98% of South Africa‟s total CO2 geological storage capacity is in the form of deep saline
formations located off-shore, while the remaining 2% is situated on-shore. Such formations may
not have a similar proven sealing capacity to that of depleted gas and oil reservoirs, and the
country must give due consideration to every theoretically conceivable option for CO2 storage.
This paper discusses a theoretical concept whereby coal fly ash slurries, composed of
homogeneously-sized ultra-fine particles with adequate shear-thinning Newtonian rheological
properties when suspended in water, could be injected in deep saline formations, alongside CO2,
to engineer a „mineral curtain‟ that could act as a barrier preventing unwanted CO2 migration
outside the boundary layers of the reservoir. The resulting pressure build-up could be managed by extracting the brine from the formations, which could then be used to produce fresh water for
local communities deprived of drinking water.