4.2.3 - Summary
The results of the evaluation of theoretical storage capacity in the North Sea are summarized in the tables. Excluding the aquifers in the petroleum systems, two aquifers with significantly greater theoretical storage potential than the others have been identified. These are the Utsira – Skade Formation aquifer and the Bryne – Sandnes Formation aquifer.
The Utsira Formation is already used by the petroleum industry for CO2 storage. Structures in the Utsira Formation which are equivalent to the site used for the Sleipner injection have been classified within the 3rd level of the maturation pyramid. Only about 25 % of the total pore volume of the Utsira – Skade aquifer has been included in the calculation of storage capacity. The reason is that the top of the aquifer is too shallow to be suitable for CO2 storage.
The Bryne-Sandnes aquifer has a lower level of maturity than the Utsira formation. In any proposed storage site, reservoir quality and seal integrity must be studied carefully. The aquifer is located in a salt basin, and closed structures formed by salt tectonics may be attractive for CO2 injection.
The Johansen – Cook Formation aquifer has a smaller pore volume than the two aquifers mentioned above, but it has good reservoir and seal properties. A potential storage site in the Johansen Formation has recently been matured by Gassnova, and is here included in the 3rd step of the pyramid.
In the petroleum provinces, the storage potential was calculated from the extracted volume of hydrocarbons in depleted fields. The main contribution to the present theoretical storage capacity comes from the abandoned Frigg Field and its satellites, which are located in the huge Frigg-Heimdal Formation aquifer. The increase of storage capacity in abandoned fields has been estimated for 2030 and 2050. The storage capacity of that part of the large Sognefjord Delta aquifer which belongs to the Troll Field has been grouped together with the abandoned fields.
CO2 storage in abandoned and depleted fields will usually require a careful study of the integrity of the wells which have been drilled into the field. If oil has been present, it is relevant to study the potential for usually require a careful study of the integrity of the wells which have been drilled into the field. If oil has been present, it is relevant to study the potential for enhanced recovery by CO2 injection. The CO2 storage potential achieved by potential EOR projects is dis-cussed, but has not been quantified in this study.
