Linking Millimeter-Scale Heterogeneity to Rapid CO2 Migration in the Otway International Test Centre for Geological Carbon Storage

Field observations at geological CO2 storage sites, including the Otway International Test Centre (OITC), report rapid plume migration, potentially driven by highly channelized flow pathways caused by small-scale heterogeneities. However, how small-scale heterogeneities govern upscaled flow behavior, particularly the role of fluid connectivity, remains unclear due to imaging resolution limitations. To address this, we combined steady-state core-flooding experiments with micro-CT imaging (10 μm resolution) to directly visualize CO2 distribution for a heterogeneous core from OITC. Strong flow channelization was observed, leading to low core-average CO2 saturations. CO2 connectivity increased at the expense of brine connectivity over a narrow saturation interval, leading to steep brine relative permeability curves. A simple reservoir model was used to demonstrate that our derived relative permeability functions produce faster lateral CO2 plume migration and improved pore-space utilization. This work provides a foundation for improving relative permeability parametrization in reservoir simulations, aiding safe and efficient CO2 storage design.