|Chadwick, R A. 2017. DiSECCS Final Summary Report. Work Packages 1 – 4 British Geological Survey Internal Report, OR/17/002.|
Seismic techniques comprise the key geophysical toolset for imaging and characterising induced changes in the subsurface associated with human activity. This ability to observe and quantify changes in fluid saturation, pressure and geological stress and strain using active and passive seismic techniques has critical application to the monitoring of geological CO2 storage.
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:
Work Package 1: Development of monitoring tools for the characterisation and measurement of induced pressure and geomechanical changes in reservoirs
Task 1.1 Hydro-mechanical simulations
Task 1.2 Tool development and testing
Task 1.3 Application to real case-studies
Work Package 2: Monitoring to understand detailed flow processes and improve in situ quantification
Task 2.1 Integrated very high resolution flow modelling and seismic
Task 2.2 Novel methods for layer characterisation
Work Package 3: Experimental rock physics
Task 3.1 CO2 rig development
Task 3.2 Manufacture of synthetic rocks
Task 3.3 Ultrasonic anisotropy measurements on synthetic rocks
Task 3.4 Ultrasonic anisotropy measurements on core samples
Task 3.5 Integration of the results with other Work Packages
Work Package 4: Public perceptions
Task 4.1 Case study analysis of analogues
Task 4.2 Citizen focus groups
Work Package 5: Guidelines and monitoring toolbox
Task 5.1 Guidelines and workflows
Task 5.2 Toolbox
To support the research DiSECCS has access to seismic and other datasets from three key storage sites, at Sleipner and Snøhvit in Norway and the Aquistore pilot-scale project in Canada.
Numerical model data were also made available from the In Salah project in Algeria.
The Sleipner storage project is located offshore of southern Norway in the central North Sea in a water depth of around 80 m. Sleipner natural gas contains about 9% CO2 and so needs CO2 removal prior to sale. After separation at the platform CO2 is injected via a deviated well into the Utsira Sand, a large saline aquifer, at a depth of just over 1000 m. Injection commenced in 1996 and, by the end of 2016, 16.55 million tonnes of CO2 had been stored.
The Snøhvit storage project is located offshore of northern Norway in the south-western Barents Sea in water depths ranging from 310 to 340 m. Snøhvit natural gas contains between 5% and 8% CO2 and so needs CO2 removal prior to sale. After separation at the Melkøya LNG plant near Hammerfest the CO2 is piped back offshore for injection via a single injector well. Initial injection, starting in 2008, was into the Tubåen saline reservoir at a depth of about 2600 metres. Subsequently injection was switched to the slightly shallower Stø reservoir. By the end of 2016 4.34 million tonnes of CO2 had been stored.
The Aquistore site in Saskatchewan is a research injection site attached to the Boundary Dam CCS project. Most of the captured CO2 is used for enhanced oil recovery but episodic offtake is stored in a deep saline aquifer, comprising the Black Island and Deadwood units at a depth of about 3250 m. Injection started in 2015 with more than 35 thousand tonnes of CO2 currently stored.
Background information and further results from DiSECCS can be found on the project website www.bgs.ac.uk/diseccs/ps://www.bgs.ac.uk/dise/