| The design of a geothermal system depends on the thermal properties of the subsurface. These properties are the thermal conductivity, thermal diffusivity and the heat capacity. These properties can vary for different geographic locations and are therefore calculated from a thermal response test. The conventional test method is however very expensive because it requires the mobilization of heavy equipment. Handling equipment in the field is also laborious. Water tanks and piping must be handled carefully to avoid leaks. The piping should be well insulated to minimize heat transfer to the external environment. A new alternative testing method that are easier to run, to lead the thermal response tests (TRT) in situ, using a heating cables inserted vertically into the wells to measure the fluid temperature at different depths. To evaluate the thermal conductivity of the subsurface the line source model is used in combination with the principle of superposition of the curves during the thermal recovery period. The analysis of the thermal response test is also performed with a three-dimensional numerical model that considers the heterogeneous state of the basement so that the fluctuations of the heat injection and the thickness of the pipe. |
