Water-Related Risks of Exploration and Exploitation of Unconventional Natural Gas Deposits in the River Ruhr Watershed

Frank-Andreas Weber1, Axel Bergmann1
1 IWW Rheinisch-Westfälisches Institut für Wasser Beratungs- und Entwicklungsgesellschaft mbH

O 14.3 in Fracking for energy and its role for groundwater and soils

30.05.2014, 15:40-16:00, H18, NW II

In the watershed of the river Ruhr, several gas companies are currently assessing the possibility to exploit unconventional natural gas deposits presumed in the Lower Carboniferous by employing the fracking technology. The responsible authority of the Bezirks­regierung Arnsberg has granted the exploration fields (Erlaubnisfelder) “Ruhr” and “Falke-South”, which cover together almost 50 % of the Ruhr watershed. On behalf of AWWR (Arbeitsgemeinschaft der Wasserwerke an der Ruhr e.V.) and Ruhrverband we have examined the water-related risks possibly associated with the exploration and exploitation of these deposits under the specific site conditions of the Ruhr watershed (IWW 2013).

Mapping the presumed shale gas deposits shows that the target formation (Hangende Alaunschiefer in the Lower Carboniferous) extents over an area of up to 679 km² in the exploration fields within the Ruhr watershed, of which approx. 2/3 occur in depths of less than 1.000 m below ground level.

Assessing the dimension of a large-scale exploitation of these deposits, we conclude that the above-ground impacts of such a venture could result in hazards especially for surface water and groundwater used for drinking water production in the Ruhr watershed.

The geologic-technical risks associated with a large-scale exploitation of these deposits is probably less relevant in comparison according to the current state of knowledge, but cannot be ruled out especially in those areas exhibiting less favorable geologic-hydrogeological conditions. The risks associated with the disposal of the extracted flowback can currently not be adequately assessed.

Based on the evaluation of water-related risks and deficits of knowledge, we recommend that exclusion zones have to be defined, in which no deep wells employing the fracking technology are allowed to be drilled, nor should these zones be passed underground (e.g. by horizontal drilling). We recommend that exclusion zones must cover all areas exhibiting unfavorable geologic-hydrogeological conditions, in which the rock overlying the frac horizon might provide a poor geologic barrier due to insufficient thickness, the presence of deep reaching faults or anthropogenic pathways. We further recommend that exclusion zones must cover all water bodies with special protection requirements in which precautionary principals dismiss the employment of the fracking technology.

After a preliminary mapping of the recommended exclusion zones, an area of less than 3  % of the exploration fields “Ruhr” and “Falke-South” remain potentially for the exploration and exploitation of shale gas in the Ruhr watershed. However, additional land use requirements of high and very high significance (Raumwiderstand) have concurrently to be considered in some of these areas.

IWW (2013): Wasserwirtschaftliche Risiken bei Aufsuchung und Gewinnung von Erdgas aus unkonventionellen Lagerstätten im Einzugsgebiet der Ruhr. Accessible at http://www.awwr.de and http://www.ruhrverband.de

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Letzte Änderung 05.02.2014