| Abstract |
Since pioneering exploration in the '70s and following hydrogeothermal evaluation in the '90s, the Ďurkov hydrogeothermal structure is considered amongst the most prospective geothermal water bodies in Slovakia. The geothermal resources were definitely proven in 1999 through the realisation of 3 geothermal wells, GTD-1 to GTD-3, quantifying 42 MWt for free-flow and 92 MWt for pumping strategy. The resource is geothermal water at up to 180 °C and moderate-high thermodynamic quality in the deepest parts of the system. Although numerous plans for production exist, there is no project online at the site yet. Reservoir characterization using a combination of geothermal techniques and geostatistical modelling tools have been used to produce a realistic 3D reservoir model consisting of the simulated convention indicators. Geostatistical simulations have become very popular in different areas of spatial modelling for spatial simulation of properties, geometries or heterogeneities. The geostatistical approach is supportive of the quantification and interpretation of possible convection formation, necessary to understand reservoir engineering and construction of reservoir prediction and response models. Turning band method of the spatial simulation was used to create multiple realisations of selected convection indicators within the reservoir body due to evident non-stationary behaviour in the vertical direction. Turning band simulations were conditioned by universal kriging using modelled directional variograms of the global trend residuals with respective drift functions for each studied convection indicator. The volumetric curves were derived from final numerical models and probable volumes above the indicator thresholds were calculated and visualised. Based on simulations carried out, the possibility of isolated convection cells has been identified in deeper parts of a system, not exposed to any bifurcation or a phase change. Limited heat and mass flux explain the observed overheating ratio distribution, implying weak breaks of generally diffuse, conduction-dominated geothermal profile in a reservoir body. |