CO2 back into the earth

Starting shot for drilling work on CO2 test storage in Ketzin

CO2 storage in Ketzin: schematic representation of the storage location and drilling arrangement © GFZ Potsdam
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In the next two years, 60, 000 tons of CO2 are to be stored below 700 meters below the ground as part of the European CO2SINK project. Now the scientists have taken a decisive step further in their pilot project in Ketzin, 30 kilometers west of Berlin. Because there was started yesterday with the drilling work for the underground carbon dioxide test storage.

Under the leadership of the GeoForschungsZentrum Potsdam (GFZ), in collaboration with 18 partners from new countries, it is being investigated for the first time in Europe as to how CO2 can be introduced and stored in low-lying porous rock strata filled with salt water. This first drilling will serve to feed CO2 into the storage horizon.

In order to monitor the storage and investigate locally the spread of CO2 in the subsurface, two additional observation wells are drilled down to 800 meters and equipped with state-of-the-art sensor technology. The drilling will go until the summer. This pilot plant will create a "large-scale laboratory" in which the behavior of CO2 in the subsurface will be investigated under realistic conditions.

99.9 percent pure CO2 used

"The storage of this greenhouse gas can be an option to gain time in the development and introduction of CO2-free energy technologies, but you have to know: What processes are triggered by underground storage and what happens in the medium and long term with the CO2 stored in the underground? that's what we want to investigate, "explains Professor Rolf Emmermann, CEO of the GFZ Potsdam.

"The amount of CO2 that we want to store there every year corresponds to the amount of carbon dioxide exhaled by the population of Potsdam each year, which - compared to the total CO2 emissions in Germany - will be sufficient marginal quantities, important insights into injection technology to gain the security of the storage and about possible long-term risks and costs ", continues Emmermann. CO2 is used at a purity of 99.9 percent, which is normally used in beverages such as mineral waters and beer. display

A laboratory underground

The selected rock formation represents a natural laboratory, which is well suited for the planned project because of its geology. Already at a depth of 400 meters above a former natural gas storage facility, there is an impermeable cover layer. The planned CO2 test storage, in turn, is almost twice as deep and has another dense surface layer above it. Drilling will take place at a point where, according to current knowledge, there is no natural gas in the subsoil.

Drilling cores will be drilled during the drilling to obtain further detailed information about the quality of the storage horizon and the cover layers. During the two-year duration of the experiment, a continuous surveillance of the area from the surface to the depth takes place. Measuring probes are inserted into the drill holes in order to quantify the properties of the rocks in the different depths with three-dimensional seismological exploration (similar to ultrasound diagnostics in medicine). Geothermal and thermal processes are used, and the reactions of the CO2 with the host rock are investigated in situ.

"Here we use the entire methodological arsenal of geosciences to obtain a comprehensive picture of the processes taking place, because the essential aspect is the long-term security of such storage and the necessary development of appropriate monitoring technologies, " Emmermann notes.

Safety first

Thorough preliminary examinations are indispensable The operational phase that is now beginning has a long history. The location of the future research reservoir has been studied from surface to depth for years. For more than two years, the natural CO2 emissions from the soil over the entire storage area have been measured at regular intervals. This carbon dioxide is produced by the decomposition of biomass by soil organisms and has a significant seasonal variation. The exploration of local geology was also part of the preliminary work.

In order to be able to determine immediately any possible changes in the geology due to the storage, an elaborate three-dimensional seismic survey was carried out beforehand. After completion of the project, the option of "CO2 back into the earth" will be assessed on a well-founded database.

Audio contribution on the start of drilling of the CO2sink project in Ketzin with the contribution of Secretary of State Dr. Ing. Wolfgang Kr ger, Ministry of Economic Affairs of the State of Brandenburg and Professor dr. Dr. hc Rolf Emmermann, GFZ Potsdam

(idw - GeoForschungsZentrum Potsdam, 28.02.2007 - DLO)