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Expérience géothermique peu profonde dans un aquifère sableux suivie par tomographie de résistivité électrique

By Thomas Hermans, Alexander Vandenbohede, Luc Lebbe and Frédéric Nguyen

Abstract

Groundwater resources are increasingly used around the world for geothermal exploitation systems. To monitor such systems and to estimate their governing parameters, we rely mainly on borehole observations of the temperature field at a few locations. Bulk electrical resistivity variations can bring important information on temperature changes in aquifers. In this paper, we demonstrate the ability of surface electrical resistivity tomography to monitor spatially temperature variations in a sandy aquifer during a thermal injection test. Heated water (48°C) was injected for 70 hours at the rate of 87 l/h in a 10.5°C aquifer. Temperature changes derived from time-lapse electrical images are in agreement with laboratory water electrical conductivity-temperature measurements. In parallel, a coupled hydrogeological saturated flow and heat transport model was calibrated on geophysical data for the conceptual model, and on hydrogeological and temperature data for the parameters. The resistivity images showed an upper flow of heated water along the well above the injection screens and lead to a new conceptualization of the hydrogeological source term. The comparison between the temperature models derived from resistivity images and from the simulations is satisfactory. Quantitatively, resistivity changes allowed estimating temperature changes within the aquifer, and qualitatively, the heated plume evolution was successfully monitored. This work demonstrates the ability of electrical resistivity tomography to study heat and storage experiments in shallow aquifers. These results could potentially lead to a number of practical applications, such as the monitoring or the design of shallow geothermal systems.Peer reviewe

Topics: electric resistivity tomography, monitoring, thermal properties, time-lapse, Engineering, computing & technology :: Geological, petroleum & mining engineering, Ingénierie, informatique & technologie :: Géologie, ingénierie du pétrole & des mines
Year: 2012
OAI identifier: oai:orbi.ulg.ac.be:2268/103103
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