The effect of permeability heterogeneity on CO2 plume size at a potential CO2 sequestration site in the Mt. Simon sandstone

Flow modeling of CO2 sequestration projects must be able to confidently predict CO2 plume migration-which affects a sequestration project's Area of Review as well as its pore space access requirements-despite geologic uncertainties stemming from heterogeneity in the subsurface. We present our study of the effect of heterogeneity in porosity and permeability on the size of an injected CO2 plume in a potential C12 Energy sequestration site in the Midwest. Flow simulations were conducted using the CMG GEM multi-phase flow simulator. Porosity and permeability data were taken from regional well logs to construct the mean and variance of permeability values over the vertical extent of the target reservoir layer, the regionally extensive Mt. Simon sandstone. The extent of vertical heterogeneity as well as the extent of horizontal channeling were varied in a suite of simulations of CO2 injection into an anticline in order to test their effect on CO2 flow as well as simulation run-time. Within the suite of simulations, the CO2 plume size differed dramatically, by more than a factor of two, although in all cases the CO2 did not escape from the boundary of the anticline, validating that boundary as an appropriate sequestration site. Vertical heterogeneity was observed to be a stronger driver of CO2 plume size than the existence of high-porosity/permeability horizontal channels. These results shows that similar studies should be undertaken for sequestration sites in which there is uncertainty in the degree of porosity/permeability heterogeneity in the reservoir layer, as such heterogeneity could have a significant effect on the plume size, and therefore site requirements, of the CO2 sequestration project.