Heat storage in the Danish subsurface is gaining increasing interest for optimizing
the use of energy resources, but no deep heat storage facilities have yet been
established. As an analogue we study the Gassum Formation in the Stenlille
structure that is presently used for gas storage. This allows us to discuss geological
and technical characteristics of an aquifer relevant for heat storage in Denmark.
We develop a 3D model for a high-temperature aquifer thermal energy storage system
using analysis of geological core data, sedimentological description, geophysical
data including well logs and seismic lines, as well as a finite difference model to
calculate the recovery efficiency, heat storage capacity and thermal breakthrough
time. Based on geostatistical methods we made three realisations and found similar
results for the three cases. In accordance with results from published simplified
models we found a high recovery efficiency of 70% after 4 years and 69% after 20
years, a high heat storage capacity of 1.8×1018 J, and a long thermal breakthrough
time of 66–77 years. These results reflect the excellent reservoir properties of the
Gassum Formation in Stenlille, characterised by a uniformly layered sand/shale
sedimentology, a high average porosity of 25% and a high permeability of 1000 to
10 000 mD of sandstone intervals.
Recovery efficiency in high-temperature aquifer thermal energy storage systems
