Utsira: storage capacity estimate
The Utsira Formation is a large saline aquifer covering some 26.000 square kilometers off the western coast of Norway. It consists of a more than hundred meter thick column of high-permeability sand located at depths ranging from 300-1400 m below sea level. It is overlaid by a layer of thick, low-permeability shale, which has proved an excellent top seal for the CO2 storage operations that have taken place at the Sleipner site since 1996. As an open aquifer with high permeability (> 1000 mD), the CO2 injected into Utsira can easy migrate and, given enough time, exit mapped aquifer boundaries. The amount of CO2 storable in the formation over time thus depends not only on the total available pore space of of the aquifer, but also on the size and exploitability of its various trapping mechanisms.