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Utilization of geothermal systems in South-East Hungary
Abstract
Thermal wells have been used in Hungary for over 140 years. As thermal water production has increased during the past decades, the pressure drawdown has increased in the geothermal systems of the Pannonian basin, showing that their sustainable management is lacking. The Hódmezővásárhely, Szeged, and Szentes case histories are presented, including the very first indications of stabilization and recharge of the Pannonian thermal aquifers, as a result of reduction of thermal water production. Sustainable production and overall resource management of geothermal systems in SE-Hungary can only be achieved by injection.
... Although sustainable utilisation requires the reinjection of cooled geothermal brine into the host rock, less than 10% of all geothermal wells have been used as reinjection wells in the country [1]. This is linked to economic constraints posed by high-pressure injection technology employed by the oil and gas industry, as well as several unsuccessful reinjection operations in Pannonian sandstone formations [2][3][4]. ...
... The latest study on the production history of the Szentes Geothermal Field is published by Bálint and Szanyi 2015 [1], who provide an in-depth overview of field development and hydraulic characteristics, such as production history of the wells based on previous hydraulic test reports [22][23][24] and the latest hydraulic test campaign, conducted in 20 wells between 2009 and 2010 [2]. They point out that continuous production over decades without reinjection results in a significant drop in production rate, i.e., approx. ...
... They point out that continuous production over decades without reinjection results in a significant drop in production rate, i.e., approx. 7.6 million m 3 The latest study on the production history of the Szentes Geothermal Field is published by Bálint and Szanyi 2015 [1], who provide an in-depth overview of field development and hydraulic characteristics, such as production history of the wells based on previous hydraulic test reports [22][23][24] and the latest hydraulic test campaign, conducted in 20 wells between 2009 and 2010 [2]. They point out that continuous production over decades without reinjection results in a significant drop in production rate, i.e., approx. ...
The Upper Pannonian (UP) sandstone formation has been utilised for thermal water production in Hungary for several decades. Although sustainable utilisation requires the reinjection of cooled geothermal brine into the host rock, only a fraction of the used water is reinjected in the country. UP sandstone formation is reported to exhibit low injectivity, making reinjection challenging, and its petrophysical properties are poorly known, which increases uncertainty in designing operational parameters. The goal of the study is to provide experimental data and to gain a better understanding of formation characteristics that control injectivity and productivity issues in Upper Pannonian sandstone layers. Petrographical characterisation and petrophysical laboratory experiments are conducted on cores retrieved from two wells drilled in the framework of an R&D project at the depth of between 1750 m and 2000 m. The experiments, such as grain density, porosity, permeability, and ultrasonic velocity, as well as thin section, grain size distribution, XRD, and SEM analyses, are used to determine Petrophysical Rock Types (PRT) that share distinct hydraulic (flow zone indicator, FZI) and petrophysical characteristics. These are used to identify well intervals with lower potential for injectivity issues. The results imply that fines migration due to formation erosion is one of the key processes that must be better understood and controlled in order to mitigate injectivity issues at the study area. Future investigation should include numerical and experimental characterisation of formation damage, including water–rock interaction tests, critical flow velocity measurements, and fines migration analysis under reservoir conditions.
... Geothermal energy utilisation is considered to be a renewable resource generally with low environmental impact, and increasing its ratio in the energy mix is an important part of energy strategies [1,2]. Maximising efficiency and minimising environmental effectsmainly the significant water level drop-the widest possible utilisation should be carried out [3][4][5][6][7][8]. One of the ways to ensure this is to rely on geological and geothermal studies on regional and subregional scales and its incorporation into spatial planning linking together with further socio-economic and land-use characteristics. ...
... Apart from research focusing on the entire or almost entire Pannonian area [20][21][22][23][24], the role of research focusing on the Great Hungarian Plain is also significant, the data density of which becomes scarce or almost zero north of the Derecske Trough where the thickness of the layers is significantly smaller than that of the layers in the southern part of the Great Hungarian Plain [12,[25][26][27]. Regional and local research has traditionally been more significant in the vicinity of hydrocarbon occurrences and in the south-eastern Great Hungarian Plain, characterised by higher yield and wellhead temperatures [4,[28][29][30], and recently in the southern and Transdanubian parts as a result of cross-border cooperation [31][32][33][34][35]. ...
... This less-studied marginal area has a more diverse development in the sandy Upper Pannonian formation, which has an impact on the exploitability due to reservoir geometry and is thus worth examining. Negative impacts on productivity are well-known in the vicinity of bathing areas and other large-scale users in most parts of Hungary including this north-eastern area [4,7,37]. However, those negative impacts could be mitigated and avoided by applying the results of complex studies and spatial planning for a more sustainable geothermal energy resource management based on detailed geological and hydrogeological models. ...
The role of geothermal energy is smaller in the global energy mix than what its potential would indicate, but it can be improved by incorporating geothermal energy potential assessments into spatial planning. For adequate decision support and sustainable utilisation, subregion-scale assessments should be applied due to the high variability in geothermal characteristics. Different GIS tools were used for the interpretation and integration of the different spatial data into one model showing areas with their geothermal characteristics on maps. Considering the present study site with a size of 83 km × 103 km located in NE Hungary, 39 2D reflection seismic sections and high-resolution geological data of 137 thermal wells were interpreted in OpendTect and then in ArcGIS to define spatial differences in geothermal potential. It was found that nine geothermal subregions (GSRs) can be distinguished in the present study site based on the applied GIS algorithms. Each GSR was characterised and land-use structure was studied based on Corine Land Cover 2018. The exploitation of water with at least 30 °C is possible in all GSRs, while the maximum achievable temperature and reservoir geometry vary; a subregion-scale delineation framework is required for regional planning.
... Geothermal wells most commonly target Upper Miocene and Quaternary porous sedimentary reservoirs (Fig. 1b). Fractured Mesozoic carbonate rocks also have significant geothermal potential, and are being utilized in several locations within Hungary (e.g., Goldscheider et al. 2010;Horváth et al. 2015;Mádl-Szőnyi et al. 2015;Szanyi and Kovács 2010). Additionally, fractured Mesozoic crystalline basement rock are also suitable targets for deep geothermal developments (e.g., Békési et al. 2018;Horváth et al. 2015;Vass et al. 2018), however, there has been no active exploitation of such resources yet. ...
... Szentes is the first area where geothermal energy has been produced for industrial application in Hungary, with the first well drilled in 1958 (Bálint and Szanyi 2015;Szanyi and Kovács 2010). There are 45 wells drilled in total (including the Szegvár and Fábiánsebestyén areas), and 32 of them were producing thermal water up to 90 °C in 2010. ...
... There are 45 wells drilled in total (including the Szegvár and Fábiánsebestyén areas), and 32 of them were producing thermal water up to 90 °C in 2010. Starting from the early 1970s, thermal water production reached ~ 6.5 million m 3 / year, which has decreased to an average of 5.7 million m 3 /year from the early 1990s (Szanyi and Kovács 2010). Yearly extracted thermal water volumes remained approximately constant after the early 1990s, although the exact yearly amounts cannot be precisely estimated due to the different owners of the individual wells, where production data are not always documented or provided. ...
Excessive thermal water volumes have been extracted from porous sedimentary rocks in the Hungarian part of the Pannonian Basin. Thermal water production in Hungary increased significantly from the early 1970s. Regional-scale exploitation of geothermal reservoirs without re-injection resulted in basin-scale pressure drop in the Upper Pannonian (Upper Miocene) sediments, leading to compaction. This compaction resulted in ground subsidence primarily through poro-elastic coupling.
We investigated surface deformation at the Szentes geothermal filed, SE Hungary, where the largest pressure decline occurred. Subsequently, hydraulic head recovery in the western part of the geothermal reservoir was initiated in the mid-1990s. We obtained data from the European Space Agency’s Envisat satellites to estimate the ground motions for the period of November 2002–December 2006. We applied inverse geomechanical modeling to estimate reservoir properties and processes. We constrained the model parameters using the Ensemble Smoother with Multiple Data Assimilation, which allowed us to incorporate large amounts of surface movement observations in a computationally efficient way. Ground movements together with the modeling results show that uplift of the Szentes geothermal field occurred during the observation period. Since no injection wells were operated at Szentes before 2018, and production temperatures remained relatively constant through the entire production period, we explain ground uplift with pore pressure increase due to natural recharge. The estimated decompaction coefficients of the reservoir system characterizing the elastic behavior of the Szentes geothermal reservoir varies between ~ 0.2 × 10 –9 and 2 × 10 –9 Pa ⁻¹ . Compaction coefficients of the reservoir system corresponding to the earlier depressurization period, from ~ 1970 to the mid-1990s, may be significantly larger due to the potential inelastic behavior and permanent compaction of clay-rich aquitards. The improved parametrization enables better forecasting of the reservoir behavior and facilitates the assessment of future subsidence scenarios that are helpful for the establishment of a sustainable production scheme.
... Nador et al., 2016). Deltaic and turbiditic sandstones deposited during the Pannonian stage of the Late Miocene form one of the main geothermal targets in the Pannonian Basin (e.g., Nador et al., 2016;Szanyi and Kovács, 2010;Toth, 2015). These rocks were deposited during a time of dramatic environmental change, resulting in rapidly-changing sedimentary environments: the ancestral southward drainage of the Pannonian Basin to the Aegean Sea became disrupted, creating an endoreic lacustrine environment, before the modern drainage to the Black Sea via the River Danube became established (Csato et al., 2007;Olariu et al., 2018;Sztanó et al., 2013). ...
... These rocks were deposited during a time of dramatic environmental change, resulting in rapidly-changing sedimentary environments: the ancestral southward drainage of the Pannonian Basin to the Aegean Sea became disrupted, creating an endoreic lacustrine environment, before the modern drainage to the Black Sea via the River Danube became established (Csato et al., 2007;Olariu et al., 2018;Sztanó et al., 2013). Despite the long experience with geothermal heat production from these aquifers, reinjection issues are common and fewer than 10% of all Hungarian geothermal wells are reinjection wells in the past decades; most projects discharge at the Earth's surface (Szanyi and Kovács, 2010;Toth, 2015). Without reinjection, aquifer pressure has reduced significantly in recent decades at most geothermal sites, limiting efficient and sustainable exploitation of these geothermal resources (Szanyi and Kovács, 2010). ...
... Despite the long experience with geothermal heat production from these aquifers, reinjection issues are common and fewer than 10% of all Hungarian geothermal wells are reinjection wells in the past decades; most projects discharge at the Earth's surface (Szanyi and Kovács, 2010;Toth, 2015). Without reinjection, aquifer pressure has reduced significantly in recent decades at most geothermal sites, limiting efficient and sustainable exploitation of these geothermal resources (Szanyi and Kovács, 2010). Chemical factors, such as scaling and clay mobilization have previously been discussed as causes of the injection problems (Balint et al., 2010;Nador et al., 2016). ...
The geothermal doublet at Mezőberény in SE Hungary has suffered from poor productivity and injectivity since it began operation in 2012. The injection and production wells of the doublet are near vertical and have ~400 m production interval, consisting of few thin sandstone bodies in a shale matrix. Previous studies have considered chemical factors, such as scaling and clay mobilisation, as possible causes of injectivity and productivity limitations. So far, however, the possible impact of poor hydraulic connectivity on these limitations has not been considered. Therefore, a geological model describing the geometry of the sandstone bodies in the aquifer and its net sandstone content have been derived in this study. The model is based on a geological dataset from the Békés Basin including core samples, 2D seismic lines and Gamma Ray logs of nearby petroleum wells. Dozens of aquifer realisations of this model were generated, which capture the sedimentary architecture of the aquifer utilising an object-based modelling approach. For each realisation, the volume of sandstone bodies that both wells intersect was calculated. We found that only a small percentage of the total sandstone volume in the realisations was intersected by both wells. This indicates that the net aquifer volume is most likely much smaller than the net-sandstone content of 11% that was derived from the well logs. Therefore, these results suggest that it is likely that hydraulic connectivity is poor between the injection and production well in the doublet, limiting injection and production rates. In addition, our results highlight the importance of sedimentary facies analysis as a tool for successful exploitation of geothermal resources
... The most intense subsidence occurred in the Pannonian Age. At the location of the former sea and lake, a huge sedimentary basin up to 6000-7000 m thick, with high-porosity sedimentary sequences (Pannonian basin), remained (Szanyi and Kovács 2010). ...
... Geothermal aquifers are located in both the Miocene and Pliocene (Varsányi and Kovács 2009 (Szanyi and Kovács 2010) due to the high (50°C km −1 ) geothermal gradient (Dövényi et al. 2002). According to the chemical composition, the waters from Körös basin (located near Szarvas) are mostly of Na-HCO 3 type and are also characterized by the presence of dissolved organic species with TOC values ranging between 2 and 550 mg l −1 (Varsányi et al. 1999). ...
... Up to now, more than 1400 registered thermal water deep wells have been found, out of which 950 are in production. Some of them are abandoned oil and gas wells, but they also include wells drilled for thermal water exploitation purposes (Szanyi and Kovács 2010). Some cities in SE Hungary use thermal water directly for communal purposes and also for district heating. ...
Geothermal waters exploited in the southeastern region of Hungary are alkali-hydrogen-carbonate type, and beside the high amount of dissolved salt, they contain a variety of aromatic, heteroaromatic, and polyaromatic hydrocarbons. The majority of these geothermal waters used for heating are directed into surface waters following a temporary storage in reservoir lakes. The aim of this study was to gain information about the temporal and spatial changes of the water quality as well as the bacterial community composition of an alkaline and saline oxbow lake operated as reservoir of used geothermal water. On the basis of the water physical and chemical measurements as well as the denaturing gradient gel electrophoresis (DGGE) patterns of the bacterial communities, temporal changes were more pronounced than spatial differences. During the storage periods, the inflow, reservoir water, and sediment samples were characterized with different bacterial community structures in both studied years. The 16S ribosomal RNA (rRNA) gene sequences of the bacterial strains and molecular clones confirmed the differences among the studied habitats. Thermophilic bacteria were most abundant in the geothermal inflow, whereas the water of the reservoir was dominated by cyanobacteria and various anoxygenic phototrophic prokaryotes. In addition, members of several facultative anaerobic denitrifying, obligate anaerobic sulfate-reducing and syntrophic bacterial species capable of decomposition of different organic compounds including phenols were revealed from the water and sediment of the reservoir. Most of these alkaliphilic and/or halophilic species may participate in the local nitrogen and sulfur cycles and contribute to the bloom of phototrophs manifesting in a characteristic pink-reddish discoloration of the water of the reservoir.
... Sustainable rate of groundwater production is not unambiguously defined in the literature (Sophocleous 2000;Loukas et al. 2006;Murad et al. 2006;Rejman, 2006;Zhou 2009), and therefore has to be evaluated by various methods relevant for a specific site because not only yield but also temperature and chemistry of thermal water control its usability. Over-exploitation and aquifer depletion have often been observed in low-temperature sandstone geothermal aquifers, e.g., in China (Axelsson and Dong 1998), Hungary (Szanyi and Kovács 2010) and Jordan (Schäffer and Sass 2013), at sites similar to the Pannonian basin. ...
... Reinjection in sandstone geothermal aquifers is essential to mitigate aquifer depletion but it challenges specific technical issues. However, successful examples are known in several large sedimentary basins world-wide, e.g., the Tianjin basin in China (Minissale et al. 2008;Liancheng and Li 2010), the Paris basin in France (Ungemach 2003) and the Pannonian basin in Hungary (Szanyi and Kovács 2010) and Slovenia (Rman et al. 2015b). ...
... Numerical thermodynamic simulation of reinjection of thermal water from the Rijswijk sandstone in the West Netherland basin (Borozdina et al. 2013), similar to the investigated ones, pointed out that no chemical clogging is foreseen and negligible reduction of porosity is expected due to precipitation of silicates in 20 years of doublet operation. Two reinjection wells in the Upper Pannonian sands in Hódmez} ovásárhely (Hungary) are set up in very similar natural settings to the investigated one and return 75-80 % of produced thermal water with average temperature of 35°C to 1450-1700 m depths (Szanyi and Kovács 2010). The injection pressure is below three bars and several filters are used to clean the water, very similar to the practice in Lendava in Slovenia. ...
This paper investigates depletion rates and available thermal water resources of the transboundary Upper Pannonian loose sandstone geothermal aquifer of the Mura Formation in the Mura-Zala sedimentary basin in north-eastern Slovenia, and outlines a regional reinjection strategy to mitigate depletion. The research monitoring network of 12 geothermal wells, which is being constantly upgraded since 2009, has highlighted that the current abstraction rate of 2.4 million m3 in 2014 is not sustainable because hydraulic state has been continuously deteriorating regionally while the chemical state is affected only locally. The average regional drawdown rate in observation wells is 0.67 m annually, while very rough average value for abstraction wells is 3.0 m per year. The cumulative historical regional drawdown is above 16 m. The available thermal water resources are addressed as the cumulative abstraction rate which reverses the observed declining trend of groundwater levels, and were numerically assessed to be ~1.3 million m3 of thermal water per year. These numerical models set up in the AUTOUGH2 code also provided the quantification tool of the regional groundwater balance and confirmed the gravity-driven regional groundwater flow with prevailing conductive heat transfer mechanism. Simulations of the regional reinjection strategy outline that the cumulative reinjection rate of ~1.48 million m3 of thermal water per year should be sufficient to reach good status of the aquifer if the cumulative regional abstraction rate does not change. If it does, the rate should be adjusted accordingly. The water is provided by eight users of geothermal heat and should be returned by the existing reinjection wells in Lendava and Murska Sobota and two new wells situated in the central part of the basin by 2021 the latest. These findings should enhance optimization of exploitation practice and implementation of geothermal doublets in the region as the successful example of a doublet in Lendava exemplifies that no major technological issues should occur if the system is properly designed.
... The Szentes geothermal field is located in the southern part of the Great Hungarian Plain (Fig. 1) on the left bank of the Tisza river, including the Szentes, Szegvár and Fábiánsebestyén areas (hereafter in this study named the Szentes area). The Szentes area belongs to the northeastern wedging part of the Makó-Hódmezősvásár hely Trough, where the pre-Neogene basement is at depths between 4,500 and 5,000 m (Szanyi and Kovács 2010). The trough was filled with gravel and conglomerate from the erosion of the Algyő and Pusztaföldvár Highs, as Pannonian porous sediments (Budai and Gyalog 2010). ...
... By this time it became obvious that long-term intensive pro- Fig. 3 Thermal well placement in the Szentes-Fábiánsebestyén (A) and in the Szegvár area (B) and outflow water temperature given in brackets duction without reinjection, with the decrease of dissolved gas content, created a significant reservoir energy drop. At the beginning of 1991 the total extracted thermal water was estimated at 250 ± 10 million m 3 (Korim 1991), and about 6.5 million m 3 /year production at this time (Szanyi and Kovács 2010). Until 1991, the majority of the thermal wells became unproductive, or the water amount with free outflow decreased at such a scale that submersible pumps had to be installed (Korim 1991). ...
... Until 1991, the majority of the thermal wells became unproductive, or the water amount with free outflow decreased at such a scale that submersible pumps had to be installed (Korim 1991). Up to 2004, moderated, 4-8 m increase of hydraulic heads were observed by Kovács and Szanyi (2010), which was assigned to the decrease of production to 5.7 million m 3 /year (Fig. 4). ...
The general characterization of the Hungarian Szentes geothermal field is presented based on the review of previous research and is supplemented with the analysis of well hydraulic tests. Forty thermal wells were included in the study area, producing mainly from Upper Pannonian sandstone reservoirs. The intensive and long-term production of thermal water reservoirs without reinjection resulted in significant reservoir pressure decrease from natural conditions. By means of deep-well pressure build-up curves, deep-well capacity curves and surface pressure curves the reservoir condition changes were described in the last half century.
... Following this, energy generation from 8000 existing wells [87] in the oil and gas fields of Hungary proved impractical. The main reasons concluded were [86] a) low production rates (30 kg/s), b) low aquifer productivity [58], c) high Gas-Water-Ratio (GWR >5), and d) higher chloride content (0.32 mg/l) [86]. ...
... In this method, output from the wells is summed up and the field potential is calculated. In the case of abandoned wells, most of the measured data available were obtained only a few hours after drilling [58,86] and may underestimate the true resource potential [26]. Therefore, it is plausible to estimate net-generation capacity only after steady-state conditions in these wells have been achieved (in around six months) [3,29]. ...
Hydrocarbon fields around the world may possess suitable features for low-temperature geothermal energy extraction (below 190 °C). Few demonstration plants prove the technical feasibility of power generation from such fields. Case studies are reviewed and discussed to identify deciding parameters for an economical geothermal system. An insightful discussion outlining the unique characteristics of a power project in oil and gas fields is presented. A low-temperature geothermal system set up on unused wells in depleted reservoirs must justify the challenging economics to become an investment opportunity. Interlinked economic, technical and geological parameters influence a profitable development. The long-term behaviour of the resource is uncertain and sustainable resource management in such fields is rarely discussed. Reservoir and wellbore simulations are likely to allow an improved understanding of resource behaviour. It will facilitate the evaluation of the reservoir capability to sustain the estimated capacity for longer.
... [2] caused by the crustal thinning that accompanied lithospheric extension in the Early-Middle Miocene [3,4]. A key geothermal aquifer target in the Pannonian Basin is the sequence of deltaic and turbiditic sandstones deposited during the Pannonian stage of the Late Miocene (e.g., [5,6]). These rocks were emplaced at a time of dramatic environmental change, resulting in rapidly-changing sedimentary environments: the ancestral southward drainage of the Pannonian Basin to the Aegean Sea became disrupted, creating an endoreic lacustrine environment, before the modern drainage to the Black Sea via the River Danube became established [7][8][9]. ...
... Despite the long experience of production of geothermal heat and hydrocarbons from these sandstones, many geothermal sites experience reinjection issues; as a result, less than 10% of all Hungarian geothermal wells have been used as reinjection wells in the past decades (e.g., [5,6]). Chemical factors, such as scaling and clay mobilization, have previously been discussed as causes of these injection problems (e.g., [19]), but effective mitigation has not been developed. ...
Hundreds of geothermal wells have been drilled in Hungary to exploit Pannonian Basin sandstones for district heating, agriculture, and industrial heating projects. Most of these sites suffer from reinjection issues, limiting efficient use of this vast geothermal resource and imposing significant extra costs for the required frequent workovers and maintenance. To better understand the cause of this issue requires details of reservoir rock porosity, permeability, and mineralogy. However, publicly available data for the properties of reservoir rocks at geothermal project sites in Hungary is typically very limited, because these projects often omit or limit data acquisition. Many hydrocarbon wells in the same rocks are more extensively documented, but their core, log, or production data are typically decades old and unavailable in the public domain. Furthermore, because many Pannonian sandstone formations are poorly consolidated, coring was always limited and the collected core often unsuitable for conventional analysis, only small remnant fragments typically being available from legacy hydrocarbon wells. This study aims to reduce this data gap and to showcase methods to derive reservoir properties without using core for flow experiments. The methods are thin-section analysis, XRD analysis and mercury intrusion porosimetry, and X-CT scanning followed by numerical flow simulation. We validate our results using permeability data from conventional production testing, demonstrating the effectiveness of our method for detailed reservoir characterization and to better constrain the lateral variation in reservoir properties across the Pannonian Basin. By eliminating the need for expensive bespoke coring to obtain reservoir properties, such analysis will contribute to reducing the capital cost of developing geothermal energy projects, thus facilitating decarbonization of global energy supply.
... The utilization of thermal water has a long tradition in the Pannonian Basin and Hungary (Szanyi et al. 2009;Szanyi and Kovács 2010;Rman et al. 2015;Rotár-Szalkai et al. 2017;Szőcs et al. 2018). Thermal water is widely used for balneological and heating purposes, especially in the agriculture sector, representing the major part of direct use (Nádor et al. 2019). ...
... This limits the amount of heat and water that can be utilized from a reservoir causing nonsustainable production (Rybach and Mongillo 2006). Unfavourable effects of excessive thermal water production (e.g., significant drop of hydraulic head, temperature, yield, changes in water chemistry) have already been reported in various parts of the Pannonian Basin (Szanyi and Kovács 2010;Tóth et al. 2016;Rotár-Szalkai and Ó Kovács 2016). The sustainable utilization of the thermal waters and the long-term productivity of the reservoirs require the clarification of the path(s) of the groundwater flow as well as the driving forces (Mádl-Szőnyi and Simon 2016). ...
In South Transdanubia (Hungary), the remarkable geothermal and hydrocarbon resources in the Drava Basin and the hypogene caves at the margin of outcropping carbonate hills were usually investigated separately and their interactions were hitherto neglected. The aim of this study is to give all these groundwater-related resources and phenomena a common framework applying the concept of regional hydraulic continuity, and to complete the regional (i.e., basin-scale) hydraulic assessment of the area based on preproduction archival measured data. Pressure-elevation profiles, tomographic fluid-potential maps and hydraulic cross-sections were constructed to determine the vertical and horizontal fluid-flow conditions. As a result, two kinds of fluid flow systems could be identified. Within the gravitational flow systems, horizontal flow conditions are dominant and the regional flow direction tends toward the S–SE. In deeper basin regions, an overpressured flow system is prevalent, where fluids are driven laterally from the deeper sub-basins towards their margins. Based on the regional-scale evaluation of fluid flow systems, conclusions could be drawn regarding the geothermal and hydrocarbon potential of the area. Additionally, local-scale phenomena could be explained, particularly in the southern foreland of the Villány Hills. Cave formation cannot be related to the present-day flow systems here. In the Harkány area, groundwater chemistry could be explained by fluid contribution from the Drava Basin. A comparison with the marginal Buda Thermal Karst area allows for generalized conclusions regarding the connections between marginal karst reservoirs and the Pannonian Basin.
... There are over 350 sites producing thermal water mostly from the Ujfalu Formation, of which >150 are used for space heating. Most geothermal systems such as for example Szentes (Szanyi & Kovács, 2010;Bálint & Szanyi, 2015) consist of multiple wells, and only produce water, which over time leads to pressure decreases in the geothermal aquifer. Reinjection occurs in only 20 wells, for example in the Hódmezővásárhely geothermal system (Szanyi and Kovács, 2010) and in the Orosháza-Gyopárosfürdő geothermal system (Szita and Vitai, 2013). ...
... Most geothermal systems such as for example Szentes (Szanyi & Kovács, 2010;Bálint & Szanyi, 2015) consist of multiple wells, and only produce water, which over time leads to pressure decreases in the geothermal aquifer. Reinjection occurs in only 20 wells, for example in the Hódmezővásárhely geothermal system (Szanyi and Kovács, 2010) and in the Orosháza-Gyopárosfürdő geothermal system (Szita and Vitai, 2013). ...
Geothermal energy is a viable alternative to gas for the heating of buildings, industrial areas and greenhouses, and can thus play an important role in making the transition to sustainable energy in the Netherlands. Heat is currently produced from the Dutch subsurface through circulation of water between two wells in deep (1.5-3 km) geothermal formations with temperature of up to ∼100 °C. As the number of these so-called doublets is expected to increase significantly over the next decades, and targeted depths and temperatures increase, it is important to assess potential show-stoppers related to geothermal operations. One of these potential hazards is the possibility of the occurrence of felt seismic events, which could potentially damage infrastructure and housing , and affect public support. Such events have been observed in several geothermal systems in other countries. Here we review the occurrence (or the lack) of felt seismic events in geothermal systems worldwide and identify key factors influencing the occurrence and magnitude of these events. Based on this review, we project the findings for seismicity in geothermal systems to typical geothermal formations and future geothermal developments in the Netherlands. The case study review shows that doublets that circulate fluids through relatively shallow, porous, sedimentary aquifers far from the crystalline basement are unlikely to generate felt seismic events. On the other hand, stimulations or circulations in or near competent, fractured, basement rocks and production and reinjection operations in high-temperature geothermal fields are more prone to induce felt events, occasionally with magnitudes of M > 5.0. Many of these operations are situated in tectonically active areas, and stress and temperature changes may be large. The presence of large, optimally oriented and critically stressed faults increases the potential for induced seismicity. The insights from the case study review suggest that the potential for the occurrence of M > 2.0 seis-micity for geothermal operations in several of the sandstone target formations in the Netherlands is low, especially if faults can be avoided. The potential for induced seismicity may be moderate for operations in faulted carbonate rocks. Induced seismicity always remains a complex and site-specific process with large unknowns, and can never be excluded entirely. However, assessing the potential for inducing felt seismic events can be improved by considering the relevant (site-specific) geological and operational key factors discussed in this article.
... In the light of all this, the solutions shown in this paper could be presented to the economy, keeping the use of agricultural water, greenhouse, vegetable and fruit production, since the goal is to keep thousands of jobs and to reduce carbon dioxide emissions by using thermal energy as well as the EU-backed usage of renewable energy. 12 A legal solution to the problem may be the modification of the Act of Water Management in such a way, that the partial or total rejection against other surface receivers should be preferred. Another change may be that the current g multiplier equaling 2 should be raised to at least 4.0-4.5 (above the multiplier of balneological use), to stimulate farmers to partially reinject or even those users who heat buildings with thermal water without any reinjection. ...
... Mindezek fényében a következő megoldási javaslatok adhatók a gazdaság számára fontosnak tartva a mezőgazdasági hévízfelhasználást, az üvegházi és fóliás zöldség-gyümölcs termelést, hiszen ez több ezer munkahely megtartását és a termálenergia felhasználásával a szén-dioxid-kibocsátás jelentős csökkentését, valamint és az EU által ösztönzött, megújuló energiára alapuló hőenergia-termelés arányának növelését is jelenti. 12 Jogi megoldási javaslat lehet a problémára, a vízgazdálkodási törvény olyan irányú módosítása, amiben legalább be lenne írva, hogy a részbeni vagy teljes visszasajtolást előnyben kell részesíteni a többi használt víz elhelyezési móddal szemben. Másik módosítás lehet, hogy a jelenlegi 2-es g szorzót legalább 4,0-4,5-re kellene emelni (a fürdő célú vízhasználat g szorzója fölé), hogy takarékosságra, vagy részben visszasajtolásra ösztönözzük a gazdákat, ill. ...
... Geothermal systems are often characterized by the interaction of complex processes as discussed elsewhere [1]. Therefore, geothermal exploration is increasingly focusing on the extensive integration of multidisciplinary data from production technology to hydrogeochemistry and geological researches [1][2][3][4][5][6][7][8]. Unfortunately, many geothermal installations (e.g., hydrothermal cascade systems) face important operational challenges such as unwanted scaling accompanying the exploitation of high-temperature waters with high salinity and gas content from deep wells [6]. ...
... Recently, some papers reported the man-made (technical/operational) effects of the district-heating geothermal systems in Szeged [2][3][4]7]. Additionally, hydrogeological and hydrochemical conditions in the Great Hungarian Plain were extensively studied applying state-of-the-art geochemical methods [9][10][11][12][13][14][15][16][17][18]. ...
The study area, Pannonian Basin (Central Europe), is characterized by high heat flow and presence of low-enthalpy geothermal waters. In the Szeged Geothermal Systems (Hungary), having Miocene to Pliocene sandstone aquifers with dominantly Na–HCO 3 -type thermal water, unwanted carbonate scaling was observed. An integrated approach consisting of host rock and scale mineralogical and petrographic analyses as well as water chemistry led to a better understanding of the characteristic natural (geogenic) environmental conditions of the geothermal aquifers and to highlight their technical importance. Analyses of the reservoir sandstones showed that they are mineralogically immature mixed carbonate-siliciclastic rocks with significant macroporosity. Detrital carbonate grains such as dolomite and limestone fragments appear as important framework components (up to ~20–25%). During water–rock interactions, they could serve as a potential source of the calcium and bicarbonate ions, contributing to the elevated scaling potential. Therefore, this sandstone aquifer cannot be considered as a conventional siliciclastic reservoir. In mudrocks, a significant amount of organic matter also occurs, triggering CO 2 producing reactions. Correspondingly, framboidal pyrite and ferroan calcite are the main cement minerals in all of the studied sandstone samples which can suggest that calcite saturation state of the thermal fluid is close to equilibrium in oxygen-depleted pore water. Analysis of the dominant carbonate crystals in the scale can suggest that growth of the feather dendrites of low-Mg calcite was probably driven by rapid CO 2 degassing of CO 2 -rich thermal water under far-from-equilibrium conditions. Based on hydrogeochemical data and related indices for scaling and corrosion ability, the produced bicarbonate-rich (up to 3180 mg/l) thermal water has a significant potential for carbonate scaling which supports the aforementioned statement. Taking into consideration our present knowledge of geological setting of the studied geothermal systems, temporal changes in chemical composition and temperature of the thermal water during the heating period can indicate upwelling fluids from a deep aquifer. Regarding the pre-Neogene basement, hydrologic contact with a Triassic carbonate aquifer might be reflected in the observed chemical features such as decreased total dissolved solids and increased bicarbonate content with high scale-forming ability. The proposed upflow of basin-derived water could be channeled by Neogene to Quaternary fault zones, including compaction effects creating fault systems above the elevated basement high. The results may help to understand the cause of the high carbonate scale precipitation rates in geothermal systems tapping sandstone aquifers.
... km) with a heat flow of 90-100 mW/m2. Gravity-driven flow dominates the upper formation and pressuredriven flow dominates the lower sedimentary formations (Jiachao 2012). The porous formations of Pannonian Basin contain water up to 130-150°C; however, the temperature in some karst and fissured carbonated reservoirs in basement rocks is up to 300°C (Szanyi et. al. 2010). Rezessy in 2005 estimated the total geothermal energy of Hungary stored in formations above 5,000 m depth to be approximately 100,000 EJ (1 EJ = 1018 J). To date, over 1,400 registered deep wells in Hungary have found thermal water, among them 950 are in production at present. Only about 20 of these are reinjection wells. Fortunately, ...
... Fortunately, recent legislation prohibits new geothermal systems from being established without reinjection; only water used for balneotherapy is allowed to be discharged at the surface. The current estimated total production from thermal wells, which are mostly used about 6 months a year, is 84 million m³ per year, with a heat content of 15.2 PJ per year (Szanyi et al. 2010). ...
Geothermal systems are distributed throughout the world in various ways on the basis of heat source, heat transfer, reservoir temperature, physical state, utilization and geological settings. Common classification of geothermal systems are: (a) volcanic systems with the heat source being hot intrusions or magma chambers in the crust, (b) convective systems with deep water circulation in tectonically active areas of high geothermal gradient, (c) conductive sedimentary systems with permeable layers at great depth (2-5 km), (d) geopressured systems often in conjunction with oil resources, (e) hot dry rock or EGS systems where abnormally hot masses of low permeability rocks are found at drillable depths, and (f) shallow resources in normal geothermal gradient areas utilized with ground-source heat pump applications. 50 years ago a classification for geothermal systems was proposed in Iceland which were divided into high-and low-temperature geothermal systems or fields based on (arbitrarily) inferred temperature, high temperature fields where a temperature of 200°C is reached at 1 km depth and low temperature fields where temperature is below 150°C in the uppermost km. The high-temperature geothermal fields are all related to volcanism whereas the low-temperature geothermal fields draw heat from the general heat flow of the crust. The geothermal systems are suitable for various applications based on subsurface temperature and fluid. Low-temperature geothermal system is directly related to the sedimentary basin which has thin conductive permeable sedimentary layers. Most of the low-temperature geothermal energy used as heating system in the winter dominant countries around the world. Bangladesh is one of the largest deltas which has a large sedimentary basin. Little prospect of geothermal resources in Bangladesh due to its geo-tectonic settings as well as thick sedimentary covers (130 m-20 km). Bangladesh has no volcanic regions, although in the east it lies close to the Eurasian-Indian plate boundary, which may be associated with high geothermal gradients. It has many abandoned gas wells which temperature is more than 100°C in the depth of 3 km to 4 km. The geothermal prospects, geological mapping of surface geothermal manifestations as well as low-temperature surveys are essential to evaluate the geothermal resources in Bangladesh. 1. INTRODUCTION The word geothermal comes from Greek words geo (earth) and thermal (heat) meaning heat derived from the earth. It is the thermal energy contained in the fluids of rocks that is filled in the fractures and pore spaces within the upper crust. The heat is generated from several sources. Normally, the heat or temperature created by decay of naturally radioactive elements which increases with depth (Figure 1).The geothermal energy is defined as the temperature energy which stored within the earth where normal or abnormal temperature or geothermal gradient occurred. It refers to all parts of the hydrological system involved, including the recharge zone, all subsurface parts and the outflow of the system. This energy essentially consists of the heat stored beneath the earth's surface and discharging from it. The main sources for geothermal energy are the heat flow from the earth's core and mantle and that generated by the gradual decay of radioactive isotopes in the earth's crust which together result in an average terrestrial heat flow. This energy is found around the world but little in exploitable. The exploitable geothermal areas are associated with the earth's plate boundaries, volcanic regions, warm ground water in sedimentary formations or conductive sedimentary system and hot dry rock. The low-temperature geothermal energy is mainly used in heating purpose but also in industrial uses and little in electricity production. Sedimentary systems are found in many of the major sedimentary basins of the world. These systems owe their existence to the occurrence of permeable sedimentary layers at great depths (> 1 km) and above average geothermal gradients (> 30ºC/km) which are suitable for prospect of low-temperature geothermal system. These systems are conductive in nature rather than convective, even though fractures and faults play a role in some cases. Some convective systems may, however, be embedded in sedimentary rocks. Bangladesh has thick sedimentary covers and considering for the prospect of low-temperature geothermal field. Reservoir rocks of Bangladesh are permeable water bearing sandstone which is a good sign of the low-temperature geothermal system. A geothermal resource mostly depends on reservoir temperature, so Bangladesh needs only temperature. But Bangladesh is a monsoon climatic region where dominant by warm climatic condition and only two or three months covered by winter climate. So, heating system of low-temperature geothermal system is suitable only in winter period for this country but in electricity production it can be used frequently.
... The chemical composition of geothermal waters often differs markedly from the receiving waters [2], therefore, the direct drainage of used geothermal waters into freshwaters is not authorized. There are applicable procedures for the management of used thermal waters such as reinjection into the source medium, temporary storage in reservoir lakes, ionization, and ozone treatment [3,4]. Nevertheless, each of them has their own limitations. ...
... However, there is a possibility that the bedrock layers get damaged through time, e.g., due to high pressure used for reinjection and salt precipitation may alter the original composition of the sourced water [5]. Although increasing efforts are being made to the reinjection of used thermal waters in Hungary [4], a significant amount of the used thermal waters is redirected into a recipient natural water following temporary storage in reservoir lakes [6]. ...
Disposal of used geothermal waters in Hungary often means temporary storage in reservoir lakes to reduce temperature and improve water quality. In this study, the physical and chemical properties and changes in the bacterial community structure of a reservoir lake system in southeast region of Hungary were monitored and compared through 2 years, respectively. The values of biological oxygen demand, concentrations of ammonium ion, total inorganic nitrogen, total phosphorous, and total phenol decreased, whereas oxygen saturation, total organic nitrogen, pH, and conductivity increased during the storage period. Bacterial community structure of water and sediment samples was compared by denaturing gradient gel electrophoresis (DGGE) following the amplification of the 16S rRNA gene. According to the DGGE patterns, greater seasonal than spatial differences of bacterial communities were revealed in both water and sediment of the lakes. Representatives of the genera Arthrospira and Anabaenopsis (cyanobacteria) were identified as permanent and dominant members of the bacterial communities.
... The cascade system in the city comprises two geothermal loops for district heating with the annual production of 350000-420000 m 3 . About one-third of the used geothermal water has been reinjected since 1998 and additional one-third since 2008 by total two reinjection wells at the end of the thermal loops (Figures 3 and 4) [10]. ...
... The pressure in front of the surface filters was between 2 bar and 6 bar and at the well's head 1.5-4 bar, depending on the filters' saturation. The applied filters were Johnson filter covered with polypropylene fabric with a guaranteed pore size of 30 m, but in the practice because of the surface adsorption it could be decreased to 10 m [10,12]. It is important to note that the volume of the buffer tank before the reinjection well was 60 m 3 in case of well number 1 and 100 m 3 in case of well number 2. During an average heating period, the temperature of water ranged from 27 to 46 ∘ C and the replacement of filters was after 2500-5000 m 3 fluid flowed through. ...
Reinjection of heat-depleted thermal water has long been in the center of scientific interest in Hungary regarding around 1000 operating thermal wells. While the physical and chemical aspects of reinjection have partly been answered in the past years, the effects of biological processes are still less known. We carried out our investigations in the surface elements of the Hódmezővásárhely geothermal system which is one of the oldest operating geothermal systems in Hungary. About one-third of the used geothermal water has been reinjected since 1998 by two reinjection wells at the end of the thermal loops. During the operation, plugging of the surface system was experienced within a few-day-long period, due to biological processes. The goal of our research was to find the dominant species of the microbial flora and to make a proposal to avoid further bacterial problems. We found that the reinjected, therefore the produced, water's chemical oxygen demand, phenol index, and BTEX composition basically determine the appearing flora on the surface. When the concentration of these compounds in the thermal water is significant and residence time is long enough in the buffer tank, certain bacteria can be much more dominant than others, thus able to form a biofilm which plugs the surface equipment much more than it is expected.
... század első felében elvégzett szénhidrogén-kutatás "melléktermékeként" jelentősen fejlődött, mert a meddő kutakat gyakran kiképezték és átadták közcélra vagy mezőgazdasági hasznosításra. Hazánkban világviszonylatban is jelentős többlépcsős közüzemi-gyógyászati-mezőgazdasági célú geotermikus energiatarmelő központ épült ki Szentes környezetében az 1970-es évek elején (KORIM & LIEBE 1973, SZANYI & KOVÁCS 2010. ...
... Kis entalpiájú területek termálvizes rendszereinek nyílt termelése esetében általános probléma a nyugalmi, illetve az adott hozamhoz tartozó üzemi vízszintek csökkenése (14. ábra, TÓTH et al. 2010;SZANYI & KOVÁCS 2010;Buday et al. 2015a). Ennek következtében nagyobb szivattyúteljesítmények szükségesek, azaz a termelés költségesebb. ...
... Limited international cooperation was based on bilateral agreements on water management which mostly date back to the 1970s [52], and joint projects focused on groundwaters were established only after the late 1990s [20,[53][54][55][56][57]. Local deterioration of the quantity and/or quality state of geothermal aquifers in the Pannonian basin was identified [58][59][60][61] together with a fundamental lack of administrative management [20,62]. However, no systematic measures have yet been taken to deal with the risk of regional over-exploitation. ...
... The drawdowns are expected to be approximately 2 m higher if freshwater production is accounted for in the flow model [20], but it is within the measured regional drawdown of above 15 m in north-east Slovenia [60]. In Hungary, an average regional drawdown of 10 m was measured in intergranular aquifers [117], while values up to 90 m were recorded at production sites in the Great Hungarian Plain [61]. ...
In the paper, a new transboundary Upper Pannonian thermal groundwater body was identified which extends over 22,128 km2 in Austria, Hungary, Slovakia, Slovenia and Croatia. The presented joint numerical simulation of freshwater and geothermal aquifers in the Pannonian sedimentary basin and weathered basement rocks provided new insights into the regional water balance and cross-border groundwater flow rates. It is highlighted that predominant thermal water flow directions in the pre-exploitation state were from Hungary to Austria, and from Slovenia and Slovakia to Hungary. The study, intended to simulate changes in regional flow patterns, revealed that the current production rates of thermal water dramatically decreased the cross-border flows in all cases, and even reversed the flow direction to be now from Hungary to Slovakia. Simulated drawdowns at the state borders are in the range of 2-10 m, and they penetrate far into the neighboring countries. The expected future production, if increased for a factor of 3.5, should maintain the regional drawdown below 30 m; however, flow reversals would occur. Although the current regional exploitation cannot be called unsustainable, the quantity status of some geothermal aquifers is deteriorating locally and demands fast management actions. The joint transboundary management should focus on regular exchange of information, on increasing energy efficiency, and on obligatory use of geothermal doublets for geothermal heat production.
... After a seismic survey, the first well was drilled in 1959, followed by numerous hydrocarbon wells (Kovács, 1965) that penetrated only the basin filling Neogene sedimentary sequences. Since then, fractured crystalline hydrocarbon reservoir studies have been the principal focus of research in the area (Szanyi and Kovács, 2010;Vass et al., 2018;Lemberkovics et al., 2020). Significant hydrocarbon reserves are still being exploited, although nowadays, the geothermal potential of the area is becoming a higher priority (Zilahi-Sebess and Gyuricza, 2013;Boda, 2016;Osvald et al., 2017;Békési et al., 2018). ...
The study aimed to find the origin of the high lithium content of groundwater in southeast Hungary. To be concerned with assessing the economic potential of lithium in these waters, it is necessary to investigate the lithium-releasing geochemical processes. For this purpose, granite and pegmatite samples were analysed for lithium content and alteration from various Battonya Complex locations. The key alteration processes are the chloritisation of biotite and the sericitisation of feldspar, which are hypothesised to mobilise Li from minerals into the geothermal waters. Whole-rock analyses show that the 36 ppm Li concentration in one sample (S1) exceeded the average crustal Li concentration (~20 ppm), while three samples have near-average crustal concentrations. The Li content of rock samples decreases along with the increasing intensity of alteration. The Li concentration of biotite, muscovite, chlorite, feldspar and quartz from granites and pegmatite was measured using laser-induced-breakdown-spectrometry (LIBS). A total of 180 data points were analysed. Biotite and muscovite of the relatively fresh granites contain Li up to ~3800 and ~2500 ppm, respectively. Chloritisation is a hydrothermal alteration process in granites that can be described by the following reaction: biotite + plagioclase → chlorite + epidote + titanite + muscovite. As a function of chloritisation, Li concentration decreases two- and three orders of magnitude from biotite to chlorite in the more altered cases. A similar trend is observed for muscovite in parallel. Feldspars have Li of 17–141 ppm, while there is no correlation between the Li content of feldspars and the degree of alteration. Quartz contains constant low concentrations around the 1 ppm detection limit, with one outlier value of 48 ppm. Chloritisation of biotite is a possible explanation for the high Li content of the geothermal waters in the study area and possibly elsewhere. The main Li-bearing minerals of the Battonya Complex are biotite and muscovite. Chloritisation and subordinate sericitisation result in significant lithium loss. Chlorite can incorporate Li in its crystal lattice but to a lesser degree than the other sheet silicates, like biotite and muscovite.
... Szűcs and Madarász (2013) describe the major challenges associated with the utilization of the Hungarian deep thermal water resources and geothermal energy. The petroleum industry and the intense exploration activity since the 1960s have been providing a lot of geosciencerelated information about the deep geological formations and the heat flow properties that facilitate the utilization of geothermal energy in Hungary (Szanyi and Kovács 2010). It is also important to mention that, due to the intense petroleum exploration campaign over several decades, there are thousands of abandoned wells with different technical conditions in the country (Buday et al. 2015). ...
An innovative methodology is introduced to study abandoned oil exploration drillings for possible geothermal energy production at a test area in northeast Hungary. An evaluation method supported by robust statistical analysis was elaborated to provide the possible future investors with adequate technical and earth-science related information for their decision-making processes. All the available data of 161 abandoned hydrocarbon wells, with different physical conditions, were examined based on the proposed evaluation system to provide information about the geothermal energy potential for each well, as well as over a bigger area. The abandoned wells and their environments, the quantity of stored heat, and the fluid temperature and geothermal heat were the key parameters determined, which are critical when considering geothermal energy utilization or thermal water production. The maximum amount of stored energy was determined as the sum of the amount of energy extractable from the rock and the fluid. The heat stored in the rock was determined by basin modelling. The evaluation process, using one-dimensional (1D) basin modelling and 3D lithological-stratigraphic modelling, was successfully applied in the pilot area. The maximum amount of heat stored in the fluid can be determined by subtracting the heat stored in the rock from the total heat. Drilling and completing geothermal wells are rather expensive in Hungary, depending on the depth and the types of geological formations. The application of this research could greatly reduce the cost and risk of creating new geothermal energy systems based on production wells or abandoned wells in Hungary or elsewhere.
... One of the main aquifers is the Pannonian sandstones formed in the Miocene-Pliocene, filling the basin. Geothermal reinjection into the sandstones has a relatively short tradition in Hungary, with only several operating reinjection sites (Szanyi, 2010). The geothermal site in Mezőberény was constructed in 2012, with the aim to utilize thermal water for district heating. ...
Reinjection of thermal waters is a key parameter for sustainability of geothermal systems. However, injection can face difficulties due to several factors, e.g. mineral precipitation, fines migration or biological processes, especially in case of clastic reservoirs. These processes can clog the well screens and the pores of the reservoir, which can result in the decrease of injectivity. Mineral precipitation, which is the focus of this paper, is controlled by hydrochemical and physical changes. In this study, we focus on injection problems at the geothermal site in Mezőberény, SE Hungary. A geochemical model was set up to simulate the geothermal reinjection processes and to model the saturation of the minerals during injection, using changing parameters: fluid composition, rock composition, air contact, injection temperature and injection pressure. For hydrochemical modelling we use PHREEQC Version 3 with the phreeqc.dat database. Based on the results general and site-specific conclusions could be drawn: In general, high concentrations of Fe and Mn content play a role at the injection problems at the Mezőberény site through precipitation of goethite, hematite and Mn-oxides. Furthermore, calcite is also oversaturated, therefore able to form carbonate-scaling. The geochemical model was validated with XRD analysis performed on scale samples from the Mezőberény site: precipitation contains goethite, calcite and magnesioferrite, which confirms our model. Our findings include that air contact radically increases the saturation of Mn minerals, slightly enhance saturation of Fe minerals and decreases the saturation indices of carbonates. Lower injection temperature enhances the saturation of Fe-Mn mineral, in contrast to carbonates. Injection pressure has a negligible effect on the saturation of minerals. The reinjection of heat depleted thermal water into sandstones has a relatively short history in Hungary. With two decades of experience and several successful projects in SE Hungary (Orosháza, Hódmezővásárhely, Szeged), reinjection is successful. Compared with these geothermal systems, saturation indices and the amount of possible precipitation are higher at Mezőberény. By preventing contact with air, iron and manganese minerals would be less saturated and the possibility of precipitation would decrease.
... Azonban a Földtani Közlöny ünnepi évadának cikkei ezekben a témákban is tájékozódási le hetőséget biztosítanak az érdeklődő olvasónak. Továbbá nem célunk Magyarország és tágabb térsége, a Kárpát-medence geotermikus adottságainak átfogó ismertetése -az utób bi évtizedekben számos kiváló publikáció született e témában (KORIM 1972, DÖVÉNYI & HORVÁTH 1988, LENKEY et al. 2002, SZANYI & KOVÁCS 2010, HORVÁTH et al. 2015, NÁDOR 2019, LENKEY et al. 2021) -, ezért csak röviden szólunk róla. ...
Jelen tanulmányban a 150 évvel ezelőtt Zsigmondy Vilmossal induló magyarországi geotermikus kutatások legfőbb eredményeit, illetve a hazai geotermikus szektor fejlődésének főbb lépéseit vázoljuk fel, megemlékezve a jeles elődökről. A tartalmi részt 4 időszakra osztottuk: 1.) A hőskor. A XIX.sz közepétől tart a rendszerváltásig. A leghosszabb időszakot fogja át, az első fúrásos hévízfeltárásoktól, a gyógy- és fürdő turizmus kiteljesedésén át a geotermikus energia mezőgazdasági hasznosításának elterjedésig. Az az időszak, amikor a földtudomány kiváló hazai szakemberi, a nemzetközi trendek előtt járva, lehetővé tették a geotermikus energia széleskörű hasznosítását, megalapozták a magyar geotermika nemzetközi elismerését. Ezt a felívelés korszakának tekintjük, ezért egyben tárgyaljuk. 2.) A közel múlt. A rendszerváltást követő kezdeti lépések, melyek főleg fürdő fejlesztéseket és a geotermikus energia távhő célú fejlesztését jelentették. Ezek közül is kiemelkedik hódmezővásárhelyi, miskolci és győri geotermikus távhőrendszer. A hódmezővásárhelyi rendszer a komplex kaszkád hasznosítással és a homokkőbe történő sikeres és fenntartható visszasajtolási technológia alkalmazásával volt úttörő, míg a két utóbbi, 50 MWth-ot meghaladó a beépített kapacitásával mutatott európai szinten is elismert példát. Ezen időszakban, a termálfürdő fejlesztéseknek és új fürdők nyitásának köszönhetően, a termálturizmus megduplázódott. Ez már a zenit korszaka, 2003-ban még Európai Geotermikus Kongresszust rendeztek Szegeden, de már nem Magyarország volt Európában a fejlődés motorja. 3.) A jelen projektek. Az éppen befejezett vagy még futó jelentősebb geotermikus projekteken keresztül bemutatjuk a geotermikus energia hasznosítás jelenlegi magyarországi állapotát. Európai Uniós csatlakozásunknak köszönhetően megnyílt a nemzetközi kutatási projekteben való részvétel lehetősége. Különösen a hazai egyetemek és kutatóhelyek – de civil szervezetek is – becsatlakozhattak az európai geotermikus kutatások főáramába. Az Európai Uniós források lehetővé tették a határon átnyúló kutatási projektek indítását, ennek köszönhetően a Kárpát-medence geotermikus viszonyait egységes szerkezetben, politikai határok nélkül lehet kutatni. 4.) A futó kutatások, jövőkép. Ismertetjük a hazai és a nemzetközi kutatásokhoz kapcsoló legújabb eredményeket és felvázoljuk a jövőbeni kutatási irányokat, lehetséges helyünket a nemzetközi geotermikus piacon. Bemutatjuk, hogy – alkalmas szakpolitikával, a geotermikus adottságaink ismeretében – milyen mértéket érhet el a geotermikus energia hasznosítása Magyarországon a közeli jövőben. Az egyes időszakok határai nem élesek, inkább tematikusak, így egy adott időszakban olykor későbbi tanulmányt is megemlítünk. Tárgyalásuk során röviden utalunk a földtani, hidrogeológiai, geokémiai és geofizikai kapcsolódási pontokra, de ezeket részletesen nem tárgyaljuk, a Földtani Közlöny aktuális ünnepi és rákövetkező évjáratában erről önálló tanulmányokat olvashatnak.
... In order to achieve optimum efficiency from a geothermal system, the main goal should be to optimize heat recovery from the reservoir to service both the electrical grid needs and to provide useful heat for habitat and industrial needs. Most geothermal power plants are designed to provide electrical energy/heat to the surrounding area, which often is a local detached grid [69][70][71][72]. If geothermal electrical power can be used in a large grid to provide special services such as peak shaving or load displacement, the value of the energy provision increases. ...
Renewable and sustainable energy sources can play an important role in meeting the world’s energy needs and also in addressing environmental challenges such as global warming and climate change. Geothermal well-doublet systems can produce both electrical and thermal energy through extracting heat from hot-water aquifers. In this paper, we examine some potential challenges associated with the operation of well-doublet systems, including heat conductivity, chemical, and mechanical issues. In these systems, geomechanics issues such as thermal short-circuiting and induced seismicity arise from temperature and pressure change impacts on the stress state in stiff rocks and fluid flow in fractured rock masses. Coupled chemical processes also can cause fluid channeling or formation and tubular goods plugging (scaling) with precipitates. Mechanical and chemical disequilibrium conditions lead to increased production uncertainties; hence risk, and therefore coupled geo-risk assessments and optimization analyses are needed for comparative commercialization evaluations among different sites. The challenges related to heat transfer processes are also examined. These studies can help better understand the issues that may arise during the operation of geothermal well-doublet systems and improve their effectiveness, subsequently reducing associated costs and risks.
... We therefore interpret the tensional strain pattern as indicative of crustal thinning with consequent increase of the geothermal regional gradient in a tectonically active intra-continental rift, suggesting an extensional type play (Moeck, 2014). However, the estimated Luhoi reservoir temperatures (close to 100°C from water geothermometers according to our estimation, 133°C according to Kraml et al., 2014) are more typical of intracratonic basins like the Paris Basin where temperatures up to 120°C have been recorded in the central area at 3000 m depth (Bonté et al., 2010) or back-arc basin like the Pannonian Basin where anomalous heat flow is related to crustal thinning giving anomalous gradients of about 40−50°C/km with water temperature in the porous formations reaching 130-150°C (Szanyi and Kovács, 2010;Horváth et al., 2015). Note that past higher temperatures than present day ones, possibly suggesting a different heating mechanism active in the past like a pluton source, are unlikely at Luhoi: the preserved kaolinite sandstones observed in Wingoyongo-1 well and the estimated low CEC values indicate not complete illitization of kaolinite that would require higher temperatures; moreover, high temperature alteration is usually unaffected by subsequent cooling and, therefore, its resistivity signature would be preserved (e.g. ...
We present the results of the gravimetric, magnetic and magnetotelluric geophysical campaign aimed to constrain the geothermal conceptual model of the Luhoi geothermal field, a poorly known system located in the Tanzanian southeastern coastal sedimentary basin. Regional assessment by existing potential field data reveals that Luhoi lies at the margin of a wide regional NE trending uplifted block that involves the Precambrian metamorphic basement complex. In the geothermal field area, 3D geophysical modelling has imaged a local asymmetric horst of Cretaceous age, 1 km wide and 5 km long, with the same regional NE trend. The horst is formed by the denser Kipatimu Lower Cretaceous sandstones surrounded by the Upper Cretaceous Ruaruke claystones that are down thrown up to 1 km by normal faulting. Far from the horst, lithology mainly controls the modelled electrical resistivity distribution: the Ruaruke claystones show low resistivity (1–6 Ωm) primarily due to its clay content, while the Kipatimu sandstones have generally higher resistivity (10–30 Ωm) because of their prevalent electrolytic conduction. However, anomalous low resistivity values (1–5 Ωm) in the shallower portion of the Kipatimu sandstones forming the horst indicate enhanced electrical conduction due to the cation exchange capacity (CEC) of clay. The CEC estimated values from electrical resistivity are in the range 2−30 meq/100 g, suggesting the presence of kaolinite and illite and excluding the occurrence of smectite, which is the typical clay mineral in the cap-rock of high-temperature geothermal systems. This shallow clay-rich layer together with the Ruaruke claystones act as a regionally continuous clay cap confining the reservoir formed by moderately hot water (close to 100 °C from water geothermometers) in the permeable Kipatimu sandstones layer that reach a maximum depth of ca. 2 km, likely heated by a slightly enhanced geothermal flux attributable to crustal extension. At Luhoi, the local horst structure imaged by the geophysical models pushes up the sandstone reservoir at very shallow depth (about 500 m from the surface), strongly enhancing the local geothermal gradient and originating the surface thermal manifestations that are controlled by the system of normal faults.
... Prograding shelf sedimentation resulted in the deposition of thick sand bodies in the shelf front environment, overlain by fine-grained sediments of the shelf and alluvial plain, representing the latest stages of the filling-up of the lake basin, referred to as 'Upper Pannonian' (Bérczi and Phillips, 1985;Magyar et al., 1999Magyar et al., , 2013. The most favourable porous geothermal aquifers are formed in these 'Upper Pannonian' shelf front sands at depths from 500 to 2000 m, where the temperature ranges from 40 to 110°C (Szanyi and Kovács 2010;Nádor et al., 2012;Rman, 2014;Horváth et al., 2015). ...
The Pannonian basin in Central Europe is well known for its rich geothermal resources. Although geothermal energy has been utilised, mainly for direct use purposes, for a long time, there are still a lot of untapped resources. This paper presents novel methods for outlining and assessing the theoretical and technical potential of partly still unknown geothermal reservoirs, based on a case study from the Dráva basin, one of the sub-basins of the Pannonian basin along the Hungarian–Croatian border. The presented methods include reservoir delineation based on combining geological bounding surfaces of the Upper Pannonian basin-fill units with a set of isotherms deriving from a conductive geothermal model. The geothermal potential of each identified reservoir was calculated by a Monte Carlo method, which was considered as being represented by the heat content of the fluids stored in the effective pore space (‘moveable fluid’). The results underline the great untapped geothermal potential of the Dráva basin, especially that of the reservoir storing thermal water of 50–75°C, which has the largest volume and the greatest stored heat content.
... The geological and geothermal data were derived from the Pannonian Basin data. In this region, due to late plate tectonic events, rapid subsidence of the surface occurred, which formed a large sedimentary basin filled with deep sea, delta and fluvial sediments with a thickness of up to 6e7000 m [13]. Due to the presence of a thin earth crust (22e26 km), a positive anomaly of the geothermal gradient (approx. ...
Geothermal energy utilization does not depend on weather conditions. Among the various types of heat supplies, ground source heat pumps are the most widely used in the geothermal sector; however, their utilization rate is considerably less than the growth rate of other renewable energy sources. This paper reports an overview of a deep borehole heat exchanger (DBHE) with high-grade vacuum insulated tubing (VIT). Using a computational software, wells with various depths and geothermal gradients are evaluated in the same lithology. The calculation method’s outputs are compared with analytical, semi-analytical and experimental steady state results to show reliability of the developed software. DBHEs are evaluated based on calculated theoretical natural convective mass flow rates (NCMFRs). Considering extended typical well structures with 7″ production casings to surface, the heat performance is evaluated, and revenue requirement (RR) is calculated by employing the theoretical NCMFR. In the calculation depth range of 1200 m–3000 m, geothermal gradient ranges from 40 °C/km to 60 °C/km, and inlet temperatures are 12 °C and 40 °C are considered. Based on the results, reliably profitable depths and geothermal gradient ranges are declared and district heating networks with promising wells are identified. It is concluded that DBHE can be financially viable if integrated into the existing local heat market and infrastructure.
... One may wonder why this article does not quantify the geothermal potential from three aspects (Rman et al. 2015a): potential of inactive wells, legislative and energy potentials as some of these data have tried to be gathered in the survey. Additionally, the sustainability of thermal water production from the regional Pannonian basin reservoirs is of major importance when planning further geothermal development (Buday et al. 2015;Rman et al. 2015b;Szanyi and Kovács 2010). The reason is that reliable geothermal source-specific data are extremely difficult to be provided to non-agencies. ...
Data on thermal water sources with outflow temperature of 30 °C and above were analyzed from the N-ern parts of Bosnia and Herzegovina, Serbia and Croatia, S-ern parts of Hungary, W-ern parts of Romania, and NE-ern parts of Slovenia, altogether from an area of 99,347 km2. The overview identified 771 geothermal sources; only 7 were thermal springs. The average well depth is about 1.2 km. About 13% of wells are younger than 10 years, additional 17% below 30 years; while 26% are older than 50 years. Average thermal water outflow temperature is 54 °C being the highest, 170 °C, in Croatia. Most thermal water is produced from basin fill sediments—Lower and Upper Pannonian (Mio-Pliocene) loose sandstones which are tapped by 86% of wells. The rest appertains to basement rocks—fissured, fractured and karstified Paleozoic, Mesozoic and Middle Miocene metamorphic, carbonate and siliciclastic rocks. In total, 72% sources hold water rights, 6% mining rights, 2% geothermal rights and 1% has no rights. The permits allow much higher water abstraction as currently listed. Usage for bathing and balneology encompasses 24% of all active sources (155), some of these also with heating (23). 104 objects (16%) are used for heating, also district heating (13) and individual space heating (3). An additional 10% (70) are used in agriculture, mainly greenhouse heating. There are 41 reinjection wells (5%). It is primarily in Hungary that drinking water (17%), industrial usage (5%) and monitoring wells (2%) are also common.
... Jelenleg közel 800 MW a geotermikus hő hasznosítására szolgáló kapacitásunk, amelynek döntő része a kommunális fűtésben és a mezőgazdaságban hasznosul. A geotermikus energia hasznosításának gyökerei és kezdeti legfontosabb eredményei hazánkban leginkább Délkelet-Magyarországhoz köthetők (Szanyi-Kovács, 2010). A jelenlegi rendszerek hidrotermális rendszereknek tekinthetők (Székely et al., 2015), hiszen a geotermikus energia a felszín alatti kőzetekben tárolt hévíz segítségével jut el a felszínig. ...
... Hazánk geotermikus adottságaival nem kívánunk részletesen foglalkozni, megtette ezt korábban számos szerző és mi magunk is (Dövényi-Horváth, 1988;Szanyi-Kovács, 2010;Horváth et al., 2015). Magyarországon az üzemelő termálkutak mintegy 60%-a felső pannóniai korú vízadókból termel, leginkább az 1000-2200 m közötti mélységtartományból. ...
... The mean temperature is approximately 10°C on the surface of the country. 47 The thermal water is used mainly for balneology but in the recent years heating and hot water preparation was also preferred. Usually the temperature of the wells head is around 60-90 o C, so it can be used for heating various facilities or for different industrial or agricultural needs and processes ( Figure II.28.). ...
... As of 2011, geothermal energy contributed to the heating of 19 settlements in Hungary. Industrial use was relatively low 84 . ...
... According to Rafferty (2000) the Rankine Cycle is the process of generating electricity from a heat source. Steam is generated and passed to the turbine where it expands against the Information compiled from Chen et al., 1977;Vedova, 1991;Bachu and Burwash, 1994;Cohut and Bendea, 1997;Veliciu and Šafanda, 1998;Dövényi et al., 2003;Blackwell and Richards, 2004;Kang, 2010;Schellschmidt et al., 2010;Szanyi, 2010;Wang, 2010;BINE, 2011;Majorowicz and Moore, 2013;Wang et al., 2013;Agemar, 2014;Hofmann et al., 2014;Homuth et al., 2014;Nádor, 2014;Homuth et al., 2015;Horváth, 2015;Liu et al., 2015;Zhu, 2015;Aretz et al., 2016. turbine blades. ...
Energy shortages and sporadic, controlled blackouts have been a defining feature of South Africa’s aging national energy grid for more than a decade. To investigate local energy sources from shale gas, two boreholes were drilled in the southern Main Karoo Basin into the Permianaged Ecca Group by the Karoo Research Initiative. Borehole KZF-1 (Western Cape) intersected thick shale successions of the lower Ecca Group and revealed the stratigraphic duplication of the Whitehill (shale gas target) and Prince Albert Formations. This structural deformation was most likely as a result of the organic-rich formations, acting as a decollement for thrust faults related to the north-south directed compression of the Cape Orogeny. Reservoir compartmentalisation and gas escape along porous fault zones hinder hydrocarbon exploration in the area. Borehole KWV-1 (Eastern Cape) revealed thick successions of turbiditic sandstones and a moderately elevated geothermal gradient. The clastic rocks have low permeabilities and high thermal conductivities. Analysis of the petro- and thermophysical data from the Ripon
Formation sandstones, from both the core and nearby Ecca Pass outcrop location, show the potential of the formation as an Enhanced Geothermal Reservoir, with temperatures exceeding 100°C being suitable for energy production from a binary geothermal power plant. The comparison of combined gamma-ray logs, geothermal potential of samples (specific heat capacity, thermal diffusivity, and thermal conductivity) and lithological logs show a correlation between lithological composition and geothermal reservoir potential that can be identified in gamma-ray log patterns. These correlations can be extrapolated for purposes of geothermal exploration in non-cored nearby boreholes. The numerous pre-existing faults, decreasing from the basin’s southern margin towards the basin interior, elevate the risk of inducing seismic events from the use of reservoir stimulation techniques associated with energy exploration, as well as wastewater management associated with future extraction activities.
... So far, it has not been an objective of geothermal exploitation strategies. The reason for this is that geothermal resources are often exploited to provide heat to local decentralised grids, instead of optimising heat recovery from the entire resource [23][24][25]. Geothermal resources are often exploited by multiple independent operators with potentially conflicting objectives [26,27]. ...
The Netherlands experienced the fastest European expansion of geothermal energy exploitation in the past decade. The first Dutch geothermal sites proved that Hot Sedimentary Aquifers exploitation can play an important role in a future low-carbon energy mix. In this study, we estimate that with the expansion rate of the past four years, geothermal heat production from Lower Cretaceous Hot Sedimentary Aquifers could cover up to 20% of the heat demand in the province of Zuid-Holland by 2050. Although this is a significant amount, we show in this study that only 1% of the potentially recoverable heat will be recovered by 2050. This is because of inefficient doublet deployment on a ‘first-come, first served’ basis with operational parameters that focus on objectives of small decentralised heat grid demands. Instead, similar to the common-practise approach in the hydrocarbon industry, a regional coordinated ‘masterplan’ approach could be used to increase heat recovery. Utilising numerical simulations for flow and heat transfer in the subsurface, we showed that the heat recovery efficiency could be increased by tens of percentages with such coordinated doublet deployment. Based on calculations of the Levelized Costs Of Heat for both deployment strategies, we also show that current financial support schemes do not favour heat recovery optimisation. This study emphasises that although Hot Sedimentary Aquifer resources have the potential to cover a significant part of our energy demand, a radical change in financial support schemes and legislation are required to unlock their true potential.
... According to Axelsson (2010), there are two sustainable geothermal energy uses: sustainable geothermal production, concerning maintaining production from a single system and sustainable geothermal use, involving integrated economic, social and environmental development. A recharge and discharge balance, overproduction and a cold-front breakthrough are discussed in several papers (Szanyi and Kovács 2010;Axelsson 2010;Buday et al. 2015). Another issue is to maximize utilisation of available resources, which should be considered in the study area. ...
The geothermal energy sector continues to develop dynamically in the world. Within this work, preliminary feasibilities of different geothermal applications were presented for the Lower Cretaceous formations for wider geothermal uses’ development in the Mogilno–Lodz trough, Central Poland. The Lower Cretaceous formations are one of the most prospective geothermal reservoirs in Central Poland. Geothermal waters that occur within them are mostly of Na–Cl type and contain specific elements like I, Br or Fe. These are low-temperature geothermal resources together with highly variable mineralization, from 0.4 to even more than 90 g/L. A simple estimation procedure for hydrogeological information, such as water and thermal conditions of the reservoir obtained from an archival chemical analysis and borehole temperature loggings was developed. The potential for geothermal applications was estimated for three zones of the Mogilno–Lodz trough. Possibilities of conjunctive geothermal applications, such as space heating, balneotherapy and balneorecreation, mineral extraction, electricity production in binary systems and aquifer thermal energy storage were examined for the Lower Cretaceous formations.
... These similarities over regional distances of 30-50 km argue against significant local water mixing close to the hydrothermal water discharge point. A significant cool meteoric contribution can also be neglected for the thermal waters from geothermal wells tapping deep Pannonian basin (Hungary) aquifers supporting long water residence times and leading to the rapid deposition of the analyzed calcite scales from well-head pipes (SCA-CL1 to CL4; [Szanyi and Kovács, 2010;Boch et al., 2016]). ...
The clumped isotope composition of CaCO3 (Δ47) is a geochemical proxy that can provide mineral formation temperatures and, together with measured carbonate δ18O, inferred fluid δ18O values. Under natural conditions carbonates form within a relatively wide pH range and varying growth rates which are typically not reflected in laboratory‐based calibrations (mostly ∼ pH 8, moderate growth rates). A pH and growth rate dependence is known for oxygen isotopes and was also postulated for clumped isotopes. Theoretical predictions suggest that Δ47 values could lie between the carbonate equilibrium value and the value inherited from the dissolved inorganic carbon (predicted: +0.04‰ pH<4 and ‐0.025 ‰ at high pH >12). Here we test whether pH (in addition to temperature) is recorded in the carbonate clumped isotope composition using modern calcites from natural travertine‐forming streams and scales precipitated in pipes of deep geothermal wells from Italy, Hungary and Turkey (pH: 6.1‐7.5, T: 33‐100°C). Although a comparison of all samples with expected equilibrium values in this pH range and known formation temperatures reveals only an insignificant Δ47 offset (0.006 ± 0.004 ‰, 1SE, n=9), the clumped isotope values of samples with the highest growth rates (0.014 ± 0.007 ‰, 1SE, n=5) are consistent with the theoretical prediction attributable to pH of 0.01‰. Similarly, deviations in δ18O of up to ‐2 ‰ follow a growth‐rate dependence. This field‐based study shows that pH‐related effects are mostly small for Δ47 in the sub‐surface environment at low pH and that high mineral growth rates control the magnitude of this disequilibrium.
... One of the issues of sustainable use of geothermal resources is balancing geothermal water extraction from the geothermal system. Overproduction and failure to inject geothermal water may relate to lowering its level in the aquifer and production decline in the future (Szanyi and Kovács 2010;Axelsson 2010;Buday et al. 2015). Another issue is also maximum utilisation of available resources, e.g., using cascaded systems. ...
Mogilno–Lodz Trough is located in central Poland. It is structural basin filled with Triassic-to-Quaternary sediments. Lower Jurassic formations in Poland have one of the best conditions for the heating purposes. Presently, on the area of the Trough, no geothermal plant operates, which utilises geothermal waters from Lower Jurassic formations. Sustainable use of geothermal waters covers, e.g., effective use of thermal energy from waters, before they are injected back to the deposit. Such sustainable use can be achieved in cascaded systems, utilising thermal energy of waters, which gradually lose temperature at following stages of cascaded systems. Geothermal waters and energy occurring in Lower Jurassic formations in Mogilno–Lodz Trough have been analysed in terms of chemical composition and temperature parameters. A dominant type of water is chloride-sodium waters, with specific components contents, such as iodine, bromine, and iron. Lower Jurassic formations are deposited at different depths, which affects, to a high extent, water mineralization and temperature, as well as some elements contents. It has been demonstrated which parameters are decisive about a possibility of using them at particular stages of a cascaded system and where one should expect to find suitable conditions for particular applications.
... Hydrodynamically, the Pannonian Basin can be subdivided into an upper and a lower regime (Almási, 2001;Tóth and Almási, 2001;Szanyi and Kovács, 2010). The upper one is a gravity driven system (Erdélyi, 1976), while overpressured zone was developed in the lower regime essentially due to tectonic compression (Almási, 2001;Tóth and Almási, 2001). ...
Fractured rock bodies are especially important in Hungary, where numerous hydrocarbon reservoirs and geo-thermal fields occur in the fractured crystalline basement of the Pannonian Basin. To simulate a 3D fracture network for both near well regions and at reservoir scale, a fractal geometry based DFN (discrete fracture network) modelling system (RepSim) was used. To perform numerical simulation of the geological-hydrogeological problem, in which the hydraulic interaction is investigated between porous and fractured rock bodies, a finite element modelling system called FeFlow was applied. Modelling results suggest that the protruding basement highs govern heat transfer and fluid flow like a "hydro-geothermal chimney" owing to their stratigraphic and structural position as well as favourable hydraulic and thermal conductivities. Thus such fractured basement highs are deemed prospective for further geothermal investigations.
... These facts mean that further investments are necessary to maintain the existing system since operating costs become higher by time. Signs of overproduction have been detected already not only in the focus area but in many other cases around the Danube Region , Szanyi -Kovács 2010, Tóth et al. 2010. The results of this study could be generalized and the role of geothermal energy utilization could be expanded for the whole Danube Region. ...
... Speciális vízgazdálkodási stratégia kialakítására van szükség annak érdekében, hogy fenntartható módon elégíthessük ki egy adott területen a felszín alatti vízre alapozó ivóvíz-, gyógyászati célú és az energetikai célú igényeket. Hazánk, valamint a Kárpát-medence kimagaslóan jó geotermikus potenciálját, hidrogeotermikus rendszereit, hévízfelhasználási lehetőségeit az utóbbi időben több kiváló tanulmány is bemutatta (Mádlné Szőnyi, 2006;Szanyi and Kovács, 2010;Székely, 2010). Magyarország területén a felszín alatt a föld belseje felől az átlagos földi hőáram értéke kb. ...
By using GIS methods for approximately the past 250 years changes of the riverbed of the Mura River were reconstructed in the study. The main point of the method is that we draw conclusions for development of the riverbed by projecting the different age current lines on each other. Separation and periodization of the anthropogenic interventions is possible by using this method. Using morphometric parameters the long-term development of the river and the meanders were analysed. The meander movement and cut-off is forecasted. Flood maps from MIKE 21 FM 2D hydraulic modelling and old historical maps were compared and evaluated.
... The Pannonian basin is one of the most favorable areas in Europe to utilize geothermal energy owing to the high heat flow density (Hurter and Haenel 2002;Rajver and Ravnik 2002;Franko et al. 1995;Lenkey et al. 2002) and abundance of thermal water stored in the porous-permeable sediments and in the fractured basement (Goldbrunner 2000;Fendek and Fendekova 2010;Rman et al. 2015;Szanyi and Kovács 2010;Horváth et al. 2015). The geothermal resources are shared amongst the countries located in the area, therefore the sustainable production of thermal water requires coordinated actions. ...
In this paper we present the results of 3D conductive thermal modeling of the Alpine–Pannonian transition zone. The study area comprises the Vienna, Danube, Styrian and Mura–Zala basins, surrounded by the Eastern Alps, the Western Carpathians and Transdanubian Range. The model consists of three layers: Tertiary sediments, the underlying crust and lithospheric mantle. The crust and mantle were homogenous with constant thermal properties. Heat production in the sediments and crust was 1 μW/m³. The thermal conductivity of sediments varied horizontally and vertically and based on laboratory measurements. We tested two scenarios: a steady-state and a time-dependent case. The conductive heat transport equation was solved by finite element method using Comsol Multiphysics. The results of the steady-state model fit to the observation in the northern part of the study area, but this model predicts lower heat flow density and temperatures than observed in the southern part of the study area including the Styrian basin. The area underwent lithospheric stretching during the Early-Middle Miocene time, therefore the temperature field in the lithosphere is not steady-state. We calculated the initial temperature distribution in the lithosphere at the end of rifting using non-homogeneous stretching factors, and we modeled the present day thermal field. The results of the time-dependent model fit to the observed heat flow density and temperatures, except in those areas where intensive groundwater flow occurs in the carbonatic basement of the Transdanubian Range and Northern Calcareous Alps, and the metamorphic basement high between the Mura trough and Styrian basin. We conclude that time-dependent model is able to predict the temperature field in the upper 6–8 km of the crust, and is a valuable tool in EGS exploration.
... resulting from (post)volcanic CO 2 contributions or CO 2 from degradation of organic matter in deep aquifers. Carbonate scales are most commonly met in the course of geothermal energy exploitation in Central Europe, e.g. from Devonian, Triassic, Upper-Jurassic and Tertiary (Neogene) limestone and dolomite aquifers of Hungary, Germany and Austria (Goldbrunner, 2000;Szanyi and Kovács, 2010;Stober, 2014). This is in contrast to the high enthalpy geothermal regions (Iceland, Tuscany, Mexico and others) where silica/silicate scaling typically dominates and carbonate precipitates occur only locally (Valdez et al., 2009;Zarrouk and Moon, 2014). ...
Exploitation of thermal water frequently entails the precipitation of various minerals (scaling) due to elevated salinity and gas contents in deep aquifers. Progressive clogging of wells, pumps, pipes, valves and heat exchangers can cause major problems in geothermal heat and electric power production. In this context scale deposits constitute an environmental archive capturing installation-specific fluid-solid interaction over time, i.e. natural vs. man-made variations in fluid chemistry, temperature, pressure, outgassing (e.g. CO₂), flow rate and microbial activity. These factors control distinct crystal growth, variable porosity/density and lamination, accessory mineral and organic contents, chemical and isotopic compositions of the scales – and therefore the rates of inner-diameter reduction (scaling progress) and mechanical/chemical resistivity. In an approach of process understanding intuitively termed " Scaling Forensics " we apply state-of-the-art mineralogical and geochemical techniques combined with hydrogeochemical modeling and facility-specific data to reconstruct individual – favorable vs. unfavorable – environmental and technical conditions of scale formation. We collected carbonate scales and thermal waters from geothermal facilities distributed over the Hungarian Pannonian Basin covering a broad range of geogenic and man-made production conditions.
First results support distinct nucleation and crystal growth mechanisms influencing carbonate scale appearance and consistency. Crystallization on surfaces (substrates) typically results in more compact and resistant fabrics, whereas spontaneous particulate crystallization within an aqueous solution (in suspension) promotes increased porosity and therefore scaling progress. Steel corrosion layers can provide a highly attractive substrate for nucleation and ongoing crystal growth due to high specific surface areas and abundant defect sites of typical corrosion products. Moreover, corrosion layers of reduced mechanical resistivity (low crystallinity, hardness) may lead to preferred shearing-off along these layers. A prominent example of interplay between steel corrosion and carbonate scaling progress is discussed regarding the formation of cemented scale fragments (shards) damaging and blocking heat exchangers. We also conducted a first series of laboratory experiments to investigate some of the findings.
Purely inorganic can further be distinguished from microbially influenced carbonate precipitation. Microbial tissues might interact with basal corrosion layers and could be the explanation for prominent feather-like calcite crystals. The filamentous to dendritic structures probably foster the entrapment and accumulation of particles from suspension or provide nucleation sites for crystal growth. Next to an applied research focus we also discuss benefits from carbonate scales for fundamental geochemical method improvement. This involves the evaluation and calibration of novel and established isotope geothermometers using scales of diverse but well characterized precipitation conditions.
... These facts mean that further investments are necessary to maintain the existing system since operating costs become higher by time. Signs of overproduction have been detected already not only in the focus area but in many other cases around the Danube Region , Szanyi -Kovács 2010, Tóth et al. 2010. The results of this study could be generalized and the role of geothermal energy utilization could be expanded for the whole Danube Region. ...
The Perspectives of Renewable Energy in the Danube Region
Conference (26–27 March 2015) and this book of proceedings were financed by the
Deutsche Bundesstiftung Umwelt (DBU) and co-organised by the Wuppertal Institute, the
Institute for Regional Studies of CERS HAS (with its own contribution and partial scientific support from OTKA – Hungarian Scientific Research Fund grant #NK 104985: New driving forces of spatial restructuring and regional development paths in Eastern Europe at the beginning of 21st century) and the Regional Committee of Pécs, HAS.
... Medium enthalpy geothermal energy has huge potential as a source of district heating and cooling and its use is expected to increase [19,20]. Examples in Europe include the district heating schemes of Ferrara [21], Southampton [22], Munich [23] and the Pannonian basin [24]. Many other plants under construction or recently completed will also increase the deployment of ORC-based combined heat and power systems [25,26]. ...
Shallow geothermal energy is of great interest for HVAC (heating, ventilation and air conditioning) designers. While increasingly popular in the residential and commercial sectors, shallow applications are still little used in the industrial sector and unfamiliar to policy makers, designers and stakeholders [1]. Despite this, geothermal applications are feasible for industrial plant for several reasons: operating at high load factors and supplying energy to a single location, geothermal systems would cut energy costs, a large slice of overall industrial production costs. This paper presents the results of a feasibility study carried out for an industrial shallow geothermal project, where the required preheating to the innovative Expanding-Gas-Power-Transformation (EGPT) process was supplied through a Hybrid Geothermal-Air Transcritical Heat Pump. Focus was given to modeling the geothermal component to comply with the heat pump working temperature requirements, integrating this with geostatistics and numerical simulation of heat/water flows.
... Depletion of a groundwater resource is usually first recognised by monitoring hydrodynamic changes, such as downward trends in groundwater levels, which are easily measurable and interpretable even though their uncertainty should be acknowledged (Custodio 2002). Hydrogeochemical or isotopic tracers of surface and groundwaters when monitoring quality provide valuable supplementary information when changed flow conditions are assumed and caused by infiltration of shallow and/or contaminated water or by mixing with deeper water of different quality (Appleyard and Cook 2009;Axelsson et al. 2010;Ceroân and Pulido-Bosch 1999;Chen et al. 2011;Druschel and Rosenberg 2001;Gikas et al. 2009;Janža 2015;Jørgensen and Stockmarr 2009; thermal water withdrawal, and discussion of their depletion largely focuses on the rate of groundwater decline or changes in water temperature (Axelsson et al. 2010;Duan et al. 2011;Szanyi and Kovács 2010). Nevertheless, hydrogeochemical tracers have a long tradition in geothermal systems as well, whether for the investigation of regional groundwater flow characteristics (Jirâkovâ et al. 2011;Kovács et al. 2011;Négrel and Giraud 2011;Szőcs et al. 2013;Varsányi et al. 1999), in identifying over-exploitation (Axelsson and Gunnlaugsson 2000;Butler and Tsou 2003;Ceroân and Pulido-Bosch 1999;Kralj and Kralj 2012;Kun 2010;Rman 2014) or in order to foresee and mitigate thermal breakthrough when reinjection is applied in geothermal aquifers (Kaya et al. 2011;Lopez et al. 2010;Minissale et al. 2008;Stefansson 1997). ...
The aim of the study was to develop and test an optimal and cost-effective regional quality monitoring system in depleted transboundary low-temperature Neogene geothermal aquifers in the west Pannonian basin. Potential tracers for identification of seasonal and long-term quality changes of the Pleistocene thermal waters were investigated at four multiple-screened wells some 720 to 1570 m deep in Slovenia. These thermal waters are of great balneological value owing to their curative effects and were sampled monthly between February 2014 and January 2015. Linear correlation and regression analyses, ANOVA and Kolmogorov–Smirnov two-sample test for two independent samples were used to determine their seasonal and long-term differences. Temperature, pH, electrical conductivity, redox potential and dissolved oxygen did not identify varying inflow conditions; however, they provided sufficient information to distinguish between the four end-members. Characteristic (sodium) and conservative (chloride) tracers outlined long-term trends in changes in quality but could not differentiate between the seasons. Stable isotopes of δ
18O and δ
2H were used to identify sequential monthly and long-term trends, and origin and mixing of waters, but failed to distinguish the difference between the seasons. A new local paleo-meteoric water line (δ
2H = 9.2*δ
18O + 26.3) was outlined for the active regional groundwater flow system in the Pannonian to Pliocene loose sandstone and gravel. A new regression line (δ
2H = 2.3*δ
18O–45.2) was calculated for thermomineral water from the more isolated Badenian to Lower Pannonian turbiditic sandstone, indicating dilution of formation water. Water composition was generally stable over the 1-year period, but long-term trends indicate that changes in quality occur, implying deterioration of the aquifers status.
... Reinjection of low-enthalpy geothermal fluid into sandstone reservoirs of a sedimentary basins were rated as a poorly understood issue by Stefansson (1997). However, since that it turned out that it seems to be manageable with proper operational practice (Szanyi and Kovács, 2011). Nonetheless, reinjection provides pressure support to the long-term operation of geothermal field and reduces the potential for subsidence (Axelsson, 2008;Kaya et al., 2011). ...
The paper proposes the involvement of preliminary regional hydrodynamic analysis for the reconnaisance phase water-based geothermal exploration in sedimentary basins. This approach is based on basin-scale pore pressure evaluation, it complements the usual reservoir and temperature analyses. Understanding of subsurface pore pressure distribution is beneficial not only in planning thermal water production but also in reinjection. The method is demonstrated for a sedimentary basin characterized by overpressured and superimposed gravity-driven flow. The key point of the approach is the understanding of regional pressure regimes and the delineation of the boundary of overpressured and gravitational flow domains.
... Geothermal energy is widely known for its reliable, weather-independent and renewable nature, which is commonly used in many countries all over the world for power generation purposes as well as direct heat applications, as in Hungary where geothermal wells have been operating for over 140 years. While there are more than 600 production wells operating on porous thermal aquifers, only a few injection wells have been drilled into sandstone, as the direct use of thermal water without reinjection has been standard procedure in Hungary (Szanyi and Kovács 2010). The safe reinjection of geothermal fluids into sandstone has posed very serious technical problems impeding the utilization of geothermal energy. ...
Our research team has developed a new well completion and rework technology involving lasers. The system is made up of a high-power laser generator and a custom-designed directional laser drilling head. The laser head is attached to a coiled tubing unit to maximize production and to carry out special down hole tasks. In this phase of the development effort, laser technology is particularly well suited to cost-efficiently drill short laterals from existing wells in a single work phase, drilling through the casing and cement as well as the formation. The technology, which is an extended perforation solution, enables a more intensive interaction with the down hole environment and supports cutting edge subsurface engineering scenarios such as barite removal. Laser-induced heat treatment appears to be a suitable alternative to effectively remove the almost immovable deposits and scales from thermal water-well pipes.
... These facts mean that further investments are necessary to maintain the existing system since operating costs become higher by time. Signs of overproduction have been detected already not only in the focus area but in many other cases around the Danube Region , Szanyi -Kovács 2010, Tóth et al. 2010. The results of this study could be generalized and the role of geothermal energy utilization could be expanded for the whole Danube Region. ...
Many thermal spas are located in the central and northern part of Hajdú-Bihar County such as the internationally renowned Hajdúszoboszló and Debrecen with great national importance. Increasing thermal water exploitation and the resulted significantly decreasing water level around the wells reveal the fact that utilization of thermal water and the adjacent heat requires more consideration. Despite increasing energy needs (possibly cheap, reliable, renewable) and favorable properties thermal water utilization in this part of the Danube Region still dominantly means balneological utilization. Potential, however, even in such low enthalpy systems is considerable energetically, as well. Being aware of the properties of thermal water reservoirs may help utilization, in general and in this case especially in the Danube Region, to be more reasonable. Our geological model is based on interpreting 2D migrated seismic sections integrated by well log correlations. The modelled aquifer and aquitard layers are the main input data of further (e.g. hydraulic, geothermal potential) modellings. The applied methods are seismic and sequence stratigraphic interpretations and well log facies analysis. Due to these approaches interpolation may be more sophisticated
resulting in more reliable flow units in order to describe the hydraulic connections more accurately. Furthermore, studying many production wells and spas, properties (utilized and waste heat per year, etc.) are considered in order to develop the technical potentials resided especially in cascade utilization of thermal water. This paper aims to point out such details of the studied reservoirs presenting the used applications, data and methods. Our results and their consequences are to serve the development of the region in the field of geothermal energy utilization.
The heat flow map of Hungary was presented in the Atlas of Geothermal Resources in Europe in 2002 and was last updated in 2005. Since that time several geothermal projects, e.g. TransEnergy (2010-13), assessment of the geothermal potential of the Drava basin (2013) Paks-II, NPP (2016) and continuous drilling activity in the country have been in progress. Large amount of temperature data became available, which allowed the update of the Geothermal Database of Hungary and the compilation of an updated heat flow map and temperature maps. The heat flow is determined based on the Fourier law using the thermal conductivities of rocks and temperature gradient calculated from temperature observations in boreholes and wells. The thermal conductivity is known from laboratory measurements made on core samples. The thermal conductivities and the temperature data are stored in the Geothermal Database of Hungary. The heat flow is calculated in 2001 boreholes and wells using the Bullard-plot technique. The mean heat flow in Hungary is 90 mW/m2, varying between 30 mW/m2 and 120 mW/m2. The high values are found over buried basement highs in the eastern and southern part of the country, while the low values are located in the recharge areas of karstic flow systems. In the sedimentary basins, where the thickness of the Neogene and Quaternary sediments reaches 5-7 km, the heat flow is slightly below the mean value (80-90 mW/m2) due to the cooling effect of sedimentation. These basins contain the main thermal water aquifer in Hungary utilized for district heating and green house heating. The buried basement highs characterized by high heat flow (100-120 mW/m2) are potential sites to create artificial geothermal reservoirs by hydraulic fracturing (EGS). Temperature maps at 500 m, 1 km, 2 km and 3 km depths were also compiled. Similarly to the heat flow, the temperature anomalies strongly reflect the local and regional groundwater flow systems.
The compilation of harmonized geological and geothermal models and maps at the W-ern part of the Pannonian basin, covering parts of Hungary, Slovenia, Austria and Slovakia made it possible to delineate potential geothermal reservoirs at regional scales, which are often cut-cross by country borders. Altogether 18 types of potential geothermal reservoirs were identified as a combination of their lithology (Upper Pannonian porous sediments, Miocene sedimentary rocks with intergranular and/or double-porosity, basement fractured crystalline Palaeozoic rocks, and basement fractured [partly karstified] Mesozoic carbonate rocks); temperatures (50, 100 and 150 °C); and hydrogeochemical character of the stored fluids. All identified reservoirs were delineated and shown on maps and the various categories were briefly characterized in terms of their porosity type, hydraulic connections, hydrogeochemistry, as well as utilization potentials. The maps outline prosperous regions for future project developments for various utilization purposes (balneology, direct use, combined heat and power), but most importantly create the basis for a harmonized cross-border management of deep geothermal resources shared by neighbouring countries in the Pannonian basin.
Temperature monitoring provides important information for the sustainable management of a geothermal field. Previous studies indicate that a decline in aquifer pressure is an obvious indicator of thermal water overexploitation. However, many thermal water producing aquifers display a subtle temperature change rather than a pressure decline. Due to the importance of monitoring temperature change, temperature detection is an important topic in the sustainable management of geothermal fields. In this study, we used borehole temperature-depth curves, obtained from boreholes measured over half-year intervals from 2011 to 2014, as well as the Mann-Kendall method, to determine trends for subsurface temperature within the Jiashi Hot Spring in Taiwan. Our results indicate that trends for subsurface temperature are related to hydrogeology and the flow field of groundwater. Groundwater/thermal water flow directions are impacted by the exploitation of thermal water in production wells, according to their depths and distributions, but pressure declines are not a dominant feature. Repeatedly measured borehole temperature-depths and their resultant curves provide important information for understanding trends in subsurface temperature change within a geothermal field.
This paper is a review of worldwide direct applications of geothermal energy. It attempts to update the surveys presented at and after the World Geothermal Congresses of 1995, 2000 and 2005. Seventy-two countries report direct utilization of geothermal energy. In May 2005, the direct-use projects had an estimated installed thermal capacity of 28,268 MWt. The thermal energy usage is 273,372 TJ/year (75,943 GWh/year), a 43% increase over 2000; the annual compound growth rate is 7.5%.The distribution of thermal energy used by category is approximately 32% for geothermal heat pumps, 30% for bathing and swimming (including balneology), 20% for space heating (of which 83% is for district heating), 7.5% for greenhouse and open-ground heating, 4% for industrial process heat, 4% for aquaculture pond and raceway heating, <1% for agricultural drying, <1% for snow melting and cooling, and <0.5% for other uses. The equivalent annual savings in fuel oil amounts to 170 million barrels (25.4 million tonnes) and 24 million tonnes in carbon emissions to the atmosphere.
Geothermal resources can be considered renewable on the time-scales of technological/societal systems and do not require the geological times of fossil fuel reserves such as coal, oil, and gas. The recovery of high-enthalpy reservoirs is accomplished at the same site from which the fluid or heat is extracted. Moreover, truly sustainable production can be achieved in doublet and heat pump systems. Generally the environmental impacts of geothermal power generation and direct use are minor, controllable, or negligible. There must be full compliance with environmental regulations, which may vary from country to country. In any case the effects must be monitored and documented (often over long periods), rated and, if necessary, reduced.
Intensive investigations into the utilisation of the geothermal potential of the North German Basin began in the early 1980s. The first production and reinjection tests from/into sandstone reservoirs started in 1982 and led to the commissioning of the first geothermal heating plant for heat supply to a residential area in the town of Waren (Müritz) in 1984. More plants were put into operation in Neubrandenburg, Neustadt-Glewe and Berlin. The use of these sandstone reservoirs for heat storage produced new technical solutions. A precise knowledge of the geological and geochemical conditions forms an essential prerequisite for the successful planning, construction and operation of geothermal plants. This paper describes the geological and geochemical conditions, as well as the technical solutions and practical experience acquired so far.
The ≈ 40 000 km² Hungarian Great Plain portion of the Pannonian Basin consists of a basin fill of 100 m to more than 7000 m thick semi- to unconsolidated marine, deltaic, lacustrine and fluviatile clastic sediments of Neogene age, resting on a strongly tectonized Pre-Neogene basement of horst-and-graben topography of a relief in excess of 5000 m. The basement is built of a great variety of brittle rocks, including flysch, carbonates and metamorphics. The relatively continuous Endrőd Aquitard, with a permeability of less than 1 md (10⁻¹⁵ m²) and a depth varying between 500 and 5000 m, divides the basin's rock framework into upper and lower sequences of highly permeable rock units, whose permeabilities range from a few tens to several thousands of millidarcy. Subsurface fluid potential and flow fields were inferred from 16 192 water level and pore pressure measurements using three methods of representation: pressure–elevation profiles; hydraulic head maps; and hydraulic cross-sections.
Injection of heat-depleted brines into clastic sedimentary reservoirs with alternating clay, sand and sandstone sequences has long been considered a delicate subject among petroleum and geothermal operators. Not only is injection an environmental pre-requisite in waste disposal, but it is also a means of achieving sound reservoir management as regards optimum heat sweep and recovery and pressure maintenance. However, without thorough and careful planning, injection can turn to disaster, for example where the formation and reinjected waters prove incompatible, or there is particle entrainment, capture and release, or unsuccessful well completion, which often leads to irreparable damage to the well and formation. This paper reviews the physics and chemistry governing these critical areas, and the problems likely to occur while pumping cooled brines into sandstone reservoirs: (i) water incompatibilities and subsequent supersaturation/precipitation of solid particles and clay swelling; (ii) fine particle migration/settling processes and relative pore throat bridging, pore retention/bridging and formation plugging; (iii) flow velocities and near well or well completion erosion impairment; and (iv) temperature-related electrokinetic and water–rock interaction effects. The foregoing are illustrated by laboratory experiments, model runs and field trials. Application of these studies to water injection in the Upper Pannonian clastic reservoir in the Great Hungarian Plain is also discussed.
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