Long-term Behavior of CO2 Stored on a Large Scale in the Utsira Formation, the North Sea, Norwegian Continental Shelf

Abstract

Subsurface storage of CO2 has a long history on the Norwegian continental shelf; in the Sleipner Field (North Sea) since 1996 and the in Snøhvit field (Barents Sea) since 2008. Several studies have pointed out the large carbon storage potential on the Norwegian continental shelf, especially in deep saline aquifers. The Norwegian Petroleum Directorate (NPD) has, for the last two years, interpreted relevant data on the Norwegian continental shelf in order to classify potential sites for CO2 storage. The CO2 storage atlas for the Norwegian North Sea indicates possible storage sites, and estimated storage capacity.The Utsira Formation is considered to be a part of a saline aquifer together with Skade Formation. The Skade & Utsira Formations are distal deposits in a great delta-complex, with sands coming from the west throughout Miocene and up into the Pliocene. On British sector sands in Miocene are named Hutton sands (informal).To estimate the capacity of CO2 storage in the Utsira formation, a reservoir model covering 1400 km2 in the south part and located in the Norwegian sector, was built to simulate the long-term behaviour of CO2 injection. The simulations estimated the amount of CO2 which can be injected into the formations. They also illustrated the distribution of the CO2 plume in the reservoir formations.With a bottom-hole pressure (BHP) change constraint of 10 bars and no water production, more than 145 Mt CO2 could be injected and stored in the segment model with 4 or 5 injection wells and 50 years injection period. There are no indications that CO2 will migrate to the shallower parts of the formation in the west after 8000 years of simulation.