DBPapers
DOI: 10.5593/sgem2017/42/S17.034

EVALUATION OF THE THERMAL CONDUCTIVITY OF SANDY, CLAYEY AND DOLOMITE CONTAINING LAYERS OF GEOLOGICAL FORMATION

Z. Palaitis
Tuesday 12 September 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-07-2 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 42, 265-276 pp, DOI: 10.5593/sgem2017/42/S17.034

ABSTRACT

The thermal conductivity of a geological structure is a paramount parameter in performing calculations for the proper design and installation of underground heat energy extraction or storage systems. Complex geological investigation must be performed to evaluate the thermal conductivity of a geological structure. It is a process that demands time and money.

An assessment of the mutual influence between the thermal conductivity of the borehole heat exchanger and the geological structure allows us to predict the thermal conductivity faster and cheaper than performing a complex geological investigation. Seventeen test borehole heat exchangers (BHE) were installed during the research. A determination of the thermal conductivity of the geological structure was performed by the Thermal Response Test (TRT) using data collected in-situ from a BHE. Geological conditions were interpreted from the gathered soil samples and the geophysical investigation data collected in the borehole.

The thermal conductivity of the separate geological layers with different lithological compositions is calculated using the weight method. The generalized thermal conductivity values of Quaternary sandy layers is 2,35 W/m*K, clayey sediments - 1,57 W/m*K, Cretaceous and Jurassic clayey rocks buried from the 80m to 110m depth is 2,27 W/m*K and 2,06 W/m*K accordingly, Devonian dolomite - 2,86 W/m*K.

The classified thermal conductivity values for separate geological bedrocks allow us to predict the thermal conductivity for the whole geological structure from the geological data alone. In the majority of cases the calculated and evaluated values are accurate within 5%.

Keywords: thermal conductivity, geological formation, geological layers conductivity.