Mathematical Modelling of a Fault Slip Induced by Water Injection

Abstract of the technical presentation presented at:
ComGeo IV Symposium, Assisi, Italy
May 2–4, 2018

Preapred by:
T.S. Nguyen
Canadian Nuclear Safety Commission

J. Rutqvist, Y. Gugliemi
Lawrence Berkeley National Laboratory

Abstract:

Faults located in the vicinity of deep geological repositories for radioactive waste may constitute preferential pathways for radionuclides potentially released from the waste. An increase in porewater pressure due to various processes, such as heat generated from the waste, might lead to fault slip, increase in permeability, and the generation of seismic events.

To better understand the above processes, CNSC staff developed a hydromechanical model for fault slip due to pressurization and calibrated it to an injection test at the Mont Terri Underground Research Laboratory in Switzerland. The modelling results compared well with the experimental data. They indicate that fault displacement is low, until a threshold injection pressure is exceeded. At that stage, the fault fails by shear, resulting in slip, dilation and increases in permeability by a few orders of magnitude, which lead to a substantial increase in the flow rate.

This research provides a better understanding of the processes of fault slip due to pressurization and provides a modelling tool to independently verify the potential reactivation of faults that might exist in the vicinity of the proposed repository.

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