Characterisation of the Upper Jurassic geothermal reservoir in the South German Molasse Basin as basis for a potential assessment to foster the geothermal installation development – Results from the joint research project Geothermal Alliance Bavaria

Abstract

Geothermal energy applications are seen as one key element for a successful heat transition in Bavaria. But there are still some barriers for a further development. To minimize these barriers the joint research project Geothermal Alliance Bavaria (GAB) is established. One important issue to foster the implementations of geothermal projects is the assessment of geothermal load prediction in the South German Molasse Basin (SGMB). This includes, aside from a reservoir temperature prognosis, an accurate description of the hydraulic properties of the Upper Jurassic Malm reservoir. Hydraulic test analyses are conducted in the framework of the GAB to obtain specific information about the hydraulic productivity of the reservoir. Results from these analyses show a decrease of rock permeability in southern direction within the reservoir. Because the spatial distribution of hydraulic test data is limited, the porosity of the reservoir is assessed by borehole core tests and logs interpretation. A trend of matrix porosity decrease with depth is recognised and correlates with the hydraulic test results. Based on these findings and combined with further information the Upper Jurassic reservoir could be classified in separated zones of similar production rates, which can now be used for a thermal output prognosis for the Bavarian part of the SGMB. To spatially expand these prognoses more data must be investigated in the next research phase of the GAB.

Inverse flow zone characterization using distributed temperature sensing in a deep geothermal production well located in the Southern German Molasse Basin

“…Here, the main target for hydrogeothermal exploration are the Upper Jurassic "Malm" carbonates, which lay in shallow depths in the North and are dipping to the South where they can be found in depths of 4000-6000 m near the northern alpine front (Flechtner et al, 2020). These sedimentary layers partly show high porosities with up to 27.5 % (Zosseder et al, 2022) and high permeabilities (for matrix permeability, core measurements range between 10 −4 to 10 2 mD, Bohnsack et al, 2020), but also high heterogeneity on small regional scales. The production temperatures range between under 40 • C in the north and over 160 • C in the south (Weber et al, 2019).…”

Uncertainty Assessment of Corrected Bottom-Hole Temperatures Based on Monte Carlo Techniques

“…In the last 15 years, a lot of geothermal projects were developed, making the Bavarian Molasse Basin one of Europe's most important low enthalpy geothermal hotspots today [39,40]. Extensive studies were conducted during the geothermal buildup to characterize the reservoir of the Molasse Basin in detail as well as regionally, hydrochemically [41], petrophysically [42], and geothermally [43,44].…”