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Abstract

Cap-rock integrity is a key issue in Carbon Capture and Storage (CCS) technologies. At the Ketzin pilot site, new drill cores of sealing- and reservoir formations were retrieved from a depth range of 620⬜701 m below ground level (b.g.l.). These strata have been exposed to injected CO2 under field conditions for more than four years. Here we present data on cap-rock and reservoir lithologies, CO2 concentrations and their stable carbon isotope ratios (View the MathML sourceδCCO213). CO2 concentrations within the mudstone-dominated cap-rock were <1% (i.e. 10 000 ppmV) with corresponding carbon isotope values between ↙18.6⬰ and ↙29.4⬰. Below the boundary between the cap-rock and the reservoir, CO2 concentrations of more than 90% with mean View the MathML sourceδCCO213 values around ↙36.5⬰ were measured. Below this section, between 648 and 655 m b.g.l., CO2 concentrations decreased again in the clayey and silty lithology of the reservoir to less than 2%, but maintained a depleted View the MathML sourceδCCO213 value of around ↙34.2⬰. At depths below 662 m b.g.l., the CO2 concentrations decreased to values of less than 10 000 ppmV and showed corresponding increases to View the MathML sourceδCCO213 values between ↙15.9⬰ and ↙27.6⬰. Both isotope and CO2 concentration confirm that no CO2 from the reservoir penetrated the cap-rock at the Ketzin pilot site after four years of injection.