Characterizing small-scale migration behavior of sequestered CO2 in a realistic geologic fabric

For typical field conditions, buoyancy and capillary forces grow dominant over viscous forces within a few hundred meters of the injection wells resulting in remarkably different fluid migration patterns. Reservoir heterogeneity and fluid properties are principal factors influencing CO2 migration pathways in the buoyancy/capillarity regime. We study the effect of small-scale heterogeneity on buoyant migration of CO2 in this regime. Capillary channel flow patterns emerge in this regime, as characterized by invasion-percolation simulations in a real meter-scale 2D geologic domain in which sedimentologic heterogeneity has been resolved at sub-millimeter resolution. As the degree of heterogeneity increased in synthetic media, CO2 migration patterns exhibited a spectrum of structures, from 'dispersed' capillary fingers with minimal rock contact to back-filled 'compact' distributions of saturation with much larger storage efficiency. (c) 2013 The Authors. Published by Elsevier Ltd.