Background

Current regulations concerned with carbon dioxide capture and storage (CCS) mean that the licensing of CO2 storage sites is likely to be undertaken to follow a first-come, first-served basis. Applications for licences (for individual projects) are submitted to regulators and the basis of the regulators’ assessment will be primarily to consider if the site is fit for purpose as a storage site for CO2. This assessment will be subject to certain region-specific exclusions, designed to protect the interests of pre-existing users of the subsurface, ground surface and seabed.

Storage sites for CO2 will be selected by the operators on a ‘most economically advantageous’ basis, to meet the needs of individual clusters of CCS projects. A recent (2013) IEAGHG study, ‘Interaction of CO2 storage with subsurface resources’, highlighted that sedimentary basins have multiple potential uses – hence there is potential for CO2 storage projects to conflict with other subsurface and surface users (see figure 1, overleaf, for a conceptual view of spatial and subsurface interactions which may limit storage site selection). This report showed that increased pore fluid pressure in any reservoir formation (resulting from the injection of CO2) may reduce storage capacity and increase costs in adjacent sites, which could potentially reduce the efficient use of the storage resource. Therefore a more strategic approach would be required when dealing with sedimentary basins to ensure such formations realise their full resource potential. This raises important questions, including:

• How can CO2 storage capacity be fully utilised in the presence of potentially competing uses of the subsurface and overlying ground surface or seabed?

• How should storage boundaries be defined in potentially pressure-interacting projects?

• How should potentially interacting resources e.g. CO2 storage, hydrocarbon exploration and production and natural gas storage be developed most economically in the light of national or jurisdictional policies?

Factors which may influence the optimisation of a basin include cost, minimising risk, access to a range of uses of the basin, ground surface and seabed, and the value of the resource. Such factors would be considered within the framework of government energy policies. It may also be necessary to look at other, perhaps less tangible potential future uses of the basin.

Key Messages

• There are many potential competing users of the surface and subsurface in both onshore and offshore environments

• There are various different approaches to storage management, all of which are highly dependent on the jurisdiction involved

• Most jurisdictions currently work under a ‘first-come, first-served’ approach

• Management of storage on a first-come, first-served basis is likely to be sustainable in the short to medium term

• Pressure increases do not always result in detrimental effects, but pressure responses in open storage sites should be the focus of a detailed assessment in all cases

• The operator and regulator must understand the consequences of a pressure increase over an area much larger than the extent of the CO2 plume itself

• The main benefit of a first-come, first-served approach is that the operator has the final decision on where to develop CO2 storage

• The first-come, first-served approach should work for multiple-stacked sites

• Potential disadvantages of the first-come, first-served approach include possible reduced storage capacities, difficulties for monitoring and a lack of regional storage optimisation with stranded sources.