Cecil Moore wrote:
Yuri Blanarovich wrote:
"Becomes very lossy" or paraphrased "lose its conductivity" to make
the point?

I agree that a wire laid on the ground does not become very lossy
although energy is lost to the lossy medium in proximity to the wire.

When I worked for the Schlumberger Oil Well Surveying Corp., I
used to run an "induction log" on freshly drilled wells before
the casing was set while the hole was filled with "mud". In basic
terms, it worked like a transformer. The primary would create an
inductive field in a donut shape out in the formation. That inductive
field would generate a voltage in the secondary of the transformer.
A little processing of the received signal yielded the conductivity
of the formation, high for shale and salt water, low for fresh water
and oil, lower for gas - same principle as metal detectors.

We also had a cheaper "electrical log" which was simply two conductive
electrodes at each end of a wire-line sonde between which conduction
current was measured. Not nearly as accurate as the induction log
because it was highly affected by the fresh water used to make the mud.
--
73, Cecil http://www.qsl.net/w5dxp



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