Influence of Grain Size Distribution and Varying Heterogeneity on Local Capillary Trapping

Simulations of buoyancy-driven CO2 migration indicate that as the degree of heterogeneity in CO2 storage domain increased, CO2 migration patterns evolved from 'dispersed' capillary channels with minimal rock contact to back-filled 'compact' distributions of saturation with much larger storage efficiency. Experiments with analog fluids and porous media made of varying degree of heterogeneity were conducted to test these predictions. It is found that the total storage capacity by local capillary trapping in such heterogeneous environment is mostly determined by the volume percentage of the beads of varying sizes. Smallest beads with maximum entry pressure contribute most to the integrity of the seal. A back-filled pattern of nonwetting phase, which corresponds to larger storage capacity, is formed in relatively heterogeneous media whose bead size difference between store and seal is large. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).