Effect of Burial Depth on Deformation and Storage Capacity of Sandstone Reservoirs

The present study investigates the effect of consolidation (burial depth) on the deformation and fluid flow behaviour of sandstone and its possible effect on the storage capacity of sandstone reservoirs. Sandstones with different degrees of consolidation from a variety of burial depths have been studied through in-situ measurements in the field and further analysis of the samples. There is a correlation between deformation mechanism and consolidation of sandstone. Unconsolidated sandstones that deform at shallow burial depth show a weak cataclasis, while well-consolidated and cemented sandstones deform mainly by fracturing. The deformation mechanism will affect the fluid flow within the rocks. Permeability reduction from host rock to fault rocks is significant within consolidated sandstone. The slip surfaces show lower permeability, while fault lenses present higher permeability values when compared to other fault related rocks. This is due to the fact that deformation is localized within the slip surfaces, while fault lens partly includes remnants of undeformed host rock. The higher capillary pressures in some of the fault rocks may contribute to trapping of CO2 through capillary forces, although, low permeability and high capillary pressure usually hamper connectivity and fluid flow within the reservoirs.