- Copyright ©2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.
Subsurface geologic storage of carbon dioxide calls for sophisticated monitoring tools with respect to long-term safety and environmental impact issues. Despite extensive research, many factors governing the fate of injected carbon dioxide (CO2) remain unclear. To identify possible risks through leakage of the CO2 storage reservoir, a program for monitoring of the CO2 flux at the surface was started at the Ketzin test site, which allows to distinguish between natural temporal and spatial flux variations and a potential leakage.
To gain adequate long-term baseline data on the local background CO2 flux variations, CO2 soil gas flux, soil moisture, and temperature measurements were conducted once a month during a 6-yr period. Furthermore, soil samples were analyzed for their organic carbon and total nitrogen contents.
The mean flux of all sampling sites before the CO2 injection (2005–2007) was 2.8 μmol m−2 s−1 (ranging from 2.4 to 3.5), with a Q10 factor of 2.4, and in the years after commencing injection (2009–2010), 2.4 μmol m−2 s−1 (ranging from 2.2 to 2.5), with the same Q10 factor. The CO2 flux rate is mainly controlled by the soil temperature. A significant influence of diurnal temperature variation and soil moisture was not detected. The spatial variability of the CO2 flux among the 20 sampling locations ranges from 1.0 to 4.5 μmol m−2 s−1, depending on the organic carbon and total nitrogen content of the soil.
Through comparison with the long-term measurements, unusual high CO2 fluxes can theoretically be distinguished from natural variations.
Martin Zimmer received his Dr. rer. nat. in mineralogy in 1993 from the Justus-Liebig-University of Giessen, Germany. Since 1993, he has been employed at the GFZ German Research Centre for Geosciences, where he has managed an ICP-MS laboratory and participated in several research projects on gas geochemistry and gas monitoring. His research interest is on gas and fluid geochemistry. Currently he is involved in CO2 sequestration projects in Ketzin, Germany.
Peter Pilz has been a postdoctoral research fellow at the GFZ German Research Centre for Geosciences since 2008, where he has worked in CO2 storage projects. He received a degree in geology (diploma) from the Freie Universität Berlin in 1997, and a Dr. rer. nat. in geosciences from the Universität Potsdam, Germany, in 2008. His research interest is mainly focused on gas geochemistry and on noble gas isotopes.
Jörg Erzinger is professor of geochemistry at University of Potsdam and head of research section 4.2: Inorganic and Isotope Geochemistry at the German Research Centre for Geosciences GFZ since 1992. He received his Dr. rer. nat. in geochemistry from the University of Karlsruhe, Germany, in 1981. His current main research interest is on geochemistry of fluids and gases.