An overlooked aquifer in the Netherlands: Medium depth geothermal potential of the Breda Formation in the Zuiderzee Low

Abstract

Geothermal energy in the Netherlands is growing in general, however, medium deep geothermal (200 - 1500 m depth) is lagging behind while the potential at these depths could be very high. Development is held back by little geologic knowledge of this interval as well as legislative constraints. Better understanding of the reservoir characteristics and well design in this depth range is necessary in order to accelerate the heat transition away from fossil fuels. The Breda Formation is deemed as one of the most promising formations within the medium depth range. Therefore, this formation, particularly the part found in the Zuiderzee Low (ZZL), is the focus point of this thesis. The reservoir characteristics are determined using newly obtained cutting information, novel biostratigraphic analyses, old and new seismic interpretations and petrophysical log data, eventually leading to a static reservoir model. Consequently, the static model is upscaled and used as input for dynamic simulations in the Harderwijk case study area. The static model provides new thickness, depth, porosity, permeability and transmissivity maps of the Breda Formation in the ZZL. These maps were generated using more data (types) than the current ones present in the REGIS model, and should therefore contain less uncertainty. The dynamic model provides insights into doublet lifetimes and flow rates for three different well trajectories in two possible reservoir scenarios. The horizontal trajectory proved superior in terms of doublet lifetime and flow rate for both reservoir scenarios. Finally, the current Dutch legislative framework covering the medium depth is limiting medium deep geothermal development in the Netherlands. A revision of the 500 m depth boundary separating the Mining and Water Law jurisdictions should be considered if the full potential of the medium depth is to be accessed.