Carbon capture and storage (CCS) is increasingly considered to be a tool that can significantly reduce the emission of CO2. It is viewed as a technology that can contribute to a substantial, global reduction of emitted CO2 within the timeframe that seems available for mitigating the effects of present and continued emission. In order to develop the CCS method the European Union (EU) has supported research programmes for more than a decade, which focus on capture techniques, transport and geological storage. The results of the numerous research projects on geological storage are summarised in a comprehensive best practice manual outlining guidelines for storage in saline aquifers (Chadwick et al. 2008). A detailed directive for geological storage is under implementation (European Commission 2009), and the EU has furthermore established a programme for supporting the development of more than ten large-scale demonstration plants throughout Europe. Geological investigations show that suitable storage sites are present in most European countries. In Denmark initial investigations conducted by the Geological Survey of Denmark and Greenland and private companies indicate that there is significant storage potential at several locations in the subsurface.
The Danish subsurface contains deep geothermal resources which may contribute for hundreds of years to the mixed Danish energy supply (Mathiesen et al. 2009). At present only a limited fraction of these resources are utilised in three existing geothermal power plants in Thisted, Margretheholm and Sønderborg (Fig. 1) where warm formation water is pumped to the surface from a production well and, after heat extraction, returned to the subsurface in injection wells (Fig. 2). Deep geothermal energy has the advantage of being a sustainable and environmentally friendly energy source which is furthermore independent of climate and seasonal variations, in contrast to wind and solar energy. The implementation of deep geothermal energy for district heating replacing conventional energy sources, especially coal and oil, may thus lead to a considerable reduction in the emission of greenhouse gases. There are therefore good reasons to include geothermal energy as a central component in Denmark's future supply of energy for district heating. Furthermore, heat-demanding industries may consider the possibility to integrate geothermal energy and energy storage in their production process. In order to facilitate the use of geothermal energy, a broad majority in the Danish parliament has granted financial support for initiatives within the geothermal field (Energy policy agreement of March 22, 2012). The present paper deals with one of the outcomes of this agreement, namely a WebGIS portal with an overview of existing and interpreted geological and geophysical data. This will be relevant for all stakeholders in the exploration of deep geothermal resources in the Danish subsurface. The portal focuses on geothermal reservoirs within the 800–3000 m depth interval and provides an overview of the amount and quality of existing geodata, the geological composition of the subsurface, and interpreted thematic products such as geological maps of potential geothermal reservoirs. A comprehensive map from the portal showing onshore and nearoffshore locations where the geological conditions are potentially suitable for extraction of deep geothermal energy in Denmark is shown in Fig. 1. Many of the thematic maps are outcomes of the project The geothermal energy potential in Denmark – reservoir properties, temperature distribution and models for utilizationunder the programme Sustainable Energy and Environment funded by the Danish Agency for Science, Technology and Innovation.
