 |
| Titel |
Geochemical changes and microbial activities during CO2 storage - Long-term experiments under in situ conditions within the frame of CO2SINK |
| VerfasserIn |
Maren Wandrey, Ann-Kathrin Scherf, Andrea Vieth, Michael Zettlitzer, Hilke Würdemann |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043277
|
|
|
|
|
|
| Zusammenfassung |
| Within the frame of the CO2SINK project, CO2 is injected into a saline aquifer of the
Stuttgart formation (Triassic, Middle Keuper) at a depth of about 640 m below surface near
Ketzin (Northeast German Basin, about 40 km west of Berlin) (Schilling et al., 2009). The
injection of CO2 may induce a variety of geochemical changes in the reservoir
system. Inorganic components may be dissolved from mineral phases (Wigand et al.,
2008) and mineral precipitation from fluid components (Ketzer et al., 2009) may
occur. In addition, organic molecules may be relocated, since supercritical CO2 is an
excellent solvent for organic components. These geochemical shifts probably affect the
microbial community composition and activity. The dissolution and precipitation of
minerals, as well as corresponding microbial processes (Bennet et al., 2001) can
affect reservoir permeability. In order to detect and quantify changes in geochemical
characteristics and microbial processes during CO2storage and to estimate their
impact on storage efficiency long-term experiments under in situ P-T conditions are
performed.
Freshly drilled sandstone sections from the target reservoir at Ketzin from a depth of
about 630 m were incubated together with synthetic brine (20 % lower total dissolved solids
than the Ketzin reservoir fluid) in high pressure vessels at 5.5 MPa and 40 Ë C since
September 2007. Since outer core sections were contaminated with drilling mud, as shown
with fluorescein tracer detection (Wandrey et al., 2010), only clean inner core sections were
used for long-term experiments to avoid contamination with microorganisms, as well
as organic and inorganic mud components. After 15, 21 and 24 month fluid and
rock samples were taken for chemical, microbial, mineralogical and petrophysical
analyses.
In fluid samples the concentrations of Ca2+, Mg2+, and K+ were found to exceed those
of the Ketzin reservoir fluid. Assuming chemical equilibrium between mineral and formation
brine, observed effects are probably caused by mineral dissolution in response to CO2
exposure. In consistence with inorganic concentration declines, XRD, SEM and EMP
analyses suggest feldspar dissolution (Fischer et al., EGU GA 2010). A shift to larger pore
radii was observed as well (Zemke et al., 2010).
Organic acids are a marker for the presence of active microorganisms. They are
intermediate products of the bacterial metabolism. Furthermore, if excreted, organic acids can
locally decrease the pH at the bacterial attachment site and may support mineral dissolution
(Welch and McPhail et al., 2003). After 15 month organic acid concentrations in vessel fluids
were 2 to 7 times lower than the expected concentration (based on pore water analysis). To
investigate the concentration trend during CO2 exposure, the analysis of further samples is in
progress.
In order to characterise the microbial community of the reservoir sandstone, initial 16S
taxonomic studies were performed. So fare 16S rRNA gene sequences of chemoheterotrophic
bacteria (Methylophilales bacterium, Rhizobium radiobacter, Arthrobacter, Sphingomonas),
and hydrogen oxidizing bacteria (Ralstonia, Hydrogenophaga) were obtained. During the
long-term exposure experiment only minor changes of the microbial community composition
were observed, reflecting the adaptation of the microorganisms to the modified conditions.
The quantification of metabolic groups and relevant microbial activities, e.g. metal and
sulfate reduction, using Real-Time PCR and FISH in untreated and CO2 exposed samples
will help to quantify bacterial processes and to assess their long-term influence on storage
efficiency.
Bennet P.C., Rogers J.R., Choi W.J. (2001) Geomicrobiol J 18, pp. 3
Fischer S., Zemke K., Liebscher A., Wandrey M., CO2SINK Group, EGU General
Assembly 2010, Vienna
Ketzer J.M., Iglesias R., Einloft S., Dullius J., Ligabue R., de Lima V. (2009) Appl
Geochem 24(5), pp. 760
Schilling F., Borm G., Würdemann H., Möller F., Kühn M., CO2SINK Group (2009)
Energy Procedia 1, 2029-2035
Wandrey M., Morozova D., Zettlitzer M., Würdemann H., CO2SINK Group (2010) Int J
Greenhouse Gas Control, accepted
Welch S.A. and McPhail D.C. (2003) Advances in Regolith, pp. 437
Wigand M., Carey J.W., Schütt H., Spangenberg E., Erzinger J. (2008) Appl Geochem
23(9), pp. 2735
Zemke K., Wandrey M., CO2SINK Group (2010) Int J Greenhouse Gas Control, accepted |
|
|
|
|
|
|