Injection of coal fly ash slurry in deep saline formations for improved CO2 confinement : a theoretical concept

Abstract

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.