Michelle Bentham

Review of monitoring issues and technologies associated with the long-term underground storage of carbon dioxide

Abstract Large-scale underground storage of CO2 has the potential to play a key role in reducing global greenhouse gas emissions. Typical underground storage reservoirs would lie at depths of 1000 m or more and contain tens or even hundreds of millions of tonnes of CO2. A likely regulatory requirement is that storage sites would have to be monitored both to prove their efficacy in emissions reduction and to ensure site safety. A diverse portfolio of potential monitoring tools is available, some tried and tested in the oil industry, others as yet unproven. Shallow-focused techniques are likely to be deployed to demonstrate short-term site performance and, in the longer term, to ensure early warning of potential surface leakage. Deeper focused methods, notably time-lapse seismic, will be used to track CO2 migration in the subsurface, to assess reservoir performance and to calibrate/validate site performance simulation models. The duration of a monitoring programme is likely to be highly site specific, but conformance between predicted and observed site performance may form an acceptable basis for site closure.

Carbon dioxide capture and storage scenarios: a case study of the East Midlands and Yorkshire (UK)

This paper uses quantitative electricity supply scenarios to explore the potential for CO2 storage at locations in the Southern North Sea basin from point sources within a case study region that consists of the East Midlands combined with Yorkshire and Humberside in the UK. The reactions to these scenarios from a variety of stakeholders from the public and private sectors are explored using an assessment process. The scenarios demonstrate that there is sufficient storage capacity within reservoirs in the Southern North Sea basin for CO2 generated within the regions power stations to 2050 and beyond, even under a high fossil fuel scenario. Carbon dioxide Capture and Storage (CCS) was typically seen as offering significant potential for CO2 mitigation by a small but varied selection of professional stakeholders, although the consensus over the preferred approach to a low carbon electricity supply was far from evident.

Efficiency of CO2 Storage in a Domed Structure

When storing CO2 in a saline aquifer, it is desirable to have a structural trap, such as a domed closure, to limit the lateral migration of CO2. Domed structures may be formed in sandstone formations by migration of underlying salt bodies (halokinesis). In this study, we have created such a model of a hypothetical storage site in a domed structure, based on a real formation, using existing geological and petrophysical data. CO2 storage was simulated using the Eclipse 300 simulator with the CO2STORE module. Injection was initially controlled by rate, but was constrained by pressure build-up in the injection wells and at the crest of the dome. In additional, we monitored migration of CO2 past the dome spill point. A base case model was simulated and the a range of sensitivity cases investigated including the effect of aquifer size and heterogeneity. The results are very sensitive to boundary conditions. Notably, if the reservoir is open, the capacity may be limited due to migration across the spill point. The storage capacity also depends on reservoir heterogeneity, particularly if there are extensive layers of low permeability.