Numerical modeling of hydro-mechanical processes during hydraulic testing of pre-existing fractures at the Grimsel Test Site, Switzerland
Josselin Ouf (Geo-engineering, RWTH Aachen University)
Kavan Khaledi (Fraunhofer IEG)
Philip J. Vardon (Geo-engineering)
Wen Luo (RWTH Aachen University, Geo-engineering)
Mohammadreza Jalali (RWTH Aachen University)
Florian Amann (Fraunhofer IEG, RWTH Aachen University)
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Abstract
This study presents a fully coupled hydro-mechanical framework for modeling hydraulic shearing in a mesoscale reservoir located at the Grimsel Test Site, Switzerland. The experiment was conducted on a ductile–brittle fault embedded in low-permeable granite. We observe that normal fracture opening increases flow channel recoverably, while fracture sliding locks asperities leading to a non-recoverable increase in flow. To couple these processes, we use a poro-elasto-plastic constitutive framework and employ a permeability function that depends on several parameters, such as dilation angle, in-situ stresses, residual aperture and maximum aperture. Our results capture the recorded pressure responses well, and indicate that the permeability changes by one order of magnitude during the experiment.
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