The MEET educational program was held on 16-19th February 2021

Geothermal is decisive for the energy transition since it provides a flexible base load renewable source of energy. The contribution of geoscientists is central for the development of this form of renewable energy. We need to train today the next generation of Geoscientists in order to develop and exploit the geothermal projects of tomorrow.

Through the Geothermal Winter School, The MEET consortium provides to future geoscientists some practical feedbacks from research and industry in geothermal. Indeed, this educational program was intended to transfer new knowledge to European students on Enhanced Geothermal Systems (EGS) and demonstration sites, based on highly advanced research approach and industrial expertise from ongoing projects.

Master and PhD students from MEET partners and European universities, but also post-doctoral fellows and engineers, were invited to register and follow the lectures in order to acquire new knowledge on EGS. The registration was free.

The Geothermal Winter School was entirely broadcasted virtually given the current pandemic and it was host on PhDTalent web platform:

Thanks to everyone’s involvement, the event was a great success that has exceeded our expectations. More than 160 people had registered and participated, represented by Master and PhD students, Post-doc fellows, subsurface engineers, senior scientists… This 3.5 days event had been the occasion to have 17 lectures, 1 public webinar, 3 thematic sessions and 1 session to promote the work of young researcher. In addition to that, 4 demosites have been presented and 3 virtual visits have been conducted during a common half day shared with European Geothermal PhD Days (EGPD).
We would like to acknowledge our Sponsors: CY Cergy Paris Université, CY Cergy Advanced studies and the International Geothermal Association. Without your support, this event would not have been so fluid and accessible. Thank you also to all speakers and chairpersons for this great event, of very high-standard training with intense discussions. Our final thanks go to the organizers of the MEET Winter School at CY Cergy Paris Université.


This geothermal school developed the main topics of the MEET project, with practical lectures and case studies showing ongoing R&D aspects of the project for the development of EGS throughout Europe:

  • Deep geothermal systems for heat & power in various geological settings
  • Increase heat production from existing geothermal plants and oil wells
  • Mapping best locations for future installations in Europe and promoting EGS

Keynote lectures covered these themes thanks to acknowledged European lecturers. In addition, several project partners from industry and academics were involved in the training, as they gave practical lectures to students on their expertise domain.

Before starting the courses, half a day of demo-sites presentations and virtual site visits took place, as a shared program with the European Geothermal PhD Days 2021 (EGPD) on Tuesday afternoon 16th February 2021.

An introductory course for the general public though an opened webinar popularized geothermal energy to a broad audience all-over Europe, with an emphasis on communication strategies to extend geothermal knowledge from the technical actors to the non-expert citizens in order to bring local communities in geothermal project development. This course was disseminated throughout Europe by different means: associations of geology/biology teachers in secondary schools, geology and geothermal associations, networks of scientists, geography associations, federations of energy companies, local energy associations, local authorities, European institutions, public decision-makers in Europe, etc.

In addition to this program, oral sessions dedicated to young researchers were planned each afternoon from 4:30 pm. This was the opportunity for students to show their latest research outcomes and share with other students and teachers what they discovered. The size of the event made it a good format for discussion and feedbacks on their work, but also a place for creating opportunities for their early career.

Prizes for the best oral presentations were awarded, as well as a certificate of participation for each student.

You can find below the schedule of the Geothermal Winter School 2021, with available video or abstracts, and PDF presentations.


Introduction of the Geothermal Winter School 2021 – H2020 MEET Project – François Germinet (CY Cergy Paris University)


Demo-site 1 – Case study from Rhine Graben / Munich area – Thomas Kohl (Karlsruhe Institute of Technology)

Demo-site 2 – Hydraulic soft stimulation of a geothermal well in Reykjavik (Iceland) – Hannes Hofmann (GFZ-Potsdam)

MEET Winter School Hofmann first slide

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Demo-site 3 – United Down Deep Geothermal Project, UK – John Reinecker (GeoT)

MEET Winter School Reinecker first slide

Demo-site 4 – Deep geothermal energy for district heating network: case histories in Paris Basin and lessons learned since 50 years – Christian Boissavy (G²H Conseils)


Virtual visit 1 -Soultz-sous-Forêts power plant and Rittershoffen geothermal heat plant for industry – Guillaume Ravier (ES-Géothermie)

Virtual visit 2 – Dammarie-les-Lys geothermal heat plant for district heating (Paris basin)- Jean-Marc Bertrand (ENGIE Solutions)

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Virtual visit 3 – A pilot Organic Rankine Cycle (ORC) installed on the Chaunoy oil field, France – André-Charles Mintsa (Enogia) & Eric Léoutre (Vermilion Energy)

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Introductory lecture – Boost your researcher career with EU funds – Fabienne Brutin (Ayming)

Webinar – Taking the Heat Out Of Geothermal: Geo-energy Communications for Publics and Policy – Iain Stewart (University of Plymouth, Director of Sustainable Earth Institute)


Keynote lecture – Engineered Geothermal Energy Systems in Europe – Ernst Huenges (GFZ-Potsdam)

Keynote lecture – Deep fractured EGS, Concepts and reservoir assessment in the Upper Rhine Graben – Albert Genter (ES-Géothermie)

Lecture 1 – Exploration workflow for deep geothermal systems – John Reinecker (Geothermal Engineering GmbH)

MEET Winter School Reinecker first slide

Lecture 2 – Planning reservoir stimulation, technical steps and risk mitigation – Kristian Bär (Technische Universität Darsmstadt)

Lecture 3 – Fractures and hydrothermal alterations: a review of fluid pathways for geothermal applications – Béatrice Ledésert & Ronan Hébert (CY Cergy Paris Université)

Lecture 4 – Death Valley granites as analogue of EGS Soultz-sous-Forêts reservoir – Ghislain Trullenque (UniLasalle)

MEET Winter School Trullenque first slide

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Lecture 5 – The role of anisotropy in geothermal systems in meta-sedimentary rocks – Yves Vanbrabant (Geological Survey of Belgium)

Lecture 6 – An unorthodox exploration and exploitation strategy for the development of an unconventional geothermal reservoir, the Göttingen University campus demo site – Bernd Leiss (Georg-August Universität Göttingen – Universitätsenergie Göttingen GmbH)

MEET Winter School Leiss first slide


Lecture 7 – Site-specific environmental and economic assessment of EGS using Decision-Making Tool (DMT) – Ivan Rasjl (UNIZG-FER)

MEET Winter School Rajsl first slide

Lecture 8 – Co-production of oil and geothermal heat: opportunities and challenges – Eric Léoutre (Vermilion Energy)

MEET Winter School Leoutre first slide

Lecture 9 – Optimization of energy valorization on EGS plant, application to Soultz-sous-Forêts demo-site – Eléonore Dalmais (ES-Géothermie)

MEET Winter School Dalmais first slide

Lecture 10 – ORC technology and implementation in different geological contexts – André-Charles Mintsa (Enogia)

Lecture 11 – Fiber optics, an adaptable and cost-effective technology for monitoring geothermal reservoirs at different scales – Vincent Lanticq (Fébus Optics)

Link to the PDF of the presentation


Keynote Lecture – Social aspects for geothermal energy development and policy implications – Adele Manzella (Consiglio Nazionale delle Ricerche – Istituto di Geoscienze e Georisorse)

Keynote Lecture – Determining the key parameters and suitable measures for successful EGS developments – David Bruhn (GFZ – TUDelft)

Lecture 12 – Concepts and data sources for mapping deep geothermal resources throughout Europe – Bianca Wagner (Georg-August Universität Göttingen)

MEET Winter School Wagner first slide

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MEET Geothermal Winter School Akos Kiss first slide visual

Talk  #1: Akos Kiss (Univ. Durham) – Safe Enhanced Geothermal System (EGS) Development of the Dinantian Carbonate play, UK

In recent years, geothermal energy has been increasingly considered as a major contributor in the future’s green energy mix. Reservoir stimulation techniques enable heat and power generation from conduction-dominated play types, found away from tectonic plate boundaries. In the UK, conduction-dominated plays of the hot dry rock and hot wet rock types can be expected around radiothermal granites and in sedimentary basins. A promising target of the latter type is the Lower Carboniferous Dinantian Carbonate play; a known hot spring aquifer with an assumed subsurface extent that spans areas of increased heat demand in the country. The confirmation of this stratigraphic unit as a regional geothermal play will be contingent on the successful identification of facies types with favourable porosity/permeability characteristics; or that are suitable for EGS development. Induced seismicity as one of the main risk factors associated with EGS should be an important focus during the development of the Dinantian play; considering it is underlain by crystalline basement and its proximity to densely populated areas. Currently, seismic risk mitigation in the UK is based on a traffic light system with prescribed threshold magnitude values at which a reduction of injection rate, or stopping of injection is prompted. A shortcoming of this system is highlighted by examples from different injection sites that experienced increasing seismicity after such mitigative measures. Injection protocols should be designed and adjusted with a focus on keeping the maximum induced magnitudes below a certain level. Here, a project is proposed that aims to help the development of best practice procedures to minimize seismic risks associated with the future EGS development of the Dinantian play.

Talk #2: Aurore Laurent (Univ. Lille) – 3D structural modelling of the Dinantian carbonates reservoir in the Nord-Pas-de-Calais coal basin area: towards a better characterization of the deep geothermal resource in Northern France

Within the Act of 17.08.2015 on energy transition voted by the French government, the Hauts-de-France region (Northern France) is committed to invest and develop massively renewable energies in the coming decades. This objective requires the development of regional alternative solutions to fossil fuels, especially low-temperature geothermal energy. The present research project aims at better characterizing the geometry of the main deep geothermal reservoir in the area of the Nord-Pas-de-Calais (NPC) coal basin: the Dinantian karstic and brecciated limestones (Lower Carboniferous, 360-330 Ma). The occurrence of a Dinantian regional geothermal resource has already been proven in Belgium in the Hainaut coal basin area where the temperature in the geothermal wells of Douvrain, Ghlin and Saint-Ghislain reaches about 70°C.
The Dinantian reservoir forms part of a large-scale transgressive carbonate platform developed onto the slowly subsiding southern Avalonian margin during the Mid-Upper Devonian to Lower Carboniferous. The Upper Carboniferous Variscan collision between Avalonia and the Armorica-Gondwana accretion complex led to the tectonic inversion of the Avalonian margin and the development of a north-vergent thrust system, whose front crosses northern France. The Dinantian platform was progressively buried under the NPC synorogenic molassic foreland basin developed along the Northern Variscan front.
Prior to our study, very little information was known on the structure of this reservoir under the coal basin. Its 3D-geometry has been investigated through the integration and interpolation in a 3D model of a large database including 590 boreholes and 532 km of reprocessed and interpreted seismic reflection profiles. First results of the 3D-modelling indicate that the Dinantian reservoir is continuous and extends over an area of at least 10750 km². It is present at 100-200 m depth in the Brabant foreland near Lille metropole. It strongly deepens southward and reaches approximately 7.5 km depth under the coal basin to the south of Cambrai. Major thickness variations (250-1000 m), often related to a complex structure involving deep variscan thrusts, have also been observed.

MEET Geothermal Winter School Aurore Laurent first slide visual
MEET Geothermal Winter School Cédric Bailly first slide visual

Talk #3: Cédric Bailly (CYU) – Enhancing the exploitation of sedimentary basins for the energy transition: From hydrocarbon resources production to geothermal heat generation

As part of the energy transition, the geothermal potential of the Earth need to be studied in order to cope with climate change. In this context, the Horizon 2020 program is funding the MEET project to investigate the development of Enhanced Geothermal Systems in different geological settings, including sedimentary basins and the conversion of oil wells for geothermal purposes. Within this European project, we are investigating a Triassic reservoir made of sandstones and dolomites in order to evaluate the co-production potential of geothermal and oil resources.
Our study is intended to provide insights on the interrelations between rock physics properties and microstructures in a newly defined stratigraphic framework. The main objectives are focused on the geological controlling factors of the transport properties. The studied rocks were accumulated on the western part of the Paris Basin during the Upper Triassic. Eight wells were characterized, combining sedimentary logging of 470 meters of rock cores and analyses of well-log dataset (Gamma Ray, Photoelectric absorption factor, Neutron Porosity, Density, Sonic). Lithofacies were defined based on core description, together with facies associations definition and depositional environment interpretation. Furthermore, a sampling of 159 plugs was done, for performing petrophysical analysis. Rock physics measurements were acquired on those plugs in order to complete an existing petrophysical dataset of more than 700 samples (permeability, κ and porosity, Φ). Furthermore, a petrographic work was conducted, including 250 thin-sections observations using conventional microscopy and 32 thin sections using cathodoluminescence.
Based on a systematic petrographic description, we show that the combination between sedimentary texture and diagenetic overprint may greatly impact the porous network of the studied rocks, conducting to the definition of 3 main rocks types displaying distinctive κ-Φ trends. Furthermore, using both sedimentary descriptions and well-log dataset, seven electrofacies corresponding to three main depositional environments were defined, namely alluvial fan deposiqts (conglomerates & sandstones), floodplain/lacustrine deposits (heterolytic clays) and dolomitic paleosols (dolomitization of siliciclastic deposits). Then, a high resolution correlation transect was designed using genetic stratigraphy principles, including seven main genetic sequences that show the spatial evolution of depositional environments. In addition, the integration of rock types within the correlation transect provides a high resolution definition of the reservoir compartmentalization. To go further, we may build a 3D static geological model that will serve as a basis for the development of future numerical simulations of fluid flow and heat transfer at the scale of the reservoir.

Talk #4: Ines Raies (CYU / IFPEN) – Identification and understanding of colloidal destabilization mechanisms in geothermal processes

In this work, the impact of clay minerals on formation damage of sandstone reservoirs is studied in order to provide a better understanding to the problem of deep geothermal reservoirs clogging due to fine particle dispersion and migration. Our study is currently carried out on cores from a Triassic reservoir in the Paris Basin (Feigneux, 60 km NorthEast of Paris). Our goal being to first identify the clays responsible for clogging, a mineralogical characterization of these natural samples was carried out by coupling X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The obtained results show that the stratigraphic interval studied contains mostly illites and chlorites. Nevertheless, several parameters, notably the spatial arrangement of the clays in the rocks as well as the morphology and size of the particles, suggest that the illites are more easily mobilized by the flow of the pore fluid than chlorites. Thus, based on the results of this first part, illite particles will next be used to carry out laboratory experiments in order to better understand the factors leading to the aggregation and deposition of this type of clay particles in geothermal reservoirs under variant physicochemical and hydrodynamic conditions. To do so, the stability of illite suspensions under geothermal conditions will be investigated using different characterization techniques including Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM). Various parameters such as the hydrodynamic radius, the morphology and surface area of aggregates will be measured. Then, core flooding experiments will be carried out in order to explain the permeability decline due to the injection of illite containing fluids in sandstone reservoirs.

MEET Geothermal Winter School Ines Raies first slide visual
MEET Geothermal Winter School Katherine Ford first slide visual

Talk #5: Katherine Ford (Univ. Göttingen) – A Multi-proxy Approach for Fracture Network Quantification of Regional Fold and Thrust Structures for Geothermal Reservoir Characterisation

Within the Horizon 2020 MEET project (Multidisciplinary and multi-context demonstration of Enhanced Geothermal Systems exploration and Exploitation Techniques and potentials) is to bring about this potential in previously considered unconventional geothermal reservoirs, focusing specifically on crystalline and meta-sedimentary Variscan basement rocks. One of the demo sites is located at the University of Göttingen with the reservoir at 4km depth, within the Variscan sedimentary basement.
With no research well and little in the way of seismic interpretation, the focus has been put onto the use of outcrop analogues within the Rhenohercynian zone to determine the potential of such a reservoir. The focus of this study is primarily within the Clausthal Culm Fold Zone (CCFZ) in the Western Harz Mountains, comprised of NW verging folds of Lower Carboniferous greywackes and slates. The planned reservoir is relying primarily on the primary permeability of the fracture network related to the folding and thrusting caused during the Variscan orogeny. Ideally one might suspect the fold hinge and thrust zones to be target zones, but due to the drilling location being fixed due to the demo-site already being active, any future drilling will be blind. This means all reasonable bases should be covered in the analogue characterisation.
With the complexity of the structural and lithological attributes of the reservoir, along with limited subsurface data, a methodology has been established to characterise the main target areas within the CCFZ for the collection of fracture network parameters for use reservoir simulation models. By collecting field data in various forms such as drone images and 3D outcrop models, the structural and lithological situations can be characterised, and an overview of the changes of the fracture network characteristics can be quantified. Throughout the analogue site fracture parameters are collected, aerial intensity, connectivity, and orientation, at sites that correspond to the structural and lithological situations listed in Fig.1.
This method focuses on the fracture characteristics based on their relationship to the lithology and placement within a fold rather than physical location, allowing for a more holistic approach for a potential development reservoir permeability in cases where subsurface data is limited.

Talk #6: Gemma Mitjanas (Univ. Barcelona) – The Vallès Basin Geothermal system in the frame of the GEO-URBAN project

The GEO-URBAN project aims to explore the potential for low enthalpy geothermal resources in urban environments. In the frame of GEO-URBAN project, two low-enthalpy deep geothermal reservoirs, Dublin basin (Ireland) and Valles Basin (Spain), will be evaluated using geophysical exploration techniques.

In the Valles Basin area (Catalan Coastal Ranges, NE Spain) the thermal anomaly is located in the northeastern limit of the basin, where a highly fractured Hercynian granodiorite act as the geothermal reservoir. Nevertheless, the geological structure of this area, as well as the role of the Vallès major normal fault, is poorly understood.
Different geological and geophysical surveys made on the 80s determined the presence of geothermal anomalies in different parts of the Vallès Basin, although their resources were not exploited [1] [2] [4]. In our study we decide to focus on La Garriga-Samalús area (northeastern edge of the basin), where the fractured nature of the crystalline bedrock represents a geological challenge.

Several geophysical techniques are being applied in this area to understand the main structure, which seems to control the heat and the hot-water flow. Magnetotellurics (MT), Gravity, Electrical resistivity tomography (ERT), Passive Seismic (H/V) and Control Source Electromagnetics (CSEM), have already been carried out, however, the models are not yet completed.
Although the geophysical study makes up most of the study, we are also improving the geological map of the area, based on a fractures study at different scales. We are working with DEM alignments analysis, and fractures study from outcrops and from thin sections.
The geological model will be built up using all the geophysical information, the surface data, and previous information, as six exploratory wells made by the Geological survey of Spain [3] [5] [6]. Moreover, it will include petrophysical data from the granodiorite rock, which would help us to correlate the geophysical results and the geology of the area, also being essential for the final flow model.

Our preliminary results show a strong gravity gradient in the NE-SW Valles half-graben system and the recent MT profiles image the main fault of that system (Valles normal fault).
Interpretations of the fractures study, together with geophysical data and models, have allowed the characterization of damage zones associated to the fault system which are directly related with the fluid flow and the hot springs. The nature of this damage areas could also be related to relay ramps, commonly regarded as efficient conduits for fluid flow.

MEET Geothermal Winter School Gemma Mitjanas Colls first slide visual
MEET Geothermal Winter School Johanne Klee first slide visual

Talk #7: Johanne Klee (UniLasalle) – Characterization of a geothermal reservoir analogue: Fractured granite of the Noble Hills Range, CA, USA

The work presented here is part of the European MEET project (Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials), which aims to enhance demonstration of geothermal energy production throughout Europe. Nowadays, active reservoirs as the Soultz-sous-Forêts (SsF) granitic reservoir (Upper Rhine Graben, Alsace, France) are not fully understood because of limited data (few cores, cuttings, parcel information only for boreholes and no direct 3D vision). To improve the understanding of the reservoir connectivity, surface analogues of the SsF geothermal reservoir are studied: the Noble Hills range (NH, Southern Death Valley, CA, USA) and the Upper Rhine Graben shoulders (abandoned mines in the Vosges Mountains, France and in the Black Forest, Germany). We have here chosen to present results from the NH analogue consisting in a highly fractured and altered Mesozoic granite. The high level of fracturation of this geological object is to be related to its location along the Southern Death Valley Fault Zone (SDVFZ). The SDVFZ is a dextral shear zone being one of the two major faults responsible for the Death Valley pull-apart basin. We focus the study on 1) the alteration processes linked to fluid circulation and 2) the impact of shear deformation on the reservoir connectivity.
Analogue studies allow us to better understand fluid circulations in a granitic fractured reservoir and gain insights in fluid rock interaction processes as these can drastically modify rock and fractures properties through time. From outcrop to thin section scale, fractures can be filled by different mineral types (carbonates, oxides, barite and sometimes quartz). Those different infills indicate the occurence of different fluid circulation episodes through the whole granitic body. Petrographical analyses were performed on 78 samples to define the composition of the altered granite and to describe the alteration processes. Among the major minerals composing the granite, plagioclase (oligoclase mainly) is transformed into illite/kaolinite/(calcite) and biotite into illite (Fig. 1). Similar alteration processes are observed in the SsF granite. However, plagioclase in the SsF granite are locally transformed into tosudite instead of kaolinite.
Fieldwork has shown a strong deformation gradient induced by strike-slip movements linked to the activity of the SDVFZ. Along this gradient, mineralized veins and high strain zones were observed and investigated. Those highly deformed zones associated to fluid circulation are most of the time sealed by clay minerals (mainly illite), a feature also observed in SsF cores. It is suspected that the onset of clay mineral formation causes a change in deformation mechanisms from the brittle to the ductile domain which in turn can drastically modify fault mechanical properties (Fig. 2).

This work has shown that 1) analogue studies are essential for the understanding of a reservoir in its entirety, 2) the SsF and NH granites react similarly to the alteration processes and 3) deformation play a major role on fault petrophysical properties.

Talk #8: Armand Pomart (UniLasalle) – Study of an analogue to the Soultz-sous-Forêts granitic geothermal reservoir: from photogrammetric acquisition to DFN modelling and fluid flow simulation

The H2020 MEET (Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials) project aims at developing Enhanced Geothermal System in various geological settings across Europe.
The study carried out at UniLaSalle focuses on geothermal reservoirs within Variscan crystalline basement rocks overprinted by post-Variscan extension. We characterise an analogue from the Soultz-sous-Forêts reservoir (Upper Rhine Graben, France) as analogue studies are an efficient way to understand fault structural interactions at depth by precisely visualizing fracture networks. It is aimed to create a 3D structural model and discrete Fracture Network (DFN) analysis which allow the simulation of flow and transport through fractured rocks. The finality is to understand the deep geothermal system. The chosen analogue site is situated in the Noble Hills (Death Valley, CA, USA) as the arid climatic conditions allow a total outcrop exposure.
We first present 3D realistic photogrammetric models using Structure from Motion Multi-View Stereo (SfM-MWS) photogrammetry, based on both Unnamed Aerial Vehicle (UAV) and aerial pictures. In both cases, models are constructed step by step, following a detailed methodology: (1) alignment of pictures, (2) creation of sparse point cloud and removal of high error points, (3) construction of dense point cloud. The georeferencing of the created point cloud is done using Ground Control Points (GCP). The multi-scale approach allows to best characterize the geological structures with a resolution ranging from centimetre to decimetre.
The second part of the workflow is conducted by the Geosciences team of UniLaSalle. The 2,5D models obtained from photogrammetry allow the extraction of planar features with a combination of both manual polyline extraction and automatic facet detection. According to the classification of the fractures, a methodology was implemented to re-scale their features to an estimated real size. In this study, a new approach has been developed to build the DFN’s models by combining deterministic and stochastic approaches. The constructed 3D DFN models are closer to reality. Finally, the hydraulic simulations will be realised in the second part of the MEET project to understand the fluid circulation in the geothermal system.
The 3,000 pictures and 18 GCP of the plane model allowed the creation of a global georeferenced 3D model. Then, 13 photogrammetric models were created along the major geological structures of the Noble Hills and referenced based on the previous large model. They are composed of hundreds of thousands to million points. On each model, between 318 and 7207 fractures were extracted. The fractures with a surface above 8m² were kept and all the smaller elements were extrapolated to reconstruct a real fractured reservoir.

MEET Geothermal Winter School Martha Nnko first slide visual

Talk #9: Martha Nnko (TU Delft) – Mechanical Characterization and Potential Evaluation of the Geothermal System in Songwe field, Mbeya, Tanzania

Tanzania is one of the East African countries with large amount of geothermal potential that has not been used yet and has only been explored to a limited extentThe national power system relies greatly on hydropower and natural gas. Willing to propose an alternative, the government of Tanzania has made geothermal development a priority.
The area around the city of Mbeya, located at the junction of two branches of the East African rift system has been identified as a first priority region from which two specific targets have been defined, the volcanic region of Ngozi and the half-graben of Songwe. In this study focus is made on the Songwe basin.
In geothermal exploration and development, numerical modelling is essential to understand both regional and reservoir scale processes. Key factors determining geothermal systems potential are temperature and fluid flow. Numerical models allow to constrain reservoir geological properties and fluid flow behaviour to better plan the well path design and field production. In Tanzania, only geophysical (MT and TEM), geochemical studies and field geology have been done. A need therefore arises for numerical modelling to evaluate and assess the potential of the geothermal fields which is the purpose of this study.
In order to evaluate the potential of the geothermal system in Songwe, the study approach includes the reconstruction of the geological model to get the geometry, thermal modelling, hydrothermal modelling, laboratory testing of hot springs fluid to find the chemical properties, and laboratory testing of rock samples to obtain their physical and mechanical properties.
The study presents a reconstructed geological model with the deep structure, a realistic geometry that is essential for the thermal modelling and geothermal modelling work (Figure 1). Thermal modelling with different scenarios to understand how temperature is distributed in the subsurface at a steady-state is also presented in the study and temperature values compared (Figure 2).
The study will also incorporate the mechanical and physical parameters from the laboratory measurements and construct a geothermal model that will help in understanding and predicting the long-term geothermal production in Songwe through testing different production scenarios to identify the related impacting factors on fluid flow and thermal production.

Talk #10: Lei Wang (GFZ) – Laboratory insight into fluid-induced fault slip behavior: Implications for induced seismicity

Understanding the physical mechanisms governing fluid-induced fault slip is important for improved mitigation of seismic risks associated with large-scale fluid injection. In an effort to investigate the effect of injection rate on slip characteristics and strain partitioning, we conducted laboratory fluid injection experiments on permeable sandstone samples in a triaxial deformation apparatus equipped with a 16-channel acoustic emission (AE) recording system. We injected fluid in sawcut samples containing a critically stressed fault at different pressurization rates. Specifically, the fluid pressure is injected stepwise from 5 MPa to 29 MPa with a pressurization rate of 2 MPa and 0.5 MPa, respectively. The experimental results demonstrate that fault slip behavior is governed by fluid pressurization rate rather than injection pressure. Episodic slow stick-slip events (peak slip velocity < 4 μm/s) are induced at high fluid pressurization rate while the fault creep (slip velocity < 0.4 μm/s) occurs in response to slow fluid pressurization rate. The strong weakening of the dynamic friction coefficient of the experimental fault is observed at elevated pore pressure, independent of fault slip mode. The polarity analysis of AE events indicates that shear failure is dominant (about 70% of all events) for both fault slip modes. Our observations highlight that varying fluid injection rates may assist in reducing potential seismic hazards of field-scale fluid injection projects.

Fault slip induced by fluid injection is partitioned in aseismic and seismic moment release. By analysing the seismic moment release of AE events caused by fluid injection, we find that fluid-induced fault deformation is dominantly aseismic. The released total seismic moment is found to be related to total injected volume, independent of fault slip behavior. Seismic moment release rate of AE is related to measured fault slip velocity. In our experiments, the fluid pressure migration is faster than rupture propagation by about five orders of magnitude, resulting in induced fault slip fully confined within a homogenous pressurized zone. The relation between moment release and injected volume is affected by fault slip behavior, characterized by a linear relation for slip at constant rate and fault creep while a cubic relation for unstable and dynamic slip. Our experimental results allow separating a stable pressure-controlled injection phase from a run-away phase, when cumulative moment release with injected volume follows a nonlinear trend.

MEET Geothermal Lei Wang first slide visual
MEET Geothermal Winter School Chaojie Cheng first slide visual

Talk #11: Chaojie Cheng (GFZ) – Long-term evolution of fracture permeability in slate as potential target reservoirs for Enhanced Geothermal Systems (EGS)

The long-term sustainability of fractures in Variscan metamorphic rocks will determine whether it is reasonable to utilize such formations as potential unconventional EGS reservoirs. During long lasting fluid flow within fractures, dissolution, precipitation, and chemical reactions between the fluid and the rock matrix may alter the flow pathway structure and flow properties. Within the framework of the European Union’s Horizon 2020 initiative “MEET (Multi-Sites EGS Demonstration)”, we performed long-term fracture permeability experiments on saw-cut slate samples from the Hahnenklee drill site, Harz Mountains, Germany, under constant pressure and temperature conditions. Two experiments were performed using deionized water as pore fluid with intermittent flow for more than one month at 10 MPa confining pressure and 1 MPa pore pressure. Three sequential investigations were performed, including (ⅰ) an initial continuous flow tests at room temperature, (ⅱ) temperature cycles between room temperature and up to 70 °C or 90 °C, and (ⅲ) measurement of the time-dependent permeability evolution at 70 °C or 90 °C. During stage (ⅲ), the effluents were sampled in time intervals of 6 days and analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The results show that (ⅰ) sample permeability first continuously decreases, but progressively converges within about three days, (ⅱ) increasing temperature leads to an additional permeability decline that is irreversible, and (ⅲ) the time-dependent permeability reduction is much more pronounced at 90 °C in comparison to that at 70 °C. The effluents are enriched with Na, Fe, K, Ca, Si, where the Na concentration is always an order of magnitude higher than the others. Except for Si, concentrations are progressively decreasing with time. During the entire experimental period, sample permeability was reduced by approximately 90% at 90 °C and 60% at 70 °C compared to their initial values. In contrast, both samples showed a negligible permeability decline over time at room temperature after cooling. Our results demonstrate that thermally-enhanced fluid-rock interactions lead to a permanent and at least partial closure of fracture aperture, which is unfavorable for geothermal exploitation. However, the degree of permeability reduction may strongly depend on initial fracture roughness, which remains to be investigated.

Talk #12: Aysegül Turan (TU Darmstadt) – Multi-parameter Petrophysical Characterization of Variscan Granite from Cornwall-UK

The EU H2020 funded ‘MEET’ project (‘Multidisciplinary and multi-context demonstration of EGS exploration and Exploitation Techniques and potentials’, grant agreement no:792037) assesses the four different geological settings of Variscan basement as reservoir rocks for potential EGSs. The study presented here, as a part of MEET project, specifically focuses on the Cornubian batholith in SW England chosen as representative of the crystalline Variscan basement not overprinted by younger tectonics.
With the ambition to increase the clean energy share in United Kingdom’s energy portfolio, Cornwall has been the focus of deep geothermal resource studies starting from 1980s with the Rosemanowes Hot Dry Rock project conducted in the region and continuing today with the United Downs Deep Geothermal Power Project (UDDGP), the first deep geothermal power project of the UK. The main reason of the high local geothermal potential is the heat flow anomaly arising from the radioactive decay of U, Th, K elements within the Cornubian batholith.
The present work aims to investigate the untapped geothermal potential of fractured Cornish granite in more detail. As surface samples; outcrop analogue samples were taken from the Land’s End, St. Austell and Carnmenellis plutons of Cornubian Batholith. 47 granitic samples were collected from both fresh as well as fractured and/or hydrothermally altered areas of 23 outcrops as analogues of the fracture and fault zones targeted by the United Downs wells. 338 core samples with different diameters were drilled in the HydroThermikum Research and Teaching Laboratory of Technical University Darmstadt to do a comprehensive petrophysical and rock mechanical characterization. 47 samples were selected to prepare thin sections, required for a detailed petrographic analysis including degree of weathering or alteration and fluid inclusions. As subsurface samples; drill cuttings were gathered from UD-1 i.e the production well of United Downs project. To understand the mineralogy and hydrothermal alteration at reservoir depth better, XRD, XRF and thin section analyses were done on drill cuttings.
Measurement of the petrophysical (grain density, permeability, bulk density and porosity, compressive and shear velocity, thermal conductivity, thermal diffusivity, heat capacity and radiogenic heat production) and rock mechanical properties (uniaxial compressive strength, Poisson’s ratio, Young’s modulus, bulk modulus and compressibility as well as tensile strength, shear strength, cohesion, coefficient of friction and shear modulus and finally Biot and Skempton coefficients) on outcrop analogue samples were performed. Although the petrophysical rock properties were analyzed at laboratory conditions and therefore deviate from in situ properties at reservoir conditions, the presented dataset enhances the knowledge of petrophysical rock properties within the study area for further geothermal applications. To predict the related properties at the in-situ reservoir conditions, the increasing pressure, temperature and salinity were accounted for.

MEET Geothermal Winter School Aysegul Turan first slide visual
MEET Geothermal Winter School Maxime Catinat first slide visual

Talk #13: Maxime Catinat (UPS) – NMR contribution in sub-horizontal well for porosity-permeability heterogeneity characterization in limestones: implications for 3D reservoir prediction and flow simulation in a world class geothermal aquifer

With around 50 heating networks today operating, the aera around Paris is the European region which concentrates the most heating network production units in terms of deep geothermal energy. In France, the energy-climate strategy plans to produce 6.4TWh in 2023, compared to 1.5TWh produced in 2016 [1]. Despite an exceptional geothermal potential, the current average development rate of 70MWh/year will not allow this objective to be achieved, it would be necessary to reach a rate of 6 to 10 times higher. The optimization of the use of deep geothermal energy is a major challenge for France, and in Ile-de-France, which has a population of nearly 12 million inhabitants. This project aims to reconstruct and simulate heat flows in the Paris Basin using an innovative methodology (1) to characterize, predict and model the properties of reservoirs (facies, porosity, permeability) and (2) simulate future circulations and predict the performance at a given location (sedimentary basin) on its geothermal potential. This study focuses on a high density area of well infrastructures around Cachan, (8 doublets, 1 triplet in 56 km2). A new sub-horizontal doublet concept has been recently (2017) drilled at Cachan to enhance heat exchange in medium to low permeability formations [2]. Nuclear Magnetic Resonance (NMR T2) logs have been recorded in the sub-horizontal well (GCAH2) providing information on pore size distribution and permeability. We integrated all logging data (gamma ray, density, resistivity, sonic, NRM T2) of the 19 wells in the area and 120 thin section observations from cuttings to derive a combined electrofacies-sedimentary facies description. A total of 10 facies is grouped into 5 facies associations coded in all the 19 wells according to depths and 10 3rd order stratigraphic sequences are recognized. The cell size of the 3D grid was set to 50 m x 50 m for the XY dimensions. The Z-size depends on the thickness of the sub-zones, averaging 5 m. The resulting 3D grid is composed of a total of nearly 8.105 cells. After upscaled, facies and stratigraphic surfaces are used to create a reliable model using the “Truncated Gaussian With Trends” algorithm. The petrophysical distribution “Gaussian Random Function Simulation” is used to populate the entire grid with properties, included 2000 NMR data, considering each facies independently. The best reservoir is mainly located in the shoal deposits oolitic grainstones with average porosity of 12.5% and permeability of 100 mD. Finally, hydrodynamic and thermal simulations have been performed using Pumaflow to give information on the potential risk of interference between the doublets in the area and advices are given in the well trajectory to optimize the connectivity and the lifetime of the system. NMR data, especially permeability, allow to greater improve the simulations, defining time probabilities of thermal breakthrough in an area of high density wells.

Talk #14: Saeed Mahmoodpour (TU Darmstadt) – Thermo-hydro-mechanical (THM) simulation of the heat extraction from geothermal reservoirs (field scale simulation of Soultz-sous-Forêts and outcrop-based simulation of Göttingen site)

Numerical simulation of the heat extraction from geothermal reservoirs provides a tool to examine different operational scenarios in lower time, cost and safety issues in comparison to the experimental or field tests and results could be used to optimize the production plan. To obtain a better result, details should be considered as much as possible in a way that the simulation be feasible from the computational machines capabilities aspect. Hopefully, with increasing the power of the computational machines in recent years, now we can go deeper into details of the involved processes in numerical simulation studies by coupling different involving physics.

Now, we are in a position that we can simulate the coupled THM processes involved in heat extraction from geothermal reservoirs. In a part of the MEET project, the possibility and consequences of colder fluid injection (in comparison to the current fluid temperature) into Soultz-sous-Forêts reservoir is examined from the THM response and enhanced energy production aspects. During this study, large scale faults are considered discretely and the equivalent permeability field is assigned based on the small-scale fractures (which are in order of hundreds of thousands) for the background reservoir rock.

The numerical model is validated based on the well-known experimental tests in the literature (Figure 1) and a hydro-thermal test which is done on the Soultz-sous-Forêts reservoir. Heat loss during fluid movement alongside wellbore and daily temperature fluctuation are found as important factors which affect the field measured results. By considering these effects, a good match obtained between the simulation results and the field test.

To shed light on the complex behavior of the faults in the three-dimensional simulation, two-dimensional simulations are conducted based on the fracture network which are obtained from outcrop analysis in the Göttingen site (Figure 2). Poro- and thermo-elastic behavior of the system, fracture aperture changes, effect of the relative orientation between wellbores and fracture network, different boundary conditions and material properties, effect of the fracture aperture distribution are examined in details. Three -dimensional simulations are done in small-scale models with discrete fractures.

The numerical tools are provided to examine the possibility of the new fractures’ initiation and propagation. Furthermore, initial models are developed to examine the fault activation and possible seismic events in response to the cold fluid injection. During the remaining time of the project, these models would be scaled up to the field scale.

MEET Geothermal Winter School Saeed Mahmoodpour first slide visual
MEET Geothermal Winter School Edoardo Pezzulli first slide visual

Talk #15: Edoardo Pezzulli (ETHZ) – A J-integral to simulate hydraulic fracturing in deep geothermal systems

Hydraulic fracturing plays a central role in developing enhanced geothermal systems. To simulate the propagation of fractures, the J-integral has been a standard technique used in the field of fracture mechanics. Its superior accuracy at coarser resolutions make it particularly attractive, especially for reservoir-scale simulations. However, the extension of the J-integral to simulate fluid-driven fracturing has not received the same attention or success. In particular, while several studies have highlighted the capacity of the method in simulating viscosity-dominated propagation, detailed investigations are missing. In this work, a finite element analysis is conducted which sheds light on the sources of error which arise when applying the J-integral in the viscosity-dominated regime. The case is put forward that the inaccurate numerical solution for fluid pressure is exclusively responsible for the loss in accuracy of the J-integral. Consequently, the extent of hydraulic fracturing which occurs is overestimated. With this new understanding, the J-integral is reformulated to minimise its dependence on inaccurate fluid pressures, bypassing the aforementioned sources of error. The reformulation is both simple to implement, and general to the numerical method. Within the framework of finite elements, a propagation algorithm using the novel J-integral is subsequently shown to perform excellently in simulating deep hydraulic fractures in both the toughness and viscosity dominated regimes of propagation; a method especially relevant to enhanced geothermal systems. Furthermore, the novel J-integral is shown to be capable of extracting the velocity of propagation of the fracture. Consequently, an inherent advantage in evolving the fracture geometry is offered compared to the original formulation. To investigate the performance of the novel J-integral with relevance to reservoir scale simulations, finite element simulations are conducted at various levels of refinement. Finally, the potential to devise more efficient algorithms to evolve the fracture networks of geothermal systems is discussed.

Talk #16: Anvar Farkhutdinov (BSU) – A numerical modelling approach for geothermal waters sustainable use (the Khankala geothermal field case)

Nowadays, geothermal waters have become an important form of energy and many researchers have put to the forefront the issue of “sustainability” of the geothermal reservoir development. “Sustainability” of the geothermal waters use is a problem of primary importance, the solution of which requires an integrated approach. Sustainable management of resource utilization is possible with an adequate development strategy as “… for each geothermal system and for each mode of production there exists a certain level of maximum energy production, below which it will be possible to maintain a constant energy production from the system for a very long time (100–300 years)…” (Axelsson et al., 2001).
Reinjection of the used fluid during geothermal reservoir exploitation is the most commonly used exploitation method. It allows minimizing the possible negative effect on the environment and maintaining the reservoir pressure and therefore the initial high flow rates. However, it has a major disadvantage – a gradual temperature decrease in an aquifer, which needs to be taken into account. The most effective methods assessing this disadvantage are based on numerical modelling, which has been actively implemented in all areas of science. Modelling is used to simulate the behavior of complex geothermal reservoir system under different exploitation conditions and predict temperature change. It helps to manage problems of geothermal water exploitation and achieve sustainability.
Modelling was used during the most recent Russian geothermal project – implementation of Khankala geothermal plant (Figure 1).
The Khankala geothermal field is located within the East Ciscaucasian artesian basin, which occupies 250 000 km2. In the beginning of 2016, the Khankala geothermal plant started operating on the basis of the XIII productive layer with a thickness of 40–60 m. The capacity of the facility is 22.8 GJ/h with a greenhouse complex as a consumer. Two wells were drilled to conduct exploitation by a “doublet” system, i.e., one production and one injection well with reinjection of all cooled geothermal water back.
Based on the results of modelling, a gradual decrease in temperature in the production well after 6–7 years of exploitation is predicted due to reinjection of used geothermal water (45 °C) (Figure 2).
One of the main advantages of the Khankala geothermal field is its multi-layered nature. Vertical extension of the cold front is therefore limited by impermeable layers, and so, reinjection in one of the main productive layers does not have an impact on others. At the same time, in the case of significant drop in the production well temperature after some period of XIII layer exploitation, there is a possibility to drill a new “doublet” at the same territory on the resource of the highly promising IV–VII, XVI, or XXII layers, so that the geothermal plant could continue working. The resource of the XIII layer could be used again after some shut-down period considering the relatively high speed of temperature recovery. The installation and the periodic use of two or more circulation systems can be beneficial and are the only true solution of the sustainability problem in long-term operation.
The sustainable use of geothermal waters is possible, but requires to choose adequate exploitation scenario and therefore numerical modelling, as it helps to forecast geothermal reservoir behavior under different conditions.

MEET Geothermal Winter School Anvar Farkhutdinov first slide visual
MEET Geothermal Winter School Lily Suherlina first slide visual

Talk #17: Lily Suherlina (TU Delft) – Characterizing reservoir behaviour changes in exploited high enthalpy geothermal field in Indonesia-integration well data

This study provides a characterization about analysis on well developments taking place in exploited geothermal field in Indonesia. A combination between various well behaviour data reveal new knowledge of changes taking place in south reservoirs due to exploitation response associate with structural geology.
Methods implemented on this study include integrated analysis among the existing data and modification well development maps through ArcMap.
A combination between integrated analysis and interpretation of the well behaviour data reveal reasons to develop south reservoirs in initial exploitation. It is followed by changes in the reservoir behaviour at some wells due to dynamics exploitation in a long time. The changes associates with structural boundary could present controlling the hydrogeological setting around the wells. Some supporting evidences toward the presence of the boundaries are supported by the well data.
The changes can indicate the boundary may have strong controls either act as barrier or composite to manage the fluid flow in subsurface. By knowing characteristic of the boundary can be expected to suggest improvements of well strategy.

Talk #18: Francisco Porturas (Geothermal Association of Peru) – Oil & Gas and geothermal coproduction

The International Energy Agency (IEA) estimates that the upper kilometers of the earth’s crust contain thermal energy that is several million times greater than the Earth’s annual energy consumption. Heat increases as depth increases.

This presentation starts from the three basic premises: 1) Geothermal energy is generally considered ecological and does not cause significant amounts of pollution, 2) Geothermal reservoirs are naturally replenished and therefore renewable (resources cannot be depleted) and, 3) Excellent for generating electricity, heating and cooling – even small homes can benefit.
It is extended with the benefits and advances offered by the technology of the oil and gas industry to optimize operations and costs in the geothermal industry.

The oil and gas industry has a lot to offer the geothermal energy industry.
This operational competence, research and technology within the exploration, management and management of reservoirs, real-time monitoring, stimulation, drilling, completion and registration of wells and instrumentation, are transferred to the geothermal industry and thus optimize operations, costs and advance the opening early to production from geothermal fields and heat drainage from surrounding rocks.
Geothermal energy provides many businesses and opportunities for companies and service companies in the oil and gas sector, which in their activity plans already include in their energy portfolio, a high percentage of transition towards renewable energies including geothermal energy.

MEET Geothermal Winter School Porturas first slide visual
MEET Geothermal Winter School Soles first slide visual

Talk #19: Ana Soles Valdivia (Independent) – Open tools for gathering and integrate data for Geothermal Prospect evaluation

As the world is heading to sustainability environment, gather and analyze valuable data to find and evealuate new getohermal projects has become relevant. In recent years many professionals have invested time and expertise to build tools that make us able to analyze and get professional results to evaluate Geothermal prospects. All these tools are spread in the web and it is important to have a summary than can give us a kick to start to use them. The intention of this paper is to classify, listed and describe this open source tools in a way it would be easier to choose the one could be useful in our work and to measure the complexity and subject needed to use them succesfully. GeothermalDataGenerator (a) pyodbc (b) GMT (c) Gppeval (d) OpenGeoSys (e) pygfunction (f)

Talk #20: Philipp Schröer (Univ. Ruhr-Bochum) – Development of a novel Percussion Mechanism for Downhole Hammer Drilling

Down-the-hole (DTH) hammer drilling technology has been used successfully for many years in the mining as well as oil and gas industry to access hydrocarbon reservoirs [4]. Typical DTH hammers use a piston moved by hydraulic power or compressed air, applying alternating loads onto the drill bit to crush the rock at the borehole bottom and thus, eroding the rock [2]. Due to this alternating movement of the piston this technology is called hammer drilling. The internal components of any DTH hammer are called percussion system and include mainly the piston itself and a valve system controlling its movement. Currently, most DTH hammer systems have a maximum operating temperature of 150 C° and are limited to use compressed air or clean water as drilling fluid [5]. As a result, the wellbore control and cuttings transport are more difficult compared to conventional rotary drilling technologies using drill mud with tri-cone or PCD bits. Furthermore, the lifetime of hydraulic type DTH hammers depends much on the quality of the liquid being used, while the achievable rate of penetration (ROP) in hard rock formation is over 10 times higher compared to other rotary drilling technologies.
The more widespread use of DTH hammer technology towards geothermal reservoirs requires the use of more conventional type of drill mud with additvies, higher lifetime of the device and tool functionality at high-pressure and high-temperature (HPHT) conditions [1]. Therefor, a novel DTH hammer for deep reservoir exploration is being developed using a fluidic switch [3], instead of a mechanical valve system, and advanced surface coatings to increase tool lifetime.
The development of the novel prototype hammer is realized by experimental as well as numerical work (simulations), and iteratively optimizing each component of the percussion mechanism. For this purpose a numerical model of this mechanism is developed based on a mass-spring-damper approach. The model allows to evaluate the efficiency of numerous variations of the mechanism and, therefore, straightens the path of investigation.

The GEODRILL project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 815319.

MEET Geothermal Winter School Schröer first slide visual


Conclusion of the Geothermal Winter School 2021 – H2020 MEET Project – Albert Genter (ES-Geothermie)