The Mandurah Terrace in the onshore Perth Basin was proposed as a suitable site for CO2 injection. Prior investigations in the area indicate that faults affect the target storage reservoir and shale barriers. Changes in the pore pressure and stress field induced by fluid injection could alter the containment integrity by either exceeding fault capillary resistance or by triggering slip on pre-existing faults. The capillary properties of faults have been assessed using the Shale Gouge Ratio predictive algorithm which can assess the maximum fluid column height trapped by a fault without leaking. Three different scenarios were investigated, representing different juxtaposition geometries. In the south of the area, potential spots for local up and across fault fluid migration are noted. The relationship between the modelled faults and the present-day stress field has been investigated to define critically stressed fault segments most at risk of reactivation resulting from pore-pressure build-up due to injection. The likelihood of fault reactivation is low in the current day stress field with pore pressures required equivalent to a CO2 column exceeding 1000m. Preliminary geomechanical modelling also shows no likelihood of fault reactivation and potential ground uplifts of less than two centimetres at the surface.


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