Page 183 - Percolation Models for Transport in Porous Media With

Chapter 11

Gas Colmatation Effect

during Electric Action on

Saturated Porous Media

Under certain conditions, the temperature of the saturating fluid can reach the
critical value, i.e., the boiling point, and the liquid can transform to the gas phase.
In this case the capillaries shut off with bubbles of gas are no longer permeable
to the liquid phase. The gas colmatation effect develops and causes the decrease
in the permeability of media to the flowing liquid. Thus the total effect of elec-
tric action is determined by two fundamental competing factors: the increase of
permeability due to the change of the pore space structure (cross-section increase
in the conducting capillaries) and the decrease of permeability when some of the
conducting capillaries are cut off from the flow of the liquid phase (being filled
with the gas phase). Domination of either of the outlined trends over the other
is determined by the parameters of the medium and of the treatment, or, when
these parameters are fixed, by the duration of electric treatment.
Colmatation can not only diminish the desired positive effect of electric treat-
ment, but also cause an altogether negative result. Therefore we shall consider
this effect in more detail and carry out theoretical analysis at the micro level and
laboratory modelling of the process.

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