Geometries of clay smears produced in a series of direct shear experiments were analyzed and related back to the monitored hydraulic response, the deformation conditions, the clay content and the strength contrast between the seal and reservoir rock. The sheared blocks were imaged by CT scanning that was interpreted to construct geomodels of the fault zones from which quantitative information was obtained. The distribution of smears varies according to the level of stress during the shearing and to the contrast in brittleness of layering. Brittle clay layers form more segmented seals while ductile soft clays form more diffuse smears.Fault drag and tapering of the smear is limited to the fault cut-offs contrasting the predictions of CSP model. Increased normal stress improved fault sealing by increasing fault zone width, which led to more clay involvement in the fault zone. The average clay proportion of the fault conforms to the prediction of the SGR model. However, the hydraulic seal performance doesn’t correlate to the SGR but the net clay volume in the fault zone.


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