Download: https://doi.org/10.1144/petgeo2024-014

Abstract

This paper combines quality-controlled pore pressure measurements and indicators with geophysical well logs of 310 deep wells to evaluate the pore pressure distribution in the overpressured North Alpine Foreland Basin, in southeast Germany. Previous studies relied chiefly on low resolution checkshots and vertical seismic profiles calibrated to only a few pore pressure measurements. Current study based on sonic and electrical resistivity logs indicates that more than one shale normal compaction trend is required to appropriately assess pore pressure from geophysical well logs. Thereby, the necessary adjustments of the derived compaction trends apply to both sonic and resistivity data, which possibly reflect a gradual change in mineralogical composition with decreasing clay content or progressing cementation from north to south or an increase of horizontal loading driven compaction towards the North Alpine Thrust Front. The newly derived compaction-based pore pressure distribution is combined with drilling data-based pore pressure evaluations and offers a comprehensive update of previous pore pressure investigations in the North Alpine Foreland Basin. Our study is therefore of key importance for optimised well planning and cost-effective drilling in the course of the recent expansion of deep geothermal energy exploration in the overpressured North Alpine Foreland Basin.

Inorder to test the detectability of shallow gas deposits, a shallow seismic acquisition campaign was carried out between Altötting and Simbach a. Inn from May 13th to 17th, 2024. The campaign was conducted in cooperation with GeoSym GmbH. To do so, both P-wave and S-wave reflection seismic profiles with a total length of approximately 2000 m were acquired. Shallow gas deposits can pose a significant drilling risk, but pre-drill detection on conventional seismic is challenging. Due to the shallow gas deposits that have been proven in the past, the study area is particularly suitable for drawing conclusions about the detectability of shallow gas through seismic measurements and for improving the safety of (geothermal) drilling in other regions in the future through preliminary measurements.

The campaign is part of TUM.GTT's research project GeoChaNce, funded by the Bavarian Environment Agency.

TUM.GTT contributed two talks and a poster to the German Geothermal Congress (Der Geothermiekongress) 2023 in Essen.

Robin Renoth talked about social acceptance of deep geothermal energy: "Sind Bedenken gegenüber der Geothermie länderspezifisch? – Deutschland, die Schweiz und Japan im Vergleich"

Peter Obermeier presented a poster adressing velocity-density relationships and the vertical stress distribution in the North Alpine Foreland Basin in SE Germany (Bavaraian Molasse Basin): "Lithologisch differenzierte Dichte-Geschwindigkeitsbeziehungen zur regionalen Spannungs- und Kompaktionsmodellierung im Bayerischen Molassebecken" 

Michael Drews gave a talk about what to learn from pore presure and stress analysis with regard to deep geothermal exploration in the North Alpine Foreland Basin: "Integration of basin analysis and regional geomechanical investigations in the North Alpine Foreland Basin (Bavarian Molasse Basin) – implications for drilling, exploration and production"

Michael Drews was invited to speak about the ongoing efforts of TUM.GTT to initiate a global and quality-ranked pore pressure magnitude database in collaboration with the World Stress Map Project at the Gussow 2023 in Banff, Canada!

Co-Authors: Indira Shatyrbayeva, Birgit Müller (KIT) and Oliver Heidbach (GFZ Potsdam)

Dr. Florian Duschl and Dr. Saeed Mahmoodpour represented TUM.GTT with a poster and talk about mechanics of the subalpine wedge at the EGU general assembly in Vienna.

The abstracts can be accessed here: 

Poster by. F. Duschl et al.: 10.5194/egusphere-egu23-16710

Talk by S. Mahmoodpour et al.: 10.5194/egusphere-egu23-7038

On January 27th, students of the Geothermal/Geoenergy Master Study Scheme had the chance to discuss opportunities for jobs, master thesis topics and internships with representatives from 9 companies active in the geothermal sector. The companies covered the entire range from project development, geoscience, drilling and operators in both deep and shallow geothermal energy.

We would like to thank the students and representatives from Erdwärme Grünwald, Erdwerk, geoENERGIE Konzept, G.E.O.S., Geothermie Neubrandenburg (GTN), Geothermie Unterhaching, Innovative Energie für Pullach (IEP), KemCo and Stadwerke München (SWM) for their interest and participation.

The event was intiated and organized by the Geothermal-Alliance Bavaria (GAB), TUM's Professorship for Geothermal Technologies, FAU's Chair of Geology and Geothermie Unterhaching.