Fluids and Rocks - Introduction to Carbon Capture and Sequestration - page 404

Let us now look at a mixture of brine and supercritical CO 2 . In this
particular case we have a two-phase system of a supercritical fl uid and a
liquid. An important question is which phase will wet the rocks? The
answer to this question is illustrated at the molecular level by a molecular
dynamics simulation shown in Movie 9.4.1. This simulation nicely illus-
trates that if we start with both fl uids in contact with the clay surface, the
water phase will slowly wet the walls. Indeed, most of the minerals that are
in the aquifers are hydrophilic and hence will be wetted by the water phase.
Question 9.4.1 Trees
Calculate, using the Young-Laplace equation the maximal height of a tree if
only capillary forces are allowed to transport water to the leaves.
Movie 9.4.1 Molecular dynamics simulation of clay wetting
Movie of a molecular dynamics simulation of water and CO 2 in a 4-nm-wide nanopore
between parallel smectite clay surfaces. The clay mineral has a negative structural
charge that is balanced by adsorbed exchangeable sodium ions (blue spheres). At the
beginning of the simulation, the water phase (O and H atoms in red and white) and the
CO 2 phase (O and C atoms in red and light blue) are placed such that the CO 2 -water-
clay wetting angle is 90°. During the simulation, the wetting angle decreases as water
spreads to coat the hydrophilic clay surface. Movie produced by Ian Bourg . It can be
viewed at : http://www.worldscientifi c.com/worldscibooks/10.1142/p911#t=suppl