Device for induction logging in the presence of metallic walls

摘要

A metallic pipe (12) is immersed in the medium (10), and a generator is connected to four points (E, F, G, H) such that unidirectional currents (I) are circulated in the pipe wall. These currents produce a magnetic field in the medium (10) which in turn causes induced medium currents. The induced currents in the medium (10) may be detected by a receiver (16). Although the effect on the receiver of the generated currents in the pipe walls is much greater than that of the induced currents in the medium sensitivity to the latter may be improved by using two receiving coils (16) arranged to cancel the generator current effect.