CO2 back into the earth

Drilling for greenhouse gas underground storage started at Ketzin

Large experiment CO2SINK. The CO2 storage site Ketzin. GFZ Potsdam
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The storage of the greenhouse gas carbon dioxide (CO2) in the ground could possibly help to stem climate change. The greenhouse gas is first isolated from emissions from power plants and then safely "shut off" hundreds of meters deep in the ground. Now drilling work for the first European carbon dioxide test storage facility has started in Ketzin near Berlin. As part of the European CO2SINK project, 60, 000 tons of CO2 are to be stored here over a depth of 700 meters over the next two years.

The drilling will show how CO2 can be introduced and stored in deep porous salt rock filled with salt water. On February 27, 2007, the first drilling was started, which will later feed almost 100 percent pure 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 project is being carried out under the auspices of the GeoForschungsZentrum Potsdam (GFZ) in cooperation with 18 partners from nine countries on the test site near Ketzin.

Large laboratory in the underground

3D seismic image of the covering layer and the underlying storage layer with location of the injection well. © GFZ Potsdam

This pilot plant will create a large-scale laboratory in which the behavior of CO2 in the subsurface will be investigated under realistic conditions. It is crucial which processes are triggered by the underground storage and what happens in the medium and long term with the CO2 stored underground. The amount of CO2 to be stored there daily corresponds to the amount of carbon dioxide exhaled by the population of Potsdam over the same period of time.

However, these small amounts will be enough to gain insights into injection technology, storage safety, and possible long-term risks and costs. The selected rock formation is particularly suitable for the planned project due to its geology. Underneath a former natural gas reservoir, there is another impermeable cover layer over a hundred meters thick.

Permanent monitoring ...

Drilling cores will be drilled during drilling to obtain more detailed information about the quality of the storage horizon and the cover layers. In addition, during the two-year duration of the experiment, a permanent monitoring 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 geophysical exploration (similar to ultrasound diagnostics in medicine). Geoelectric, seismic and thermal methods are used and the reactions of the CO2 with the host rock in situ are investigated. display

and safety first

Laboratory experiments to investigate petrophysical properties of reservoir rocks under the influence of CO2 under simulated in-situ pressure conditions. GFZ Potsdam

The drilling phase, which began in the spring of 2007, already has a long history: the site of the future research storage facility has been studied from surface to depth for many years. For more than two years, scientists have been measuring the natural CO2 emissions from the soil over the entire storage area 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. Upon completion of the project, the CO2 back to earth option will be judged on a well-founded database.

Left:

www.gfz-potsdam.de

www.co2sink.org

www.co2sink.org/newsline/FaltblCO2-09-05.pdf

(Prof. Dr. Frank Schilling / GeoForschungsZentrum Potsdam, 23.03.2007 - AHE)