Large-Scale Geological Carbon Sequestration - Introduction to Carbon Capture and Sequestration - page 467

each simulation grid block. An important consequence of this assumption
is that if a simulation grid block contains even the smallest amount of
CO 2 -rich phase, the entire aqueous phase in the grid block is assumed to
be in equilibrium with the CO 2 -rich phase. In reality, CO 2 , water, and min-
erals may not be instantaneously well-mixed at the grid-block scale (see
for e.g., Question 10.2.1 ). Because of effects like capillary and viscous
fi ngering caused by heterogeneous mineral distribution ( Figure 10.2.7 ) or
heterogeneity in the fl ow properties of geological formations ( Figure
10.2.8 ) [10.6], the durations required to equilibrate the CO 2 , brine, and
mineral phases in a simulation grid block can be substantial ( Figure
10.2.7 ), as in Question 10.2.1. One implication of slow mixing is that the
Figure 10.2.7 CO 2 invasion in water-fi lled porous media
Upon invasion in a porous medium, CO 2 forms capillary or viscous “fi ngers.” The fi gure
shows a photograph of a CO 2 invasion pattern (in darker gray) in an initially brine-fi lled
micromodel (an idealized porous medium made of fused etched silica plates). It shows
that fi nger formation can occur even if the porous medium is essentially homogeneous.
Figures reproduced with permission from Kim et al. [10.5]. Copyright (2012) American
Chemical Society .