High-resolution simulations of migration pathways and the related potential well risk at the IEAGHG Weyburn-Midale CO2 storage project

The Weyburn region has over 4000 wells within a risk assessment area of 2000 km2. The high well density and regional scale present a major challenge for flow modelling: conventional simulations require coarse grids, leading to a significant loss of geological detail. A high-resolution approach, using hydrodynamic capillary flow to simulate CO2 migration throughout the region, overcomes this problem. The resolution is sufficient to identify wells along migration pathways where leakage may occur into aquifers, which may act as secondary storage zones. This indicates a subset of 62 wells that are marked for further risk assessment. To a first approximation, the modelled storage volumes for traps associated with the identified subset of wells provide secondary containment equivalent to about 10% of the final containment mass (3 of 30 Mt). As such, the overlying aquifers increase the storage security for Weyburn.