Publication Overview
The combined meeting of the IEAGHG Monitoring and Modelling Networks took place at the Edinburgh Centre for Carbon Innovation from the 6-8th July 2016. The meeting brought together leading experts from research and industry to discuss the latest work and developments, with around 60 participants from 11 countries participating.The theme for this meeting was ‘using the modelling-monitoring loop to demonstrate storage performance more effectively’. Sessions on monitoring included induced seismicity, novel monitoring techniques, monitoring costs, near-surface natural variability, monitoring CO2-EOR, wellbore integrity issues, modelling environmental conditions, updates from ongoing and closed projects, lessons from other industries, modelling reservoirs and overburden, pressure measurements and conformance in the monitoring modelling loop.
Publication Summary
- DAS can offer a new paradigm potential with permanent installation and continuous moni-toring in space and time. Comparison of DAS data quality with conventional geophones is demonstrating improvements with technology advancements. Helical cable is being tested to measure strain in all directions, not just longitudinally along the well. Helical cable also improves signal:noise responses for both vertical and horizontal orientations. DAS de-ployment is feasible for application at full-scale (i.e. at wellbore depths of 1,000s of me-tres).
- DAS could enable significant cost reduction for remote geophysical monitoring by eliminat-ing the need for geophone deployments in the well(s). DAS can be installed in existing wells by attaching the cable to tubing, but signal:noise challenges may exist due to a lack of direct coupling with the geological formation.
- A lightsource leakage detection system, tested at Quest, is a low-cost large-area surface monitoring technique that has been successful at the site with a detection resolution of ~50 kg/hr. There are currently spatial limits. The system was tested over ~100m, but it can be extended to 1 km. Atmospheric conditions including dust, rain and particularly snow can interfere with the signal, but continuous monitoring can build a comprehensive baseline of CO₂ variation. The technology is still under development.
- Pressure-based down-hole measurements are more effective (detection and cost) than geochemical analyses from wellbore samples for leakage detection.
- For offshore attribution monitoring the relationship between pCO₂ and dissolved oxygen (DO) can be used for attribution monitoring to establish the source of CO₂ .
- Baseline complexity needs to be investigated and understood. There is a continuing dis-cussion on the purpose of near surface monitoring and its optimization. Temporal and spa-tial variability may reveal long-term trends. If leakage does occur then it may not neces-sarily affect a specific site in a uniform pattern. Comparison with background trends will be important to detect any anomalies and reassure stakeholders. However baselines are shifting due to climate change and using baseline comparisons to attribute potential leak-age signals may risk false positives for leakage and project shutdowns.
- Microseismic monitoring that incorporates the use of Earth-tides can be used to identify changes in geomechanical conditions. Microseismic monitoring includes good examples of data comparisons between induced and natural events from two more projects (Rousse and Tomakomai).
- The risk of Induced Seismicity at large scale storage sites needs to be anticipated. The management of events large enough to be felt will play a larger role for onshore sites in populated vicinities. The risk management of these sites will need to include pressure monitoring.
- The use of new technologies can reduce MMV costs on future projects and bring cost/detection requirement thresholds down. Even projects starting in the next decade could be considered first of kind until the public becomes familiar with CCS. Monitoring costs can be a function of specific decisions including: the detection thresholds required; tolerable leakage rates; and the time within which a leak has to be detected, in addition to the “more obvious” site-specific geological parameters. Monitoring cost data is essential for economic-based model analysis perspectives. Cost data feeds into improved under-standing of monitoring cost-benefits. The value of monitoring can be a function of the ability to detect early indications of leakage compared with delayed detection and associ-ated remediation measures. MMV costs averaged 20% of the storage costs, with storage costs being only 1% of total full-chain project costs (in a study of Australian projects for a relatively short transport distance). Limited publically available data on monitoring costs constrains economic-based modelling conclusions
