Field to laboratory assessment of subsurface thermal conductivity: a geothermal case study in SloveniaBorko, Karlo (Avtor) Chapman, Fiona (Avtor) Raymond, Jasmin (Avtor) Ryżyński, Grzegorz (Avtor) Rman, Nina (Avtor) distributed temperature sensingthermal response testgroundwater flowthermal conductivityKrško BasinReliable characterization of subsurface thermal properties is essential for designing efficient shallow geothermal systems and assessing the potential of Ground Source Heat Pump and Underground Thermal Energy Storage systems. The objective of this study is to evaluate the reliability of thermal conductivity estimations from different approaches by comparing three in situ methods - conventional Thermal Response Test (TRT), Enhanced Thermal Response Test (ETRT), and Distributed Thermal Response Test (DTRT) - against each other and laboratory measurements on core samples. The tests were conducted in a 100 m deep borehole heat exchanger in the Krško Basin, Slovenia. Laboratory measurements employed needle probes and an optical Thermal Conductivity Scanner (TCS), while in situ testing utilized fibre-optic Distributed Temperature Sensing (DTS) for high-resolution temperature profiling. Results show that needle probe measurements consistently underestimate thermal conductivity relative to TCS- and DTS-based methods, by 22% to 48%, mainly due to sample desaturation and limited probe contact. DTS-based ETRT revealed vertical variations and groundwater-flow-influenced zones. Cemented fibre-optic cables introduced greater uncertainty and yielded 44% higher conductivities than the ETRT with the composite cable. TCS yielded thermal conductivities most consistent with in situ measurements while providing a favourable balance of time, cost, and reliability of results.20262026-07-08 09:40:49Neznano30882UDK: 550.3ISSN pri članku: 0375-6505DOI: 10.1016/j.geothermics.2026.103747COBISS_ID: 283962627sl