Page 169 - Percolation Models for Transport in Porous Media With

166 CHAPTER 9 ELECTRIC ACTION EFFECT. EXPERIMENT

Ejection of substance (clay and fine sand} during the electric treatment was
observed in both cases. Fig. 62 illustrates the dependence of the value of the
irreversible change in the permeability on the energy consumption. Continuous
lines represent the results of the calculations for impulse current according to
§8.2 and for alternating current according to §8.4. It can be seen from fig. 62
that the calculations for alternating current agree with experiment satisfactorily
(within the error of experiment). Calculations for impulse current yield somewhat
overestimated values, as compared to experiment. Apparently, this fact is due
to the cement destroyed by impulse current, the cement that was moving slowly
(compared to the duration of treatment) with the flowing fluid. It also gradually
precipitated on the surface of the capillaries, a fact that was not taken into account
in §8.2. Good agreement of the calculated and the experimental data for electric
treatment with alternating current is caused by the fact that such treatment lasts
longer, and the cement precipitating in thin capillaries does not have time to
"settle," since the electric treatment destroying it keeps going. As a result, the
destroyed cement reaches the side of the tube with the flow and leaves the rock.
Comparison of the efficiency of the electric treatment with impulse and alter-
nating current proves the conclusion made in chapter 8, which states that electric
treatment with impulse current is much more effective than treatment with alter-
nating current.
The following conclusions can be drawn.
1. Passage of the electric current is capable of substantially increasing the con-
ductivities of sandy-argillaceous rocks. Experimental dependence of the reversible
changes in the permeability of sandy-argillaceous media on the value of the electric
energy put in a unit mass of the medium, was obtained.
2. The threshold nature of the irreversible changes in the permeability of
sandy-argillaceous media was confirmed experimentally. It was shown that these
changes can be accompanied by the ejection of a suspension of the destroyed
cement. They are caused primarily by the notable changes in the pore space
structure of the medium, with relatively small variations of the average effective
radius of the capillaries.
3. The theoretical conclusion about the efficiency of electric treatment with
impulse current being much greater than that of electric treatment with alternating
current with industrial frequency, was proved experimentally.