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

Ninety-eight percent 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. (C) 2014 Elsevier Ltd. All rights reserved.