Publication Overview
The theme for this meeting was ‘The Cost and Value-effectiveness of Monitoring: what key drivers are required to deliver an optimum outcome’. Sessions included project updates, the application of oil and gas production experience, innovative monitoring techniques, offshore monitoring developments, overburden research including controlled release experiments, wellbore integrity and micro-seismicity. Delegates also took part in a group exercise on how to respond to a hypothetical leak scenario.
The meeting highlighted the impressive advances that have been made in the use of fibre-optic distributed acoustic sensors (DAS) at projects, including helical configured cables, to overcome the limitations of directional signals. The technology is now under trial at pilot CO2 storage sites.
Publication Summary
- Commercial-scale projects are now able to evaluate and implement reductions in complexity of monitoring.
- The monitoring strategy applied at recent commercial scale projects (Petra Nova, IL-ICCS, Quest) has built on knowledge transfer and expertise gained from early projects (Secarb, Decatur 1) especially the selective deployment of different monitoring techniques.
- There is a trend towards right-sizing the number, type, and timing of technologies deployed at commercial-scale For example, the ‘tiered and phased monitoring, measurement and verification (MMV) strategy’ approach at Quest, that has been approved by the regulator. This approach reduces monitoring and its associated costs. Technology maturation and a more simplified monitoring programme has not had a negative impact on project success.
- DAS technology and permanent seismic sources, plus other permanent receivers, have led to several beneficial advances including lower cost, decreased surface impact, and increased subsurface resolution. Surface seismic gives better quality images but is more expensive compared with DAS.
- Stakeholders may have an input into MMV technology choice (does this relate to regulatory requirements and in what context?)
- There is clear progress towards the adoption of more derived, quantitative and targeted environmental monitoring both onshore and offshore.
- Environmental monitoring is useful for characterisation and to determine well defined performance metrics instead of simple baseline thresholds.
- There is a convergence towards more nuanced evaluation of methods, detection performance and probabilistic leakage detection plus the identification of false positives.
- The use of lower cost monitoring can be effective to define where and when more expensive monitoring is required to verify the presence of CO2, for example conducting 2-D seismic before 3-D.
- DAS VSP can be a more cost-effective monitoring technique under certain scenarios compared with surface seismic even with lower resolution images. DAS helps facilitate permanent monitoring.
- Some improvements in DAS can be achieved with pre-installed optical fibre (cemented in well or placed in trenches). The overall DAS technology is improving at a fast pace, for example, DAS – helical wound cable improvements are moving DAS into surface horizontal seismic configurations.
- Determining the exact position of a plume edge is not necessarily crucial. The level of monitoring required depends on risk and the complexity of reservoir conditions. A series of several simulations can be used to generate probability contours of a plume’s aerial extent and boundary.
- There has been substantial progress in monitoring technologies over the last decade. For example advances in microseismic monitoring have provided greater insights into geomechanical processes during and post-injection.
