Process‐dependent residual trapping of CO2 in sandstone

Abstract

This paper demonstrates that the nature and extent of residual CO₂ trapping depend on the process by which the CO₂ phase is introduced into the rock. We compare residual trapping of CO₂ in Berea Sandstone by imbibing water into a core containing either exsolved CO₂ or CO₂ introduced by drainage. X‐ray computed tomography measurements are used to map the spatial distribution of CO₂ preimbibition and postimbibition. Unlike during drainage where the CO₂ distribution is strongly influenced by the heterogeneity of the rock, the distribution of exsolved CO₂ is comparatively uniform. Postimbibition, the CO₂ distribution retained the essential features for both the exsolved and drainage cases, but twice as much residual trapping is observed for exsolved CO₂ even with similar preimbibition gas saturations. Residually trapped exsolved gas also disproportionately reduced water relative permeability. Development of process‐dependent parameterization will help better manage subsurface flow processes and unlock benefits from gas exsolution.