Présentations Colloques

Oral Presentation
8.01
Session 8.01: Fiber-Optic Distributed Temperature Sensing as an innovative method in hydrogeology and geothermal energy
Munn Jonathan
Multi-corehole thermal tracer tests using DTS to identify flow pathways in a fractured dolostone aquifer
Modern fibre optic distributed temperature sensors (DTS) with improved spatial and temperature resolutions have allowed for the development of novel borehole applications in many different geoscience fields. We present recent advances in the application of DTS for identifying hydraulically significant fractures and karst features within a regionally important fractured dolostone aquifer. Several thermal tracer tests were conducted at the Bedrock Aquifer Research Station on the University of Guelph campus in Guelph, Ontario, Canada. The site was designed to study the Silurian dolostone aquifer used by the City of Guelph (population 125,000) for its municipal water supply and includes a cluster of 9 bedrock coreholes (6 vertical and 3 inclined), closely spaced from 7.5 to 70 m apart in a 75 x 75 m area. A network of custom designed composite fibre optic cable was installed in 8 of the coreholes and spliced together on the surface to form a continuous loop of approximately 1750 m. The coreholes were then sealed with flexible borehole liners to prevent vertical flow and hydraulic cross-connection between hydrogeologic units. Two different thermal tracer tests were conducted to assess the hydraulic properties of the aquifer sequence including- (1) multi-corehole active-DTS tests to identify and quantify ambient groundwater flow and flow features+ and (2) forced gradient hot water injections to identify hydraulic connections between coreholes. Results are repeatable and identify several discrete hydraulically active flow zones throughout the aquifer sequence and provide critical information as to which porosity features are laterally continuous and hydraulically significant. Thermal tracer tests using the multi-corehole fibre optic network and high performance DTS delivers an efficient way to test a large number of boreholes and provides insights in three dimensions often not achieved through single corehole tests.
Canada