Characterization of shale rocks under dynamic geochemical interaction with brine-CO2 fluid

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Conference Proceeding

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Caprock integrity is critical in ensuring that geological sequestration of anthropogenic carbon dioxide (CO ) meets engineering and carbon accounting goals. The interaction of shale caprock with brine enriched CO under continuous contact conditions should be investigated in order to adequately characterize geological reservoirs for their ability to effectively sequester CO in large quantity. Simulation results reported in literature had predicted that influx-triggered mineral dissolution/precipitation reactions within typical shale caprocks can continuously reduce micro-fracture networks, while pressure and effective-stress evolution initially increase then gradually constrict them. This experimental work applied specific analytical techniques in investigating changes in surface/near-surface properties of crushed shale rocks after exposure (by flooding) to CO -brine. Nano-scale measurement of changes in internal specific surface area, pore volume and linear/cumulative pore size distribution (using the BET Technique) showed that changes in the shale caprock due to geochemical interaction with aqueous CO can affect petrophysical properties. Diffusive transport of CO as well as carbon accounting could be significantly affected over the long term. The estimation of dimensionless quantities such as Peclet (Pe) and Peclet-Damkohler (PeDa) Numbers that are associated with geochemical reactivity of rocks and acidic fluid transport through porous media revealed the impact of diffusion and reaction rate on shale caprock in CO sequestration. Copyright 2013 ARMA, American Rock Mechanics Association. 2 2 2 2 2 2 2

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47th US Rock Mechanics / Geomechanics Symposium 2013

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