Task 3.3: Monitoring
Overall objective: The main objective of the monitoring task is to improve CO2 storage safety by accurately localizing the CO2 plume, quantifying CO2 volumes, and enabling early detection of potential leakage.
Contribution to one or more of the overall goals/objectives of BIGCCS
CO2 storage is the final link in the whole CCS chain, as defined in the overall BigCCS centre objective of enabling sustainable power generation from fossil fuels based on cost-effective CO2 capture, and safe transport and underground storage of CO2. Monitoring to avoid, and remediation measures in cases of leakage are the indispensable knowledge to ensure permanent removal of GHG from the atmosphere.
Task 3.3 achievements thus far
- Several geophysical methods succeed in visualizing the CO2 plume in the Sleipner reservoir, despite its structure in thin layers. We now can zoom in on the topmost plume layer and see it appear from the repeat seismic surveys on site; this is good news for our ability to detect leakages early on. Moreover, good progress is made on separating useful signal from background noise, indispensable for detection of very thin CO2 layers, while the seismic velocity changes can be separated in terms of pressure increase and saturation changes.
- Detection of CO2 in the underground using electro-magnetic sources has been demonstrated. This will be a promising addition to the traditional seismic methods.
- Laboratory ultra-sonic velocity measurements on rock plugs subjected to stress changes simulating injection into a reservoir have given vital information for interpreting integrity compromising stress developments, opening the door for sonic well-to-well monitoring. In addition, the data will help calibrate the velocity interpretation of seismic monitoring schemes.
Major achievements in 2014
- Performed Snøhvit pressure/saturation discrimination study (collaboration BGS/NTNU, see Fig. 1).
- Developed a novel methodology for quantitative leakage detection
- Developed and tested framework for 2D/3D elastic time-lapse FWI on real data (see Fig. 2).
- Initiated new KPN project on quantification/reduction of uncertainties in monitoring. First version of work bench for uncertainty estimation and reduction in high-resolution monitoring methods to be delivered during November.
- Completed study of 2D high-resolution plume imaging at Sleipner (see Fig. 3).
- First 3D high-resolution image of Sleipner plume (using 2008 data set).
- Completed synthetic study of CO2 volume estimation using constrained CSEM inversion and noisy data (see Fig. 4).
- 12 publications!
Fig. 1: Pressure and saturation changes from Grude et al. (2014). Results using spectral decomposition (top row) and time-lapse AVO (bottom row) show a striking correlation.
Fig. 2: 3D vp image obtained by inverting 1994 Sleipner data using elastic FWI.
Fig. 3: Sleipner high-resolution plume imaging (2D vp model, f=45Hz)
Fig. 4: (top left) Conductivity model after 9 iterations of inversion constrained to the plume area. (bottom left) CO2 saturation corresponding to the conductivity model. (right) Dimensionless gas volume with true volume indicated by dashed line.
