Trapped Gas Fraction During Steady-State Foam Flow |
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Authors: | G-Q Tang A R Kovscek |
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Institution: | (1) Department of Physics, Trinity College, Dublin, 2, Ireland;(2) Department of Physics, Swain Hall West 159, Indiana University, 727 East Third Street, Bloomington, IN 47405-7105, USA |
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Abstract: | Trapped or stationary gas contributes significantly to the extent of gas mobility reduction for aqueous foams. Simultaneous
measurements of effluent bubble sizes and trapped gas saturation in sandstone are reported for the first time. Roughly 80%
of the gas saturation in an aqueous foam is stationary at steady state in this permeable porous medium. The experiments show
that as gas velocity increases, the trapped gas fraction decreases. Similarly, as injected gas–liquid ratio increases, the
trapped gas fraction decreases. Hence, the absolute velocities of gas and aqueous surfactant solution are fundamental to foamed-gas
mobility reduction for they help determine in situ foam texture. Effluent foam bubbles range in size from 60 to 120 μm in diameter. The smaller the effluent bubble, the smaller
is the fraction of mobile gas. Scaling laws from network percolation theory are used to engender a mechanistic understanding
of the various parameters identified as important in the experimental program. The closed form approimation predicts that
the trapped gas fraction is a weak function of pressure gradient, foam-bubble size, and the permeability of the porous medium.
Moreover, the theory reproduces well the newly obtained experimental data. |
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Keywords: | |
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