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| Titel |
Compositional changes of reservoir rocks through the injection of supercritical CO2 |
| VerfasserIn |
Ann-Kathrin Scherf, Hans-Martin Schulz, Carsten Zetzl, Irina Smirnova, Jenica Andersen, Andrea Vieth |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034643
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| Zusammenfassung |
| The European project CO2SINK is the first project on the on-shore underground storage of
carbon dioxide in Europe. CO2SINK is part of the ongoing efforts to understand the impact,
problems, and likelihood of using deep saline aquifers for long term storage of CO2. In
Ketzin (north-east Germany, 40 km west of Berlin) a saline sandstone aquifer of the younger
Triassic (Stuttgart Formation) has been chosen as a reservoir for the long-term storage of
carbon dioxide.
Our monitoring focuses on the composition and mobility of the organic carbon pools within
the saline aquifer and their changes due to the storage of carbon dioxide. Supercritical carbon
dioxide is known as an excellent solvent of non- to moderately polar organic compounds,
depending on temperature and pressure (Hawthorne, 1990). The extraction of organic matter
(OM) from reservoir rock, using multiple extraction methods, allows insight into
the composition of the OM and the biomarker inventory of the deep biosphere.
The extraction of reservoir rock using supercritical CO2 may additionally simulate
the impact of CO2 storage on the deep biosphere by the possible mobilisation of
OM.
We will present compound specific results from laboratory CO2 extraction experiments on
reservoir rocks from the CO2 storage site in Ketzin, Germany. A total of five rock samples
(silt and sandstones) from the injection well and two observation wells were applied to
supercritical CO2 extraction. In the experimental setup, a supercritical fluid extractor is used
to simulate the conditions within the saline aquifer. The results show distinct quantitative and
qualitative differences in extraction yields between the rock samples. This may be due to
differences in mineralogy and porosity (12 – 27%; Norden et al., 2007a, b, c), which seem to
be extraction-controlling key factors. Furthermore, the results illustrate that the amount of
extracted materials depends on the length of the time interval in which CO2 flows through the
rock, rather than saturation of extracted compounds in the solvent when CO2 is
stationary.
Total extraction yields seem to be low compared to the OM present in the reservoir rock, but
yields still have to be extrapolated to the large volumes of reservoir rock that are in contact
with supercritical CO2 at the test site. In the future, our lab results may be combined with
models to determine how much of the mobilised organic acids and non organic material will
occupy the entire reservoir (pore space) or could be used by organisms and induce
growth.
Additionally, the rock samples were analysed after the extraction with supercritical CO2,
using a variety of organic and inorganic geochemical techniques. Thus, changes in the
composition of the rocks were also observed. Here, amongst others, scanning electron
microscopy was done and indicated corrosion effects on mineral surfaces due to exposure to
supercritical CO2.
References
Hawthorne, S.B. (1990) Analytical Chemistry 62, 633-642.
Norden, B. (2007a) Geologischer Abschlussbericht der Bohrung CO2 Ktzi 200/2007.
Norden, B. (2007b) Geologischer Abschlussbericht der Bohrung CO2 Ktzi 201/2007.
Norden, B. (2007c) Geologischer Abschlussbericht der Bohrung CO2 Ktzi 202/2007. |
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