The Effect of Geological Structure and Heterogeneity on CO2 Storage in Simple 4-way Dip Structures; a Modeling Study from the UK Southern North Sea

Abstract

The Bunter Sandstone Formation in the Southern North Sea is folded into a number of simple 4-way dip-closed structures (domes). Most of these structures are saline water-bearing, although some of them do contain significant gas accumulations, suggesting that the brine-saturated domes may have potential for the long-term storage of CO 2 . This study investigates the effect of geological structure and heterogeneity on CO 2 storage through the use of geological models and reservoir simulation. Dynamic modeling focussed on the determination of the storage efficiency of a particular dome and from this, its CO 2 storage capacity. Under initial modeling conditions, a storage efficiency of around 19% was derived, though this is shown to be highly sensitive to a range of uncertain parameters. An interesting interplay exists between the reservoir heterogeneity and dome structure, whereby the evolving CO 2 plume is prevented from rising buoyantly to the top of the formation by the presence of impermeable horizons, which facilitates rapid migration towards the structural spill-points. Sensitivity analysis further emphasizes the importance of characterizing reservoir heterogeneity in studies for long-term carbon capture and storage.