Effect of upscaling heterogeneous domain on CO2 trapping mechanisms

AbstractWe study the effect of upscaling (based on single-phase properties) on buoyancy-driven vertical flow of CO2. The mechanism of CO2 immobilization of interest in this situation is local capillary trapping, resulting from competition between buoyancy and capillarity in fine-scale heterogeneity. Different degrees of coarsening are considered and based on average gas saturation and mass of CO2 in storage aquifer, these upscaling methods are found to underestimate the extent of local capillary trapping. Then, we upscale the simulation of a leak at the top seal of the aquifer after buoyancy-driven flow has stabilized, again with the single phase upscaling method. The predicted amount of escaped gas is larger for the upscaled simulations, and as such, single-phase upscaling appears to underestimate the security of CO2 sequestration in heterogeneous formations. Using a corrected value of residual gas saturation in coarse-grid simulations is shown to give an acceptable result for the mass percent of escaped CO2