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Experiments in the Tournemire Underground Laboratory

The 3D-US Lab is active again in the Tournemire underground laboratory operated by the IRSN (Institut de Radioprotection et de Sûreté Nucléaire) in southern France, conducting seismic measurements to monitor the injection tests in the fault zone. In the tunnel of the underground laboratory, hydraulic stimulation experiments with gas and water are being conducted to generate fractures in intact rock or reactivate existing fractures in fractured rock. Tests are being carried out in two intervals of a horizontal borehole with lengths of 2 and 8 meters, respectively. These intervals enter different areas of a fault zone in clay/shale rock. The success of the stimulation is indicated by changes in hydraulic permeability in the intervals and the acoustic signals associated with fracture formation or opening, which are recorded in neighbouring boreholes. The injection is monitored through acoustic, seismic monitoring, fibre-optic measurements, and active seismic campaigns.

The hydraulic measurement system at the injection borehole (foreground) and the active seismic source, which is coupled to the tunnel wall in Tournemire. Photo by Kai Thißen.