Novel secure carbon sequestration methods

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Two novel technologies not heretofore considered for large-scale carbon-sequestration will be studied: slurry injection (SI), and carbon dioxide-enriched gas injection. SI is direct deep placement of C-rich solids (petcoke, biosolids...) into sediments; C is permanently sequestered as a solid, the injection liquid is waste water, and for biosolids SI, recoverable CH4 is generated and CO2 from biodecomposition dissolves in formation water. Research issues include simulation of SI, biosolids decomposition rates and products, dissolving behaviour in formation water and chromatographic produced gas separation because of different solubilities. Major advantages of biosolids SI are waste water and solids co-disposal while sequestering carbon securely in solid and dissolved form, CH4 generation, and ability to co-dispose other waste streams. SI can also be implemented at a municipal scale (50,000 population). CO2-enriched gas injection (after partial membrane enrichment) fosters rapid dissolution, reduces compression costs, and reduces high costs and serious escape hazards of pure supercritical CO2 placement. Adequate dissolution rates can be achieved by maximizing in situ surface area for exchange, maintaining a high concentration gradient, and co-injecting waste water and CO2-enriched gas to maximize mixing. Research issues include study of exchange rates in co-injection and adsorption in situ (horizontal wells are envisioned), understanding and maximizing density-driven convective mixing in situ to sustain high concentration gradients, the role of buoyancy-driven dispersion, chromatographic separation of CO2 and N2 (changes in gas concentration), and means of improving predictive models for gas mixture injection into porous media with convection, dispersion, buoyancy and dissolution to undertake reservoir simulation. These are novel world-class technologies with high environmentally secure; they promise to achieve lower-cost long-term C-sequestration because of major positive synergies such as co-disposal of other waste streams. They will have a major impact on carbon sequestration policy in the long run.