Geothermal Reservoir Characterization of the Brussels Sands in the North German Basin
Majdi Al-Howidy1,2, Hartwig von Hartmann1, Inga Moeck1,2
1LIAG-Institute for Applied Geophysics (LIAG), Stilleweg 2, D-30655, Hannover, Germany; 2Georg-August Universität Göttingen, Goldschmidtstr. 3, D-37077 Göttingen, Germany
The North German Basin faces unique challenges and prospects for geothermal reservoirs due to its geological structure and geothermal potential. Eocene deposits show particular challenges as they are mainly marine in nature with calcareous influences. Transgressive sequences signify former sea level changes. Furthermore, diagenetic processes during geological time can change sediments' original depositional characteristics greatly leading to uncertainty of reservoir features. This research focuses on identifying and studying shallow to medium-deep geothermal plays within the Brussels Sands found in the middle Eocene and upper part of the lower Eocene section. This formation was chosen for its appropriate thickness and suitable lithology properties for geothermal reservoirs. This study introduces an approach that combines well and mud logs to understand the sedimentary environments and to build rock model with geothermal reservoir characterization. A comprehensive evaluation of the geothermal potential of the North German Basin has been carried out, focusing on play type classification. This is important for understanding the range of geothermal systems as well as their characteristics. The first step involves selecting areas that could have geothermal potential depending on the thickness of deposits, the presence of 3D seismic data, and the density of drilled wells. Based on these available data, primary analysis and literature review showed that the formation‘s sand bodies have good geothermal prospects, especially in sandstone layers which are characterized by promising potentials.
Medium deep geothermal energy exploration in Göttingen – current status and next steps
Alena Sophie Broge1,2, Bernd Leiss1, Inga Moeck1, Gerd Rappenecker2
1Georg-August-Universität Göttingen; 2Stadtwerke Göttingen AG, Deutschland
In the Göttingen region of Germany, Variscan metasedimentary rocks are expected at a depth of about >1500m, and are overlain by Permomesozoic rocks. The Zechstein layers are composed of rock salt, potash salt, gypsum, and carbonate layers (up to 500 m thick). The Zechstein lithologies are overlain by ~ 1000 m of Mesozoic sandstones (Buntsandstein), carbonates (Muschelkalk) and the clay-rich Keuper lithologies. The sedimentary cover is structurally overprinted by the N-S trending, Cenozoic Leinetal Graben. Analogue studies of the Paleozoic greywackes and slates in exposures in the Western Harz Mountains have been carried out for the exploration of deep Enhanced Geothermal Systems (EGS) within the EU-funded project MEET. Limited well data are available, but valuable information comes from two recent seismic lines.
Scientifically supported by the Geoscience Center of the University of Göttingen, The Stadtwerke Göttingen AG aims in a first step to implement a medium deep geothermal doublette system with the Middle Bunter Sandstone as a target horizon and assigned economic feasibility studies while the geosciences are running further field and experimental analogue studies to better parametrize the geological input data. Focus is on the primary and secondary permeabilities of the local sandstones in regard to burial and exhumation history as well as the tectonic overprint. In such an underexplored area, however, only a research well can decisively help to reinterpret the existing seismic lines and derisk the geothermal development path for Göttingen and the wider region.
Geothermal target horizon characterisation for a medium-deep exploration well in the Leinetal Graben
Sibel Melisa Gürsoy1, Alena Sophie Broge1, Marco Fazio2, Bernd Leiss1, David Charles Peter Peacock1, Tom Schintgen3, Inga Moeck1,3
1Georg-August-University Göttingen, Dept. Structural Geology and Geothermics, Goldschmidtstr. 3, 37077 Göttingen; 2Georg-August University Göttingen, Dept. Applied Geology, Goldschmidtstr. 3, 37077 Göttingen; 3Leibniz Institute for Applied Geophysics, Dept. Geothermics and Information Systems, Stilleweg 2, 30655 Hannover
Stadtwerke Göttingen AG aims to develop medium-deep geothermal systems in various potential target horizons. To support this, field and experimental analogue studies were conducted to parameterize better the geological input data necessary for economic feasibility studies. Variscan metasedimentary rocks in the Göttingen region of Germany are overlain by up to 1500 m of Permo-Mesozoic rocks. Zechstein layers, up to 500 meters thick, consist of rock salt, potash salt, gypsum, and carbonates, and are overlain by up to 1000 meters of Mesozoic sandstones (Buntsandstein), carbonates (Muschelkalk), and clay-rich Keuper layers. The sedimentary cover is structurally affected by the N-S trending Cenozoic Leinetal Graben.
Sixteen samples from the Zechstein, Buntsandstein, and Muschelkalk formations were collected from local natural exposures and quarries. Parameter measurements show porosities of 4 to 20% for the sandstones, 0.2 to 22% for carbonates, and 2.4 to 16.4% for dolomitic rocks. Respective density values are 2.0 g/cm3, 2.1 to 2.7 g/cm3, and 2.4 to 2.7 g/cm3. Permeability values range from 4.3 mD for the carbonates to 210 mD for the sandstones. Thermal conductivity values are 1.4 to 3.0 W/(m·K) for sandstones, 1.7 to 2.6 W/(m·K) for carbonates and 4.3 to 5.4 W/(m·K) for dolomites.
Samples from the Middle Bunter sandstone, with their high porosities and permeabilities, indicate significant geothermal potential when considering primary matrix permeability. Secondary permeability, such as through joints and faults, could greatly enhance reservoir quality. Therefore, this parameter needs further study.
Numerische 3D-Studie der Leistungsfähigkeit geothermischer Reservoire, die in typischen mesozoischen Formationen des Norddeutschen Becken zu finden sind, unter Verwendung von smarten Multi-Well Anordnungen
Niklas Mantei1,2, Ernesto Meneses Rioseco1,2, Inga Moeck1,2
1Leibniz-Institut für Angewandte Geophysik, Deutschland; 2Georg-August-Universität Göttingen
Bezüglich der Fernwärmenutzung in städtischen Gebieten in Deutschland bieten die Ressourcen der mitteltiefen Geothermie ein großes Potenzial, das aufgrund der erforderlichen Mindesttemperatur in Fernwärmenetzen noch nicht vollständig ausgeschöpft wird. Auch sind die entscheidenden Faktoren für die optimale und nachhaltige Entwicklung dieser mitteltiefen Ressourcen noch nicht vollständig geklärt. Innerhalb des ArtemIS Projektes analysieren wir systematisch den Einfluss der Lagerstättenqualität und betrieblicher Steuerungsfaktoren auf die Leistung typischer mesozoischer Sandsteinlagerstätten im Norddeutschen Becken (NDB), unter Verwendung von smarten Multi-Well Anordnungen. Zum ersten Mal vergleichen daher wir umfassend frühere analytische Ergebnisse mit unseren numerischen Resultaten, um den Einfluss verschiedener Kontrollfaktoren auf die Zeit des Auftretens des thermischen Durchbruchs, die maximale Abkühlrate nach dem Auftreten des thermischen Durchbruchs und die endgültige Produktionstemperatur zu quantifizieren. Basierend auf unseren numerischen Ergebnissen erstellen wir ein Ranking-Schema, das den Einfluss variierender Eingabeparameter auf die betrachteten Leistungsparameter zeigt. Weiterhin präsentieren wir eine beispielhafte Prognoserechnung für die geothermische Wärmenutzung von zwei typischen städtische Gebiete des NDB. Unsere umfassende numerische Studie veranschaulicht daher im Detail die komplexe thermohydraulische Wechselwirkung von geothermischen Dubletten-Arrays, die Steuerung der definierten thermischen Lebensdauer sowie die Optimierungsmöglichkeiten mitteltiefer geothermischer Ressourcen.
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