Single‐hole GPR reflection imaging of solute transport in a granitic aquifer

Caroline Dorn (1) , Niklas Linde (1) , Tanguy Le Borgne (2) , Ludovic Baron (1) , Olivier Bour (3)

1 Institute of Geophysics
2 Transferts d'eau et de matière dans les milieux hétérogènes complexes
3 GR - Géosciences Rennes

dentifying transport pathways in fractured rock is extremely challenging as flow is often organized in a few fractures that occupy a very small portion of the rock volume. We demonstrate that saline tracer experiments combined with single‐hole ground penetrating radar (GPR) reflection imaging can be used to monitor saline tracer movement within mm‐aperture fractures. A dipole tracer test was performed in a granitic aquifer by injecting a saline solution in a known fracture, while repeatedly acquiring single‐hole GPR sections in the pumping borehole located 6 m away. The final depth‐migrated difference sections make it possible to identify consistent temporal changes over a 30 m depth interval at locations corresponding to fractures previously imaged in GPR sections acquired under natural flow and tracer‐free conditions. The experiment allows determining the dominant flow paths of the injected tracer and the velocity (0.4-0.7 m/min) of the tracer front.

Domaines: Sciences de la Terre

Caroline Dorn, Niklas Linde, Tanguy Le Borgne, Ludovic Baron, Olivier Bour. Single‐hole GPR reflection imaging of solute transport in a granitic aquifer. Geophysical Research Letters, 2011, 38, pp.L08401. ⟨10.1029/2011GL047152⟩. ⟨insu-00611672⟩