Dusan Rajver

Geothermal waters belong to the natural resources of Croatia and Slovenia. As all other natural resources these are also limited in quality, while their hydrogeothermal systems are sensitive to exploitation and activities that exert influence on environment. Considering that geothermal waters are optimally exploited, preserved and protected in the sense of sustainable development strategy it is necessary to know them well and to exploit them in a supervising manner. Hydrogeothermal systems in the border zone of Croatia and Slovenia are very probably connected in the underground. For this reason the harmful activity on the geothermal aquifers on the one side of the border can have negative effects on exploitation and protection of these waters on the other side. As regards their protection it is necessary to act in a coordinative way in both countries as to avoid detrimental unwanted consequences for geothermal waters in the neighbor country. Considering this it is foreseen in the European Directives that the border countries conduct a mutual care on water protection (incl. geothermal). Unfortunately, Croatia and Slovenia had no common projects and activities so far in this sense. The project “ Geothermal map of Republic of Croatia” is in the preliminary stage in Croatia. Within this project it is planned to investigate the bordering area to Slovenia in the following years, which is why the cooperation between Croatian and Slovenian geological surveys is reestablished. Within the sphere of this cooperation basic data on thermal water localities in the border area of both states are collected which is a good start of mutual care for the protection of these waters there. There are 16 known localities with thermal water on Croatian side. Natural springs of geothermal water from the NE to SW are: Harina Zlaka, Tuhelj Spa, Krapina Spa, St. Helena (at Samobor), Spa at St. Jana, Lesce Spa and Istrian Spa. Water temperatures on these localities are between 25 and 40.2 °C, and the aquifers are mostly in Triassic dolomites. Boreholes that have discovered thermal water, and are deeper than 500 m, are: Vuckovec-2, Mursko Sredisce-2, Međimurje-1, Kumrovec-1, Tuhelj Spa, Krapina Spa, Samobor-2, Nedjelja-1, PDT-1 and 2, Lucanka-1, Mladost – 1, 2 and 3, KBNZ-1, 2, and 3, St. Jana– 1 and Lescanka-1. The pertinent aquifers are predominantly Triassic dolomites, while the water temperature is between 25 and 82 °C. On the Slovenian side there are 13 known thermal water localities. Natural springs are: Buseca vas, Toplicnik at Kostanjevica, Klevevž and in former times also Dolenjske Spa (boreholes today). Water temperature on these localities ranges from 23 to 34 °C, the aquifers are Mesozoic carbonate rocks. Boreholes with depth of at least 500 m that have discovered thermal water are: Lendava (Pt-20, -74, Le-1g, -2g), Veržej-1, -2, -3, Rogaska Slatina RT-1, Terme Olimia V-4, Catež V-10, L-1, Dobova AFP-1, Smarjeta Spa V-11 (227 m depth), Metlika-1 and Portorož HV-1, LU-1. The aquifers found by these boreholes are Tertiary sandstones (Lendava, Veržej), tuffs with sandstone (RT-1), but mostly Triassic dolomites, Jurassic limestones in Metlika, and Cretaceous limestones in Portorož. Temperatures range from 22.5 to 68.4 °C. Based on the collected data on geothermal waters in the border region so far one can infer that there is not enough data to confirm or to reject a link-up and unity of geothermal aquifers on both border sides. Theoretically the possibility of such link-up is very great, therefore, it is necessary to continue to collect the data, and if there is a need, to perform new investigations to confirm or to reject such link-up.

U okviru projekta Geotermalna karta Republike Hrvatske (181-1811096-1790) kojeg financira Ministarstvo znanosti obrazovanja i sporta RH, a izvodi Hrvatski geoloski institut u suradnji s Slovenskim geoloskim zavodom, prikupljeni su osnovni podaci o lokacijama s geotermalnom vodom u granicnom podrucju Hrvatske i Slovenije. U spomenutom podrucju poznato je 37 lokacija na kojima su izvori i/ili busotine s geotermalnom vodom. Ukupna kolicina te vode za sada se ne koristi, ali interes i potrebe za njom stalno rastu te se bližoj buducnosti ocekuje znatno povecanje kolicina koristene geotermalne vode kao i izrada busotina na poznatim i novim lokacijama. Kako bi se spomenute vode, u smislu strategije održivog razvoja, optimalno koristile, ocuvale i zastitile, potrebno ih je dobro poznavati i kontrolirano koristiti. Vjerojatno su neki hidrogeoloski i geotermijski sustavi s geotermalnom vodom u granicnom pojasu u podzemlju povezani, odnosno cine zajednicko prirodno dobro obiju zemalja. Prema prikupljenim podacima, teoretska mogucnost te povezanosti na nekim lokacijama je vrlo velika, ali dok se ne obave potrebna istraživanja o tome nije moguce dati mjerodavan sud. Neophodan element za takva istraživanja su podaci kontinuiranog monitoringa geotermalnih voda. Bez provedbe potrebnih istraživanja koja ukljucuju kontinuirani monitoring nece biti moguce provesti djelotvornu zastitu geotermalnih voda u granicnom pojasu Hrvatske i Slovenije.

<p>The compilation of global heat-flow data is currently under major revision by the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). Heat flow represents a fundamental parameter in thermal studies, e.g., the evolution of hydrocarbons or mineral and geothermal resources. Comparable, comprehensible and reliable heat-flow data are of utmost interest also for geophysical and geological studies on the global scale. Here, we present the first results of a stepwise revision of the IHFC Global Heat Flow Database based on a researcher driven, collaborative approach. The first step comprises the review and revision of the most recent database structure established in 1976. The revised structure of the Global Heat Flow Database considers the demands and opportunities presented by the evolution of scientific work, digitization and the breakthroughs in database technologies over the past decades.  Based on the new structure, the existing dataset will be re-assessed and new data incorporated. By supporting the ideas of FAIR and open data principles, the new database facilitates interoperability with external data services, like DOI and IGSN numbers, and other data resources (e.g., world geological map, world stratigraphic system, and International Ocean Drilling Program data). We give an overview of the new database and introduce the community workflow of global heat-flow data revision.</p>

The Slovenian Geological Congress offers our leading geologists a celebration of their research achievements in the last four years. It is a great opportunity to exchange experience internationally also, and this bilaterally organized field trip offers just that, an opportunity for many international informal contacts. The field trip is organized as a collaboration of many institutions: the Slovenian Geological Society, the Geological Survey of Slovenia, the Faculty of Natural Sciences and Engineering of the University of Ljubljana, the Slovenian Committee of the International Association of Hydrogeologists, the Croatian Geological Society and the Croatian Geological Survey. It also has the honnor to form a part of the annual assembly of the Commission on Mineral and Thermal Water of IAH of the International Association of Hydrogeologists (CMTW-IAH). Most of the field trip is perfomed in the west part of the extensive Pannonian basin where in the past hydrocarbon industry used to pl...

Periodic revisions of the Global Heat Flow Database (GHFD) take place under the auspices of the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). A growing number of heat-flow values, advances in scientific methods, digitization, and improvements in database technologies all warrant a revision of the structure of the GHFD that was last amended in 1976. We present a new structure for the GHFD, which will provide a basis for a reassessment and revision of the existing global heat-flow data set. The database fields within the new structure are described in detail to ensure a common understanding of the respective database entries. The new structure of the database takes advantage of today's possibilities for data management. It supports FAIR and open data principles, including interoperability with external data services, and links to DOI and IGSN numbers and other data resources (e.g., world g...

ABSTRACT Direct use of geothermal waters continues to be the only type of use from geothermal reservoir sources in Slovenia, at 29 localities at present. A small progress was achieved in geothermal development during the last five years with four new users appearing in the north-eastern part of Slovenia, belonging to the Pannonian Basin geothermal region. Two of them, still in a testing phase, use thermal water from metamorphic and carbonatic basement rocks respectively, the other two (thermal leisure resort, orchids greenhouses) use the same Upper Miocene-Pliocene aquifer as other users in vicinity. Beside, new reinjection well has been drilled there for a doublet system in Lendava. Due to newish legislation thorough reports on geothermal conditions and present utilization are demanded from the users in recent years, which slowly provoked the monitoring introduction. The installed capacity amounts to 66 MWt and the annual energy use to roughly 773 TJ. Most localities comprise installations that include centralized heating units, thermal spas combined with space heating, and with district heating and greenhouses in a few cases. In addition, ground source heat pumps are also increasingly used, especially in residential applications. There are roughly 3440 ground-coupled heat pump and ground water heat pump units of about 40 MWt capacity removing additional 379 TJ/year in energy use while 13 TJ/yr are rejected to the ground in the cooling mode. The investments were directed for some basic research, but even more for feasibility studies and project implementation with new drillings. Drilling activity reached incredible 23.8 km of new wells, both production and exploration, including the temperature gradient boreholes. Of course, not all wells were successful. For the future prospective geothermal options may include: the adaptation of some abandoned oil wells, small size heat pumps and also groundwater heat pumps of greater capacity, some clusters of ground heat exchangers used for heating or cooling, hopefully some more reinjection wells, and probably multipurpose integrated system.

... A similar structure has been proposed for the Central AlpsSouthern Alps contact zone, based on the lat CR i) a 'l' 1 . Or,.,l ., mGal . i est deep seismic data (Pfiffner, 1992; Giese et al., 1992). ... Geologija, 36: 223248 (in Slovenian, with English summary). ...

At the site of the Ombla permanent karst spring, near Dubrovnik, Croatia, it is planned that an underground hydroelectric power plant with an installed capacity of 60 MW be built. This assumed power capacity is based on the results of measurements of average annual discharge of the spring, which is approximately 24 m3 s−1. The positions and dimensions of all

In the paper we present a method of seasonal heat storage with boreholes and thermal response test for determination of ground parameters. Analysis methods for concrete calculations of thermal conductivity as well as error determination are explained. In the continuation measurements made in research of the ground in Turkey and situation in afield of seasonal thermal energy storage in Slovenia are presented.

... While the intention of geothermal research in northeastern Slovenia has been conditioned by oil research, for the Kr ko basin it was necessary to ... have been constructed from the acquired data: • Map of the base of the Tertiary basin, ie map of isobaths of the contact Tertiary or ...

ABSTRACT Historical utilization of regional and transboundary geothermal resources was identified between Austria, Hungary, Slovakia and Slovenia. Its status was determined for the period 2010-2011 and based on a unified methodological approach and field inspections. The assembled data were verified and harmonized in a database with three levels applied: organizational (user’s contact details), formational (hydrogeological data) and object-linked (production characteristics). The web-database is linked to Google maps and available on http://akvamarin.geo-zs.si/users/, while the results and a web-map service are published on http://transenergy-eu.geologie.ac.at/. The research identified 148 active and 65 potential geothermal energy users with 403 geothermal objects spread over the area of 47,700 km2. The 307 active wells produced above 30 million m3 of thermal water in 2009 (no data from Austria is included due to confidentiality reasons). The amount is rising. Among the 11 lithostratigraphical categories of geothermal aquifers, the highest discharge is estimated from the Mesozoic carbonate basement rocks which have transboundary settings in many cases. The Paleozoic carbonates produce water with 109°C in Austria, which is used for electricity production in Bad Blumau together with constant reinjection. Unfortunately, reinjection is not a common practice as only two more periodical reinjection systems are applied in the Mesozoic carbonates in Podhájska (Slovakia) and the Upper Pannonian sands in Lendava (Slovenia). The latter reservoir is regional, cross-cut by the state borders and captured by the majority of abstraction wells in the area, providing thermal water with temperatures up to 91°C. The individual space heating, sanitary water heating, greenhouse or district heating is applied in Slovakia and Slovenia often but drinking and industrial water as well as agricultural use are more common in Hungary. The predominant utilization is still the traditional category - bathing & swimming. The current abstraction has caused overexploitation in some areas, plus the lack of reinjection significantly deteriorates the quantity status of geothermal aquifers and the surface water ecology. The waste water management is often inappropriate, while operational monitoring is not harmonized nor executed sufficiently. The further geothermal development can focus on activation of the inactive boreholes at first, where from the surplus of about 20% of the current thermal water abstraction may be produced. The most promising aquifers are hosted in the Pannonian-Pontian clastic and the Mesozoic carbonate rocks, which may have a transboundary character. Moreover, the concession permits foresee the increase of production for at least twice the current abstraction. The hypothetic thermal water abstraction may rise to over 60 million m3 per year consequently, but it was not investigated during the research whether this is hydrogeologically feasible or which would be the effects on the current and among various users. New geothermal development needs to be based upon: unified and transboundary (where needed) management strategy of exploitation, including best available technologies, harmonized operational monitoring, high thermal energy efficiency, public awareness activities and proper waste water management, including reinjection where possible. This has to be applied as soon as possible among current users also in order to control interference between them and regional impacts on the aquifers status.

Podzemno shranjevanje toplotne energije ali na kratko UTES (Underground Thermal Energy Storage) je zanesljiva in energetsko varčna tehnologija shranjevanja toplote in je namenjena hlajenju in ogrevanju v stavbnih objektih in industrijskih procesih ter je sedaj že široko razširjena po celem svetu. V zadnjih dvajsetih letih je bila ta metoda aplicirana že v več različicah. Na podlagi Mednarodne Agencije za energijo (IEA - Implementing Agreement) ter ECES (Energy Conservation through Energy Storage )je bila temu namenu strokovno razvita znanstvena oprema. V splošnem se za metodo podzemnega shranjevanja toplotne energije uporablja kratica UTES, katera je pogosto razdeljena na podskupine glede na tip uporabljenega medija za shranjevanje energije. Ena takšnih je metoda z vrtino (BTES- Borehole Thermal Energy Storage), katera se nanaša na sistem shranjevanja energije z uporabo vrtine v zemlji in vanjo nameščenih cevi. Toplotna prevodnost zemlje in toplotna upornost izmenjevalca toplote v v...

Basic features and problems of the method of reconstruction of the ground surface temperature history from the temperature-depth profiles measured at present in boreholes are outlined and illustrated. The main methodological problem is the one-dimensional, purely conductive representation of the subsurface temperature field used by all existing systematic inversion algorithms. It prevents considering lateral inhomogeneities of thermophysical parameters of rocks, effects of topography and space variations of the surface temperature as well as any departures from the conductive mode of the subsurface heat transfer. It can be overcome by "non-systematic" approaches like Monte-Carlo method, which requires solution of the direct problem only. The main practical problem is the presence of noise in the temperature logs which contributes, together with the diffusive character of the downward propagation of the surface changes, to the rapid lost of resolution of the more remote sur...

Temperature maps for depths of 500, 1000 and 2000 m are described, based on enlarged data base of 395 boreholes with geothermal data. Together with heat flow density map they emphasize the Pannonian basin geothermal anomaly, and some other anomalies, such as the Čatež field. In central Slovenia and coastal area average depth temperatures prevail.

Thermal water in the Slovenian part of the Mura-Zala basin, which appertains to the SW part of the Pannonian basin, is produced from low enthalpy geothermal system set in the Neogene sediments as well as from basement aquifers in the Pre-Neogene metamorphic and carbonate rocks. The water discharges from 26 geothermal wells managed by 14 users. Their density is especially high in the central Pomurje area between towns Murska Sobota and Moravske Toplice. Utilization schemes depend on water temperature mostly but the scaling potential and gas content also play an important role. The highest wellhead temperatures reach 72 °C in Benedikt and Moravske Toplice, however, temperatures between 50 and 60 °C are gained most often. The use is more diverse than a decade ago but the individual space heating, sanitary water heating and bathing with balneology still prevail as direct utilization schemes. Both, the installed capacity and the used geothermal energy show an increasing trend in the peri...

Neposredna uporaba geotermalne energije v Sloveniji se nanaša predvsem na ogrevanje prostorov, kopanje in plavanje (vključno z balneologijo), manj pa za tople grede, daljinsko ogrevanje, klimatizacijo zraka, industrijsko uporabo in za geotermalne toplotne črpalke. V letu 2004 je na 27 lokacijah z instalirano kapaciteto 45 MWt znašala skupna neposredna uporaba okrog 616 TJ. Upoštevane so tudi geotermalne toplotne črpalke v petih termalnih centrih. Instalirana moč vsaj 300 talnih toplotnih črpalk pa dosega 3,35 MWt. Le te izrabljajo letno dodatnih približno 70 TJ zemljine toplote. Vključno z geotermalnimi toplotnimi črpalkami znaša torej instalirana termalna moč vseh uporabnikov 48,4 MWt, izkoriščena toplotna energija pa 686 TJ/leto.

In order to have a better understanding on the geothermal conditions of the Mura–Zala Basin, temperature, geothermal gradient, heat conductivity and heat-flow data from boreholes have been collected both in Slovenia and in Hungary. Datasets were different: in Hungary more borehole-temperature data were available, while in Slovenia steady-state temperature measurements were overwhelming with measured data available on the heat conductivity and heat production capacity of the rocks, too. In Hungary complementary temperature logging was performed in five boreholes. Based on the joint evaluation of the datasets, temperature distribution maps were edited for the depths of 500, 1000 and 2000 m below the surface and for the top and bottom of the main thermal water aquifer, the Mura and Újfalu Formation. The constructed temperature field shows some characteristic positive anomalies, which are either related to the convective heat transport in the fractured-karstified basement (e.g. Benedikt...

Geothermal energy is an important alternative and local heat source in Slovenia. As long as natural, technological and legislative conditions and boundaries are considered, geothermal heat pumps represent ecologically acceptable heat source at a reasonable price. Thermal water direct use, especially in connection with tourism, district and greenhouse heating, is a promising and increasingly more important economic branch. On the contrary, geothermal electricity is still in an idea phase. All known projects are currently unfeasible, uneconomical or both. In order to determine the possibility of geothermal energy production geothermal potential has to be verifiedfirst,whichrequireshigh investments, but sooner or later this will have to be dealt with also.