Development of a thermal conductivity map of Stockholm

Abstract

New methods have been suggested to spatially extend in situ thermal response test (TRT) assessments based on geostatistical analysis. These methods can be used to determine a stochastic distribution of the subsurface thermal conductivity beyond the test borehole on larger scales by interpolating the data with geostatistics, including sequential Gaussian simulations (SGS) used in the present study. This paper presents a simulated thermal conductivity map for Greater Stockholm in Sweden, based on the SGS method with input data from in situ measurements (TRT and DTRT). The geology of Stockholm is used as a background raster in the simulations, based on bedrock maps from the Geological Survey of Sweden (SGU). The resulting maps are compared with a point map of punctual ground thermal conductivity of Greater Stockholm earlier derived by SGU, compiled from laboratory data that were obtained by thermal conductivity scanning and modal analysis of surface rock specimens of the area.

A workflow for bedrock thermal conductivity map to help designing geothermal heat pump systems in the St. Lawrence Lowlands, Québec, Canada

“…The preceding two approaches are limited and hardly illustrate the spatial variation of thermal conductivity. Attempts were previously made to interpolate thermal conductivity with geostatistical simulations, but to a smaller area and with fewer data Malmberg et al 2018).…”

“…Oppositely, the bulk thermal conductivity evaluated in the field can be affected by groundwater flow increasing the apparent conductive heat transfer capacity (Bozdağ et al 2008;Fujii et al A c c e p t e d M a n u s c r i p t 2009; Lehr and Sass 2014), and making difficult the comparison of thermal conductivity evaluated on samples and in the field (Vieira et al 2017). Nevertheless, researchers have tried to map the thermal conductivity distribution of the subsurface based on laboratory analysis of rock samples (Di Sipio et al 2014;Raymond, Sirois, et al 2017), interpretation of geophysical signals (Santilano et al 2015) or compilation of TRTs Malmberg et al 2018), but the three approaches have never been combined in a comprehensive mapping exercise. How to prepare the map and adequately illustrate the results can be complex while potential use needs to be discussed.…”

“…The choices are to present a map of thermal conductivity with measurements show by distinct points (Raymond, Sirois, et al 2017), to assign a range of thermal conductivity to the different geological units (Di Sipio et al 2014) or to interpolate thermal conductivity values based on the field observations (Teza et al 2015;Malmberg et al 2018) in two or three-dimensional space (Santilano et al 2015).…”

Calibration and Uncertainty Quantification for Single-Ended Raman-Based Distributed Temperature Sensing: Case Study in a 800 m Deep Coaxial Borehole Heat Exchanger

“…DTS offers interesting perspectives in BHE and GSHP applications and has gained interest in recent years, be it for monitoring, field tests (DTRTs), validation of heat transfer models, estimation of the geothermal gradient, evaluation of undisturbed temperature or thermal conductivity maps [19,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]47].…”

“…Besides their application to DTRTs, fiber optic cables have also been used to monitor operation of Borehole and Aquifer Thermal Energy Storages (BTES and ATES) [29][30][31][32][33]. Additionally, DTS data have indirectly been capitalized on to create thermal conductivity maps [34] or to measure the undisturbed temperature profile and evaluate its effect on design procedures [19,[35][36][37].…”