Page 167 - Percolation Models for Transport in Porous Media With

164 CHAPTER 9 ELECTRIC ACTION EFFECT. EXPERIMENT

the permeability 5 days later made up 2.25 times for the rocks from the first series
and 1.95 for those from the second series.

9.3 Research on Irreversible Change of Conduc-

tivities for Sandy-Argillaceous Media after
Electric Treatment

Experiments were conducted to find the values of thresholds E'(r) for the electric
treatment with impulse current and t'(Eo) for the electric treatment with alter-
nating current, and also to determine the nature of the permeability and the
electric conductivity change for two sandy-argillaceous media whose characteris-
tics were presented in §9.1. Part of the studied medium was used to determine
f(r) according to the methods outlined in §9.2.
The experiment studying comparative effectiveness of electric treatment with
impulse and alternating current consisted of several stages. At the first stage,
successive packing of three tubes with rock was carried out (the diameter of each
tube Dt = 1.6 em, height L = 10 em). Filling of the tubes and ramming of the
rock there was done gradually with a dilute solution of CaC12 being injected from
the bottom side of the tube. This allowed to displace air out of the tube and
the rock. At the second stage, long-lasting (around 5 days) flow of the solution
through the rock took place, until the production rate steadied. A significant drop
in permeability was observed at this stage. At the third stage, electric treatment
of the first and the second tubes with a given value of energy input w per unit
mass was carried out. The third tube was kept for references. The first tube was
treated with alternating current. Energy input was calculated using the formula

tp
w = ~ EgP I u(t)dt
0
Here Eop is the amplitude of the intensity of the alternating current field, t, is
the duration of the electric treatment. The second tube was treated with impulse
current. Energy consumption was determined using the formula

t,.
1
w = ~r00 Eou I E(t) dt
0
Here Eou is the amplitude of impulse current, tu is the duration of the impulse
electric treatment. At the fourth stage, durable flow of the solution in the tubes
took place until the production rate of the latter steadied (3 to 5 days). Then the