Slobodan Vidovic, Sava Djuric: UTILISATION OF GEOTHERMAL WATERS AND GEOTHERMAL ENERGY IN VOJVODINA UTILISATION OF GEOTHERMAL WATERS AND GEOTHERMAL ENERGY IN VOJVODINA Slobodan Vidovic1, and Sava Djuric2 1 Sloboda Vidovic, B Sci., NIS-Naftagas, 21000 Novi Sad, Narodnog fronta 12, Serbia and Montenegro, phone: ++ 021- 481-3122, fax: ++ 021-481-4340, E-mail: [email protected] 2Sava Djuric, B Sci., NIS-Naftagas, 21000 Novi Sad, Narodnog fronta 12, Serbia and Montenegro, phone: ++ 021-481- 3103, fax: ++ 021-481-4340, E-mail: [email protected] Figure 1: The map of hydrothermal facilities in Vojvodina Key words: thermomineral waters, geothermal day. At its early stage, these explorations have regionalization, hydrothermal system, use of advanced rather fast and efficiently, owing to rich geothermal waters, water quality. expert documentation inherited from the process of oil and gas exploration activities, as well as to sub- INTRODUCTION stantial financial and expert resources of NIS-Naf- tagas. In such background, the planned and system- Recent exploration of thermomineral waters and atic approach to the regional, and later also the de- hydrothermal power in Vojvodina have been con- tailed exploration was possible. In a relative short ducted continuously since 1969 until the present period of time the conditions of occurrence were 317 International Geothermal Days POLAND 2004. Zakopane, September 13-17, 2004 International Workshop on Geothermal Energy Resources in Central and Eastern European Countries: State-of-the-Art and Possibilities for Development known, as well as the geotemperature regime and The most intensive period of drilling was in the physical and chemical properties of the waters, period between 1977-1990, when 2-7 wells were which all allowed the second phase of application drilled annually. Since 1991, when NIS-Naftagas of the thermomineral waters and hydrogeothermal completely ceased its financing, the drilling power. activities dropped abruptly. The lack of financial The use of thermomineral healing waters in me- means on the part of potential users, who now had dical therapy and disease prevention has always had to finance the drilling either completely of partially, a significant place in development of the civiliza- as well as high initial investments and impossibility tion, and has not been any less important in the of getting any bank credits, have all contributed to modern society as well. The use of thermo-mineral the sudden drop of development rate. waters for energy and power purposes is of a more In the beginning, only exploration wells have recent date, and a wider use started with the occur- been drilled, to introduce regional knowledge of rence of the first energy crisis during the 70s. hydrogeological properties, quantity and quality of During the last thirty five years 73 hydrothermal waters, etc. At a later stage, when selecting wells have been drilled in Vojvodina, which total locations, it was taken into consideration that the depth is 62.847 m. The majority of the wells have wells were located in the vicinity of an object, so been drilled in Backa (42), Banat (18), and the least that in case of positive results they could be number in Srem (13). Also, 23 systems for the use practically used. Finally, only production wells of thermomineral waters have been constructed, were drilled, for a known user and known purpose. partly for energy use, and partly for the purpose of The average well depth in the past was 860 m, healing, medical treatment and sports and which is relatively small for the Panonian basin recreation use (Fig. 1). conditions. However, drilling at greater depths has In the last 7-8 years the tendency of deve- often been limited by highly mineralized waters, lopment has been on a certain stand-by, although inconvenient for wider use and especially for dis- the interest of potential users has been in increase. posal after the use. Such a state is the result of general stagnation of the To acquire the knowledge of hydrogeological country’s economic development, and particularly properties of Vojvodina, besides drilling and testing of the lack of financial means and credits, and the hydrothermal wells, about 40 wells negative to oil lack of any aid by the Government [1]. and gas have also been tested in the past period. Apart from gaining valuable data, these wells have 1. A SHORT HISTORY OF RECENT EXPLO- also served for evaluation of the possibilities to RATIONS OF THERMOMINERAL WA- transfer negative oil wells into hydrothermal. It TERS IN VOJVODINA turned out that only in a small number of cases they could be adapted to produce thermomineral water. The first knowledge of thermomineral waters Such are the cases when the producing layer, i.e. existence in Vojvodina were acquired at the turn of water environment, is built of solid rock (carbons, the last century, drilling artesian wells. Searching dolomite, sandstone, etc.). In any other cases this for artesian (“live”) water, the drillers had often transfer was not possible, owing mostly to reached the depths of 400 and even 600 m, at which producing sand and to small well capacities. there had been discovering hot waters. These wells Optimal well production in self flow ranged were mostly used for public baths, such as those in mostly between 10-15 l/s, and the output water Becej, Temerin, Kanjiza, Senta, Prigrevica, Zma- temperatures between 45 and 65 °C. jevo etc. With the start of oil and gas explorations in Voj- 2. GEOTHERMAL REGIONALIZATION vodina in 1949, much greater depths have been dril- OF VOJVODINA led (over 2000 m). These activities allowed for the gaining of new knowledge and experience in the Groundwater temperature reflects the geotem- frequency and quality of thermomineral waters perature regime of geological surroundings in from greater depths, which later allowed faster and which it is accumulated. The temperature grows more efficient exploration. with depth, and the rate of growth depends on geo- Initial systematic and organized exploration of thermal gradient. Vojvodina has the conditions of thermomineral waters in Vojvodina began in 1969, high geotemperature influences. when “Nafta-gas” from Novi Sad, at the recom- Based on a great number of temperature mea- mendation of the Provincial Energy Committee, ac- sures in wells geothermal gradients were calculated cepted programming, financing and realization of for the whole of Vojvodina. The majority of data the project for exploration and application of regards the neogenic complex, and a very small thermomineral waters in Vojvodina. The first ex- number on older formation. Geothermal gradients ploration well within the project was drilled in Su- of Vojvodina range between 4,5 - 7,5 °C/100 m. botica, in 1969 [2]. High gradients have been recorded in parts of Backa and Srem, particularly in areas where the 318 Slobodan Vidovic, Sava Djuric: UTILISATION OF GEOTHERMAL WATERS AND GEOTHERMAL ENERGY IN VOJVODINA bases of neogenic sediments are made of Triassic pliocene period, and lay in depths between 750 and carbons and dolomites, in which convex heat 1700 m. Production rates of 10-28 l/s (average of transmission in the reservoir prevails, and also in 12,6 l/s) per well could be achieved. areas where neogenic sediments are thin, namely Because of very suitable conditions for produ- where Mesozoic and Paleozoic formation lay in cing thermomineral waters, areas of carbons and small depths. dolomites of mostly Triassic period (III) have been Higher Triassic depressions in northern and emphasized, that could yield waters of output middle Banat are characterized by lower geother- temperatures 45-75 °C. These areas are located in mal gradients. southern and eastern Srem and western Backa, and To allow easier evaluation of hydrogeological are of about 1300 m 2 in size. Hydrogeological conditions for production of thermomineral water, collectors are built of cracked and cavernous carbon geothermal regionalization of Vojvodina has been rocks of mostly Triassic period, that lay in depths conducted and a map of output water temperatures ranging between 500-1300 m. They could produce has been drawn (Fig. 2). Regionalization was based 14-42 l/s (average of 22,5 l/s) per well. on three criteria: depth of hydrogeological collec- In other parts of Vojvodina, except the Fruska tors (depth structure map of Vojvodina on neogenic Gora mountain and Vrsac mountains, thermo- base was used), geothermal gradients (map of mineral waters of output water temperatures under geothermal gradients of Vojvodina), and physical __ 50 °C can be expected, that could mostly be and chemical properties of thermomineral waters used in healing and sports and recreation purposes, (laboratory analyses from a great number of wells). for growing fish, etc. Areas, i.e. geological formations, from which waters of output temperatures over 80 °C have been 3. PHYSICAL AND CHEMICAL PROPER- separated, then areas with output water tempera- TIES THE THERMOMINERAL WATERS tures between 50 and 80 °C, and finally areas with output water temperatures under 50 °C. Owing to With occasional exceptions, all ground waters specific hydrogeological conditions (high producti- of Vojvodina from depths over 400-500 m could be on rate wells, low collector depth, good water qua- determined as thermomineral, since they contain lity), some areas have been particularly emphasized more than 1 g of soluble mineral matters per 1 liter ° - those with collectors built of cracked and ca- of water, and also have the temperature over 20 C. vernous carbons and dolomites of the Triassic pe- [3]. riod, with output water temperatures ranging As for the ionic compositon, certain paradigms between 45-75 °C. could be derived. As a rule, waters of pliocenic and upper pontiassic age belong to HC_ -N_ type, Waters up to 160 °C could also be produced in 3 Vojvodina, but owing to their unsuitable physical water of miocenic age to Cl-N_ type, and waters of and chemical properties (high mineralization, lower pontiassic age belong to intermediate Cl- HC_ -N_ type.