Assessing Seal Rock Integrity for CO2 Geological Storage Purposes
Résumé
Prior to any CO2 geological storage project, an assessment is needed to confirm the ability of the formations overlying the storage reservoir to act as a seal with respect to the underlying pressurized CO2. The chapter first presents the "standard" procedure for determining gas breakthrough pressures in water-saturated tight rocks and the ensuing gas effective permeability. Then, it reviews the interfacial properties, namely the interfacial tension (IFT) between brine and CO2-rich fluids and the wetting (contact) angle. Further, it presents the method for inferring a lower bound on the CO2 breakthrough pressure of depleted hydrocarbon reservoirs. Finally, the chapter discusses the gas breakthrough experiments available in the literature. It turns out that the mechanism of capillary invasion in a rigid porous medium does not account for many of the observed features, which witness some quasi-permanent deformations of the porous structure.