German Basin Research Articles

Repurposing idle wells in the North German Basin as deep borehole heat exchangers

This study investigates the feasibility to repurpose wells from gas production for geothermal closed-loop application in the North German Basin (NGB). The objective for this research topic is to extend the value-added chain of idle wells by re-completion as coaxial deep borehole heat exchangers as an efficient way to produce green energy without drilling new wells by saving the carbon emission and costs of building a new geothermal well. With numerical models of two typical geological settings of the NGB and two different completion schemes, it is possible to simulate the thermal performance over a lifetime of 30 years. The calculated heat extraction rates range from 200 to 400 kW, with maximum values of up to 600 kW. Sensitivity analyses demonstrate that re-completion depth and injection temperature are the most sensitive parameters of thermal output determination. The heat demand around the boreholes is mapped, and heat generation costs are calculated with heating network simulations. The initial production costs for heat are comparable to other renewable energy resources like biomass and competitive against gas prices in 2022. This study highlights available geothermal resources’ environmental and economic potential in already installed wells. The application has almost no geological and no drilling risks and may be installed at any idle well location.

Variability of Middle Triassic vermicular limestone ichnofabrics: the Anisian Hisban Formation in Jordan

The strongly bioturbated Middle Triassic (Anisian) limestones, referred to as vermicular limestone, are the dominant lithology of the Hisban Formation in Jordan. This limestone exhibits the monotonous Oravaichnium– Planolites ichnofabrics, which are known and common in the northern Peri-Tethys and the Germanic Basin. The most abundant and widespread trace fossil here is Oravaichnium carinatum, which is produced by bivalves. Specimens of O. carinatum from the Hisban Formation are typically strongly elongated in the vertical axis and have a smooth surface, whereas specimens from the Germanic Basin mainly have a pear-shaped cross-section. Nevertheless, both morphologies and transitional morphotypes between these ichnospecies are present in both areas. The difficulty in distinguishing between Oravaichnium and Planolites causes the intense bioturbation by bivalves to be underestimated. The wide occurrence of the Oravaichnium ichnofabric in the northern and southern Peri-Tethys suggests that small burrowing bivalves played a significant role in the colonization and infaunalization during the long-term recovery of the benthos after the Permian–Triassic crisis. They experienced intense development during the Middle Triassic, when they were responsible for extensive bioturbation.

Osteology and relationships of the Late Triassic giant dicynodont Lisowicia

Abstract Unexpectedly abundant remains of herbivorous therapsids in the Late Triassic strata of southern Poland have significantly supplemented knowledge of their evolution. The skeletal morphology of the Late Norian (or Rhaetian) dicynodont Lisowicia bojani supports its close relationship to the Carnian Woznikella, both known from the Polish part of the Germanic Basin. Three evolutionary lineages of dicynodonts—Laurasian–Gondwanan Rhadiodromus klimovi → Jachaleria candelariensis lineage, Laurasian lineage Shaanbeikannemeyeria xilougouensis → Lisowicia bojani, and the Gondwanan lineage Kannemeyeria simocephalus → Dinodontosaurus brevirostris—are distinguished based on characters of cranial and postcranial elements. In the lineages characterized by the parietal oval in cross-section and the two distinct articulations on the sternum, there is a tendency to exclude the frontal from the orbital margin and to reduce the number of sacral vertebrae. In the lineage with the parietal narrow and triangular in cross-section, the frontal forms part of the orbit margin, there is a single joint on the sternum, and there is a tendency towards flattening the skull roof. In both lineages the shoulder girdle is convergently modified, the acromion process decreased, and joints on the sternum moved posteriorly.

Facies architecture, pedogenesis and palynology of the Olenekian dryland setting – A sedimentary record of Early Triassic climate oscillations in the SE Germanic Basin

The Early Triassic period was characterised by significant climatic perturbations driven by generally high global temperatures. Several significant shifts in the stable carbon and oxygen isotopes were recognised in the marine settings in the Olenekian age deposits that were linked to short-lasting but relatively high-amplitude climatic events. The record of these events in the continental strata is far less understood due to the stratigraphic incompleteness of such deposits. However, in the Holy Cross Mountains (Poland), the Olenekian continental deposits are well preserved, and sedimentation was relatively continuous, making them an ideal candidate for studying the effects of climate changes and their preservation in continental settings. As such, sedimentological analysis of five wells and one outcrop (over 530 m logged in total), integrated with new and legacy palynological data, allowed the reconstruction and dating of major steps in the palaeoenvironmental evolution of the SE part of the Central European (Germanic Basin), and its comparison with the marine-based climatic models for the Early Triassic. The lower and middle Olenekian stage is represented by fine-grained deposits of dry floodplain interbedded with sandstones deposited within fluvial distributary channels and terminal splays. The palaeosols are mainly represented by aridisols (calcisols), indicating a relatively dry, though not extreme, climate as some water was necessary to support relict plant cover. Towards the mid-Spathian times, the climate became more humid - lacustrine deposits appeared, and palaeosols displayed features of an elevated water table (gleyed vertisols and inceptisols). Frequent storms and floods also affected the lacustrine sedimentation, reflecting volatile climatic conditions. In the late Spathian time, continental sedimentation continued, and the dominance of vertisols and more stacked fluvial channels in the sequence is linked with an increased seasonality, with more pronounced humid seasons. The continental setting lasted until the latest Spathian time, when a marine transgression occurred, marking a new phase in the basin development.

Hydrogeochemical and microbial characterization of a Middle Triassic carbonate aquifer (Muschelkalk) in Berlin and geochemical simulation of its use as a high-temperature aquifer thermal energy storage

The geological formation of the Muschelkalk is widespread in the center of the North German Basin (NGB) and is increasingly attracting interest for application of geothermal energy extraction or high-temperature aquifer thermal energy storage (HT-ATES). This study investigates the Middle Triassic “Rüdersdorfer Schaumkalk”, which was the former injection horizon of the natural gas storage facility in Berlin, Germany. For the first time, detailed chemical and microbiological analyses of formation water of this Lower Muschelkalk limestone formation were conducted and hydrogeochemically characterized. In addition, a hydrogeochemical model was developed to quantify the potential reactions during HT-ATES focusing on calcite dissolution and precipitation. The main objectives of this study are: (1) to determine the origin of the water from the three wells targeting the Muschelkalk aquifer, (2) to understand changes in hydrochemistry after system operation, and (3) to evaluate the long-term sustainability of a potential HT-ATES system with increasing temperature. The target formation is encountered by several wells at about 525 m below the surface with an average thickness of 30 m. Two hydraulic lifting tests including physical, chemical, and microbial groundwater as well as gas monitoring were carried out. In addition, several downhole samples of formation fluid were collected from the aquifer at in situ pressure and temperature conditions. Fluid analysis of the saline formation water indicate a seawater origin within the Muschelkalk with subsequent evaporation and various water–rock interactions with anhydrite/gypsum, dolomite, and calcite. With a salinity of 130 g/L, dominated by Na–Cl, a slightly acidic pH between 6 and 7, and a low gas content of 3%, the formation water fits to other saline deep formation waters of the NGB. Gas concentrations and microbial communities like sulfate-reducing bacteria and methanogenic archaea in the produced water indicate several geochemical alterations and microbial processes like corrosion and the forming of biogenic methane. Geochemical simulations of calcite equilibrium over 10 HT-ATES cycles indicated a pronounced propensity for calcite precipitation up to 31 mg/kgw, within the heat exchanger. At the same time, these models predicted a significant potential for calcite dissolution, with rates up to 21 mg/kgw, in both the cold and hot reservoirs. The results from the carbonate aquifer characterized in this study can be transferred to other sites in the NGB affected by salt tectonics and have provided information on the microbiological-chemical processes to be expected during the initial use of old wells.

A new species of Neocalamites from the Upper Buntsandstein (Anisian) of Üdingen (Rur Eifel, Germany)

Well preserved Early-Middle Triassic plant fossils from Northwest Europe are relatively rare due to the environmental conditions within the Germanic basin during this time period. The only sphenophyte species commonly described in the floras that are found in the area, is Equisetites mougeotii. However, only stems without leaf sheaths were ever reported. Here, we describe sphenophyte stems with free standing leaves from the Upper Buntsandstein of Üdingen, Germany, which we attribute to the genus Neocalamites based on this characteristic and the difference, mainly in stem size, of the Üdingen material to E. mougeotii. Most of the material consists of internodal, infertile stems that are unbranched and vary in width. A few of these stems are three-dimensionally preserved. Due to the difference of the material to the other, rarely present, Neocalamites species reported from the Anisian of Western Europe, we propose the plant fossils from Üdingen to be a new species called Neocalamites vanderburghii n.sp.

Influence of Hydrogen on the Failure Mechanism of Standard Duplex Stainless Steel X2CrNiMoN22-5-3 Exposed to Corrosion Fatigue

IIn a geothermal environment, cathodic protection is employed to improve resistance against corrosion fatigue. However, during the cathodic reactions under applied potential, hydrogen is generated and assimilated, leading to a reduced lifetime expectancy of high-alloyed steels. The corrosion fatigue mechanism of a standard duplex stainless steel X2CrNiMoN22-5-3 (1.4462) specimen loaded with hydrogen was studied in a corrosion chamber specifically designed for the purpose, surrounded by the electrolyte of the Northern German Basin at 369 K. The microstructural reactions resulting in hydrogen incorporation significantly decrease the number of cycles to failure of the specimen. This reduction is attributed to hydrogen enhancing crack propagation and causing early failure, primarily due to the deterioration of the mechanical properties of the ferritic phase rather than corrosion reactions or corrosive degradation.

A synthetic chronostratigraphy for the upper Campanian–Maastrichtian of the Boreal Realm based on the Danish and German basins

Abstract New carbon isotope results obtained from cores from the Fehmarn Belt (German Basin), along with hitherto unpublished detailed results obtained from brachiopods collected in the 1970s from the Hemmoor section, NW Germany, present the opportunity to revise the holostratigraphy of the Danish Basin and erect a complete chronostratigraphical scheme for the upper Campanian–Maastrichtian of the Boreal Realm based on records from the Danish and North German basins. The correlation of all studied sections is ensured by previously erected high-resolution bulk carbonate carbon isotope records. A number of issues arising from the standard Upper Cretaceous (UC) calcareous nannofossil biozonation scheme for the Boreal Realm are discussed and lead us to propose a new subzonation for the Danish Basin. Carbon isotope records allow correlation to Gubbio, Italy, the Tethyan bio-magnetostratigraphic reference, and to the astronomically calibrated ODP site 762C, Indian Ocean. Revised correlations ensure the application of magnetostratigraphy, a numeric timescale and stacking of 405 kyr cycles to the new scheme, thus erecting a detailed chronostratigraphy for the upper Campanian–Maaatrichtian of the Boreal Realm.

Late Triassic to Early Jurassic carbon isotope chemostratigraphy and organo-facies evolution in a distal to proximal transect of the North German Basin

AbstractThroughout the Latest Triassic and the Early Jurassic, major changes in paleogeography, climate and eustatic sea-level impacted on the development of shelf depositional environments. Secular trends in environmental conditions were punctuated by transient perturbations that occurred in relation to large-scale volcanic events, such as the emplacement of the Central Atlantic Magmatic Province at the Triassic/Jurassic boundary and the Karoo–Ferrar Large Igneous Province in the early Toarcian. We here present bulk organic (HAWK programmed pyrolysis) and organic carbon isotope (δ13Corg) data for three drill cores recovering Latest Triassic and Early Jurassic strata (Rhaetian to Toarcian). Study sites are located in the northeastern part of the Central European Epicontinental Sea and were positioned along a distal–proximal transect of the North German Basin. This allows discussing the differential response of depositional settings and organo-facies toward secular and transient environmental change. Biostratigraphically anchored trends in δ13Corg values allow the precise correlation along the transect, as well as with distant sites. At all North German locations, diagnostic secular trends in δ13Corg are punctuated by transient negative carbon isotope excursions, reflecting perturbations of the global carbon cycle at the Triassic/Jurassic boundary and in the early Toarcian. Stratigraphic gaps occurred during sea-level lowstands and are most pronounced at shallow proximal sites. Programmed pyrolysis data indicate spatiotemporal organo-facies trends that on a temporal scale occurred in response to sea-level and climate trends, while spatial patterns were governed by basin morphology and paleobathymetry. Substantial marine organic matter accumulations occurred at high sea level during the Toarcian only, and were most continuous at distal sites. Graphical Abstract

Climate cyclicity-controlled recurrent bottom-water ventilation events in the aftermath of the Toarcian Oceanic Anoxic Event: the Jenkyns Event

AbstractEnvironmental perturbations of the Toarcian Anoxic Event and its associated carbon isotope excursion (CIE) occurred in a cyclic fashion indicating an orbital control mechanism. Sedimentary strata of the E. elegantulum ammonite subzone in the Lorraine Sub-basin, Luxembourg, exhibit eight sedimentary cycles, most of which postdate the CIE, implying that its termination did not coincide with a full recovery from environmental stress. Sea-level and temperature fluctuations of the Toarcian crisis were linked to a cryosphere demise in the Northern Hemisphere, which modulated stadial versus interstadial phases on the orbital 100 ka eccentricity frequency band. Upon stadial phases, enhanced wind strength in combination with lowered sea level disrupted stratified shelf waters and shifted the storm wave base close to the sea floor. Ventilation of bottom waters interrupted accumulation of laminated and organic-rich black shales, but formed organic-lean and non-laminated gray claystones enriched in terrigenous wax lipids and spores provided via aeolian transport from the hinterland due to the enhanced wind strength. Wind systems are assumed to have been driven by high pressure differences between the cryosphere in the North of the Tethyan shelf and the warmer costal lowland. This distinguishes the atmospheric turbulences after the CIE from the postulated intensification of the cyclones that accompanied the rapid warming at the beginning of the CIE. The deep-water ventilation event following the CIE in the Lorraine Sub-basin was accompanied by a parallel evolution in the SW German Basin, indicating a supraregional driving mechanism in paleobathymetric sub-basins susceptible to lowering of storm wave base. In sub-basins with greater water depth on the NW-Tethyan shelf, post-CIE orbitally driven atmospheric turbulences had a minor or no effect on water column stratification and deposition of organic-rich laminated black shales persisted. Graphical abstract

Physical modeling of ice-sheet-induced salt movements using the example of northern Germany

Abstract. Salt structures and their surroundings can play an important role in the energy transition related to a number of storage and energy applications. Thus, it is important to assess the current and future stability of salt bodies in their specific geological settings. We investigate the influence of ice sheet loading and unloading on subsurface salt structures using physical models based on the geological setting of northern Germany, which was repeatedly glaciated by the Scandinavian Ice Sheet during the Pleistocene. Apparent spatial correlations between subsurface salt structures in northern Germany and Weichselian ice marginal positions have been observed before, and the topic is a matter of ongoing debate. Recently described geomorphological features – termed surface cracks – have been interpreted as a direct result of ice-sheet-induced salt movement resulting in surface expansion. The spatial clustering and orientation of these surface cracks has not been well understood so far, owing to only a limited number of available studies dealing with the related salt tectonic processes. Thus, we use four increasingly complex physical models to test the basic loading and unloading principle, to analyze flow patterns within the salt source layer and within salt structures, and to examine the influence of the shape and orientation of the salt structures with respect to a lobate ice margin in a three-dimensional laboratory environment. Three salt structures of the northern German basin were selected as examples that were replicated in the laboratory. Salt structures were initially grown by differential loading and buried before loading. The ice load was simulated by a weight that was temporarily placed on a portion of the surface of the models. The replicated salt structures were either completely covered by the load, partly covered by the load, or situated outside the load extent. In all scenarios, a dynamic response of the system to the load could be observed; while the load was applied, the structures outside the load margin started to rise, with a decreasing tendency with distance from the load margin, and, at the same time, the structures under the load subsided. After the load was removed, a flow reversal set in, and previously loaded structures started to rise, whereas the structures outside the former load margin began to subside. The vertical displacements during the unloading stage were not as strong as during the load stage, and thus the system did not return to its pre-glaciation status. Modeled salt domes that were located at distance from the load margin showed a comparably weak reaction. A more extreme response was shown by modeled salt pillows whose margins varied from sub-parallel to sub-perpendicular to the load margin and were partly covered by the load. Under these conditions, the structures showed a strong reaction in terms of strain and vertical displacement. The observed strain patterns at the surface were influenced by the shape of the load margin and the shape of the salt structure at depth, resulting in complex deformation patterns. These physical modeling results provide more evidence for a possible interplay between ice sheets and subsurface salt structures, highlighting the significance of three-dimensional effects in dynamic geological settings. Our results lead to a better understanding of spatial patterns of the surface cracks that were mapped at the surface above salt structures and offer further room for interpretation of the influence of salt movements on the present-day landscape.

New data on the occurrence of echinoderms in the Muschelkalk (Middle Triassic) of Upper Silesia

In the Sadowa Góra quarry in Jaworzno, southern Poland, the Muschelkalk deposits are exposed (Lower and Upper Gogolin Beds). The occurrence of echinoderms seems to be particularly interesting. The isolated ossicles of asteroids were found already in the 1st Wellenkalk of the Lower Gogolin Beds (Aegean), which is one of the oldest post-Paleozoic occurrence in the world. Until recently, it was believed that the first echinoids appeared in the Germanic Basin during the Bithynian (above the Conglomeratic Horizon of the Upper Gogolin Beds). Currently, they have been found, similarly to the remains of asteroids, already in the 1st Wellenkalk. Attention was also drawn to the fact that the stratigraphically important crinoid species Holocrinus dubius may have appeared in Upper Silesia earlier than previously thought.

Form of salt rises as an indicator of interaction of geodynamic systems

The forms of salt uplifts are formed under the influence of stresses developing in the earth’s crust and, therefore, can be considered as sensitive indicators of the interaction of geodynamic systems. In the North German basin, in the Cis-Ural trough on the border with the Caspian depression and in the Pripyat trough, under the influ- ence of various sources of stress and deformation, forms of salt uplifts arose, reflecting the superposition of these systems. The mechanisms of such a superposition were both the formation of forms associated with the resulting addition of deformation vectors and the interference of forms associated with each geodynamic system separately.

Modeling the influence of climate on groundwater flow and heat regime in Brandenburg (Germany)

This study investigates the decades-long evolution of groundwater dynamics and thermal field in the North German Basin beneath Brandenburg (NE Germany) by coupling a distributed hydrologic model with a 3D groundwater model. We found that hydraulic gradients, acting as the main driver of the groundwater flow in the studied basin, are not exclusively influenced by present-day topographic gradients. Instead, structural dip and stratification of rock units and the presence of permeability contrasts and anisotropy are important co-players affecting the flow in deep seated saline aquifers at depths >500 m. In contrast, recharge variability and anthropogenic activities contribute to groundwater dynamics in the shallow (<500 m) freshwater Quaternary aquifers. Recharge fluxes, as derived from the hydrologic model and assigned to the parametrized regional groundwater model, reproduce magnitudes of recorded seasonal groundwater level changes. Nonetheless, observed instances of inter-annual fluctuations and a gradual decline of groundwater levels highlight the need to consider damping of the recharge signal and additional sinks, like pumping, in the model, in order to reconcile long-term groundwater level trends. Seasonal changes in near-surface groundwater temperature and the continuous warming due to conductive heat exchange with the atmosphere are locally enhanced by forced advection, especially in areas of high hydraulic gradients. The main factors controlling the depth of temperature disturbance include the magnitude of surface temperature variations, the subsurface permeability field, and the rate of recharge. Our results demonstrate the maximum depth extent and the response times of the groundwater system subjected to non-linear interactions between local geological variability and climate conditions.

The Insignificant Improvement of Corrosion and Corrosion Fatigue Behavior in Geothermal Environment Applying Boehmit Coatings on High Alloyed Steels

The efficacy of alumina-sol based coatings in a water-free atmosphere at high temperatures suggests a potential solution for enhancing the corrosion resistance of high-alloyed steels in Carbon Capture and Storage (CCS) environments. In this study, coupons of X20Cr13, designed for use as injection pipes with 13% Chromium and 0.20% Carbon (1.4021, AISI 420), were sol-gel coated with water and ethanol-based alumina. These coated coupons were then exposed to CO2-saturated saline aquifer water, simulating conditions in the Northern German Basin, for 1000 h at ambient pressure and 60 °C. Corrosion fatigue experiments were also conducted using specimens of X5CrNiMoCuNb16-4 (1.4542, AISI 630), a suitable candidate for geothermal applications, to assess the impact of the ethanol-based coating on the number of cycles to failure at different stress amplitudes. Unfortunately, the coating exhibited early spallation, resulting in corrosion kinetics and corrosion fatigue data identical to those of uncoated specimens. Consequently, the initially promising Boehmit coating is deemed unsuitable for CCS applications and further research therefore not advisable.

Organic matter influence on ooid formation: New insights into classic examples (Great Salt Lake, USA; Triassic Germanic Basin, Germany)

ABSTRACTOoids are coated grains composed of a tangential or radial cortex growing around a nucleus. They are common in carbonate deposits of almost any geological age and provide insights into environmental conditions. However, abiotic or biotic factors influencing their formation remain unclear. This study aims to advance current understanding of ooid formation with a multi‐analytical approach (for example, field emission scanning electron microscopy, Raman spectroscopy and micro X‐ray fluorescence) to classic examples from Great Salt Lake, USA, and the Lower Triassic Germanic Buntsandstein Basin, Germany. Both of these deposits represent hypersaline shallow‐water environments where ooids are closely associated with microbial mats. Great Salt Lake ooids are dominantly 0.2 to 1.0 mm in size, ellipsoidal to subspherical in shape, composed of aragonite and contain organic matter. Germanic Buntsandstein Basin ooids are mainly ≤4 mm in size, spherical to subspherical in shape, composed of calcite and currently contain little organic matter. Despite the differences, both ooids have the same cortex structures, likely reflecting similar formation processes. Some Great Salt Lake ooids formed around detrital grains while others exhibit micritic particles in their nuclei. In Germanic Basin ooids, detrital nuclei are rare, despite the abundance of siliciclastic particles of various sizes in the host rocks. Germanic Basin deposits also include ‘compound ooids’, i.e. adjacent ooids that coalesced with one another during growth, suggesting static in situ development, which is supported by the lack of detrital grains as nuclei. Germanic Basin ooids also grew into laminated microbial crusts with identical microstructures, further indicating a static formation. Such microbial crusts typically form through mineral precipitation associated with organic matter (for example, extracellular polymeric substances), suggesting a similar formation pathway for ooids. The inferred key‐role of organic matter is further supported by features in radial ooids from the Great Salt Lake, which commonly exhibit, from their nuclei towards their surface, increasing organic matter contents and decreasing calcification.

Lower Jurassic (Pliensbachian–Toarcian) marine paleoenvironment in Western Europe: sedimentology, geochemistry and organic petrology of the wells Mainzholzen and Wickensen, Hils Syncline, Lower Saxony Basin

AbstractOver the past few decades, Toarcian (Early Jurassic) black shale deposits of NW Europe have been extensively studied, and the possible global and regional mechanisms for their regional variation have been discussed. In this context, the black shales of the Northwest German Basin are still sparsely studied with regard to their palaeo-depositional history. This study aims to understand the connection between regional and global influences on the widespread Early Toarcian oceanic anoxic event by examining two wells covering the Upper Pliensbachian to Upper Toarcian sediments in the Northwestern German Basin. The core intervals were analysed using a multidisciplinary approach, including geochemistry, biostratigraphy and organic petrography. Marine palaeoenvironmental changes were reconstructed, and sediment sequences were stratigraphically classified to allow a supra-regional stratigraphic correlation. The results reveal complex interactions between sea level changes, climate warming, basin confinement, and Tethys–Arctic connectivity resulting in the Toarcian black shale deposition. Upper Pliensbachian sediments were deposited under terrigenous influence, shallow water depths, and predominantly oxic bottom water conditions. The deposition of black shale is characterized by algal organic material input and anoxic bottom water conditions. Strong correlations between water stratification, anoxia, and bioproductivity suggest that global warming and intensification of monsoonal rainfall, continental weathering, and increasing freshwater and nutrient inputs were the main factors controlling the formation of black shales. Prolonged deposition of OM-rich sediments in the NWGB may be related to intensified monsoonal precipitation in northern Europe and enhanced Tethys–Arctic connectivity at the serpentinum–bifrons transition. Graphical Abstract

The oldest teleosts (Teleosteomorpha): their early taxonomic, phenotypic, and ecological diversification during the Triassic

As the fossil record reveals, neopterygians had a major diversification after the great mass extinction at the Permian-Triassic boundary, including the appearance of the major clade Teleosteomorpha. Detailed studies of new taxa (Pseudopholidoctenus germanicus, Barschichthys ruedersdorfensis, and Ruedersdorfia berlinensis) from the lower Anisian (middle Muschelkalk) of Germany and their comparisons with other Triassic relatives are presented, including new information concerning size, shape, and diet. Two families, Pholidophoridae and Marcopoloichthyidae, made a modest appearance during the Anisian of Europe and Asia almost simultaneously, with Pseudopholidoctenus (and the teleosteomorphs Barschichthys and Ruedersdorfia) from the Germanic Basin, being the oldest stem teleosts (244 Ma), followed shortly by Marcopoloichthys ani from Italy. The early teleostean diversification was fast—already in the late Ladinian three lineages were present: Prohalecitiidae (Europe), Pholidophoridae (Asia, Europe), and Marcopoloichthyidae (Asia, Europe), with ca. 20 species inhabiting the Tethys Ocean during the Middle–Late Triassic. Most Triassic teleosteomorphs were small, ca. 50 mm standard length, and a few as possibly miniature, with torpedo or oblong shapes, and suction feeders—probably a plankton based-diet. These first Triassic radiations were replaced during the early Sinemurian of marine ecosystems of Europe with two major groups: (a) non-monophyletic ‘pholidophoriforms’ and (b) proleptolepids and leptolepids, having an average size (ca. 100 mm SL) longer than Triassic forms, with oblong and fusiform shapes. A fast dispersion from the Tethys to the Paleo-Pacific followed, as demonstrated by the presence of small (ca. 50 mm SL) suction feeder proleptolepids in the early Sinemurian of Chile.

Underground Hydrogen Storage in the Bunter Sandstone Formation in the North German Basin: Capacity Assessment and Geochemical Modeling

With planned hydrogen import terminals and production sites along the North and Baltic Seas, the German coast is likely to become the center of the hydrogen economy. Underground hydrogen storage in the sedimentary reservoirs of the region, particularly in the Bunter Sandstone Formation, could provide the required storage capacity for the future hydrogen economy due to its widespread occurrence and proven sealing system. Herein, the storage capacity is assessed using a probabilistic volume approach and possible reactions between the Bunter Sandstone and hydrogen based on geochemical simulations with PHREEQC are determined. This assessment gives an effective storage capacity of 0.84–4.14 PWh in the saline aquifers of the Bunter Sandstone, of which 0.52–2.57 PWh could be stored onshore. If production from currently operating fields are to cease, additional capacities of between 89.43 and 285.53 TWh could be found in its hydrocarbon fields. Mineralogical reactions are shown to be restricted to redox reactions, which do not affect the formation integrity of siliciclastic reservoirs. As a result, pore storage facilities in the Bunter Sandstone could provide an important storage option for the hydrogen economy, but will require further investigations in the lab and in the field.

Modeling and economic evaluation of deep geothermal heat supply systems using the example of the Wealden near Hannover, Germany

Germany desires to become climate-neutral in its heat supply by 2045. From 2024 onward communities are legally required to develop a plan documenting how the objective will be achieved. Geothermal resources can be a major building block to reach the aspirational target if they can be developed at competitive costs. To evaluate the economic potential of geothermal resources is time and money consuming. Questions which need to be addressed in the context of such evaluations are: how can an economic recovery of geothermal heat be achieved, how can subsurface risks associated with an exploration be managed, and how competitive is a deep geothermal energy recovery compared to other options of heat supply? These questions are key to a development of deep geothermal heat, especially if the geothermal conditions are not as prominent as in already realized projects, but less favorable as in the deep clastic sediments of the North German Basin. With this contribution a procedure is presented and used to determine net present values and the associated levelized costs for deep hydrothermal heat recovery systems. It consists of modelling the geothermal cycle, sizing all necessary components, costing them, and calculating net present value and levelized cost. The thermal model is verified by comparing the modelled state variables pressure and temperature at relevant state points of the thermal cycle with actual data of a geothermal project. The cost model is validated with biding results and cost information from actual projects and modified as appropriate. In applying the model to a setting in the Hannover–Celle area with temperatures of around 70 °C, conditions are determined, which lead to positive net present values. The degree of their influence is determined in sensitivity analyses allowing a systemic optimization. The results show that for a coupled heat plant with geothermal heat supplied at baseload conditions, levelized costs of approx. 8 cents/kWh are achievable. The presented thermodynamic and cost models are considered helpful instruments for developing preliminary conceptual estimates, strategies for optimization, and portfolio management.