Special Issue "New Perspectives on Geothermal Energy Exploration and Evaluation of Geothermal Potential"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Geo-Energy".

Deadline for manuscript submissions: 30 September 2021.

Special Issue Editors

Dr. Renato Somma
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Guest Editor
1. Istituto Nazionale Di Geofisica e Vulcanologia Sezione Di Napoli Osservatorio Vesuviano, Via Diocleziano 328, 80124 Napoli, Italy
2. Consiglio Nazionale Ricerche Istituto di Ricerca su Innovazione e Servizi per lo Sviluppo Napoli, Via Guglielmo Sanfelice 8, 80134 Napoli, Italy
Interests: geothermal energy; environmental geochemistry; pullution
Prof. Daniela Blessent
E-Mail
Guest Editor
Environmental Engineering, Universidad de Medellín, Medellín, Colombia

Special Issue Information

During the past decade, strong efforts have been made to unravel the links between volcanic and non volcanic areas throughout the world and their geothermal energy resources. This effort, in volcanic areas, has provided the basis for converting volcanic risk into a potential clean energy resource, especially in densely inhabited areas. Due to the increasing need for energy in emerging countries, it becomes necessary to characterize geothermal reservoirs as either low/intermediate-temperature resources (for heating and cooling of buildings, district heating, and greenhouses) or high-temperature resources (for electricity generation or co-generation). On the other hand, high-temperature geothermal resources are exploited through deep wells (1–5 km) drilled to reach reservoirs, which can be located in highly heterogeneous volcanic complexes, sedimentary basins, or old basement rocks. Reservoir permeability can be enhanced through different engineering techniques to improve productivity, although such techniques may raise hard problems of social acceptability. Low or intermediate temperature resources are exploited within shallow (few meters) or intermediate boreholes (up to 1 km) and mostly provide heating and cooling capacity. In recognition of these conditions, development of a robust interdisciplinary methodology to characterize such geothermal systems from a volcanological, geophysical, geochemical, and geo(hydro)thermal point of view is fundamental. We welcome contributions pertaining to all these disciplines in order to quickly locate areas within volcanic complexes, sedimentary basins, or old basement rock that are most likely to contain exploitable hydrothermal systems. Well calibrated, multidisciplinary geophysical and geochemical investigation can greatly reduce uncertainties involved in the determination of the geothermal potential, thus stimulating the use of resources able to reduce environmental pollution in emerging countries and in densely populated areas worldwide.

Dr. Renato Somma
Prof. Daniela Blessent
Guest Editors

Manuscript Submission Information

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Keywords

  • geothermal energy
  • volcanic districts
  • geothermal productivity
  • hydrology of geothermal systems
  • induced seismicity
  • low enthalpy
  • high enthalpy
  • hydrogeology
  • modeling of fractured geological media
  • numerical modeling of groundwater flow
  • heat transfer
  • transport of contaminants
  • characterization of geothermal resources

Published Papers (6 papers)

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Research

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Article
Multidisciplinary Approaches for Assessing a High Temperature Borehole Thermal Energy Storage Facility at Linköping, Sweden
Energies 2021, 14(14), 4379; https://doi.org/10.3390/en14144379 - 20 Jul 2021
Viewed by 287
Abstract
Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) [...] Read more.
Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) system at Linköping in Sweden. The storage is required to shift approximately 70 GWh of excess heat generated from a waste incineration plant during the summer to the winter season. Ideally, the site for the HT-BTES system should be able to accommodate up to 1400 wells to 300 m depth. The presence of major fracture zones, high groundwater flow, anisotropic thermal properties, and thick Quaternary overburden are all factors that play an important role in the performance of an HT-BTES system. Inadequate input data to the modeling and design increases the risk of unsatisfactory performance, unwanted thermal impact on the surroundings, and suboptimal placement of the HT-BTES system, especially in a complex crystalline bedrock setting. Hence, it is crucial that the subsurface geological conditions and associated thermal properties are suitably characterized as part of pre-investigation work. In this study, we utilize a range of methods for pre-site investigation in the greater Distorp area, in the vicinity of Linköping. Ground geophysical methods, including magnetic and Very Low-Frequency (VLF) measurements, are collected across the study area together with outcrop observations and lab analysis on rock samples. Borehole investigations are conducted, including Thermal Response Test (TRT) and Distributed Thermal Response Test (DTRT) measurements, as well as geophysical wireline logging. Drone-based photogrammetry is also applied to characterize the fracture distribution and orientation in outcrops. In the case of the Distorp site, these methods have proven to give useful information to optimize the placement of the HT-BTES system and to inform design and modeling work. Furthermore, many of the methods applied in the study have proven to require only a fraction of the resources required to drill a single well, and hence, can be considered relatively efficient. Full article
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Article
Small Unconventional Hydrocarbon Gas Reservoirs as Challenging Energy Sources, Case Study from Northern Croatia
Energies 2021, 14(12), 3503; https://doi.org/10.3390/en14123503 - 12 Jun 2021
Viewed by 357
Abstract
Small possible hydrocarbon gas reservoirs were analysed in the Bjelovar Subdepression in Northern Croatia. This area includes the Neogene–Quaternary, mostly clastics, sequences, reaching 3000+ metres in the deepest part. The shallow south-eastern part of the Drava Depression contains a subdepression characterised with several, [...] Read more.
Small possible hydrocarbon gas reservoirs were analysed in the Bjelovar Subdepression in Northern Croatia. This area includes the Neogene–Quaternary, mostly clastics, sequences, reaching 3000+ metres in the deepest part. The shallow south-eastern part of the Drava Depression contains a subdepression characterised with several, mostly small, discovered hydrocarbon fields, where the majority are located on the northern subdepression margin. The reason is the large distance from the main depressional migration pathways and main, deep, mature source rock depocenters. However, two promising unconventional targets were discovered inside the subdepression and both were proven by drilling. The first are source rocks of Badenian, of kerogen type III in early catagenesis, where partially inefficient expulsion probably kept significant gas volumes trapped in the source rock during primary migration. Such structures are the Western Bjelovar (or Rovišće) and the Eastern Bjelovar (or Velika Ciglena) Synclines. The second promising unconventional reservoir consists of “tight” clastic lithofacies of mostly Lower Pontian located on the north-eastern margin of the subdepression. These are fine-grained sandstones with frequent alternations in siltites, silty and clayey sandstones. They are located on secondary migration pathways, but were never evaluated as regional reservoirs, although numerous drilling tests showed gas “pockets”. Full article
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Article
New Insights into Crust and upper Mantle Structure in Guangdong Province, China and Its Geothermal Implications
Energies 2021, 14(8), 2236; https://doi.org/10.3390/en14082236 - 16 Apr 2021
Viewed by 426
Abstract
Southeast Asia contains significant natural geothermal resources. However, the mechanism for generating geothermal anomalies by the crust–mantle structure still needs to define. In this study, we focused on Guangdong Province, China. We conducted three magnetotelluric profiles to interpret the crust and upper mantle [...] Read more.
Southeast Asia contains significant natural geothermal resources. However, the mechanism for generating geothermal anomalies by the crust–mantle structure still needs to define. In this study, we focused on Guangdong Province, China. We conducted three magnetotelluric profiles to interpret the crust and upper mantle structure beneath the Guangdong Province and its geothermal implications. Based on data analysis results, a two-dimension inversion was conducted on the dataset. The inversion model revealed that there is a presence of upwelling channels, and some channels are connected with shallow crustal fault zone; the thickness of crust and lithosphere in Guangdong Province is relatively thin. Such a special crust and upper mantle structure form high surface heat flow. Merged with previous research, our results imply that massive Late Mesozoic granites, which contain high radioactive heat generating elements, are distributed on the surface and underground of Guangdong Province. Based on the correlation between high radioactive Late Mesozoic granites, crust-upper mantle structure, surface heat flow, and locations of natural hot springs, we established a geothermal conceptual model to visualize the origin of a current geophysical and geothermal anomaly in Guangdong Province. Full article
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Article
New Insights into Hydrothermal Fluid Circulation Affected by Regional Groundwater Flow in the Asal Rift, Republic of Djibouti
Energies 2021, 14(4), 1166; https://doi.org/10.3390/en14041166 - 22 Feb 2021
Viewed by 446
Abstract
The Asal Rift hosts a lake located in a depression at 150 m below sea level, where recharge is influenced by regional groundwater flow interacting with the Ghoubbet Sea along the coast of Djibouti. This regional groundwater flow is believed to influence hydrothermal [...] Read more.
The Asal Rift hosts a lake located in a depression at 150 m below sea level, where recharge is influenced by regional groundwater flow interacting with the Ghoubbet Sea along the coast of Djibouti. This regional groundwater flow is believed to influence hydrothermal fluid circulation, which we aim to better understand in this study, having the objective of developing concepts for geothermal exploration in the area. To this end, magnetotelluric data acquired in the Asal Rift were processed and analyzed. 1D inversion models of electrical conductivity were interpolated for interpretation. These data were then used to build a 2D hydrogeological model, allowing multiphase flow and heat transfer simulations to be performed, considering the regional groundwater flow near the surface and the site topography, in order to confirm the preferred path of fluid flow. Geophysical data analysis indicates the presence of normal faults, notably the H fault, which may act as a conduit for the circulation of hydrothermal fluids and where the hanging wall can be a hydrogeological barrier within the hydrothermal system of the Asal Rift. The results from the 2D numerical flow and heat transfer modelling show the importance of groundwater flow responsible for thermal springs located at the periphery of Asal Lake. Reservoir temperature inferred by means of geothermometry ranging from 200 to 270 °C was shown to correspond to simulated temperature at potential reservoir depth. Moreover, simulated temperature between 600 and 1700 m depth is close to the temperature profile measured in the geothermal well Asal 6 of the area, with less than 20 °C difference. Simulations indicate that hydrothermal fluid circulation is likely influenced by the regional groundwater flow controlled by the topography and the major water bodies, the Ghoubbet Sea and Asal Lake, feeding buoyant fluids interacting with a deep magmatic source and where tectonic activity created normal faults offering a preferred path for fluid circulation. Full article
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Article
Uncertainty and Risk Evaluation of Deep Geothermal Energy Source for Heat Production and Electricity Generation in Remote Northern Regions
Energies 2020, 13(16), 4221; https://doi.org/10.3390/en13164221 - 14 Aug 2020
Cited by 1 | Viewed by 1122
Abstract
The Canadian off-grid communities heavily rely on fossil fuels. This unsustainable energetic framework needs to change, and deep geothermal energy can play an important role. However, limited data availability is one of the challenges to face when evaluating such resources in remote areas. [...] Read more.
The Canadian off-grid communities heavily rely on fossil fuels. This unsustainable energetic framework needs to change, and deep geothermal energy can play an important role. However, limited data availability is one of the challenges to face when evaluating such resources in remote areas. Thus, a first-order assessment of the geothermal energy source is, therefore, needed to trigger interest for further development in northern communities. This is the scope of the present work. Shallow subsurface data and outcrop samples treated as subsurface analogs were used to infer the deep geothermal potential beneath the community of Kuujjuaq (Nunavik, Canada). 2D heat conduction models with time-varying upper boundary condition reproducing climate events were used to simulate the subsurface temperature distribution. The available thermal energy was inferred with the volume method. Monte Carlo-based sensitivity analyses were carried out to determine the main geological and technical uncertainties on the deep geothermal potential and risk analysis to forecast future energy production. The results obtained, although speculative, suggest that the old Canadian Shield beneath Kuujjuaq host potential to fulfill the community’s annual average heating demand of 37 GWh. Hence, deep geothermal energy can be a promising solution to support the energy transition of remote northern communities. Full article
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Review

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Review
Review of Recent Drilling Projects in Unconventional Geothermal Resources at Campi Flegrei Caldera, Cornubian Batholith, and Williston Sedimentary Basin
Energies 2021, 14(11), 3306; https://doi.org/10.3390/en14113306 - 04 Jun 2021
Viewed by 624
Abstract
Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources [...] Read more.
Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources are already used. Three recent drilling experiences focused on the characterization of unconventional resources are described and compared: the Campi Flegrei Deep Drilling Project (CFDDP) in Italy, the United Downs Deep Geothermal Power (UDDGP) project in the United Kingdom, and the DEEP Earth Energy Production in Canada. The main aspects of each project are described (geology, drilling, data collection, communication strategies) and compared to discuss challenges encountered at the tree sites considered, including a scientific drilling project (CFDDP) and two industrial ones (UDDGP and DEEP). The first project, at the first stage of pilot hole, although not reaching deep supercritical targets, showed extremely high, very rare thermal gradients even at shallow depths. Although each project has its own history, as well as social and economic context, the lessons learned at each drilling site can be used to further facilitate geothermal energy development. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Optimal configuration of Polymeric Heat Exchangers for Geothermal direct applications
Authors: Francesca Ceglia, Elisa Marrasso, Carlo Roselli, Maurizio Sasso
Affiliation: Department of Engineering, University of Sannio, 82100 Benevento, Italy
Abstract: //

Title: 3DHIP-Calculator - A new tool to stochastically assess deep geothermal potential using the Heat-In-Place method based on 3D geological models
Authors: Piris, G.. (1), Herms, I. (2)(*) , Griera, A. (1), Colomer, M. (2), Arnó, G. (2), Gomez-Rivas, E. (3)
Affiliation: (1) Departament de Geologia, Universitat Autònoma de Barcelona, 08193 Bellaterra (Cerdanyola del Vallès), Spain (2) Àrea de Recursos Geològics, Institut Cartogràfic i Geològic de Catalunya (ICGC), Parc de Montjuic, s/n, 08038 Barcelona, Spain (3) Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franqués s/n, 08028 Barcelona, Spain
Abstract: The assessment of the deep geothermal energy potential is an essential part of any geothermal project in its early phases. The well-kown “Heat In Place” volumetric method, is still the most widely used technique to estimate the available stored heat and the recoverable heat fraction of deep geothermal reservoirs at the regional scale. Different commercial and open-source software packages have been used to date to estimate these parameters. However, these tools are either not freely available, only consider the entire reservoir volume or a specific part as a single-cell model, or are restricted to certain geographical areas. A novel MATLAB-based tool named 3DHIP-Calculator has been developed for the assessment of the regional deep geothermal potential using the volumetric method following a stochastic approach. The tool allows the user to estimate the Heat-in-Place and recoverable thermal energy using as inputs a 3D geological model and a 3D thermal model. This tool can also be used to carry out estimations depending on data availability. It includes an easy-to-use graphical user interface for visualising the results and export them in files for further postprocessing. To test its applicability, the sedimentary basin of Reus-Valls (NE, Spain) was considered. The new tool bridges the gap between the first phases of field exploration and geological 3D modelling, and the necessary phase of quantification of the geothermal heat available in deep hot reservoirs. The tool will help investors and research organizations determine the suitability and risk of continuing to advance with new investments in pre-feasibility studies of future projects. The tool has been ended, presented and afterwards used in the framework of the GeoERA H2020 HotLime project.

Title: A combined approach for mapping regional geothermal resources in deep aquifers using stochastic and 3D modelling techniques. The case study in the Empordà basin (NE of Catalonia). GeoERA HotLime project
Authors: Ignasi Herms (1) *, Montse Colomer (1), Gerold W. Diepolder (2), Guillem Piris (3), Georgina Arnó (1), Enrique Gómez-Rivas (4), Anna Gabas (1), Irene Cantarero (4), Fabiant Bellumnt (1), Anna Travé (4
Affiliation: (1) Institut Cartogràfic i Geològic de Catalunya (ICGC), Parc Montjuïc E-08038, Barcelona, Spain (2) Bavarian Environment Agency (LfU) – Geological Survey, Bgm.-Ulrich-Str. 160, 86179 Augsburg, Germany (3) Departament de Geologia. Universitat Autònoma de Barcelona (UAB) 08193 Cerdanyola del Vallès, Barcelona, Spain (4) Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franqués, s/n, 08028 Barcelona, Spain
Abstract: This paper presents the results of the characterization of the low enthalpy geothermal resource in the lower Tertiary fractured limestone aquifer within the Empordà Basin, located in the north-eastern sector of the untrusted foreland basin of the Pyrenees in NE Catalonia. The case study is included in the GeoERA H2020 HotLime project, which addresses the mapping and assessment of geothermal plays in deep carbonate rocks from different pilot areas in Europe. A new 3D geological and thermal model of the reservoir-bedrock system has been developed through an integrated interpretation of the previous geological, geophysical and geothermal information available in the study area, complementing it with new geophysical and rock sampling campaigns. The overall available information has been used to develop a 3D conductive layered based steady state regional heat flow model applying a heat uncertainty analysis, to infer the probable temperature distribution within the basin. The geothermal potential assessment has been addressed using the new 3DHIP-Calculator tool, a Matlab-based software compiled for windows which allows to stochastically apply the Heat-In-Place method by using 3D voxel models. Then by means of geographical information system, the georeferenced output results have been converted in raster maps showing among them the spatially distributed stored heat energy (PJ/km2) under different probability scenarios (P10%, P50% and P90%). These maps allow to identify the most favourable and promising areas to go forward for the planning and development of new prospections at local scale.

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