OR/17/002 Executive summary
| Chadwick, R A. 2017. DiSECCS Final Summary Report. Work Packages 1 – 4 British Geological Survey Internal Report, OR/17/002. |
The DiSECCS project (Diagnostic Seismic Toolbox for Efficient Control of CO2 Storage) has developed seismic monitoring tools and methodologies to identify and characterise injection- induced changes, whether of fluid saturation or pressure, in storage reservoirs. We have developed guidelines for the monitoring systems and protocols required to maintain the integrity of storage reservoirs suitable for large-scale CO2 storage. The focus is on storage in saline aquifers (comprising the largest potential global storage resource), where considerable amounts of in situ water have to be displaced and both pressure and two-phase flow effects have consequences for storage integrity and storage capacity. Underground storage of CO2 is associated with significant levels of public concern. A better understanding of this is a key element of establishing monitoring protocols to instil wider public confidence in CO2 storage. DiSECCS draws on analogue activities, such as ‘fracking’ for shale gas, in conjunction with a discursive process involving lay participants, to gain insights into how people engage with similar underground activities and how controversies surrounding particular projects develop and evolve.
DiSECCS has five work packages, the first four carrying out the basic research and the fifth integrating findings into recommendations and tools. Datasets from the Sleipner, Snøhvit and Aquistore injection projects underpinned much of the applied seismic research, whilst the social research obtained data from online sources and from public interviews and focus groups.
Work Package 1 assessed the hydromechanical effects induced by CO2 injection where pressure increase was significant. A sensitivity analysis was carried out to determine the sensitivity of geomechanical response to different reservoir parameters. Feasibility studies were carried out on the effectiveness of Amplitude versus offset (AVO) and amplitude versus offset and azimuth (AVOA) in anisotropy and fracture characterisation. Detailed assessments of CO2 detectability in the presence of noise were carried out and noise reduction techniques investigated. Tools were tested on the time-lapse 4D datasets from the Aquistore pilot-site. In addition a coupled fluid flow-geomechanical model for Snøhvit has been built to study the seismic response to pressure and fluid saturation changes. This work is supported by a separate funding stream.
Work Package 2 focussed on the seismic characterisation and quantification of migrating thin layers of CO2 in high quality reservoirs, utilising time-lapse datasets from Sleipner and Snøhvit. Techniques focussed on forensic interpretation of small reflection time-shifts integrated with numerical and analytical fluid flow models, novel spectral and dispersion analysis and theoretical rock physics.
Work Package 3 carried out advanced laboratory measurements of seismic changes in samples analogous to the Sleipner storage reservoir. Geophysical and geomechanical responses to changes in fluid saturation (brine/CO2 mixtures) and fluid pressure were measured on both synthetic rock specimens and real core samples.
Work Package 4 conducted research into social attitudes to underground storage. Using fracking for shale gas as an analogue a media survey and social network analysis (of both online and offline networks) was carried out. A study was then undertaken to assess interested stakeholder responses to offshore CO2 storage by means of interviews and citizen focus groups at two contrasting locations in northern England.
Work Package 5 integrated results from WPs 1 to 4 into a toolbox of seismic analysis software tools and a set of guidelines for optimal storage monitoring, and gaining social licence to operate. Results from WP5 are reported separately.