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| Titel |
Long-Term CO2 Exposure Experiments - Geochemical Effects on Brine-Saturated Reservoir Sandstone |
| VerfasserIn |
Sebastian Fischer, Kornelia Zemke, Axel Liebscher, Maren Wandrey |
| 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 |
250040811
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| Zusammenfassung |
| The injection of CO2 into deep saline aquifers is the most promising strategy for the
reduction of CO2 emissions to the atmosphere via long-term geological storage. The study is
part of the CO2SINK project conducted at Ketzin, situated 40 km west of Berlin. There, food
grade CO2 has been pumped into the Upper Triassic Stuttgart Formation since June 2008.
The main objective of the experimental program is to investigate the effects of long-term
CO2 exposure on the physico-chemical properties of the reservoir rock. To achieve
this goal, core samples from observation well Ktzi 202 have been saturated with
synthetic brine and exposed to CO2 in high quality steel autoclaves at simulated
reservoir P-T-conditions of 5.5 MPa and 40 Ë C. The synthetic brine had a composition
representative of the formation fluid (Förster et al., 2006) of 172.8 g/l NaCl, 8.0 g/l
MgCl2-
2H2O, 4.8 g/l CaCl2-
2H2O and 0.6 g/l KCl. After 15 months, the first set of
CO2-exposed samples was removed from the pressure vessels. Thin sections, XRD,
SEM as well as EMP data were used to determine the mineralogical features of the
reservoir rocks before and after the experiments. Additionally, NMR relaxation and MP
was performed to measure poroperm and pore size distribution values of the twin
samples.
The analyzed samples are fine- to medium grained, moderately well- to well sorted and
weakly consolidated sandstones. Quartz and plagioclase are the major components,
while K-feldspar, hematite, white & dark mica, chlorite and illite are present in
minor and varying amounts. Cements are composed of analcime, dolomite and
anhydrite. Some samples show mm- to cm-scale cross-beddings. The laminae comprise
lighter, quartz- and feldspar-dominated layers and dark-brownish layers with notably
less quartz and feldspars. The results are consistent with those of Blaschke et al.
(2008).
The plagioclase composition indicates preferred dissolution of the Ca-component and a
trend toward albite-rich phases or even pure albite during the experiments. Additionally, XRD
data suggest anhydrite dissolution in the course of CO2 exposure. The chemical
evolution of the brine displays increasing Ca2+ concentrations (Wandrey et al., 2010) in
line with the preferred dissolution of the anorthite component of plagioclase. SEM
photomicrographs show corrosion textures on mineral surfaces of, e.g., plagioclase. The
petrophysical properties of the sandstone samples also suggest slight changes. NMR
and MP data indicate a slightly increased porosity and a shifting to larger pore
sizes.
The physico-chemical measurements imply (i) Ca2+ dissolution from the rock by the
fluid, and (ii) slightly increasing porosity, but decreasing permeability. However, additional
evaluation is still needed to interconnect the changes suggested to occur during CO2 exposure
and to better understand CO2-brine-rock interactions. Supplementary core samples have been
removed from the pressure vessels after 21 and 24 months and will soon be analyzed.
Further core fragments will remain in storage in the autoclaves for longer-term
experiments.
References
BLASCHKE, A.-W., SCHöNER, R., GAUPP, R. AND FöRSTER, A. (2008): Sandstone
petrography and pore system of the Upper Triassic Stuttgart Formation from a CO2 pilot
storage site (Ketzin, Germany), Geo 2008 - Resources and Risks in the Earth System,
International Conference and 106th Annual Meeting of the Deutsche Gesellschaft für
Geowissenschaften e.V. (DGG) and 98th Annual Meeting of the Geologische Vereinigung
e.V. (GV) (Aachen 2008), 301.
FöRSTER, A, NORDEN, B., ZINCK-JORGENSEN, K., FRYKMAN, P., KUHLENKAMP,
J., SPANGENBERG, E., ERZINGER, J., ZIMMER, M., KOPP, J., BORM, G., JUHLIN, C.,
COSMA, C.-G., HURTER, S. (2006): Baseline Characterization of the CO2SINK
Geological Storage Site at Ketzin, Germany, Environmental Geoscience, 13, 3,
145-161.
WANDREY, M., FISCHER, S., ZEMKE, K., LIEBSCHER, A., SCHERF, A.-K., VIETH,
A., ZETTLITZER, M. and WüRDEMANN, H. (2010), Monitoring petrophysical,
mineralogical, geochemical and microbiological effects of CO2 exposure – Results of
long-term experiments under in situ condition, submitted to the 10th International
Conference on Greenhouse Gas Control Technologies (GHGT 10), Amsterdam. |
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