Nuclear waste storage

Frictional properties of Opalinus Clay for nuclear waste storage in Mont Terri

In this project, we will focus on the effect of pore fluid pressure and micro-structural texture on the frictional properties of Opalinus Clay. This formation is the host rock for a high-level radioactive waste repository in Switzerland. Indeed, with a hydraulic conductivity of 2.10-13 m/s, the rock is practically impermeable. The objective of this project is to provide a better understanding of the various couplings between hydraulic and mechanical interactions in a shale reservoir. In particular, this project provides a detailed study of how the friction properties control the transport properties of reactivated fractures in Opalinus clay. Most previous studies do not address some complex phenomenon accompanying frictional slip, such as dilatancy [e.g., Marone and Kilgore, 1993; Samuelson et al., 2009], which can, in return, produce different frictional responses.  However, shear induced dilatancy of a fluid saturated fault is critical for reservoir safety.  Here, we will experimentally study the evolution of both the fluid transport properties (porosity, and permeability) and friction properties during slip evolution at pressures up to 50 MPa and at ambient temperature. These data will provide new constraints on the evolution of permeability during the creation and use of a nuclear waste repository.

This study will also provide the opportunity to correlate specific fault zone structures with fluid flow and mechanical properties, in particular the non-linear relationship between hydraulic aperture change and mechanical fracture opening. For the first time, fault zone structures observed in the Mont Terri laboratory could be related to seismic behavior. This project would also help interpreting the FS experiments at the Mont Terri laboratory.
Joint study
Prof. Marie Violay Prof. Felipe Orellana (University of Chile)