Modelling CO2 migration in aquifers; considering 3D seismic property data and the effect of site-typical depositional heterogeneities

Geological sequestration is one proposed measure for greenhouse gas mitigation; and deep, saline aquifers are considered to hold large storage potentials for CO2. The Johansen Formation has been suggested by Norwegian authorities as a potential reservoir candidate due to its relative proximity to land and point sources for CO2. Reservoir evaluations must consider the given premise of zero interference with ongoing gas production in the Troll Field, providing geographical constraints. Recent data contributions; new 3D seismic data, attribute analyses, and revision of the depositional model form the basis of this modelling study. Porosity distributions were generated from quantified relations with acoustic impedance. The reservoir quality varies according to sedimentary facies, and differentiated relative permeability curves were assigned accordingly. Effects of directional anisotropy and site-typical geological heterogeneities were considered through scenario-modelling. The potential for dissolution and residual trapping of CO2 varies according to migration paths; and was estimated to 50-80% of injected CO2 after 150 years. Immobilisation was more efficient with increased sweep through reservoir zones with high irreducible gas fractions, and in scenarios where plume separation occurred. The main determinant, however, for improving trapping efficiency is the well location and injection scheme.