'White spots' maps

A limited amount of subsurface data is available in parts of the Netherlands. These data are described in the 2017 report 'Framework for exploration work programme geothermal in areas with low data density' by EBN and TNO (in Dutch). For some areas, the scarce information is nevertheless enough to determine from an aquifer whether it has geothermal potential or not. For example, the Rotliegend in the Western Netherlands basin is very thin and also deeply buried. Notwithstanding the low data density, for this aquifer at this location, it can be stated with a relatively high degree of reliability that its geothermal potential is low. The Rotliegend in the province of Utrecht is also relatively unknown and poorly sampled. However, the aquifer here is locally thick (>100 m), while the maximum burial depth is relatively unknown. The current depth (~2 km) suggests that the aquifer here may have good potential, but this is uncertain ('white spot').

A 'white spot' map has been generated for each aquifer. This map reflects the available subsurface information. These areas may be interesting for geothermal energy exploration, despite a possibly low predicted geothermal potential. Based on available data, classes have been defined, the lower the value of the class the less certain we are of the subsurface parameters:

  • class 5: 3D seismic
  • class 4: 2D digital seismic > 1980 (reliable)
  • class 2: 2D digital seismic <= 1980 (moderately reliable)
  • class 4: Wells that have interpreted aquifer with radius of 4 kilometres

If 3D and 2D seismic is present at a site, the class of the 3D seismic applies . Then the classes of seismic (class 5, 4 or 2) and wells (class 4) are added together, creating the "white spots" map. The possible combinations are:

  • 9: 3D seismic + well
  • 8: 2D seismic > 1980 + well
  • 6: 2D digital seismic <= 1980 + well
  • 5: 3D seismic
  • 4: 2D digital seismic > 1980 or well
  • 2: 2D digital seismic <= 1980
  • 0: no data

The white spots maps are shown in the Mapviewer as semi-transparent overlay, in which a higher value (higher certainty) has a higher transparency.