A numerical study of the impurity effects on CO<inf>2</inf> geological storage in layered formation

Abstract

© 2017 Elsevier Ltd The effects of two kinds of common impurities (i.e., N 2 and H 2 S) on CO 2 geological storage in layered formations were investigated by numerical simulations. This study was focused on the migration behaviour and spatial distribution of CO 2 plume. The effects of capillary pressure on the spread of CO 2 plume in the layered formations were examined first. The results suggested that the capillary pressure was a minor influence when injecting, but it affected the migration and distribution of CO 2 plume significantly during post-injection period in which, the contact area between CO 2 plume and formation brine became smaller with increased capillary pressure, leading to a decrease of dissolved CO 2 mass fraction. In the case of co-injection of CO 2 with N 2 impurity, it was found that as the N 2 concentration rose up, the horizontal migration distance of CO 2 plume extended, and the plume inclined to accumulate below the impermeable caprock. The phenomena were due to the enhancement of buoyance effect of CO 2 plume and accordingly, the contact area between the CO 2 plume and the formation brine enlarged, resulting in an increase of dissolved CO 2 mass fraction. However, the effects of H 2 S impurity were less obvious compared with N 2 , by showing an inconspicuous shrinkage of CO 2 plume spread.