Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005 State, Possible Future Developments in and Barriers to the Exploration and Exploitation of Geothermal Energy in Austria – Country Update Johann Goldbrunner Geoteam Ges.m.b.H., A-8200 Gleisdorf, Weizerstraße 19, Austria [email protected] Keywords: Geothermal Energy, Austria, Molasse Basin, Republic's area is covered by the Eastern Alps, which reach Styrian Basin, Alps, Vienna Basin, deep geothermal, wells, a maximum altitude of nearly 4,000 m (mountain thermal capacity, ORC, Geinberg, Altheim, Simbach, Grossglockner). Braunau, Waltersdorf, Blumau, Fuerstenfeld, Laengenfeld. Favourable conditions for exploiting geothermal energy ABSTRACT exist in the Alpine–Carpathian intramontane basins (Vienna Basin, Pannonian/Danube and Styrian Basin) and the In the 1977-2004 period a total of 63 geothermal Molasse Basin. The Vienna Basin, which is situated in the exploration wells with a total length of some 100 km have transition zone between the Alps and the Carpathians and been drilled for geothermal energy in Austria. A large was created by lateral movements and subsidence during number of wells were intended for tapping thermal waters and after the Alpine orogeny, has not seen intensive for balneological use (curing, thermal spas, leisure resorts, geothermal exploration so far. It is a main target for hotels etc.). Drilling activities focused on the Styrian Basin hydrocarbon exploration. Some 3,500 wells have been and the Upper Austrian Molasse Basin where a high drilled here since the 1930s for exploration and exploitation number of geothermal installations and wells for of hydrocarbons from the basin filling and the basin floor, balneological use exists. Since the mid-1990s thermal consisting of allochtonous Alpine units and subthrust floors exploration has also taken place in the hard rock formations (HAMILTON, WAGNER & WESSELY, 2000). of the Alps. These projects have a much higher geological Favourable geothermal conditions exist in some parts of the risk than projects in the sediment basins that have been basin due to convective heat flow (examples: Oberlaa High explored by the hydrocarbon industry for centuries. All south of Vienna and south-eastern part of the basin). An wells in the Alps were drilled for balneological purposes. open hole test in the hydrocarbon drilling Aspern proofed temperatures > 100 °C from an aquifer in dolomites of the Installed thermal capacity (deep geothermal) in Austria Calcareous Alps in the allochtonous basin floor (drilling equals 61 MW. 7 geothermal doublets are operating in Aspern 1, interval 3,106 – 3,296, artesian overflow 11.6 l/s, Austria at present, 6 of them are in the Upper Austrian RONNER, 1980). Molasse Basin. Electric power generation is performed at two sites with a total installed capacity of 1.2 MWe. The Main geothermal exploration and drilling activity took reinjection of thermal fluids after use had a positive effect place in the Styrian Basin, followed by the Upper Austrian on the aquifer pressure at a regional scale. Molasse Basin. The area of the Eastern Alps has seen increased drilling activity since 1998 (Table 1, Figure 1). Some legal and economic barriers hamper a broader use of geothermal energy in Austria. Economic problems can be overcome by combining different users at one site as it was Table 1: Drilling for thermal water in Austria (period demonstrated by the Geinberg cascade. Cascade use 1977 – 2004). including generation of electrical power will be very important for the future development of the geothermal Unit No. Average Cumulative business in boosting the economic viability of the projects. of depth depth wells (m) (m) Styrian Basin 26 1,565 40,699 Upper Austrian Molasse 12 2,088 25,056 Basin Vienna Basin and Lower 5 1,072 5,360 Austrian Molasse Basin Northern Calcareous 9 1,577 14,190 Alps and Upper Austroalpine Units carbonate rocks) Figure 1: Geothermal exploration wells in Austria Lower, Middle and 11 1,674 18,415 (1977-2004). Upper Austroalpine Units (mainly crystalline 1. INTRODUCTION rocks) Austria (area 83,858 km², 8.05 million inhabitants in 2002) Total 63 103,720 is subdivided into different geological units, which differ grossly in their hydrogeological properties and their geothermal conditions. Approximately two thirds of the 1 Goldbrunner 2. UPPER AUSTRIAN MOLASSE BASIN Table 2: Geothermal installations in the Upper Austrian 2.1 Geological conditions Molasse Basin. The Upper Austrian Molasse Basin offers the best Locality Alt- Gein- Obern- Sim- St. Haag conditions for the exploitation of geothermal energy. This is heim berg berg bach/ Martin due to enhanced terrestrial heat flow values (up to 95 Brau- mW/m²) and low mineralized geothermal fluids. The main nau aquifer is in autochthonous Upper Jurassic limestones and Type D, E I, D, D, E D D D dolomites in the pre-Neogene/Paleogene basin floor, which B, G are covered by Upper Cretaceous and/or Paleogene- Capacity Neogene mainly clastic sediments. The Upper Cretaceous 18.8 7.8 1.7 9.3 3.3 2.2 (MWt) sediments, which are mainly pelitic, act as a cap rock. Due Flow Rate to the generally southward dipping, top of the Upper 80 25 20 74 20 20 l/s Jurassic Carbonate Rocks is more than 4,000 m below surface at the border of the Alps. Maximum thickness of the Tempera- 105 105 80 80 90 86 carbonate rocks is in the order of 750 m (NACHTMANN & ture (°C) Year of 1990, 1981, WAGNER, 1987). Aquifer properties are given by 1996/ implemen- doub- dout- 2001 2000 1995 dolomitization and fracturing linked with fault systems of 97 different age. Pre-Neogene faults with vertical throws of up tation let let to 1,000 m strike mainly NW-SE and cut the Jurassic and 1999 1998 Cretaceous sediments, whereas the Oligocene extensional District- 14.5 6 17 30 25 12 faults show a W – E trend and a vertical throw of up to heating net 300 m. (km) I = Industrial use, E = Electricity, B = Balneologic, G = The most favourable conditions for tapping thermal waters Greenhouse, D = District heating from the Upper Jurassic Carbonate Aquifer are found in the Innviertel region near the border with Germany, where a 2.2 Geinberg Project high density of geothermal installations and wells for balneological use in spas can be observed (Figure 2). The In the small village of Geinberg, situated 5 km from the depth of the Upper Jurassic aquifer ranges from 1,000 m to German border, one of the first geothermal projects was 2,300 m in this region thus allowing water temperatures launched in 1980. It was based on an abandoned from 50 to 105 °C (Figure 3). hydrocarbon exploration well drilled in 1974, which reached the Upper Jurassic carbonate rocks at 2,127 m The thermal waters are uniform in their hydrochemical depth and had to be terminated at 2,166 m after heavy mud properties. They are of the sodium-bicarbonate-chloride losses. After a re-entry and deepening to 2,180 m in 1978, type, their TDS range from 1.2 – 1.5 g/l. Isotope the well was completed as a single geothermal well investigations showed that the proportion of meteoric producing some 22 l/s thermal water at artesian overflow at recharge in these waters is > 90 %. Water production by a temperature of > 100 °C. A small district heating project single wells during the 1980s and 1990s led to a significant in the village of Geinberg has been developed since 1980. pressure decrease. The negative development was Due to the general pressure decrease in the Innviertel overcome by reinjection measures by the Austrian region, artesian overflow dropped to some 11 l/s in the geothermal installations starting in 1998 and leading to a 1990s. In 1998 a spa and hotel resort was built, thus regional pressure increase of about 1 bar within one year. increasing the need for geothermal energy on the one hand and thermal water for bathing, cures and recreation on the other. The precondition of the water authorities for stabilisation of the aquifer pressure and the growing demand for thermal water caused the planning of a second well to complete a geothermal doublet. The new "Geinberg Thermal 2" well, partly financed by the THERMIE European programme, was designed as a deviated well situated 20 m from the existing well. In order to prevent a hydraulic shortcut between abstraction and reinjection, the distance of the wells in the aquifer is some 1,600 m. Deviation was directed north, the inclination reached a maximum of 64 °, the build-up rate was 2 °/30 m at maximum. The top of the Upper Jurassic carbonate rocks was tapped at 2,910 m MD (2,117 m TVD). So the vertical depth of aquifer differs only slightly from Geinberg 1 (2,127 m). The bore reached a measured depth (MD) of 3,155 m corresponding to a true vertical depth (TVD) of Figure 2: Geothermal wells and wells for balneological 2,225 m. use in the Upper Austrian/Bavarian border region. Table 2 gives a view of the geothermal installations in the Geinberg is an example of geothermal cascade use. Upper Austrian Molasse Basin. The most important Thermal water is produced at the Geinberg Thermal 2 well installations are Geinberg, Altheim and Simbach-Braunau. at a maximum artesian free overflow rate of 25 l/s. The primary use in the upper thermal segment is for the dairy for industrial processes and the district heating of the village of Geinberg, where 24 private houses and public buildings are heated. The next step in the cascade is the heating of the spa centre and the hotel resort, where the 2 Goldbrunner water is cooled down from 75 to 43 °C.