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| Titel |
Mineral-microbial interaction in long term experiments with sandstones and reservoir fluids exposed to CO2 |
| VerfasserIn |
Monika Kasina, Daria Morozova, Linda Pellizzari, Hilke Würdemann |
| 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 |
250082147
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| Zusammenfassung |
| Microorganisms represent very effective geochemical catalysts, and may influence the
process of the CO2 storage significantly. The goal of this study is to characterize the
interactions between minerals and microorganisms during their exposure to the CO2 in a long
term experiment in high pressure vessels to better understand the influence of biological
processes on the composition of the reservoir sandstones and the long term stability of CO2
storage. The natural gas reservoir, proposed for the CO2 storage is characterized by high
salinity (up to 420 g/l) and temperatures around 130°C, at depth of approximately 3.5
km.
Microbial community of the reservoir fluid samples was dominated by different H2-oxidising,
thiosulfate-oxidising and biocorrosive thermophilic bacteria as well as microorganisms
similar to representatives from other deep environments, which have not previously been
cultivated. The cells were attached to particles and were difficult to detect because of low cell
numbers (Morozova et al., 2011).
For the long term experiments, the autoclaved rock core samples from the core deposit were
grinded, milled to the size of 0.5 mm and incubated with fresh reservoir fluids as inoculum
for indigenous microorganisms in a N2/CH4/H2-atmosphere in high pressure vessels at a
temperature of 80°C and pressure of 40 bars. Incubation was performed under lower
temperature than in situ in order to favor the growth of the dormant microorganisms. After
three months of incubation samples were exposed to high CO2 concentrations by insufflating
it into the vessels. The sampling of rock and fluid material was executed 10 and 21 months
after start of the experiment.
Mineralogical analyses performed using XRD and SEM – EDS showed that main mineral
components are quartz, feldspars, dolomite, anhydrite and calcite.
Chemical fluid analyses using ICP-MS and ICP-OES showed that after CO2 exposure
increasing Si4+ content in the fluid was noted after first sampling (ca. 25 relative %), whereas
after the second sampling it decreased (to 31 relative %) in comparison to the reservoir fluid
sample. This may suggest dissolution of silicate minerals at first, and secondary precipitation
at second stage of experiment. In addition, immobilization of heavy metals dispersed within
silicate minerals was also detected. An increase of Ca (3.2 up to 13% relative), SO4
(up to 14 relative %) and Fetot (47 and 24% relative) were also detected after first
and second sampling respectively and may suggest dissolution of cements and
iron rich minerals. The concentration of organic acids increased relatively by 12.5
% and 25% after first and second sampling respectively might be an indication
for metabolic activity of microorganism or an effect of mobilisation due to CO2
exposure.
The presence of newly formed mineral phases was detected using SEM-EDS. Quartz, albite
and illite precipitation is a common process in all studied samples. However only illite is
considered to be of bacterial origin, nevertheless its crystallization can also occur as a
consequence of inorganic diagenetic processes.
Further analyses of the microbial community composition, quantity and activity will bring a
more insight into the CO2 exposure processes.
Daria Morozova, Dagmar Kock, Martin Krüger, and Hilke Würdemann. Biogeochemical and
microbial characterization of reservoir fluids from a gas field (Altmark). Geotechnologien
2011 |
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