Exploitation Of Geothermal Energy Research Articles

Resurgent dome and super-hot enhanced geothermal system: The Sahinkalesi Massif within the Hasandag Stratovolcanic Province, Central Anatolia, Turkey

The Sahinkalesi, a volcanic dome located NNE of Hasandağ, Türkiye exhibits anomalous heat flow value, geothermal gradient and the Curie point depth is located at very shallow depth in this region. Our investigation indicates presence of super-critical thermal regime (378°C) at about 4 km depth and the MT analysis indicate shallow magma chamber at about 5 km depth. The crust is relatively thin below this region with the low-velocity region located at depth of about 36 km. Thermo-Hydro-mechanical model investigation has been carried out using finite element discretization technique. For faulted zone reservoir models, 30 years of geothermal energy exploitation does not cause thermal breakthrough for mass flow rates up to 500 kg/s, however, the mean stress developed in the reservoir becomes much larger and may be unsustainable for the reservoir stability. To ensure the success of a fractured reservoir model, the use of multiple wellbores is recommended. In the case of a closed-loop geothermal system, the primary concern is the control of thermoelastic stress. This can be achieved either by increasing the wellbore depth while reducing the injection mass flow rate, or by extending the wellbore's horizontal component. The outlet temperature in both the cases maintained at 275°C. This is the first time a superhot EGS site has been identified in Türkiye.

GIS analysis for the selection of optimal sites for mine water geothermal energy application: a case study of Scotland's mining regions

Water within flooded coal mines can be abstracted via boreholes or shafts, where heat can be extracted from (or rejected to) it to satisfy surface heating (or cooling) demands. Following use, water can be reinjected into the mine workings or discharged to a surface water receptor. Four criteria have been applied, using ArcGIS, to datasets describing mine workings and mine water below the Midland Valley of Scotland to provide an initial screening tool for suitability for mine water geothermal energy exploitation. The criteria are: (i) the presence of two or more worked coal seams below site; (ii) the absence of potentially unstable shallow (<30 m) workings; (iii) a depth to mine water piezometric head of less than 60 m; and (iv) a depth of coal mine workings of less than 250 m. The result is the Mine Water Geothermal Resource Atlas for Scotland (MiRAS). MiRAS suggests that a total area of 370 km 2 is ‘optimal’ for mine water geothermal development across 19 local authority areas, with greatest coverage in North Lanarkshire. This result should not be taken to suggest that mine water geothermal potential does not exist at locations outside the identified ‘optimal’ footprint. The MiRAS does not preclude the necessity for specialist engineering and geological input during a full feasibility study.

The analysis of potentially toxic heavy metal contamination in the Lake Bogoria geothermal springs

Lake Bogoria geothermal system is a natural geological site in Kenya that boasts a habitat for Flamingos which attract tourists, and its water find applications in agriculture and recreation. Accordingly, its geological processes, closed water systems and anthropogenic activities may lead to accumulation of potential toxic metal contamination. The present study focused on the analysis of potentially toxic metals — manganese (Mn), cadmium (Cd), lead (Pb), copper (Cu) and nickel (Ni) using atomic absorption spectrometry (AAS) in geothermal spring water samples after acid digestion method, and evaluated their health risks through dermal and ingestion exposures. Principal component analysis (PCA), enrichment factors (EF) and Pearson correlation coefficient (PCC) were performed to determine the sources and correlation between the metals investigated. Manganese, Cu and Ni recorded mean concentrations (ppm) of 0.19 ± 0.08, 0.02 ± 0.02 and 0.03 ± 0.02, respectively, which were below the permissible World Health Organisation (WHO) limits, whereas Pb (0.06 ± 0.04) and Cd (0.05 ± 0.02) levels were above the threshold standards. PCA revealed that these metals may have originated from geological regimes and surface run-offs. Copper and Cd metals were highly enriched indicating an anthropogenic origin. The Hazard quotients (HQ) of Pb and Cd were >1,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$>1,$$\\end{document} hence they are potential precursors for non-carcinogenic and carcinogenic risks in both children and adults. The findings of this study showed possible Pb and Cd metal contamination from geothermal waters. Therefore, there is need for remediation, continuous monitoring and assessment of geothermal waters before utilization for recreation, crop production and geothermal energy exploitation to ensure environmental conservation and human safety.

Numerical modeling and thermal performance analysis of deep borehole heat exchangers considering groundwater seepage

Exploitation of deep geothermal energy based on a deep borehole heat exchanger (DBHE) system significantly promotes green and low-carbon development. The DBHE is the core apparatus of this system, and many mathematical models have been proposed to investigate its thermal performance. However, groundwater seepage which is one of the most important factors has not been considered in most previous numerical models. In addition, the temperature distribution of rock and soil with different seepage velocities during the thermal recovery period is still unclear. Therefore, to fill this research gap, there is a strong need to propose a novel numerical model for DBHEs that considers groundwater seepage and can be solved quickly. In this paper, a computationally efficient numerical model that considers groundwater seepage is proposed. Compared with the experimental data from a field test, the model’s root mean square error is 1.33 °C. Moreover, the time required for the simulation of DBHE operation for one year using this model is only 47.3 s. Then, the effects of groundwater seepage on the DBHE and rocky soil are investigated. The findings demonstrate that when the seepage velocity is high, the thermal performance of the DBHE will be underestimated if groundwater seepage is neglected. At the seepage velocities of 1 × 10-7, 3 × 10-7 and 5 × 10-7 m/s, the heat extraction rate of the DBHE increased by 4.92 %, 10.83 %, and 15.34 %, respectively, compared to the heat extraction rate of the DBHE calculated without taking the groundwater seepage into account. Furthermore, groundwater seepage can increase the temperature recovery capacity of rock and soil. The natural temperature recovery rate of rock and soil without seepage is 86.20 %, and the temperature recovery rate is 93.11 % if the seepage velocity reaches 1 × 10-7 m/s. This study provides essential theoretical guidance for DBHE system design in areas with high groundwater seepage velocities.

Integrated Underground Analyses as a Key for Seasonal Heat Storage and Smart Urban Areas

The design and performance of a shallow geothermal system is influenced by the geological and hydrogeological context, environmental conditions and thermal demand loads. In order to preserve the natural thermal resource, it is crucial to have a balance between the supply and the demand for the renewable energy. In this context, this article presents a case study where an innovative system is created for the storage of seasonal solar thermal energy underground, exploiting geotechnical micropiles technology. The new geoprobes system (energy micropile; EmP) consists of the installation of coaxial geothermal probes within existing micropiles realized for the seismic requalification of buildings. The underground geothermal system has been realized, starting from the basement of an existing holiday home Condominium, and was installed in dry subsoil, 20 m-deep below the parking floor. The building consists of 140 apartments, with a total area of 5553 m2, and is located at an altitude of about 1490 m above sea level. Within the framework of a circular economy, energy saving and the use of renewable sources, the design of the geothermal system was based on geological, hydrogeological and thermophysical analytical studies, in situ measurements (e.g., Lefranc and Lugeon test during drilling; Rock Quality Designation index; thermal response tests; acquisition of temperature data along the borehole), numerical modelling and long-term simulations. Due to the strong energy imbalance of the demand from the building (heating only), and in order to optimize the underground annual balance, both solar thermal storage and geothermal heat extraction/injection to/from a field of 380 EmPs, with a relative distance varying from 1 to 2 m, were adopted. The integrated solution, resulting from this investigation, allowed us to overcome the standard barriers of similar geological settings, such as the lack of groundwater for shallow geothermal energy exploitation, the lack of space for borehole heat exchanger drilling, the waste of solar heat during the warm season, etc., and it can pave the way for similar renewable and low carbon emission hybrid applications as well as contribute to the creation of smart buildings/urban areas.

Municipal Geothermal Systems: Evaluation of Three Hungarian Cases

Geothermal energy holds great potential for a sustainable future, as it is a clean and weather-independent form of energy. In addition to energy production, it can also serve the population of a region through direct use. In this paper, three municipal geothermal systems (Szarvas, Nagyszénás, Békéscsaba) in the same Hungarian region which have been recently installed or expanded are presented and analysed. Here, the direct usage of geothermal energy for heating purposes is a very important issue. The three systems show several differences and to some extent face different challenges in the various phases of the projects. Particular attention has been paid to engineering solutions to the problems that arise. The challenges, such as technical difficulties during installation, maintenance difficulties, or problems arising during operation are introduced. The strengths, weaknesses, opportunities, and threats of similar geothermal systems were summarized, based on the relevant literature. These points were evaluated by their appearance and characteristics in the examined systems. This study aims to provide insights, based on recently gained experiences, into geothermal projects, thus providing feedback and practical information for researchers and practitioners.

Seismic Monitoring of a Deep Geothermal Field in Munich (Germany) Using Borehole Distributed Acoustic Sensing.

Geothermal energy exploitation in urban areas necessitates robust real-time seismic monitoring for risk mitigation. While surface-based seismic networks are valuable, they are sensitive to anthropogenic noise. This study investigates the capabilities of borehole Distributed Acoustic Sensing (DAS) for local seismic monitoring of a geothermal field located in Munich, Germany. We leverage the operator's cloud infrastructure for DAS data management and processing. We introduce a comprehensive workflow for the automated processing of DAS data, including seismic event detection, onset time picking, and event characterization. The latter includes the determination of the event hypocenter, origin time, seismic moment, and stress drop. Waveform-based parameters are obtained after the automatic conversion of the DAS strain-rate to acceleration. We present the results of a 6-month monitoring period that demonstrates the capabilities of the proposed monitoring set-up, from the management of DAS data volumes to the establishment of an event catalog. The comparison of the results with seismometer data shows that the phase and amplitude of DAS data can be reliably used for seismic processing. This emphasizes the potential of improving seismic monitoring capabilities with hybrid networks, combining surface and downhole seismometers with borehole DAS. The inherent high-density array configuration of borehole DAS proves particularly advantageous in urban and operational environments. This study stresses that realistic prior knowledge of the seismic velocity model remains essential to prevent a large number of DAS sensing points from biasing results and interpretation. This study suggests the potential for a gradual extension of the network as geothermal exploitation progresses and new wells are equipped, owing to the scalability of the described monitoring system.

Assessment and Modeling of Geothermal Potential in Northeastern Morocco

The northeast of Morocco is known for many hot water aquifers that emerge at Liasic formations which are the source of the primary thermal springs. In this region of Morocco, the geothermal gradient and heat flow are in relationship with the upward water circulation from Neogene volcanism at depth to the surface of their path through the area's tectonic fractures. Studies on thermal characteristics have revealed promising potential. However, no study has been carried out to estimate the possible exploitation of geothermal energy at the origin of thermal manifestations on the surface. In this paper, we model the geothermal potential stored in thermal reservoirs, using the volumetric method to evaluate and model the power potential through frequency distribution results by Monte Carlo simulation with Python. The model reveals a promising result for the Beni Snassen-Triffa and Eastern Rif areas an advantage for power generation and they could initially support 36-47.4 MWe and 10.6-13.9 MWe power plant respectively for 25 years.

The effects of pore structure on wave dispersion and attenuation due to squirt flow: A dynamic stress-strain simulation on a simple digital pore-crack model

Squirt flow, a phenomenon typically observed in porous cracked rocks, occurs due to the contrasting compressibility between the pores and cracks, leading to the pore pressure diffusion and dissipation of wave energy. Understanding the influence of pore structure on wave dispersion and attenuation signatures due to squirt flow is essential for interpreting seismic and sonic logging data in various fields of earth and energy sciences, such as hydrocarbon exploration, geothermal energy exploitation, and CO2 sequestration. In this study, we construct a simple digital pore-crack model with varying pore structures and use a dynamic stress-strain simulation approach to characterize wave dispersion and attenuation signatures due to squirt flow. Numerical simulation suggests that, in addition to the commonly considered parameters such as porosity, crack density, and crack aspect ratio, additional pore structure parameters, such as pore size, pore aspect ratio, crack orientation, crack length, and crack width, significantly affect the wave dispersion and attenuation signatures. Increasing the pore size leads to the pronounced enhancement of attenuation magnitude and a decrease in characteristic frequency. We demonstrate that variations in crack length have a pronounced impact on attenuation magnitude, whereas crack width is decisive in controlling the characteristic frequency. Furthermore, it is found that the saturation paths (the gas filling the pore first or gas filling the crack first) considerably affect the velocity-saturation and attenuation-saturation relationship, suggesting that the coupling effects of pore structure and fluid distribution complicate the fluid pressure diffusion and wave attenuation behaviors. The presented results offer insights for deciphering pore structure parameters using attenuation- or dissipation-related seismic attributes.

Characterisation of the fracture- and karst-controlled geothermal reservoir below Munich from geophysical wireline and well information

The Upper Jurassic carbonate aquifer in the German Molasse Basin (S Germany) below Munich is the focus of exploitation of geothermal energy. To implement geothermal wells, meaningful prediction of reservoir quality (e.g., volume, temperature, location of aquifers, porosity, permeability) is required. However, permeability of this aquifer is often highly heterogeneous and anisotropic, as in other karst- and fracture systems. Based on geophysical well logs from six wells, a 3D porosity model, and side-wall cores, we provide a comprehensive characterisation of the reservoir. We investigate the correlation between rock porosity and matrix permeability, and the impact of hyper-facies on fractures and karstification. We locate and analyse hydraulic active zones and compare them with hydraulic inactive zones within equivalent depth ranges, to characterise promising exploration targets. We show that fracture system parameters vary strongly between wells and within a single well. However, we observe local trends between the fracture systems and rock properties. For instance, fracture intensities and compressional wave velocity increase, while porosity decreases, in dolomitic reefal build-ups (massive facies). We observed substantial karstification dominantly within the massive facies. The main indicators for hydraulic active zones in the reservoir seem to be karstification, fractures, and fault zones. Although matrix porosity has neglectable impact on permeability, the identified hydraulic active zones appear more frequently in sections with higher porosity. We conclude, similar to previous studies, that the massive facies is a suitable exploitation target. Despite the favourable conditions within the massive facies, the strongest hydraulic active zones are nevertheless in the bedded facies, often considered as aquitard, directly below the top of the reservoir within the lithostratigraphic group of the Purbeck, at the transition between the Jurassic and the Cretaceous.

Geothermal extraction performance in fractured granite from Gonghe Basin, Qinghai province, China: Long-term injection and production experiment

The efficient exploitation of geothermal energy through enhanced geothermal systems (EGS) has been a relevant topic for hot dry rock (HDR) geothermal resources. When cryogenic fluid is injected into a thermal reservoir, improving heat exchange efficiency is key to achieving the optimal exploitation of HDR. In this paper, granite outcrops from Gonghe Basin were used as the testing sample. The natural fractures in the granite samples were relatively well developed. To simulate long-term injection and production from multi-wells in situ, physical experiments were performed in a newly-developed, in-house large-scale true triaxial experimental system. Geothermal extraction performance of an HDR was simulated for long-term injection and production operations. Simultaneously, the mode of one-injection and multiple-production wells was represented. In the paper, the effects of the production-injection well spacing, the number of production wells and the injection rate on the production temperature and flow rate are discussed. The results show that, during long-term injection and production, there are two stages of production temperature variation, namely stabilization and attenuation. When the number of the production wells is increased, the heat extraction efficiency is accelerated. Moreover, competitive diversion of fluid among fractures occurred due to different conductivities. Furthermore, under different production modes, the production flow rate contributed differently to the heat extraction. Finally, the effect of the production-injection wells spacing on the heat exchange performance was analyzed; this is mainly reflected in the change of the effective heat exchange area between the rock and the injected fluid. The results emphasize the importance of designing an appropriate production mode and optimizing the injection-production parameters to ensure efficient HDR exploitation.

Experimental and numerical simulation research on hot dry rock wellbore stability under different cooling methods

The exploitation of geothermal energy commonly occurs at depths ranging from 3000 to 10000 m. At these depths, the surrounding rocks experience substantial temperature and pressure, leading to alterations in their physical and mechanical properties. The infiltration of drilling fluid into the wellbore result in thermal exchange with the surrounding rocks, causing a decrease in their strength and stability. Consequently, the wellbore becomes more susceptible to instabilities. This objective of this study was to investigate the physical and mechanical properties of heated granite under three distinct cooling methods: liquid nitrogen cooling, water cooling, and natural cooling. Based on experimental findings, this study enhanced the failure criteria for high-temperature granite and established a thermal-solid coupling model to assess the stability of wellbores in high-temperature granite formations. To examine the impacts of temperature variations between the wellbore and drilling fluid, analyze the stress distribution around the wellbore at various depths, and evaluate the consequences of high-temperature fluid intrusion on wellbore stability. The research indicates that: (1) Under identical high-temperature conditions, it has been observed that liquid nitrogen cooling causes the most significant damage to granite, followed by water cooling. On the other hand, natural cooling has the least detrimental effect on the rock. (2) With increasing temperature, the physical and mechanical properties of the rock undergo two distinct stages of change. The first stage is a gradual variation that occurs between 25 and 400 °C, while the second stage is a rapid variation observed between 400 and 800 °C. Notably, the temperature of 400 °C serves as a critical threshold for the observed property changes in this granite. (3) The rock failure criteria have been modified based on the thermal damage characteristics of cold fluid intrusion into granite and a thermal-hydraulic-mechanical coupled wellbore model has been established. (4) The numerical simulation results revealed that liquid nitrogen cooling had the greatest impact on wellbore temperature, stress, and damage zone. At 500 s, the temperature on the wellbore surface decreased by approximately 700 °C due to liquid nitrogen cooling. The circumferential stress and radial stress decreased by 180 MPa and 35 MPa, respectively. (5) After the intrusion of cold fluid into high-temperature granite, the stress around the wellbore decreases and the rate of decrease in circumferential stress is significantly greater than that of radial stress. This will increase the likelihood of wellbore instability.

Analysis of physical and mechanical properties of granite under different cooling methods under high-temperatures thermal cycles

This study explores the impact of external pressure and high-temperature erosion on the physical and mechanical properties of granite, the geothermal well storage medium, during geothermal exploitation. Objectives include evaluating the effects of repeated heating and cooling cycles at different temperatures on porosity, permeability and mechanical performance, with a focus on confining pressure's influence on permeability. The results indicate that under water-cooling and ambient conditions, porosity and permeability increase with cycle repetition, whereas compressive strength and elastic modulus decrease. Notably, Group B's (water-cooled) mechanical performance surpasses that of Group A (room temperature cooling) when porosity is below 1.5%. However, with increasing porosity owing to thermal cycling, Group B's granite becomes inferior to that of Group A. Micro-computed tomography scans reveal a post-cycling granite pore structure dominated by horizontal cracks, with primary uniaxial compression damage in the vertical direction. Thermal cycling reduces crack paths and load-bearing capacity, diminishing granite's mechanical performance. This study offers insights into subtle interactions between cooling methods and porosity during geothermal energy exploitation. It provides valuable guidance for optimizing geothermal energy use and mitigating potential adverse impacts on rock integrity, laying a foundation for further research and practical applications in geothermal energy exploitation.

Origin of high heat flow in the back-arc basins of Sumatra: An opportunity for geothermal energy development

Volcanic arcs such as the Barisan Mountains have been identified as attractive areas for the utilization of geothermal energy, as exemplified by Ulubelu in Lampung and Sarulla in North Sumatra. However, environmental factors in the Barisan Mountains remain a primary obstacle to the exploration and exploitation of geothermal energy. The back-arc basins of Sumatra exhibit the highest heat flow worldwide; however, the heat source in this area remains a controversial issue. This study aims to investigate the origin of the high heat flow in the back-arc basins of Sumatra (North, Central, and South Sumatra basins) based on geothermal data from 384 oil wells and the current literature for geological evaluation. The findings of this study indicate that the back-arc basins of Sumatra experienced severe extensional deformation during the Tertiary Period through a large pull-apart and slab rollback mechanism. This deformation resulted in the thinning of the continental crust in this region (27–32 km) and the formation of multiple normal faults. Consequently, the presence of magma resulting from mantle upwelling implies a high heat flow in the back-arc basins of Sumatra. This condition ranks the back-arc basins of Sumatra among the highest heat flow regions of the world, with heat flows >100 mW/m2. These findings indicate that the back-arc basins of Sumatra have significant opportunities to exploit their geothermal energy potential. This study provides novel insights into the potential of geothermal energy, particularly in the back-arc basins of Sumatra.

Developing kilometers-long gravity heat pipe for geothermal energy exploitation

The world-longest SLGHP (4149 m long) and the world's first SLGHP output vapor-driven power generator are developed for the exploitation of geothermal energy.

KEPASTIAN HUKUM WILAYAH KERJA PENGUSAHAAN PANAS BUMI EX KONTRAK OPERASI BERSAMA DIENG DAN PATUHA DALAM KERANGKA PERIZINAN PANAS BUMI DI INDONESIA

Legal certainty in the area of geothermal energy exploitation is very important to ensure the sustainability of geothermal operations in Indonesia. One interesting case to be analyzed is the joint operation contract in the Dieng and Patuha areas. Legal certainty regarding geothermal licensing in these areas has a significant impact on investment and the development of geothermal technology in Indonesia. This study aims to find out the legal status of the Decree of the Minister of Energy and Mineral Resources No. 2789 K/30/MEM/2012 and Minister of Energy and Mineral Resources Decree No. 2192K/30/MEM/2014 reviewed with the licensing theory and legal certainty theory. This study uses a normative legal method with a juridical-normative approach. The results found that the legal product from the geothermal authority in the form of a Decree of the Minister of Energy and Mineral Resources concerning Affirmation of the Working Area for Geothermal Resources Concession has an impact on the absence of legal certainty even though the existing regulations are sufficient to regulate geothermal permits. This should be an urgency to implement laws that apply as a form of guaranteeing absolute legal certainty. Keywords: Geothermal, Licensing, Dieng-Patuha, Legal Certainty, Urgency

Evolution, Hotspots and Trend of Global Geothermal Energy Research

The exploitation of geothermal energy plays an important role in meeting human energy demand and reducing greenhouse gas emission. Firstly, using HistCite scientific metrology visualization software and using WoS (Web of Science) database as literature source, the published years and citation time series of the literature on geothermal energy research was analyzed, which shows that the global geothermal energy research has been very active in recent 20 years, it is a high-yield period for the important literature in this field. Starting from the early basic theory of geothermal energy, it has evolved into two relatively obvious research areas: direct utilization of geothermal energy and geothermal power generation, since then it has continued to evolve into a number of sub-domains that blend with each other and have different themes.

Numerical simulation of the thermal response of seabed sediments to geothermal cycles in Suvilahti, Finland

Renewable thermal energy from seabed sediment is used for heating and cooling houses in Suvilahti, Vaasa, Finland. Innovative coaxial polyethylene pipes (Refla) filled with heat collection fluid are laid horizontally in the sediment layer. This study aims to evaluate the adequacy and possible overuse of this shallow geothermal energy. This entailed a numerical analysis of the heat relations of a “coaxial closed-loop geothermal system (CCGS)" to investigate the thermal behavior of the sediment. The numerical model was developed in Midas GTS NX software with a thermal analysis module. The objective was to understand temperature fluctuation in the sediment, which is influenced not only by geothermal energy exploitation, but also by seasonal weather. The numerical model, due to its design, provided information mainly about changes in sediment temperature due to the geothermal energy exploitation during the different seasons. The results show that in the first third of the total length of the Refla pipes, the sediment environment is significantly affected by energy exploitation's temperature loading. It is advisable to exclude the first third from an analysis of total geothermal energy reserves. The remaining two-thirds of the length shows potential to provide sustainable, long-term geothermal energy (GE) exploitation at the current rate.

Structural properties and failure characteristics of granite after thermal treatment and water cooling

In a variety of fields such as exploitation of geothermal energy and the reconstruction of nuclear waste storage, both of high-temperature and cooling process change the physical and mechanical properties of granite. Uniaxial compression tests were performed on five groups of granite samples at 25 °C, 200 °C, 400 °C, 600 °C and 800 °C after water cooling, and CT scanning, acoustic emission(AE) monitoring and X-ray diffraction(XRD) scanning were used to investigate the structure properties and failure characteristics of granite. It is found that the proportions of pore volume greater than 106 μm3 and less than 105 μm3 with are positively and negatively correlated with the thermal treatment temperature respectively. The mechanical properties of granite are significantly deteriorated by temperature gradient shock, and crack development scale during failure process overall increases as implied by AE response. The failure intensity index η is proposed to characterize the failure severity of granite, and the value of η descends with the increase of thermal treatment temperature, indicating the failure severity of granite is alleviated. Three types of loading failure mode are classified for water-cooled high-temperature granite. The failure mode of granite at 200 °C and 600 °C is tensile failure and tensile-shear failure respectively, while the granite samples are dominated by shear failure at 25 °C, 400 °C and 800 °C.

Geothermal Potential of the Republic of Srpska and the Possibility of Using Low Enthalpic Subgeothermal Resources in the Function of Climate Changes Prevention

Geothermal energy is the part of the geothermal heat that can be used as a useful heath for its direct use or for the conversion into other forms of energy. Geothermal and hydrogeothermal energy are unique sources of renewable energy whose main advantages are in the easy and clean way of use with relatively simple and cheap technology. The rough division of the territory of Republic of Srpska, from the aspect of potential geothermal energy, was performed during not so extensive research that were carried out in the past and based on the registered occurrences of thermal and thermomineral water that occurs in this area. The division was made into two drastically different zones, the zone of Outer Dinarides ‒ the southern part of the territory of the Republic of Srpska, with relatively weaker geothermal characteristics and the zone of Inner Dinarides and the southern part of the Pannonian Basin ‒ the northern part of the Republic of Srpska with exceptional geothermal characteristics, especially in the Semberija area. The potential of these areas needs to be confirmed by detailed systematic hydrogeological research because most of the conducted research so far has been for the needs of oil and gas discovery and exploitation. The usage of geothermal energy in our areas and in the region is insufficiently represented and it is reduced just on the spa tourism and in some places for heating facilities, people are still not adequately introduced with this valuable resource that can largely replace nonrenewable energy and thus affect the preservation of the environment and the reduction of climate change.