Impact of Faults on the Mechanical and Petrophysical Properties of Sandstone Reservoirs - An Implication for CO2 Storage

To assess reliable candidate reservoirs/aquifers for CO2 storage, enhanced understanding of the structure and the mechanical and petrophysical properties of strain localization zones in comparison to the surrounding undeformed rock is essential (Torabi 2007). To understand the possible effect of deformation structures on CO2 storage, a fieldwork was performed in the Navajo and Entrada sandstones in southeastern Utah to investigate the elastic and petrophysical properties of a fault core and damage zone. Deformation structures, air permeability and rock hardness have been logged along scan-lines perpendicular to the fault. In the foot-wall fractures are observed just within distance of three meters from the fault, but deformation bands are spread to about hundreds of meters. In the hangingwall fractures are observed in a distance of more than seventy meters, while deformation band have been concentrated within forty meters from the fault. Our preliminary results show a strong correlation between deformation structures intensity and distance from the fault, but weak correlation between Schmidt Hammer rebound and mini-perm values versus deformation pattern. The spread in the measured data might be related to variation in internal layering in the sand dunes, the orientation and weathering of the surface used for testing or other structural effects.