Well-based stable carbon isotope leakage monitoring of the first aquifer overlying the CO2 storage reservoir at the Ketzin pilot site, Germany

Martin Nowak1, Anssi Myrttinen1, Martin Zimmer2, Robert v. Geldern1, Johannes AC Barth1
1 GeoZentrum Nordbayern Friedrich-Alexander University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany
2 GFZ German Research Centre for Geosciences, Helmholtz Centre, Telegrafenberg, 14471 Potsdam, Germany

O 11.4 in Wärme-, Energie- und Kohlenstoffspeicherung im Untergrund

29.05.2014, 15:00-15:20, H18, NW II

Geo-engineering might be an unavoidable tool to mitigate greenhouse gas emissions and reduce global warming. Carbon Capture and Storage (CCS) is a feasible bridge technology, as it promises storage of large amounts of CO2 in the subsurface instead of emitting it to the atmosphere. However, considering the application of CCS, one has to be conscious about possible risks such as leakage from abandoned wells (Nowak et al., 2013).

At the pilot site for CO2 storage in Ketzin, a new well-based leakage-monitoring concept was established, comprising geochemical and hydraulic observations of the aquifer directly above the CO2 reservoir (Wiese et al., 2013). This shall allow early detection of un-trapped CO2. Within this study concept, we established a stable carbon isotope monitoring of dissolved inorganic carbon (DIC). If baseline isotope values of aquifer DIC (δ13CDIC) and reservoir CO213CCO2) are known and distinct from each other, the δ13CDIC has the potential to be an early indicator for an impact of leaked CO2 on the aquifer brine.

Data acquisition for this study was conducted between January 2012 and November 2012. The observation well of the overlying aquifer was equipped with a U-tube sampling system that allowed frequent sampling of unaltered brine. Our results show, that in the early stage, the high alkaline drilling mud that was used during well drilling masked δ13CDIC values, which ranged around -27 ‰. However, subsequent monitoring allowed observing on-going re-equilibration of the brine, indicated by changing δ13CDIC and other geochemical values, until values ranging at -23 ‰ were reached, which appears to be close to baseline values.

Baselineδ13CDIC and δ13CCO2 values were used to derive a geochemical and isotope model that predicts evolution of δ13CDIC, if CO2 from the reservoir would leak into the aquifer under equilibrium conditions. The model shows that isotope fractionation has to be considered if CO2 dissolves in the brine.

Further, the model suggests that stable carbon isotope monitoring is a suitable tool to assess the impact of injected CO2 in overlying groundwater aquifers. However, more data are needed about fractionation behaviour within the CO2(g) - DIC system under elevated pressure and temperatures. 

Nowak, M., Myrttinen, A., Zimmer, M., Wiese, B., van Geldern, R., Barth, J.A.C., 2013. Well-based, Geochemical Leakage Monitoring of an Aquifer Immediately Above a CO2 Storage Reservoir by Stable Carbon Isotopes at the Ketzin Pilot Site, Germany. Energy Procedia 40, 346-354.

Wiese, B., Zimmer, M., Nowak, M., Pellizzari, L., Pilz, P., 2013. Well-based hydraulic and geochemical monitoring of the above zone of the CO2 reservoir at Ketzin, Germany. Environmental Earth Sciences, 1-18.

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Letzte Änderung 07.11.2013