Page 163 - Percolation Models for Transport in Porous Media With

160 CHAPTER 9 ELECTRIC ACTION EFFECT. EXPERIMENT

the field intensity for a fixed value of total energy used for the electric treatment
of a unit mass of the rock
t
w = ~E~ I ~(t)dt

0
Intensities E = 0.29E0 , 0.75E0 , l.2Eo, 2.16Eo, and 2.83Eo V /m correspond to the
numbers 1 - 5 of curves.
The master schedule of the dependencies K/Ko = f(w) for a series of ex-
periments (around 200) is presented in fig.58. It can be seen that for w > 0.2
kilowatt-hours per kilogram, after the electric treatment with alternating current,
notable irreversible increase of the permeability is observed. Also note that after
the electric treatment, a substantial increase {by two to five times) in the concen-
tration of the useful component {metal) in the solution filtered out occurs.
Scattering of the experimental points in the region w $ 40 kilowatt-hours per
kilogram is minor {the relative error is no more than 10 %). For w > 40 kilowatt-
hours per kilogram, the relative error can be as big as 30 % {the average error is
~ 15%). This fact is due to water boiling and consequent necessity to take into
account the heat emission during its cooling and the energy efflux with the flowing
fluid.
Using the plot of the dependence K/Ko = f(w) (see fig.58), one can calculate
the change of K(w) {or K(T), where T is the temperature of the medium) as
a function of the duration t of treatment according to the energy w put in a
unit mass of the given ore and the intensity Eo of the field responsible for the
electric treatment. The expected value of the irreversible change to K can also be
calculated using this plot.

9.2 Pore Space Structure of a Sandy-Argillace-
ous Medium after Electric Treatment

In §9.1, the results of studies of both the reversible and the irreversible changes
of permeability for different parameters of electric treatment were described. For
sufficiently large values of the field intensity, irreversible changes of the permeabil-
ity are constantly observed. In particular, this phenomenon is accompanied by
evident discharge of substance {clay, small sand) with the flow of the fluid. This
proves indirectly that the pore space structure of the medium changes.
In this section, experimental data of the research on the irreversible changes
of the permeability and the pore space structure of the medium after electric
treatment with impulse and periodic current are presented.
Studies were carried out using cores of sandy-argillaceous rocks whose fractional
structure was determined beforehand (see table 9.1). To determine the pore space