Evaluation of ground thermal conductivity from drilling data

• Published in: International journal of rock mechanics and mining sciences (Oxford, England : 1997) Vol. 41; no. Suppl 1; pp. 241 - 247
• Main Authors: Tuomas, G, Gustafsson, A-M
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2004
• Subjects: Borehole; Conductivity; Drilling; Energy; Ground; Thermal response test; Urban Water Engineering; VA-teknik; Vattenteknik; Water Resources Engineering
• ISSN: 1365-1609; 1873-4545; 1873-4545
• DOI: 10.1016/j.ijrmms.2004.03.048

In this paper a new method for evaluating ground thermal conductivity is suggested. The principle is based on ordinary drilling where energy is injected into the borehole in the form of pressurised fluid, mechanical torque, and mechanical feed force, which all dissipate into heat. Part of the heat leaves the borehole with the fluid while the rest is mainly transferred into the formation. By determining the energy flows, ground thermal conductivity can be estimated. This new measurement method would have many advantages. Ground conductivity values would be continuously estimated along the borehole, meaning that values are obtained through the formation. This quality could, for example, be used during production drilling in a mine to instantly detect lithological boundaries, resulting in increased ore extraction efficiency. Energy storage systems could be dynamically designed since the system capacity could be recognized and verified during drilling. Presented simulation results, where realistic drilling parameters were used, show that the method has the potential to be practically applied.