The role of structural compartmentalization in carbon storage site selection in Permian (Rotliegend Group) reservoirs in the Southern North Sea

The Southern North Sea gas basin is a key area for CO 2 storage projects in the UK. Many of the now-depleted Permian (Rotliegend) Leman Sandstone Formation fields are being re-evaluated as carbon stores. However, the reservoir is known to be highly faulted, often leading to field compartmentalization. This has historically impacted field development and production, and will challenge suitability for CO 2 storage by limiting site capacity, requiring a high number of injector wells, and increasing capital costs. It is necessary to understand the nature of these pressure compartments – and whether any individual culmination can house sufficient capacity – before devising a carbon storage development programme. The highly compartmentalized Indefatigable Field was evaluated as a case study. A static model of the field was constructed using 3D seismic and well log data, and subsequently used to calculate the CO 2 capacity of each of the 12 compartments. Five compartments were found to have capacities larger than 10 Mt, with the large Main Horst found to host 51% of total CO 2 capacity. A sequential filling-and-sealing storage site development plan is suggested based on the evaluation and ranking of these compartments.