engleski

Utilization of Vintage Hydrocarbon Exploration Data in Geothermal Research: the Case Study of Zagreb Geothermal Field (Croatia)

The interest of scientific and stakeholder communities on the exploration of deep carbonate geothermal resources is rapidly increasing due to their widespread occurrence and the possibility of local scale uses for hydrothermal heat and power generation. Within the framework of the HotLime project, funded by Horizon2020 GeoERA program, the pilot area of Zagreb (Croatia) was chosen for detailed geological and thermal reconstructions of the thermal reservoir hosted in up to 400 m thick Miocene and Triassic carbonate rocks at a depth of approximately 1 km. Despite promising temperature (up to 82 °C) and significant number of wells drilled during 1980s (27 wells on 54 km2), geothermal exploration of this area did not continue in the following decades. Notwithstanding the number of wells, some of which are fully equipped for production and reinjection, and the location of the wells in the national capital with numerous possible users, only one doublet system is in operation. Stratigraphic logs of the wells, borehole logging data and 30 seismic sections were collected, digitalized and arranged in a database including chemical analyses of the waters, porosity and permeability measurements and bottom hole temperatures. These data allow obtaining a comprehensive picture of the geological, hydro-geochemical and thermal settings of the reservoir. In particular, seismic and borehole data are used to perform a 3D geological reconstruction of the subsurface consisting of 5 layers and highlighting the principal fault systems. 3D geological model will be used to numerically reconstruct the subsurface thermal regime. Coupled fluid flow and heat transport numerical simulations will be performed using data on the hydrodynamic and thermal properties of the formations. First, the simulations will be run at the steady state to assess the contribution of conductive processes to the thermal regime. Further transient simulations will be performed to evaluate the impact of the most likely convective processes occurring in the fractured carbonate reservoir and contributing to the local temperature increase. The obtained results of temperature model will be compared and calibrated with available bottom hole temperatures and thermal logs. Contemporary approach to the research of the geothermal resource will serve to demonstrate the resource potential to the decision-makers and decrease the risks for future development.

geothermal field ; vintage data ; resource classification ; Zagreb ; Croatia

nije evidentirano