Measurements of dispersion coefficients of CO2 in CH4 for sequestration and enhanced gas recovery

T. Hughes1, B. Graham1, A. Chauhan1,2 and E. May1

1Centre for Energy, University of Western Australia, Australia
2Shell Development Australia, Australia

Keywords: sequestration
property: dispersion
material: carbon dioxide, methane

To ascertain whether CO2 sequestration can be employed as a method of enhanced gas recovery, the dispersion of CO2 in CH4 in porous media at reservoir pressures and temperatures needs to be quantified. A specialized core flooding apparatus has been constructed that allows displacement experiments to be conducted at reservoir conditions. Experimental breakthrough profiles and dispersion coefficients are presented of the displacement of CH4 by CO2 for temperatures between (313.15 and 353.15) K, pressures between (8 and 12) MPa and CO2 flow rates of between (0.5 and 2.0) ml. min-1 (at 277 K) in a homogenous sandstone core (porosity, φ = 0.157 and permeability, k = 13 mD). As CO2 is a supercritical fluid under these conditions, its density is between 3.5 and 9 times higher than the density of CH4. This means that horizontal displacements may not be gravity stable, and the CO2 front may roll-under leaving CH4 behind. Displacement experiments have been conducted in both horizontal and vertical orientations to investigate gravitational effects. To obtain meaningful dispersion coefficients so called "system effects" need to be removed from the experimental data. These systems effects are associated with dispersion in the tubes and fittings and any volumes outside of the core in the experimental apparatus. The methods of correcting for these system effects are discussed.

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