Modelling Thermal Response Tests for Deep Coaxial Borehole Heat Exchangers

Brown, C. S. , Kolo, I. , Banks, D. , Doran, H. R. and Falcone, G. (2023) Modelling Thermal Response Tests for Deep Coaxial Borehole Heat Exchangers. In: World Geothermal Congress 2023, Beijing, China, 4-6 Sept 2023,

Abstract

Deep borehole heat exchangers (DBHEs) have been proposed as a method for repurposing petroleum and geothermal exploration wells for further use, yet, typically the in-situ rock properties may be poorly defined or not recorded. Therefore, thermal response tests (TRTs) can provide estimates of the subsurface radial thermal conductivity and borehole thermal resistance. This data can then be utilised to model the resource, determining the thermal capacity and potential. In this study, we focus on the capability of several modelling tools (T2Well-EOS1/TOUGH2, MATLAB and OpenGeoSys) to simulate thermal response tests and their ability to estimate subsurface parameters. The Newcastle Science Central Deep Geothermal Borehole was selected as a case study as plans are in place to carry out a TRT as a DBHE. The borehole was initially drilled as a geothermal exploration well targeting the Mississippian Fell Sandstone Formation; however, it proved to have low hydraulic conductivity and subsequently would not be suitable for development using conventional methods. The borehole was drilled to a total depth of 1821 m, but we regard only the top 922 m as being available for testing due to a 4.5 inch liner inserted below this depth meaning it is hydraulically unattractive to repurpose the well at depths exceeding the casing. In this study we are, therefore, able to compare data and model results from the case study to develop an understanding of subsurface characteristics. Model results show that the accuracy of thermal conductivity and thermal resistance estimates improve in comparison to model inputs with increased TRT time. The analytical solution estimate of thermal conductivity converges more quickly towards the true input value, compared to numerical modelling methods.

• Item Type: Conference Proceedings
• Additional Information: This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) grant EP/T022825/1 and EP/T023112/1. The funding sources are for the NetZero GeoRDIE (Net Zero Geothermal Research for District Infrastructure Engineering) and INTEGRATE (Integrating seasoNal Thermal storagE with multiple enerGy souRces to decArobonise Thermal Energy) projects, respectively.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Banks, Mr David and Kolo, Dr Isa and Brown, Dr Christopher and Falcone, Professor Gioia and Doran, Hannah
• Authors: Brown, C. S., Kolo, I., Banks, D., Doran, H. R., and Falcone, G.
• College/School: College of Science and Engineering; College of Science and Engineering > School of Engineering > Systems Power and Energy
• Copyright Holders: Copyright © World Geothermal Congress 2023
• First Published: First published in Proceedings of World Geothermal Conference 2023
• Publisher Policy: Reproduced in accordance with the publisher copyright policy

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