Theoretical analysis of how pressure buildup and CO2 migration can both constrain storage capacity in deep saline aquifers

Abstract

Estimating the carbon dioxide (CO2) storage capacity of deep saline aquifers is important for identifying those most suitable for sequestration, and for planning the future development of CO2 storage projects. Currently, capacity estimates are highly uncertain due in part to uncertainty in the dominant constraint on capacity: both the pressure buildup from injection and the space available to trap CO2 have been identified as constraints, but have not been rigorously compared to determine the conditions under which each is more limiting. In this study, we evaluate their relative importance in an idealized aquifer using simple, but dynamic models of how pressure rises during injection and how CO2 becomes trapped in the pore space. We show that there exists a crossover injection duration, Tc, below which pressure constraints dominate, but above which the CO2 migration becomes the more limiting constraint. We illustrate this behavior by applying the models to the Fox Hills Sandstone.