Evaluation of possible geothermal reservoirs in the Brønderslev area. Contribution to an evaluation of the geothermal potential

This report is prepared by GEUS for Brønderslev Varme A/S based on a local dataset and GEUS' regional geological models of the Danish subsurface. The report is a contribution to the assessment of the geothermal potential for possible geothermal reservoirs in the Northern Jutland area. The area of interest was defined by the client and with special focus on an evaluation of the Gassum and Skagerrak formations, however, the Frederikshavn and Haldager Sand formations, though shallowly buried, may constitute potential geothermal reservoirs and are considered as well.

GEUS has conducted studies of the regional development and geothermal potential of the prospective formations (Mathiesen et al. 2009), and has recently assessed the geothermal potential at several local areas in Denmark including the Hjørring area.

This report builds on available and released data that are relevant to an evaluation of the geothermal potential in the area of interest. The results of the study reported here show no discrepancies from the regional trends that GEUS has observed previously for the Danish area.

The report contains a quantitative petrophysical interpretation of the potential reservoirs based on the existing conventional cores and well logs in order to estimate the net/gross ratio including porosity permeability and transmissivity. Furthermore, an interpretation of the existing 2D seismic data in the Northern Jutland area has been carried out in order to map the depth to the formations and to investigate the presence of faults.

Focus will be on the Gassum and Skagerrak formations, both of which are buried deeply enough in the Fjerritslev Trough (i.e. above ~1000 m) to have geothermal potential in the Brønderslev area. As mentioned, the shallow Frederikshavn and Haldager Sand formations are considered possible geothermal reservoirs. The extent of the sand intervals in the Flyvbjerg Formation in itself is insufficient in terms of geothermal exploitation, however these intervals may contribute to the geothermal potential of the adjacent Haldager Sand Formation.

The report includes:

1. An assessment of the geological evolution of the Permian-Mesozoic succession in the licence area based on the Børglum-1, Flyvbjerg-1, Vedsted-1, Haldager-1 and Sæby-1 wells and GEUS' regional and general geological model for the Northern Jutland area.
2. An interpretation of relevant and available seismic data in the licence area in order to identify faults and map the distribution, depth and lateral continuity of possible reservoir-bearing formations.
3. A petrophysical interpretation based on available well logs from the Børglum-1, Flyvbjerg-1, Vedsted-1, Haldager-1 and Sæby-1 wells in order to assess the net/gross ratio, porosity and permeability of the potential reservoirs