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Modeling Subsurface Petroleum Hydrocarbon Transport

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Irregular Water/NAPL/Air Distribution Copyright 1988 CRC Press

In a three phase water/NAPL/air system the pore space is occupied by all three fluids. A three-phase distribution would represent the vadose zone.

There is again an order of preferential wetting. The pieces of the three-phase puzzle fit together from what we've seen for two-phase systems. Let's review:

Water is wetting relative to air
NAPL is wetting relative to air
Water is wetting relative to NAPL

Here goes: The water is wetting relative either to air or NAPL, air is non-wetting relative to either water or NAPL. Thus the two extremes are set and NAPL is left to occupy a position of intermediate wettability. Although this fits logically from what we've seen, these relationships were determined through experiment, and they only apply to strongly wetted systems.

In the photograph, the NAPL (red) can be seen to be coating the water (blue), and is surrounded by air. Now air occupies the largest pores; water still has the smallest, and NAPL forms films coating the water. In some places NAPL accumulates.

The color photograph on this page is reprinted with permission from Dense Chlorinated Solvents, Friedrich Schwille, Translated by James F. Pankow, 1988, Copyright CRC Press, Boca Raton, Florida c 1988

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