Constraining fluid migration in low density data area: successful use of integrated modelling in the Southern Perth Basin

Abstract

Constraining trap integrity or CO2 containment potential in areas with low density of data is challenging. We show here how the integration of hard data and modelling improved our understanding of the subsurface tectonic and stratigraphic architecture and ensured an initial definition of hydraulic behaviour of faults and fractures in the onshore Southern Perth Basin. A first-order geomodel was built based on interpretation of low-density 2D-seismic data and constrained by well, geophysical, and outcrop data. Forward stratigraphic models were deformed and implemented in the geomodel to predict the distribution of the phyllosilicate content. Membrane fault-seal prediction was performed based on the Shale Gouge Ratio algorithm to estimate the lateral migration potential. Characterisation of the stress state of fault planes was used to define the likelihood of reactivation and to predict vertical migration and caprock bypass. The elastic dislocation method was used to model the density and mode of failure of subsidiary sub-seismic faults that can impact on the caprock integrity. This was also used to constrain and validate the structural model. The integrated modelling significantly decreased uncertainties on the subsurface architecture and ensured the first-order definition of the CO2 migration and containment potential for the Wonnerup reservoir in the SW Hub. The maximum CO2 column heights supported by faults and potential leak points were estimated and migration scenarios and risks were defined.