HT-ATES (high-temperature aquifer thermal energy storage) systems target seasonal storage of large amounts of thermal energy enabling to meet the demand of e.g. industrial processes or district heating systems. The high injection temperatures or pressures of HT-ATES systems, however, cause thermo- and poroelastic stress changes close to the injection well, which may induce fault reactivation and seismicity. In this contribution, we focus on assessing the risk of fault reactivation and induced seismicity of the planned HT-ATES demonstrator DeepStor in the Upper Rhine Graben close to Karlsruhe, Germany, which aims at utilizing a former oil reservoir for HT-ATES. The risk assessment starts with a geological model of the planned storage site as input for thermo-hydraulic numerical modeling. The resulting changes in reservoir pressure and temperature are entered in a semi-analytical calculation of stress changes on a fault next to the HT-ATES system. A parameter sensitivity and subsequent Monte Carlo analysis with 1000 realizations show that the strongest influence is related to uncertainties in the stress state, especially the horizontal–vertical stress ratio and the orientation of the maximum horizontal stress. The calculated slip tendency on the fault next to the injection well, however, exceeds the friction coefficient only for c. 1 % of all parameter combinations of the Monte Carlo analysis, i.e. only for a very unfavorable combination of reservoir and operational parameters. Thus, the risk of fault reactivation and subsequent induced seismicity for HT-ATES at the DeepStor demonstrator can be expected to be relatively low.

We like to present calculated results for a hypothetical ATES system based on a geological reservoir model for the Breisgauer Bucht in the southwest of Germany. The storage configuration consists of two 8” horizontal filter sections with a length of 500m at a distance of 100m within the Buntsandstein in a depth of 700m below surface. Calculations were made with the FEA-Program COMSOL..

The seasonal storage system is powered by a solar thermal field (4ha) based on extrapolated hourly heat power data from 2016 to 2020, published for the solar thermal field in Vojens, Denmark. On the consumer load side, the monthly heat demand of 1000 households in Munich 2013 were taken.

Aim of the study was to calculate time dependent flow rates, pressure changes and temperature distributions to derive a realistic estimation of the production heat power, the storage capacity and the storage efficiency during operation. Dependent on the input data, storage efficiencies between 60% and more than 80% were calculated.

Since the optimal operation of an ATES is a trade-off between storage production power and storage efficiency, these models can be a powerful tools during the planning, construction and operation of an ATES system and, after validation in early operation phases, result in a digital twin for control (and cost) optimisation.

The City of Vienna is committed to become climate-neutral by the 2040. Its vast district heating grid, with a pipe length of over 1,300 Km connects more than 400,000 households and prevails in the heating sector by using 50% of the energy demand. Amongst other technologies, ATES is deemed one important building block in decarbonising the energy sector.

Evaluation of Neogene strata for ATES usage in the Vienna Basin involved interpretation of a modern 3D seismic survey and a large pre-existing dataset from oil & gas wells. Although the hydrocarbon prospective areas are generally situated in more proximal parts of the depositional systems, sedimentological interpretations can be extrapolated into the ATES study area with limited well control when applying sequence stratigraphic principles.

A geological concept is proposed for three sequences, each representing one specific depositional system. Each system contains a defined number of architectural elements such as slope, channel, fan, prodelta and delta plain. The geometry of the potential reservoirs is then assessed, whilst depositional environments have been calibrated with sedimentological data available from cores. Additionally, wireline log data from key wells have been used to calculate reservoir properties. Modelling of subsurface temperature data from offset wells resulted in a temperature model in 3D, which allows for accurate predictions of the reservoir temperatures.

By integrating data from all the disciplines, several GDE maps (Gross Depositional Environment) have been created. These maps highlight the high potential areas for ATES applications, in which leads and prospects will be explored in the near future.

Aquifer Thermal Energy Storage (ATES) systems are recognized for their substantial storage capacity at relatively low costs, making them an increasingly appealing technology. In densely populated urban areas like Berlin, where excess heat resources are abundant, geothermal district heat supply is of utmost importance. Therefore, ensuring the sustainable operation of ATES systems necessitates precise evaluation and prediction of hydraulic and heat transport processes.

Our research primarily focuses on the Adlershof ATES site located in the south-eastern region of Berlin. This ATES utilizes fine-grained Jurassic and Triassic sandstones to store and provide heat for the district heating network. To investigate the interaction between fluid and solid phases in porous media and their influence on storage behavior, we adopt an integrative approach that combines multiscale field measurements, laboratory experiments, core analysis, and numerical modeling.

Field measurements and laboratory experiments contribute to establishing the parameter ranges and identifying critical values for a medium-scale model. This model is employed for stochastic simulations to study the relevant system parameters, providing insights into sensitive parameters and their potential values. We confirm the hypothesis that the influence of dispersivity and porosity is dominating over the heat capacity. The model calibration can be improved by high-resolution measurements. Subsequently, a 3D large-scale model incorporates this information to facilitate the optimal design of the ATES system and ensure accurate long-term forecasting of its performance. Simulations account for varying injection temperatures and distances between wells to show the shared effect of these parameters and facilitate technical solutions.

Surplus heat as stored in an MTES (Mine Thermal Energy Storage) system in summer could partly meet the increasing demand of energy in winter. Better understanding the process of heat and mass transfer in the subsurface of an MTES during the injection-production cycles helps improving the budgeting of the stored mass and heat, and permits sustainable operation of such systems. Therefore, a concurrent injection and production test was conducted at a doublet wellbore system built in a previous mine site, Bochum, Germany. In this test, water of defined temperatures up to 55 °C was injected into the gallery of a horizontal mine drift down to 64 m in the subsurface, and the temperature of the concurrent produced water was below 25 °C. The depth-resolved temperature at both wellbores as monitored using the distributed temperature sensing (DTS) technique revealed such a heat transition in the storage that was much faster than the one which could be presumed for the porous rock matrix in the studied subsurface. By numerical modelling, it could be shown that the fracture flow-dominated heat transition in the storage yielded wellbore temperatures comparable to the values as monitored throughout the present test. Flow of water along the fractures as well as the concomitant heat transition into the surroundings resulted in lower temperature of the produced water as compared to the concurrent injected water.

High lithium concentrations of up to 162 mg kg^-1 in highly saline hydrothermal fluids occur in the calcareous Muschelkalk aquifer. We have combined and with modern investigation methods newly interpreted geological, hydraulic, hydrochemical, isotopic, thermal, and stress field data of the Muschelkalk aquifer beneath the Cenozoic and Jurassic sediments, i.e. the Molasse basin, for a spatial synopsis to constrain the origin of these brines. Low gradient groundwater flow in the Upper Muschelkalk aquifer is to the north, enabled by the regional recharge from west, southwest, south, and southeast, leading to a conspicuous flow field pattern. However, the north-south-trending maximum horizontal stress orientation might provide fracture permeability in the competent carbonates of the Upper Muschelkalk aquifer. Surprisingly, high lithium concentrations of up to 162 mg kg^-1 in highly saline hydrothermal fluids occur in the Muschelkalk, i.e. in a carbonate-rich aquifer. The highest lithium concentrations and total dissolved solids (TDS) can be found in the southern part of the Muschelkalk aquifer, close to the Vindelician High, a former crystalline basement land surface. Both trace elements and isotope data were used to get information on the origin and development of the highly saline, lithium-rich fluids in the Muschelkalk aquifer. In order to identify possible lithium sources within the aquifer, high temperature alteration experiments with rock material from a quarry in the Muschelkalk Group were carried out. Our investigations do support an extra-reservoir origin of the lithium-rich fluids from crystalline basement rocks. The marginal sand-rich facies of the Muschelkalk Group enables inflow of brines.

With the continuing search for clean energy resources, geothermal energy can play a pivotal role in providing a resource with continuous baseload energy. However, for geothermal projects to be successful, both geologically and economically, a proper investigation must be performed on potential locations for exploitation. Here, we present the results of an assessment of the geothermal resources of the northern Upper Rhine Graben.

Starting with initial geological studies of the lithological formations, an analysis is performed to assess their thermal energy-bearing potential. Using a heat-in-place calculation approach, a new model is presented, using the latest available data. But while the energy is present, it is not always retrievable. Therefore this presentation will not only look at the heat-in-place analysis but also at how much of the energy can technically be recovered for consumption.

However, subsurface modeling is a venture with uncertainty. And while the best efforts give a good indication of geothermal potential, uncertainty remains. Thus this presentation will also dive deeper into the uncertainties that remain in the study. The results presented here are publicly available and provide a starting point for stakeholders to accelerate initial geothermal investigations.

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The electrification in the mobility sector and plans for a large-scale domestic battery cell production makes lithium a highly critical raw material and highlight the strategic importance of its supply. However, Germany is projected to face a significant lithium deficit in the short term. One potential solution lies in the lithium dissolved in geothermal brines of the Upper Rhine Graben (URG) and the North German Basin (NGB). Extracting lithium from these fluids, known as direct lithium extraction (DLE), offers geostrategic advantages, is environmentally friendly and can potentially also help boosting the large geothermal technology roll-out. Currently, with an intermediate technology readiness level of 5-6, DLE has proven its applicability in small-scale demonstrators and is about to be scaled up. To assess the feasibility and implementation of geothermal lithium extraction, an evaluation of geothermal deposits and extraction processes has been done. Based on the current geothermal capacities in Germany the lithium quantities that could be extracted are quantified and compared to the forecasted German demand. Furthermore, the necessary expansion of geothermal in Germany to access the required reservoir volumes is extrapolated. To assess the long-term behavior of a reservoir under production, a generic model, based on the URG geothermal setting, was developed, and extraction over a 30-year operation time was simulated. Despite a significant depletion, a mean production of 231 t/a (1230 t/a LCE) is achieved, for a current state-of-the-art doublet type geothermal power plant. Implementing DLE has the potential to greatly enhance the economic viability of geothermal.

Geothermal energy utilization can be traced back to the Paleolithic era, an impressive 14,000 years ago. Although the majority of ancient societies predominantly relied on surface geothermal activities to extract heat and minerals, the remarkable Persian civilization ingeniously constructed a geothermal system that integrated wells, water channels, heat exchangers, and heat storage systems. The ancient Persian cooling methods were primarily centered around the Badgirs, which are windcatchers, and their amalgamation with Qanat, the underground water channels, and Ab-Anbar, the underground water storage cisterns. In a meticulously-designed integrated energy system comprising geothermal, wind, and hydrothermic thermal energy storage, the Qanat embodies the geothermal section, the Badgir represents the wind section, and the Ab-Anbar represents the hydrothermic thermal energy storage system.

This paper aims to examine the historical legacy of ancient Iran in the development of geothermal energy utilization for refrigeration. In addition, the paper seeks to verify whether Iran's cooling systems were the first geothermal cooling systems in history. By exploring the historical roots and unique features of this innovative energy system, the paper intends to shed light on how ancient civilizations utilized geothermal energy for cooling purposes and how this knowledge can be leveraged to develop sustainable and efficient cooling technologies in the modern world.

Mineral mapping from satellite images is crucial in assessing and exploring geothermal fields, providing valuable insights into mineral alteration and helping identify potential geothermal resources. Previous research has employed various methodologies for spectral identification, including ACE, CEM, MF, MTMF, OSP, SAM, TCIMF, and MTTCIMF. However, the quality of mapping results remained a major concern for application.

This study utilized ASTER satellite images of the Coso Geothermal Field in California, USA, with geological samples obtained from the field as the primary ground truth. Hyperspectral data were collected from these samples using the ASD FieldSpec 4 Hi-RES NG portable spectrometer. By analyzing samples from the Coso Geothermal Field, the research established a ground-truth dataset and a spectral library specific to the field. The spectral library was subsequently examined using the CSIRO TSG and ENVI THOR Material Identification, with supporting information from SEM, pXRF, and sample occurrence. The study acquired multiple high-purity spectra of alteration minerals such as alunite, chalcedony, hematite, kaolinite, and opal.

A limited number of studies have been dedicated to accurately assessing spectral mapping for geological materials, particularly in evaluating all eight algorithms mentioned above. The research used the abovementioned methods to leverage pre-processed satellite data and the spectral library to perform mineral spectral target detection. The accuracy of each method was calculated based on the ground-truth data, yielding the highest accuracies for ACE, CEM, MF, and MTMF methods. We performed a fusion of the four best methods to generate mineral alteration maps for the Coso Geothermal Field.

For the drilling and the completion of shallow geothermal wells (to 400 m) a lot of technical improvements were developed over the last 20 years. But wells are drilled with 2 m short pipes and casings still, which takes a lot of time and logistic efforts.

Using a Coil Tubing Rig with a 500 m long coil the drilling will be much faster and will deliver a better borehole integrity (hole geometry), because flushing the hole while drilling is not interrupted when drill pipes have to be added. The non- productive time will be much shorter because the BHA can be pulled from 500 m depth to surface in less than 40 minutes.

The transport dimensions of such a Coil Tubing Unit are 2.7 m width and 3.1 m height with a length of 6 m only. The tracks of the rig are 60 cm wide and 4.00 m long. By these dimensions and a perfectly balanced centre of gravity a good stability during moves and drilling operation is guaranteed even on slightly inclined drill pads. Drill pad size required is much smaller than for conventional rigs and doesn’t need a lot of improvement neither levelling, because the rig can correct up to 10 degrees inclination and can operate on uneven grounds.

Hydraulic downhole hammer drilling technologies have been widely used in the mining as well as O&G industry to speed up especially hard rock drilling operations. Typically, any DTH hammer principle is based on an axially reciprocating piston, powered via intensified fluids. Subsequently, the rather dynamic forces are being transferred onto a drill bit to crush the rock ahead. All of today’s hydraulic DTH percussion systems have a certain water quality limit, needing rather clean fluids for smooth operation, whereby the fluid quality heavily impacts the service and tool life. Also, wellbore control and cuttings transport are more of a challenge with current, water powered DTH tools compared to standard mud rotary drilling technologies. Therefore, an all-new DTH hammer concept for deep, hard rock drilling applications has been designed and developed at IEG based on a new control switch for the percussion mechanism instead of a mechanical system. The final percussion mechanism and DTH hammer works with only one single, main moving part inside and without the need for overly accurate tolerances and, therefore, does tolerate much better low-quality water / fluids and drill mud without excessive wear. The development of this prototype percussion hammer system was realized via iterative design, experimentally as well as numerical simulation work. A final, 4 inch DTH hammer percussion unit has successfully been validated and tested at the Fraunhofer IEG drill site in Bochum, Germany.

Due to accumulations of minerals in deep, geothermal type waters or brines, massive precipitation and deposits, so called scaling, repeatedly do occur during thermal water production out of geothermal wells as pressures and temperatures are changing. Especially during thermal production from carbonate type reservoirs, large amounts of e.g. calcium carbonate are deposited inside casings and other production equipment. As a result, pipe´s cross sections and thus, flow rates, are being reduced, decreasing overall thermal output and efficiency of such wells and power plants. Today’s methods for scaling removal, having been mainly used and developed in the oil and gas industry, are rather costly and time consuming, and, moreover, may involve large amounts of water / drilling fluid and environmental pollution. Thus, the occurrence of scaling and its required removal does pose some major challenges for operators of many geothermal power plants.

Therefore, developing a for-purpose scaling removal workover procedure especially for geothermal type wells, only requiring the use of ambient well water encountered in the well is rather desirable. Such an environmentally sound scaling removal, mechanical drilling process has been developed and tested at Fraunhofer IEG together with the geothermal Power Plant in Traunreut, Bavaria, Germany, back then still operated by Grünwald Equity. The developed, mechanical scaling removal process is based on multiphase, underbalanced drilling conditions (UBD). Results of the successful developments and full scale field operation in Traunreut in 2021 are being presented here.

The European funded GEOTHERMICA GRE-GEO project rallies a multinational consortium of geothermal experts to develop a new glass fiber reinforced epoxy casing system for geothermal wells. Such a system would solve the corrosion and scaling challenges of conventional steel based well designs.

Glass Reinforced Epoxy (GRE) tubular are already being used for decades in highly corrosive oil wells (e.g. H2S, CO2, Sulfide Reducing Bacteria based corrosion). However, the industry-standards describing such tubular are missing and design envelopes representing their load capacities have not been verified. This presently limits the down-hole use of GRE tubular.

One of the objectives of the project is the development of product qualification procedures to provide the basis for the construction and verification of a final product suitable for installation in the conventionally used well designs.

In order to provide these procedures, a Full-scale performance-based test program on GRE down-hole tubular is presently being developed by the GRE-GEO consortium. This includes the tests carried out under external pressure in combination with axial loads, which are novel for fiberglass casings and have created new insights in the collapse failure modes and have stimulated the development of dedicated test methodologies and test instrumentation.

Another critical subject is the definition of the threshold (condition, under which the first damage occurs to the pipe) for the different loads, which must be in line with ISO14692. But also, to try to combine this design methodology with the traditional ISO13679 used for qualification of casing connections.

Cementing is one of the most critical steps during the drilling process of geothermal wells. Here, we employ many techniques and technologies well-known in the oil & gas industry. However, weak formations and CO₂-containing formation water may entail the use of specially customized recipes. Thus, a dedicated design based upon extensive lab research and thorough engineering is crucial.

This paper presents our dream team for geothermal projects in the Netherlands. Here, to counteract losses into weak formations, the use of lightweight slurries is essential. The HOZlite consists of blast-furnace slag cement and contains hollow spheres providing low densities with a high compressive strength after hardening. This system provides excellent mechanical properties as determined via tri-axial tests. The HMR⁺ Blend, on the other hand, is chemically and physically optimized ensuring durability of the resulting sheath, even in the presence of CO₂. The gas-tightness of the hardened system was confirmed via lab experiments with H₂.

Recently, we employed the well-established combination of HOZlite (lead @ 1.35 kg/L) and HMR⁺ Blend (tail @ 1.88 kg/L) in the 20″, as well as in the 16″ casing section with great success. Prior to the actual cementation, our abrasive spacer effectively removed residual mud and its filter cake facilitating premium cement bonding. Thus, laboratory and field results impressively proved the premium properties of our new technologies for cementing geothermal wells.

The areas of Paris and Munich are early users in utilizing geothermal energy, esp. for providing it to their heating networks. Together, they have 70 years of practical experience consistently improved by means of applied research. Both pursue an extension of geothermal projects in a challenging urban context. The French-German tandem presentation will highlight the role of geothermal energy in both metropolitan areas: their success story, the further geothermal strategy, urban challenges as well as lighthouse and synergy effects.

In the last two decades, it has become obvious in hydrocarbon exploration that a standardization of project evaluation was needed. On the one hand, to evaluate projects in relation to each other, but also to ensure a standardized risk assessment of the projects. In order to accelerate project assessment, projects were divided into different phases, with a project description going from the rough to the detailed reservoir identification and quantification. The concept of dividing the phases into a play, lead and prospect phase is widely used internationally in hydrocarbon exploration. This approach makes it possible to make a quick decision, especially in the play phase, whether to proceed with the project or not. The decisive factor here is the correct identification of the reservoir and assessment of the associated risks. In the following lead phase, generally areas with similar deposit-specific properties are grouped together. In the prospect phase, the main focus is to identify a drilling candidate in each of the preselect leads. The risk assessment is therefore already defined with regard to the drilling location. This approach of evaluation for finding new hydrocarbon deposits has been adopted and adapted for geothermal project assessment. This paper will illustrate this implementation with an example of a geothermal project development near Vienna. In detail, the tasks that were carried out in the individual phases as well as the technical disciplines that were necessary will be highlighted.

The research project Eva-M 2.0 investigates two methods for the mitigation of calcium carbonate scaling at geothermal facilities in the Bavarian Molasse basin. The first is based on the injection of a liquid polymer inhibitor, and the second relies on the injection of CO2. In this paper the results of the economic efficiency of both applied are presented. The key performance indicators (saving of costly acidification jobs, lifetime of electric submersible pump (ESP), yield increase, increased yield losses through heat transfer degradation, costs for scaling prevention measures) are thoroughly analysed and evaluated. The results show that both methods have the potential to improve the economic efficiency of medium enthalpy hydrogeothermal projects in the South German Molasse Basin.

Geothermal energy is a highly reliable, eco-friendly, sustainable, and clean energy source that has proven to be a game-changer in the residential and industrial sectors. It can be developed from hot rocks saturated in geologically favorable reservoirs, in which water is produced at temperatures greater than 120 °C from a depth of up to 4 km utilizing an Electric Submersible Pump (ESP). Once its heat is converted to electricity in the power plant, the water is cooled and reinjected into the reservoir.

Due to the flow rates required, high-enthalpy fluids, and harsh downhole conditions of geothermal wells, a real-time well manager system was implemented to improve the ESP design, operation, reliability, and well performance. This paper details the operating conditions of a high-efficiency geothermal ESP system in Germany with in-house developed machine learning models. Our geothermal ESP well manager system has advanced to obtain virtual measurements, visual operating indices, vibrations tracking, real-time pump and well performance evaluation, electrical unbalance tracking, and scale detection.

The machine learning models predicted pump intake pressure, motor temperature, fluid temperature, flow rate, and overall operating parameters with less than 3% error. Additionally, the virtual parameters and real-time total dynamic head were analyzed together to indicate potential scale buildup within the flow meter, organic deposition on the motor housing, and changes in fluid composition.

A thorough assessment was made by continuously monitoring (24/7) the physical and digital aspects of the system, enabling recommendations to be made for improving efficiency and increasing the lifespan of the ESP.

Drilling costs hinder access to deep geothermal reservoirs, demanding innovative technologies for improved Rate of Penetration (ROP). The H2020 ORCHYD project focuses on developing hybrid high-pressure water jet (HPWJ) – percussive rotary hammering drilling technology, offering great potential for revolutionising drilling and advancing deep geothermal exploration. The project integrates experimental and numerical approaches to achieve its goals.

From a numerical perspective, ORCHYD takes advantage of novel multiphysics modelling techniques, utilising our powerful in-house software, Solidity and Fluidity, which combine advanced contact detection and analysis, multibody impact simulations, rock dynamic fracture based on the Finite-Discrete Element Method, and non-Newtonian high velocity water jet using adaptive mesh optimisation techniques. These integrated modelling components effectively address the extraordinarily complex interactions between the rock, bit, and jet, providing invaluable insights into the drilling process.

We strive to optimise the design of a new hard rock cutting system by collaborating with experimental drilling researchers and extend validated simulations to model conditions at 5 km depth, surpassing the limitations of laboratory settings that can only replicate depths up to 2 km. The proposed system significantly enhances ROP, a critical parameter for drilling efficiency. Our work overcomes computational challenges, showcasing dynamic rock destruction caused by bit hammering while the HPWJ simultaneously cuts a groove. Through precise simulation and analysis of the rock-bit-jet interaction, our modelling technology identifies optimal drilling system configurations and operating parameters.

This abstract underscores the immense potential of our modelling technology in driving breakthroughs in deep geothermal drilling.

Deep geothermal energy (DGE) may play an important role for future energy production considering its base load capacity and ubiquitous availability. Funded by the EU Interreg North-West Europe (NWE) Programme, DGE-ROLLOUT promotes the DGE potential of Lower Carboniferous carbonate rocks following a multi-disciplinary geoscientific approach.

With the Geological Survey of North Rhine-Westphalia as lead partner, project partners include the national geological surveys of Belgium, France and the Netherlands, as well as industry partners (DMT GmbH & Co. KG; Energie Beheer Nederland B.V.; RWE Power AG) and research institutions (Fraunhofer Institution for Energy Infrastructures and Geothermal Systems; Technical University Darmstadt; Flemish Institute for Technological Research). Furthermore, DGE-ROLLOUT collaborates with ten sub- and associated partners, including the national geological surveys of Great Britain and Ireland and the European Geothermal Energy Council.

DGE-ROLLOUT comprises three administrative, one investment and three implementation work packages (WP T1-T3): T1 provides a reconciled knowledge baseline for the DGE market development in NWE, including a transnationally harmonised depth and thickness map of the Lower Carboniferous. T2 fills information gaps through the acquisition of 2D seismic surveys, drillings, reprocessing vintage seismic data, and developing 3D subsurface models. T3 increases the efficiency of existing geothermal systems, implementing new or improved production techniques regarding reservoir behaviour, cascading systems and thermal energy storage.

After five years of excellent collaboration, DGE-ROLLOUT comes to an end in October 2023. We are keen on presenting our final results, including two webtools comprising the results of WPs T1-T2. DGE-ROLLOUT collaborations will continue through annual network meetings.

The Bavarian Molasse Basin, is one of Europe’s most successful hydrothermal energy plays. The geological potential of hydrothermal usage of the prolific Upper Jurassic carbonate reservoir also suggests that a significant development of the geothermal output is very feasible, in particular for heating purposes. In order to master this development, challenges associated with exploration, drilling and production have to be further mitigated: For example, around 20% of all deep geothermal exploration wells yielded reduced or insufficient flow rates, at least 25% of all deep geothermal projects experienced severe drilling problems in at least one well and, although not a critical risk in the Bavarian Molasse Basin, few geothermal sites have also been associated with minor microseisimicity. These challenges are mostly related to the complex nature of the exploited Upper Jurassic carbonate reservoir and the foreland basin setting of the Bavarian Molasse Basin, suggesting that an improved regional understanding of the geological and geomechanical evolution and present-day state is necessary. Over the past years, we analysed and integrated geophysical and drilling data of more than 300 deep wells (hydrocarbon and deep geothermal) from the Bavarian Molasse Basin to gain a better understanding of sediment distribution and compaction (basin analysis) as well as the distribution and magnitudes of subsurface stresses and pore pressure (geomechanics). In this contribution we will provide an update and synopsis of these results and discuss possible implications for challenges associated with future geothermal drilling, exploration and production in the Bavarian Molasse Basin.

Geothermal brines in the Upper Rhine Graben (Germany) are highly saline and contain a significant load of dissolved gases, leading to operational challenges in the surface facilities. The decreasing pressure during production of the brine and the thermal transfer from the geothermal fluid to a secondary fluid used to produce electricity results in scaling and corrosion issues, reducing the efficiency of the geothermal energy system.

A thorough characterization of the brine and understanding of the chemical processes are essential to prevent scaling and corrosion and thus to increase the efficiency of the heat transfer and secure a long-term and sustainable extraction of lithium from the geothermal fluid, which is the aim of the Zero Carbon Lithium^TM Project from the Vulcan Energy Group. To avoid degassing and the resulting scaling and corrosion issues, an effective system of pressure control in combination with chemical treatments is used in the Insheim geothermal power plant in Rhineland Palatinate (Germany).

In frame of the European H2020 project GEOPRO (Grant Agreement 851816), Vulcan contributes to a better understanding of the gas behavior in the brine of the Insheim geothermal power plant to prevent degassing related issues by using a joint field and modelling approach. In the presented Insheim case study the operational influence of slight variations in the composition and of minor elements in the geothermal fluid are investigated and the origin of the dissolved gases in the geothermal fluids of the Upper Rhine Graben are studied using the composition of the gases and their isotopic signature.

Fault zones in granites and granodiorites exhibit distinct structural, geochemical, and petrological features that have significant implications for hydraulic heterogeneities. These features arise due to the brittle deformation and fluid-rock interactions within fault zones. The interconnected fractures and fault planes provide preferential pathways for fluid flow, enhancing the permeability contrast compared to the surrounding rock matrix. Additionally, the presence of hydrothermally altered or weathered minerals can modify locally the permeability, resulting in heterogeneous fluid flow patterns.

The aim of this contribution is to integrate refined mineralogical analysis through, XRD, EMP, and ICPMS, along with structural analysis from borehole logs, to characterize the heterogeneities present in faulted granodiorites and granites in two locations in the crystalline Odenwald.

The first location, e.g. the SKEWS demo-site (Projektträger Jülich, 03EE4030A), is a heat-storage demonstrator targeting granitic and granodioritic units, in which the upper section is affected by a fault. The second location is the Otzberg Fault Zone at the Eastern Border of the Tromm Granite, which is a major large-size structural element, which can serve as an analog for structures targeted in deep geothermal reservoirs, and thus is a potential site for the realization of GeoLaB.

These geological features influence fluid flow pathways, storage capacity, and fluid-rock interactions within the fault zones, ultimately affecting the development and distribution of hydraulic heterogeneities. Such understanding is vital for subsurface resource exploration and management, from deep geothermal EGS to heat-storage potential subsurface assessments in regions characterized by granitic and granodioritic rocks, in Germany or Europe-wide

The decision for the site of the GeoLaB (geoscientific underground laboratory) infrastructure considers many aspects. One of the geoscientific aspects comprise the mineralogical-petrological, petrophysical and geomechanical properties which will be investigated in the exploration stage of the project. Potential targets comprise on the one hand the Tromm ridge and the Otzberg fault zone in the Odenwald and the Omerskopf area and Glashütte fault zone in the Black Forest on the other hand.

In a recent field campaign more than 50 samples, comprising fresh, altered, and cataclastic rocks as well as fault gouge material, from the Odenwald and the Black Forest were probed. This first set of samples will be investigated for quantitative mineral composition and clay mineralogical composition, mineral chemistry, the presence of micro-fractures and alteration patterns in the thin sections via element mapping.

The investigation of micro-structures at microscale will be linked to the structural geology at macroscale. Furthermore, the same analytical approach will be applied to core samples from exploration drilling as soon as they will be available.

These first results will be combined with structural geological field data, geophysical and geomechanical experiments to generate a scientific database for the GeoLaB site selection and future scientific work. In the future the samples will undergo a complex thermo-hydraulical-mechanical and chemical investigation routine established in pre-runner projects.

TRANSGEO is a regional development project that aims to explore the potential for producing geothermal energy from abandoned oil and gas wells in central Europe. Supported by 11 partner organizations and 10 associated partners in 5 countries, TRANSGEO will develop a transnational strategy and action plan to address this technical and economic opportunity. The project partners will start by identifying and characterizing thousands of abandoned wells in the North German Basin, the South German Molasse Basin, the Vienna Basin, and the Pannonian Basin. A web-based well selection tool will then be developed to assess the wells’ suitability for a variety of thermal storage and energy production technologies. These activities will be supplemented by modelling studies at selected sites, to inform the assessment tool and validate procedures that will be developed for each reuse technology. Next, we will match well reuse potential with local energy demand and heating networks to highlight redevelopment priorities, with a focus on wells that could support rural communities and industries in the energy transition. Finally, the partnership will propose a legal policy and incentive framework to facilitate and expand reuse of abandoned wells for geothermal energy production and storage across the region.

TRANSGEO is co-funded by the European Commission’s Interreg CENTRAL EUROPE programme.

Worldwide, hydrocarbon wells are being abandoned. At the same time, energy demand is rising and most countries are struggling to meet their carbon reduction targets. Furthermore, in Nordic countries like Canada, heating buildings and transporting fresh food over long-distances both contribute significantly to CO2 emissions. Could inactive hydrocarbon wells be re-purposed to produce renewable heat for buildings and greenhouses in winter ?

This case study evaluates the potential for repurposing a 1048 m deep inactive gas well into a deep borehole heat exchanger (DBHE) or a well used in a geothermal doublet to heat an 8.1-ha bell pepper greenhouse in the St. Lawrence Lowlands (Eastern Canada). This region has a low geothermal gradient (~23°C km^-1), but contains a ~1 km deep permeable unit. 3D numerical models were built using the FEFLOW software to simulate heat transfer and groundwater flow generated by these systems. Additionally, Python functions were developed to estimate heat and pressure losses, as well as simulate the dynamic operation of heat pumps, modify injection temperature and flow rate in the models as required, and calculate the systems’ electricity consumption.

Preliminary results indicate that the doublet and associated heat pumps would meet the entire heat demand, provided the good permeability value is confirmed. However, the DBHE system would supply only 68% of heat demand, but would also produce 34% of the cooling demand in summer and presents fewer risks associated with uncertain properties, geochemistry and gas emissions. Cost of both systems are currently being estimated for further comparison.

In this paper, we present an overview of the development of the first commercial geothermal system leveraging horizontal drilling and multi-stage stimulation. The project is located near an existing geothermal power plant in Northern Nevada.

The target zone for the development was a low permeable Mesozoic metasedimentary formation at a temperature of approx. 190 °C. One vertical monitoring well and two approx.1000 m long horizontal wells were drilled into the reservoir. The horizontal wells featured a cemented 7" production casing. The well design needed to accommodate multiple drilling hazards in the shallower sections as well as all complex stimulation and production loads.

The stimulation treatment was designed to create a large fracture surface area between the two lateral wells by maximizing fracture initiation points through a combination of multi-stage and multi-cluster limited entry stimulation techniques. Proppant was placed in the fractures to increase conductivity.

This paper will review planning, drilling, stimulation, and well test operations. Furthermore, key learnings and their applicability in other geographies and geologies will be discussed.

Seit Jahren befinden sich die betrieblichen Anforderungen im Zusammenhang mit Sicherstellung der Integrität der technischen Einrichtungen in den Bereichen E&P und Geothermieanlagen in einem stetigen Wandel. Gründe hierfür sind vielschichtig: steigende Betriebs- und Servicekosten, Ergänzungen behördlicher Auflagen und sich verändernde Förderbedingungen.

Im Bereich der Geothermie bestehen ähnliche Notwendigkeiten, da das für den Betrieb der Anlagen erforderliche technische Equipment den Komponenten aus dem E&P-Bereich ist und auch zum Schutz von Menschen und Umwelt Sicherheitsstandards abverlangt werden.

Die Vielzahl und ständigen Ergänzungen der Vorschriften bringt die Anlagenbetreiber zwangsläufig unter Zugzwang Lösungen zu finden, die Kosten für vorgeschriebene Wartungen einschließlich der Integritätsmaßnahmen an den Produktionsanlagen nicht in ein betriebswirtschaftliches Missverhältnis zum operativen Betrieb laufen zu lassen und somit zwangsläufig einen "Cost-cut“ zu erzeugen.

In dieser Präsentation sollen aktuellen Stillstands- und Außerbetriebnahmeprobleme zur Sicherstellung der WI an Bohrungen aufgezeigt werden. Bereich des WIMS wird erläutert und innovative Lösungen und Technologien zur Fehlersuche, -bestimmung und -behebung aufgezeigt.

Besonderes Augenmerk wird auf in jüngster Zeit zu beobachtenden Tendenzen der „Thinking outside of the box“ Strategien bei der Umsetzung der Herangehensweise an Problemlösungen gelegt. Technisches Know-how, welches ursprünglich für völlig andere Anwenderapplikationen entwickelt und erfolgreich eingesetzt wurde, kann auch allein oder in Kombination mit bereits vorhandenen Serviceoptionen im Bereich der Medienförderung über Tiefbohrungen zur Steigerung Anlagenintegrität genutzt werden.

Mehrere praktische Fallstudien haben gezeigt, dass durch den Einsatz dieser Herangehensweise eine deutliche Steigerung der Effizienz während des Betriebes bei gleichzeitiger Steigerung WI gegenüber technischen Risiken und der Umwelt sowie deutliche Kosteneinsparungen bei Service- und Aufwältigungsarbeiten erreicht werden können

This paper will highlight how one country, Scotland, is using its wealth of experience from the oil and gas sector to develop a new, but experienced, supply chain of companies to help drive new geothermal projects.

The Scottish offshore oil sector was characterised by innovation and engineering developments in harsh conditions. Now Scotland is leading a transition away from oil. We talk about a Just Transition, ensuring workers, companies and social and economic structures are not left behind. The skills and experience from the oil sector are transferable and valuable across new renewable energy industries, especially so in the geothermal field.

The paper highlights Scottish companies, with experience of drilling deep oil wells, that are now using that experience to cover many aspects of drilling 5km deep in Northern European geothermal projects, and also the role of the new National Geothermal Innovation Centre, a central hub for geothermal technology challenges both in Scotland and globally.

With both public support and private company buy in, the future for the Scottish Geothermal sector appears rosy. The focused effort to use the expertise and experience of its previous industries in a Just Transition is helping Scotland develop a supply chain of geothermal focused companies that see innovation, engineering excellence and environmental responsibility as a long established and fundamental part of the business. This offers advice, examples and expertise for German geothermal projects and can only be good news for the German and wider European geothermal sector.