The impact of angular unconformity at the caprock interface on CO2 storage

The work presented here follows on from Shariatipour et al (2012), and investigates the effect of unconformities, one type of interface, on the storage capacity and security.Besly et al. (1993) studied the base Permian Unconformity in the Southern North Sea and they analysed the petrophysical properties of some wells logs (Cygnus field, UKCS Block 44/12). They presented a theory that a zone just beneath the Permian unconformity had been weathered, and consequently the permeability and the porosity of this zone were increased dramatically (average porosity changed from 0.1 to 0.2 and average permeability changed from 0.1-10 mD to 500 mD). In this work, we have studied the effect a high permeability layer associated with an angular unconformity would have on CO2 storage.We have conducted a range of 2D and 3D numerical simulations to study the impact of unconformities on CO2 storage.The results indicate that unconformities could improve CO2 equestration by providing pathways for CO2 migration to access other storage formations.With appropriate placement of the injectors in a case where there are parallel aquifers, it is possible to maximize CO2 storage.A very thin weathered zone (10 cm – 1m) can contribute significantly to pressure diffusion across the model.