ZAVOD ZA GEOLOGIJU I I INŽENJERSKU GEOLOGIJU
Geothermal Research
In Croatian Geological Survey geothermal researches has a long tradition since the survey foundation. Famous geologist Gorjanović-Kramberger Dragutin, PhD, was studying geothermal issues long before as he has established the Geological Commission of the Kingdom of Croatia and Slavonia. He is particularly known for his work from 1894 where he mentions geothermal lines in northwestern Croatia which are quoted later frequently.
Kramberger's "thermal lines" (Jazu, Zagreb, 1894)
Geothermal researches in Croatian Geological Survey today are part of scientific (HyTheC), European (DARLINGe) and commercial projects of the Department of Hydrogeology and Engineering Geology.
- Scientific topics:
Due to a variety of geothermal issues, which are currently one of the most important topics in numerous programs, both on national and European level, scientific researches are focused on several topics:
producing of the Map of geothermal gradients and thermal flow of the Republic of Croatia
- producing of the Map of geothermal gradients and thermal flow of the Republic of Croatia based on drilling data
- delineation of the most promising areas based on the thermal flow analysis and the structure convenient for water flowing closer to the surface
2. Geothermal waters exploration
- geothermal waters exploration in due to producing of the Map of appearance, study of hydrogeochemical facies, change of water in hydrothermal circulation and the chemical geothermometry. Catalog of the chemical and balneological characteristics of water
Locations of geothermal objects in exploitation
3. Cross-border geothermal aquifers - cooperation with similar neighboring institutions with goal of determination of cross-border geothermal aquifers based on lithology, geothermal gradients, hydrochemical facies and regional numerical models and monitoring planning and their protection.
Assumed cross-border geothermal aquifers in Međimurje County
4. termogeologija/plitka geotermija
- Catalog of thermal properties of sediments and rocks in the heating pumps system area (up to 100 m)
- determination of the functional dependence of thermal parameters of sediments and hydrogeological/geomechanical parameters
Core determination and measurement of thermal parameters of sediments
- Delineation of the most optimal locations for ATES system creation
- delineation of the most optimal locations for ATES systems (Aquifer Thermal Energy Storage) based on geological and hydrogeological characteristics (high porosity and hydraulic conductivity and lower water flow)
5. Geothermal potential studies
- Geothermal potential studies are based on the previously collected data about geothermal features of the investigated area and additional researches that determines the geothermal potential of the investigated area has. Studies of the given area are including: data on objects with geothermal water, the average geothermal gradient and possible value deviations, the average thermal conductivity and capacity values of certain lithostratigraphic units, the average value of surface thermal flow and possible deviations, occurrence possibility of aquifers with geothermal water, narrower areas for perspective further research, recommendations on technologies for the geothermal energy of the investigated area use. Geothermal potential studies are made for larger regions, counties and cities as well as municipalities. Expert opinions are made for the smaller area.
Natural geothermal spring in Daruvar
6. Projects of optimization of geothermal springs usage
- On locations where geothermal water is used, often we have a problem with amount of water (not enough) or with the water temperature (too low). In cases like that, we try to determine the available amount of water and, if is possible, to obtain the required amount of water with matching temperature. Researches with issues like that, may have different content, perimeter and methodology. For example: geological mapping and modeling of structurally tectonic sets, geophysical research, pumping test, flow measurements, groundwater level measurements, heat conductivity levels and thermal capacity of individual lithostratigraphic units, geothermal gradients and thermal flow density calculations, hydrogeochemical and isotopic analysis, numerical modeling et al.
Geothermal water sampling, in situ analysis and measurements
Numerical simulation of the functionality of the Daruvar hydrothermal system
7. Geothermal springs protection studies
- Extensive construction works near geothermal springs, excessive pumping, nearness of industrial drives that pollute the environment, roads close to the spring and similar can affect on geothermal springs. By researching and proposing of geothermal springs protection measures, we can prevent harmful impact of human activities on the environment and geothermal waters. For example, we have locations where amount of geothermal water is reduced and locations where we used to have surface springs and now we have to exploit water only by drilling because the level of geothermal water dropped down from surface to a larger depth. Our goal is to research and determine the causes of lowering geothermal water levels and recommend what to do to protect the spring from further level lowering.
8. Geological projects of geothermal water wells
- Geological projects of geothermal water wells are based on previous research. The project contains a forecast profile of wells, possible geothermal water aquifers and expected geothermal and hydrogeological parameters.
Bušenje geotermalne bušotine u Daruvaru
9. expert opinion
- Results from geothermal resources researches as well as other geological researches are not always unique. Because of that, investments in such researches and exploitation are very risky. By creating an expert opinion as a first step, the investor can reduce the risk to the minimal level. Assistance in the design of tender - project task for public tender, and assistance in bids (or project for exploration and exploitation works) for geothermal water and energy usage, can be provided to investor as a part of expert opinion preparation. Expert opinion is also made for geothermal potentiality of smaller areas.
10. geological surveillance
- We provide geological surveillance services over the performance of the work with the aim of gaining geothermal waters and geothermal energy. We help the investor in the work evaluation and give advise about the necessity and usefulness of additional works.
11. Thermal properties measurements
- Geothermal researches are unimaginable without knowing the thermal properties of the material through which the heat is passed on the way from the inside to the surface. Therefore, measurements on rock samples from the investigated areas are performed.
Apart from the samples of rocks and sediments, we also perform measurements of thermal parameters on other material samples (for example: construction, insulating). Thermal conductivity - the needle probe measurement range 0.015-2.0 W/mK and surface probe range 0.04-6 W/mK. Volume heat capacity - measurement range 4.0 × 104-3,0×106 J/m3K.
Thermal characteristics measurement
