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Free keywords:
Molasse Basin, Malm, Geothermal energy, Coupled fluid and heat
transport, Thermal anomaly
Abstract:
The European Molasse Basin is a Tertiary foreland basin at the northern front of the
Alps, which is filled with mostly clastic sediments. These Molasse sediments are under‑
lain by Mesozoic sedimentary successions, including the Upper Jurassic aquifer (Malm)
which has been used for geothermal energy production since decades. The thermal
field of the Molasse Basin area is characterized by prominent thermal anomalies. Since
the origin of these anomalies is still an object of debates, especially the negative ones
represent a high risk for geothermal energy exploration. With our study, we want to
contribute to the understanding of the thermal configuration of the basin area and
with that help to reduce the exploration risk for future geothermal projects in the
Molasse Basin. For this, we conducted 3D basin‑scale coupled fluid and heat transport
simulations to reproduce the present‑day thermal field of the Molasse Basin by con‑
sidering conduction, advection, and convection as heat‑driving mechanisms. Within
this paper, we show how the temperature distribution of the Molasse Basin, including
the pronounced thermal anomalies, can be reproduced by coupled fluid flow and
heat transport simulations following a multi‑scale 3D‑modelling approach. We find
that the shallow thermal field is strongly affected by basin‑wide fluid flow. Further‑
more, we show that the temperature distribution at the depth of the Malm aquifer is
strongly influenced by the hydraulic conductivity of the Foreland and Folded Molasse
Sediments and that hydraulically conductive faults have only a minor influence on the
regional temperature distribution. Moreover, we show that the positive and negative
thermal anomalies are caused by the superposed effects of conductive and advective
heat transport and correlated with the geological structure.
