oa The Effect of Top-Surface Structure Upon CO2 Storage Capacity in Open Aquifers

We considered the effect of top-surface structure and heterogeneity upon the storage capacity and efficiency of open aquifers. In particular structure that in national-scale capacity estimation may be omitted from dynamic models. For this purpose the storage capacity of a section of the North Sea Forties sandstone member is considered under a set of constraints for safe storage. Capacities of this section are considered with and without top-surface structure for a variety of average reservoir dip and permeability combinations. It is observed that top-surface structure introduces both structural closures and regions of high dip. The effects of these regions compete to either increase or decrease storage efficiency respectively. In this work we observe that the balance of these competing effects depends upon the average permeability and dip of the models under consideration. In higher permeability and dip cases where mobile CO2 migrates faster, when top-surface structure was introduced the dominant influence came from structural closures increasing capacity. However, in cases with lower migration velocities, when topsurface structure was introduced the dominant influence came from the effect of new high dip regions reducing storage capacity. This is explained by the high amount of slow-moving but mobile CO2 stored within smooth models.