced CO2 leakage. Part 2: reversed numerical simulation with PHREEQC |
| VerfasserIn |
Corinne Loisy, Grégory Cohen, Olivier Le Roux, Bruno Garcia, Virgile Rouchon, Philippe Delaplace, Adrian Cerepi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078676
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| Zusammenfassung |
| The interest in CO2 capture and storage as a method of reducing CO2 emissions has
underlined the need for more knowledge regarding the geological storage capacity. Because
the ultimate failure of geologic CO2 storage occurs when CO2 seeps out of the
ground into the atmospheric surface layer, it is of primary interest to understand how
much vadose zone could buffer a CO2 leakage. To assess the buffering capacity
of the carbonate vadose zone with respect to this diffuse CO2 leakage, numerical
simulation using PHREEQC were performed with data obtained from CO2 leakage
experiment.
One of the aims of the CO2-Vadose Project is to perform an experimental release of CO2 and
associated tracers (He and Kr) in order to study CO2 transport and geochemical reactions
along the carbonate vadose zone. Experimental site, which is a cavity of about 9 m3 located at
about 7 m in depth in a former underground limestone quarry in Saint-Emilion (Gironde,
France), was set up with more than ten gas probes around the injection cavity in order to
follow CO2 concentrations before and after injection thanks to micro-GC and infrared
analyser. Micro-climatic parameters were also recorded by a weather station at the
site surface and around the injection room (barometric pressure, relative humidity,
temperature). About 11 m3 of gas mixture was released in the injection room and
different concentrations of CO2 were observed inside and all around the cavity, in
limestone.
At the end of the gas mixture injection, the observed CO2 concentrations were about 90 % in
the experimental cavity. A few meters away from the source, CO2 concentrations varied from
atmospheric level (about 400 ppm) to about 11,000 ppm. Numerical simulations were done
with PHREEQC to understand the kinetic and thermodynamic equilibrium of reactions
occurring in limestone, to figure out how the carbonate vadose zone could buffer this CO2
leakage. Field characterisation data, moisture content data, pore-water analyses results and
CO2 concentrations observed during experiment were integrated to the simulations to
determine how much calcite was dissolved and in which time scale. Results from numerical
simulation show that reaction reached equilibrium in few hours, mainly because
of the low thickness of irreducible water layer in macropores, where gas transfer
occurred. |
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