Large-Scale Geological Carbon Sequestration - Introduction to Carbon Capture and Sequestration - page 468

Figure 10.2.8 CO 2 fl ow and diffusion in water-fi lled porous media
The fi gure shows measured electrical resistivity changes as a function of depth (vertical
axis) and time (horizontal axis) at an observation well at the Nagaoka sequestration pilot
site in Japan; red shows resistivity increases caused by the arrival of supercritical CO 2
at the observation well; green shows resistivity decreases caused by CO 2 dissolution in
water. The regions of CO 2 -rich water that form above and below the CO 2 plume (dark
green) grow very slowly — on time scales of hundreds of days. Figure reproduced from
Sato et al. [10.6], with permission from Elsevier .

weathering reactions involving minerals, water, and CO 2 may be rate-
limited by the slow diffusive mixing of these three components.

Impact of weathering reactions on permeability

In many sequestration simulations, the infl uence of weathering reactions
on fl ow parameters such as permeability and capillary pressure is
neglected. This is a signifi cant approximation, because weathering reac-
tions could cause large porosity changes (up to 50% porosity increase

or decrease in different regions of the storage formation if the injected
CO 2 contains sulfur impurities [10.7]). Porosity changes are well known to
infl uence the permeability of porous media, but the various models that
have been proposed to describe this phenomenon predict very different
relationships between

∼

φ and k .