| Abstract |
In general, there are two different regions in the Republic of Croatia, both in geological and geothermal respect. In the southeastern part of the country, there is the Dinarides mountain chain with predominantly Mesozoic carbonate rocks, characterized by the low geothermal gradients ranging from 0.01 to 0.03°C/m. In the northeast part of the country we find the Pannonian basin, up to several thousands meters deep. There, the geothermal favorite area is marked by a geothermal gradient higher than 0.04 and more than 0.07°C/m at some geothermal fields. The main geothermal reservoirs are in the fractured Mesozoic and older carbonates rocks, mid Miocene carbonates, under the Panonnian basin and younger clastic sediments, with important geothermal reservoirs in their sandstone sequences. So far, that potential has been used at numerous spas, and occasionally on few geothermal fields, developed by drilling. Most of the further development should relay on the experience, wells and other technical facilities remaining from oil and gas exploration and production in the area. In the last fifty years several thousands exploratory and producing wells were drilled and nearly fifty oil and gas fields and five geothermal fields were put in production. A huge amount of direct information from wells comes in the set with massive and partly modern geophysical measurements including 3D seismic. To define these geothermal resources and to indicate the full range of potential and delineate the best objects, regional geological and detailed studies are performed. Further hydrodynamic tests are performed and technical and legislative documentation is prepared for several most developed objects. Only 18 spas or fields have been utilized to tap the geothermal resources of the area, and the percentage of usage of their available power is very small. Installed capacities have a thermal power of 67 MWt, with an annual energy production of 469 TJ/yr. Improvement of such a condition can be significant for the future economic development of certain regions in Croatia. Increase of direct geothermal energy usage in the past five years was indicated, while the plans for construction of a geothermal electric power plant are postponed to the year 2010. |