## 5 Discussion
### Application of Our Results  
Our experiments provide detailed information on the mineralogy, porosity, and permeability of the analyzed sandstone core fragments. However, upscaling these resultsfor reservoir modelling purposes remains a challenge because only three core fragments have been analyzed. To generate actual distributions of hydraulic properties of Ujfalu Fm. sandstones, more experiments like those described will be required on core fragments from other sandstone intervals and also from different wells. Our experiments nonetheless indicate how the understanding of these properties could be improved by future work. Another difficulty limiting the application of our work in future reservoir modelling or feasibility studies is that the properties that we have measured cannot be simply related to gamma ray log signals, such as those depicted in Figure 2. This is because the core fragments from each of the cored intervals were stored in bags, without keeping track of the original stratigraphic order. Furthermore, for core interval 1 of well Kond-1, no GR log is available at all (Figure 2). An analysis, using the methods in our present study, should be carried out on a suite of core samples that are accurately located within a well for which a GR log is also available. It should ultimately be feasible to convert the general association, evident in Figure 2, between low GR readings and favourable reservoir properties, into a quantitative calibration tool where GR readings can act as a quantitative proxy for reservoir porosity and permeability. In principle, exploration techniques developed for the petroleum industry are transferable to the geothermal sector. However, the lower value of heat compared with hydrocarbons precludes use of expensive exploration methods (e.g., [55]). X-CT analysis followed by numerical flow experiments is not yet recognized as a standard approach to determination of reservoir hydraulic properties [56; 57], being considered an emerging technology (e.g., [37]), facilitated by the growing availability of both X-CT scanners in universities and other laboratories [58] and high memory computers, capable of the necessary processing. Although this approach has already been applied to the analysis of sandstone samples (e.g., [36; 37]), we are not aware of its previous use in the geothermal sector. Many geothermal projects (e.g., [59]) indeed depend on existing reservoir permeability data from studies of core on behalf of the petroleum sector; where new data are needed, the options have hitherto been limited. In one recent case study [60], where (as at Mezobereny) existing core was scarce, only a few laboratory measurements of permeability were possible; much more information could have been obtained using X-CT. In another [cost of developing geothermal energy projects, thus facilitating decarbonization of global energy supply. Conceptualization, H.M. and R.W. ; methodology, J.M. and H.M.; software, J.M. ; validation, C.J.L.W. and R.W. ; formal analysis and investigation, C.C., S.M.W., A.W. and D.W.; resources, J.M. ; data curation, C.J.L.W., C.C. and J.M. ; writing--original draft preparation, C.J.L.W., C.C. and J.M. ; writing--review and editing, R.W. ; visualization, C.J.L.W., J.M. and R.W. ; supervision, H.M., N.M.B. and R.W. ; project administration, N.M.B. and R.W. ; funding acquisition, R.W. All authors have read and agreed to the published version of the manuscript. This research and the APC were funded by European Commission Horizon 2020 research and innovation programme under grant agreement No. 691728 (DESTRESS). Existing data used in this study are available from the sources stated in the text. Our X-CT images and porosity and permeability estimates from X-CT analysis followed by numerical flow experiments are available from the University of Glasgow online repository at doi:10.5525/gla.researchdata.1140. The remaining data generated in this study are reported in the body of this article.