COMPARING GEOCELLULAR MODELS OF FLUVIAL ARCHITECTURE IN SIMULATIONS OF RESIDUAL CO2 TRAPPING

Understanding subsurface flow dynamics, including carbon dioxide (CO₂) plume migration and trapping, requires understanding a diverse set of geologic properties of the reservoir, from the pore scale to the basin scale. The uncertainty about site-specific geology stems from the inherent variation in rock types, depositional environments, and reservoir properties. Methodologies and tools are needed to represent reservoir properties from the pore to field scale and to take into consideration small-scale features that could significantly affect the storage integrity. Traditional geostatistical methods for creating digital (geocellular) models of reservoir architecture tend to focus at properties at a single scale and upscale features that are too small to be captured. A new geometric and depositional based approach has been used which creates geocellular models that represent multi-scaled and hierarchical fluvial architecture with new rigor within simulations of residual CO₂ trapping. The results show that coarser- and finer-grained sets of cross strata have a significant influence on entry pressure pinning and snap-off trapping. Traditional geostatistical approaches are being challenged to reproduce these results. Though traditional geostatistical methods cannot yield geocellular models of cross set architecture with the same rigor, the proportions of the cross set types are correct, and the connectivity of the coarser-grained cross sets is reasonably well represented, and thus our hypothesis is that that simulations with traditionally created geocellular models for the architecture will approximate the general processes of entry pressure pinning and snap off trapping reasonably well. Results to date are supporting this hypothesis.