Ensuring Containment of Carbon Dioxide: Detailed Investigations of the Structural Integrity of the Captain Sandstone

Abstract

Summary The Captain Sandstone Member of the Moray Firth, offshore UK, has been identified as a promising target for carbon dioxide storage as a means of reducing anthropogenic greenhouse gas emissions. The Goldeneye Field, which ceased production in 2010 was considered for storage in the UK Government’s carbon capture and storage programme, however significant storage potential also exists in saline aquifer parts of the formation. Potential structural risks to storage integrity in the Captain Sandstone have been identified, resulting from early Cenozoic uplift, including subcrop beneath the seabed at its western extent, and faults that cut the formation and extend upwards into the Palaeogene section. Previous reservoir simulation shows that carbon dioxide injected into deeper parts of the reservoir will not migrate to shallow areas where it would be at risk of migrating towards the subcrop. Analysis of fault throw indicates that juxtaposition against potentially permeable Palaeogene strata does not occur, although juxtaposition against Chalk Group strata is common. Characterisation of the in situ stress field suggests that few of the through-going faults would be optimally-oriented for reactivation under the present-day stress regime. The Captain Sandstone therefore appears to be a secure reservoir capable of sequestering significant volumes of carbon dioxide.