Shale fault zone structure and stress dependent anisotropic permeability and seismic velocity properties (Opalinus Clay, Switzerland)

Given shale's potential to serve as both a caprock for geological carbon sequestration and the host nuclear waste disposal, this study focuses on structural characterization around 1.5–3 m thick fault within Opalinus Clay rock petrophysical of core. Seven boreholes were drilled at Mont Terri Rock laboratory in late 2018 constrain orientation so-called ‘Main Fault’ several fracture families core using image logs. Contrary typical models, matrix permeability seismic velocity measurements show similarities Main Fault. In clay-rich samples, performed varying confining pressures indicate p-wave velocities range from 2.60 2.95 km/s perpendicular foliation 3.38–3.58 parallel near in-situ pressures, which increase with similar anisotropy higher (200 MPa). Since zone is very low (10?19–10?21 m2) flow expected prevail along fractures, where critical stress analysis suggests that hydraulically conductive fractures are actually conjugate Fault trend.