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Modelling and measuring shallow CO2 migration (SRD 3.3)

Predicting the influence of geological faults on the migration of injected CO2 is important for understanding long-term safe CO2 storage.

In partnership with our industry and research partners, CO2CRC is developing and testing new methods to predict CO2 migration pathways in the near surface to enable enhanced modelling of stored CO2 behaviour. The primary interest is to identify fault-bound structure traps and investigate the risks of vertical migration through fault zones.

Site characterisation is currently underway around a shallow fault at the CO2CRC’s Otway International Test Centre. This will determine its suitability for hosting a small controlled release of a CO2 into the fault.  This includes how the CO2 would spread, dissolve and react, whether the injected CO2 could be detected and how these factors could be best monitored and tracked.

The site characterisation around a shallow fault (Brumby’s fault) at the Otway site is completed and in 2019 two appraisal wells were drilled and cored through the shallow fault. The work undertaken to date by Geoscience Australia for this project confirms that the site is suitable for hosting a small (~10 tones) controlled release of a CO2 into the fault.

The range of survey techniques used for this characterisation, included:

  • ultra-high resolution shallow focused 3D seismic
  • electrical resistivity imaging
  • core flooding and geomechanical analysis
  • nuclear magnetic resonance spectroscopy in wells to determine porosity and estimate vertical permeability assessment of core
  • a survey using 3D laser scanning or LiDAR from a light plane to map surface features

The injection and verification phase of the project is subject to funding and dates for the execution have not yet been set. This final phase will use geophysical and environmental monitoring techniques to image the migration of a small slow release of CO2 up a shallow fault. Proceeding to this phase offers significant value to future large scale carbon storage facilities including:

  • Determining optimal methods for predicting fluid migration pathways around faults.
  • Determining optimal methods for predicting fluid migration pathways around faults.
  • Determining optimal methods for monitoring of CO2 flow around faults.
  • Investigation of mitigation techniques in the event of CO2 leakage through faults
  • Measurement of vertical fault permeability
  • Learnings from the shallow fault for deeper faults.

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