Buoyant and countercurrent flow of CO2 with capillary dispersion

Abstract Analytical modeling of CO2 flow is essential for the rapid evaluation of CO2 plume evolution and possible leakage risk during geological carbon sequestration (GCS). Here we adapt the model of describing the secondary migration of oil proposed by Siddiqui and Lake (1992) to characterize CO2 upward migration and backfilling for buoyant and countercurrent flow in a saline aquifer. Both water- and CO2-wet reservoirs are examined under typical buoyant fluxes. We present self-similar solutions of CO2 saturation waves without capillary pressure and traveling wave solutions after adding capillarity. We demonstrate that saturation wave types, CO2 migration, and saturation profiles are influenced by buoyant flux, capillary pressure, wettability, and relative permeability. The stabilized zones resulting from capillary dispersion inside a CO2-wet reservoir generally extend wider than those for a water-wet reservoir. The presented model and results are potentially useful to understand field scale CO2 plume behaviors as well as to guide the design of corefloods for studying CO2 buoyant flow characteristics.