The Bureau of Economic Geology The University of Texas at Austin Jackson School of Geosciences
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From Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
For more information, please contact the author.

Bureau Seminar, October 9, 2009

Buoyancy driven flow of CO2: Experiments & Analysis

Marc Hesse
Department of Geological Sciences, UT Austin

Link for streaming video: available 10.09.09 at 8:25am CST

a.         b.
 

Buoyancy is expected to be the main driving force for the migration of the CO2 plume beyond the radius of influence of the injection well(s). Immiscible buoyancy driven flow occurs during the rise of the supercritical CO2 plume towards the top of the storage aquifer (a), and miscible buoyancy driven flow occurs upon dissolution of the CO2 into the brine (b). In both cases complex flow patterns emerge that are challenges for the numerical simulation of geological CO2 storage.

First the effect of a set of small scale flow barriers on the buoyant rise of immiscible fluids is considered. Hele-Shaw cell experiments and a simple analysis show that the macroscopic effect of the barriers is to disperse the flux of CO2. The theory can quantify the dispersion in terms of the geometry of the layers and the dynamics of the interaction of a rising plume with a single barrier. In buoyancy driven flow the macroscopic effect of the shale layers is not just a reduction of the apparent vertical permeability, but also a cross-flow diffusive term.

Second, experiments modeling convective CO2 dissolution are discussed. The non-ideal mixing between water and methanol ethylene-glycol is exploited to obtain density behavior similar to that of CO2 and brine, but at ambient conditions. Experiments in beadpacks show that the convective dissolution rate is only dependent on the buoyancy flux due to the induced density increases and independent of hydrodynamic dispersion and molecular diffusion. This is in stark contrast to the diffusive mass transfer in the absence of induced convection. Experimental results compare well with high resolution numerical simulations and a simple scaling analysis suggests the observed dependence of the convective dissolution rate on the buoyancy flux.

 

 
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