The UK site in the northern North Sea has been chosen to provide an example of the characterisation of large-scale offshore geological storage in salt-water sandstones in an area of active oil and gas production. Rocks under the North Sea are well known from exploration and production of oil and gas but most North Sea rocks contain salt water.
Deeply buried sandstone rocks containing salt water (saline aquifers) have Europe’s greatest potential for the offshore geological storage of carbon dioxide gas. The carbon dioxide injected into microscopic pores within the rock displaces the salt water, oil or gas that is already there. Storage will be assessed in the Captain Sandstone and an oil or gas field, considered together as an example of a multi-store site.
The reservoir rocks of oil and gas fields are known in great detail but their capacity to store carbon dioxide is relatively small (mostly 10’s of million tonnes) compared to the potential capacity of saline aquifer sandstones (100’s to 1000’s of million tonnes).
Diagram showing how carbon dioxide captured at an industrial plant is transported by an offshore pipeline and injected into deeply buried rocks as part of a Carbon Capture and Storage project.
Oil or gas fields are expected to be used for the first pilot and demonstration projects with the saline aquifers providing larger, commercial-scale storage capacity. A realistic forecast will be made of injection into this potential multi-store site over a period of 25 to 50 years suitable for the storage of large volumes of carbon dioxide expected to be captured at existing and planned industrial plant.
The UK North Sea site will investigate the relationship between carbon dioxide injection into an oil or gas field and the associated saline aquifer sandstone because injection into the sandstone may start while there is active production from nearby oil or gas fields. The changes in pressure from injection of carbon dioxide into both types of store will be calculated; the impact on the saline aquifer sandstone of injection into an old oil or gas field and the impact on a producing field from injection into the sandstone. The effect on oil and gas fields by any future use of rock formations for carbon dioxide storage will be assessed and adjustments to the injection will be calculated to minimise any disadvantage and maximise any advantage.
The UK North Sea site will prepare a ‘dry-run’ application for a storage licence appropriate for any future multi-store site in the UK North Sea. Research from the UK North Sea site will inform the licence application which will be fully assessed by the regulatory authorities co-ordinated by the Scottish Government.