On the use of thermal response tests for deep geothermal exploration in urban areas: A case study made on the Greater Montréal (Canada)

Exploring deep geothermal resources can be challenging in dense urban environments and therefore a preliminary screening for suitable target areas using existing data from, for example, the geothermal heat pump industry can help de-risk projects at the early exploration phase. Thermal response tests (TRTs) with initial ground temperature measurements can be used to estimate terrestrial heat flux, a metric to indicate suitable areas for deep geothermal development. The greater the heat flux value, the greater the area suitability. This does not replace deep geothermal exploration drilling for a more accurate assessment of the ground temperature but can help target areas of interest and provide a source of unexploited data. This hypothesis was tested in a study aiming to improve knowledge on deep geothermal resources over the Greater Montréal Area (Canada). TRT datasets were analyzed at 22 locations to estimate the terrestrial heat flux. The results were then compared to heat flux estimates made with bottom-hole temperature data and equilibrium temperature profiles from the 6 deep wells available in the area. Both datasets show a certain degree of correlation. To support these findings, a 400 m deep geothermal exploration well was drilled to provide an accurate equilibrium temperature profile in a zone of interest. The data retrieved from this well validated the results and confirmed that, in this setting, TRT can be used as a de-risking tool for deep geothermal exploration.