The Application of Upscaling to a CO2 Injection Project

In reservoir simulation upscaling is used to obtain much faster execution times. Upscaling for CO2 storage has additional challenges such as accounting for CO2 dissolution into the surrounding formation water. Here we describe a study of upscaling applied to a 15,000 t injection at the CO2CRC Otway Research Facility. For this study 11 different coarse reservoir model geometries were created with different cell sizes. For each of the 11 geometries, 5 different methods of absolute permeability upscaling were implemented before fluid flow simulations at fine and coarse scales were performed for both single phase tracer and pure CO2 injection. The simulation computing time varied from a couple of minutes to 4.5 h for the coarse models, compared to 48 h for the fine-scale model. The results were compared for volumetric analysis, plume dimensions, pressure observed and effects on boundary conditions. In our simulation model, the different coarse model results show reliable and consistent estimation of the plume behaviour and pressure distribution. We found that flow-based permeability upscaling combined with a 0.85 factor on the solubility parameter on a 15x15x1 m grid give a good result with a substantial improvement in execution time. This study indicates the limits of coarse-scale models for CO2 storage simulations, and illustrates how these limits can be largely overcome by a careful application of absolute permeability upscaling techniques.