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Curve form of imaginary electrical resistance method for
layer may have a different image depending on many factors (type
of probe, ratio between the probe size and thickness of the
reservoir), etc.
The shape of the curve for potential probe is symmetric, in
extreme value (maximum or minimum) for the middle layer and an
abrupt change in the approach to the boundaries of layer (Fig.1.2).
For gradient probes curve shape is asymmetric, in extreme
values (maximum and minimum) at the base (maximum) and roof
(minimum) for consecutive probes (Fig.1.2) (for the case when
investigating a high-ohm layer); and mirror image of curve shape
has a place for inverse (roofing) gradient probe (Fig.1.2).

Determination the boundaries of layers and their thickness
according to the imaginary resistance curves

Based on the analysis of the behavior of the IR curve shape
for different probes (Fig.1.1), when determining the boundaries of
layers, it is advisable to use a gradient probe in which the size less
than the thickness of layer L p <h
Then the base and the roof of high-resistance layer can be
determined by formulas:

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