Overview of the current activities related to deep geothermal energy utilisation in the Republic of Croatia

• DOI: 10.1007/s10098-022-02383-1
• Publication Date: 2022-08-28T07:02:31Z
• Authors: Martina Tuschl; Tomislav Kurevija; Marijan Krpan; Marija Macenić
• Keywords: 2. Zero hunger; geothermal energy, deep wells; 13. Climate action; 0211 other engineering and technologies; 02 engineering and technology; 7. Clean energy; 6. Clean water

The Pannonian Basin, partly located in Croatia, is well known for its higher-than-average geothermal gradient with good potential for geothermal energy exploitation. Most of the currently known geothermal potential locations in the Croatian part of the Pannonian Basin (CPB) were discovered during the oil and gas exploration and exploitation from the mid-twentieth century onward. Unfortunately, recent geothermal energy utilisation in Croatia, which began in the late 1980s, developed very slowly and sporadically, even though the utilisation of it has been known since the Roman times. Most of the discovered geothermal sources are used for balneology in numerous thermal spas. In the last decade, low-temperature geothermal resources have also been used in agriculture, namely in greenhouses. However, with the change of legal framework in 2018, the market showed an increase in the number of issued geothermal exploration blocks. With Croatia’s first geothermal ORC power plant Velika 1, commissioned in 2019, the interest in developing geothermal projects is seen in 13 exploration and six production licenses issued in the last three years, focusing on deep geothermal potential. The planned use of these granted licenses varies from electricity production to agricultural use. Aside from classic geothermal brine production, there is also a good potential of geothermal brine exploitation from bottom aquifers in depleted oil and gas fields. Many hydrocarbon reservoirs in Croatia consist of oil and gas in the upper part of the reservoir and aquifer in the bottom part. During initial depletion-drive exploitation, pressure in the reservoir declines, causing brine from the aquifer to slowly invade the oil zone. While the reservoir is in its final stages of production, some waterflooded peripheral wells could be turned into geothermal ones, even if oil is still produced or after the field is abandoned. So far, several locations with relatively high temperatures of the bottom aquifer have been identified as a good potential for deep geothermal energy exploration and exploitation. This work gives an overview of the current state of geothermal energy utilisation in Croatia and future prospects.