Impact of layered heterogeneity on thermal response test interpretation performed on a standing column well operated without bleed

Abstract

This paper presents a comprehensive field testing programme conducted in Mirabel, Quebec, that aims to demonstrate the thermal effectiveness of a standing column well installed in a pervious layered aquifer. The first-order approximation of the infinite line source model of a thermal response test in the absence of bleed suggested that heat conduction alone could not explain the thermal response obtained at a test standing column well. To further investigate this hypothesis, a numerical model that couples the state equations for heat transfer and groundwater flow is developed and exploited to assess the contribution of advective heat transfer. A comparative study involving four cases is presented to analyse the effect of the aquifer heterogeneity in terms of hydraulic and thermal conductivity on the thermal response of test well. The results show that in contrast to the work currently available in the literature, the advective heat transfer mechanism can have a large contribution to the thermal response in specific geological environment, even without bleed. In this particular case, advection is approximately 265 times more important than conduction. This shows that layered heterogeneity and mean hydraulic conductivity can significantly impact the thermal response of a standing column well operating without bleed. The results presented in this study show that hydrogeological conditions should be given greater consideration by incorporating local hydrogeological features to replicate the experimental measurements of the thermal response test.