1.
n. [Formation Evaluation]
The reactive (X)
signal, or that part of the alternating signal at the
receiver of an
induction logging tool that is out of
phase with the transmitter current. This signal, also known as the quadrature signal, is less sensitive to
formation conductivity and must be separated from the
R-signal, which is the main or, in older tools, the only source of the induction log. In a simple two-coil
array, a large component of the X-signal is caused by direct
coupling between transmitter and receiver coils. This direct signal is largely eliminated by use of a
bucking coil. The X-signal provides a first-order correction to the
skin effect of the R-signal.