Buoyant dispersal of CO2during geological storage

Carbon capture and storage is currently the only technology that may allow significant reductions in CO2emissions from large point sources. Seismic images of geological CO2storage show the rise of CO2is influenced by horizontal shales. The buoyant CO2spreads beneath impermeable barriers until a gap allows its upward migration. The large number and small scale of these barriers makes the prediction of the CO2migration path and hence the magnitude of CO2trapping very challenging. We show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events. This approach allows the analysis of two‐dimensional plume dispersal from a horizontal injection well. We show that the plume spreads laterally with heightyabove the source according to (y/h)1/2L, whereLis the width of the shales andhis their vertical separation. The fluid volume below successive shale layers, and therefore the magnitude of trapped CO2, increase as (y/h)5/4above the source, so that every additional layer of barriers traps more CO2than the one below. Upscaling small scale flow barriers by reducing the vertical permeability, common in numerical simulations of CO2storage, does not capture the dispersion and trapping of the CO2plume by the flow barriers.