Increased storage capacity with improved fault models
Main impact: Reduced uncertainty resulting in improved safety for storage sites and increased storage capacity
Implementation of large-scale CO2 storage will require utilization of a wide range of storage reservoirs including faulted reservoirs with structural traps. The sealing properties of faults are challenging to predict, and conservative estimates and high uncertainty may limit the total injection volume or even disqualify a storage site. Existing industrial models have limitations when addressing fault risk related to CO2 injection in faulted aquifers.
Development of an improved fault derisking framework that includes dynamic pressure changes related to CO2 injection and addressing along-fault fluid migration is a main ambition of NCCS Task 9.
Such framework can:
- Reduce uncertainty related to fault properties
- Increase confidence in site integrity and confinement
- Enable qualification of increased storage capacity.
The development of the Horda Platform area for CO2 injection showed that high uncertainty in existing fault seal prediction models for shallow, fault-bound aquifers like Smeaheia, limits the capacity and provides major obstacle for site qualification. The Norwegian CO2 storage atlas (NPD, 2012) indicates around 40 GT storage capacity in North Sea aquifers. The effective volumes found suitable for safe and long-term storage during technical maturation may be as low as 10% of the estimated capacity For the North Sea this gives a suitable safe capacity around 4 Gt. Assuming this volume could be increased with roughly 10% if risk related to fault sealing is reduced, a total 400 Mt increase in storage capacity can be estimated, enabling 20 years of storing 20 Mt CO2 per year (NCCS DC2030). Improved fault seal models and reduced uncertainty is a necessary, although not sufficient, step towards qualification of additional storage capacity.