Page 179 - Percolation Models for Transport in Porous Media With

176 CHAPTER 10 PRODUCTION CHANGE: ELECTRIC ACTION

of w;/(E"Qo) are presented, and 1/J;(L") are presented in fig. 66, b.
It is clear from these plots that w; / ( E" Qo) decreases and 1/Je increases as F"
grows and L" diminishes. These dependencies are more sensitive to the changes
in the quantity L" than they are to the changes in F". The value Q/Qo depends
weakly on the parameters of the problem and varies from 1.5 to 2.5.
Two regions are shown in fig. 67 in the plane of the parameters F" and L".
The boundaries of those regions, where the optimal electric treatment regime is
possible, form region I. The boundaries of those regions, where the maximum
of 1/Je does not exist, and consequently the treatment regime with small currents
(we <we) is optimal as far as the energy consumption costs are concerned, form
region II.
Therefore depending on the values of the parameters L" and F" determined
from the plot of K(T), both the presence and the absence of an extremum of the
function 1/Je are possible. In principle, the optimal electric treatment regime can
be determined based on the calculated data (see figs. 65 - 67) and the economic
calculations. For an arbitrary form of the K(T) dependence, the optimal electric
treatment regime is determined similarly from the solution to the equation (10.28).
Note that even when the electric treatment is carried out in non-optimal regimes,
the economic effect is positive. This is due to the fact that the time of maintenance
of the wells, necessary for the development of a deposit (i.e., for reaching the
established level of the recovery of the useful component), is made less.

10.3 Results of Field Studies

Typical diagrams of electric energy supply to the reservoir, which have already
been tested, are presented in fig. 63 for the case of a single well. In diagram I I I
voltage is supplied from the source directly to the casing column. In this case it
is not necessary to immerse an electrode into the well. This diagram is rather
simple and efficient, but if the reservoir lies more than 300 meters deep, then the
electric energy consumption due to the current flow through the lateral area of the
wells becomes very large. In this case it is advisable to use a different diagram of
energy supply. Experimental work done with objects of various geological types
in different regions (over 80 places) showed that the well production rates can
increase by 2 to 20 times (at an average of 1.5 to 2 times) after electric treatment.
Experiments showed that well production rates keep stable for two to three
years after the electric treatment. A positive effect is observed for electric treat-
ment of different types of rocks, e.g. sandy-argillaceous, carbonate, or fractured
ones. The studies involving observation wells showed that the changes of perme-
ability after the electric treatment are registered at distances up to 10m (fig. 68).
A typical correlation for the modification of a hydrogeological well production rate