METHOD OF ELECTROMAGNETIC DEFECTOSCOPY-THICKNESS MEASUREMENT IN MULTI-COLUMN WELLS Russian patent published in 2017 - IPC E21B47/00 G01N27/82 G01B7/16 

FIELD: physics.

SUBSTANCE: method includes excitation of a non-stationary electromagnetic field by current pulses in generator coils of different lengths and measurement of the EMF induced in the receiving coils by eddy currents flowing in the metal magnetic tubes under investigation. Herewith all the generator coils are excited by a current pulse of duration T simultaneously. Then they are successively disconnected with interval T_i from the generator, starting with a short generator coil, and sequentially with each measuring coil corresponding to the disconnected generator coil, the EMF (E) is measured as a time function of E(t_j,). And the signal from the latest, long measuring coil is recorded as a decay constant according to the given mathematical expression.

EFFECT: increasing the accuracy of measurements by eliminating the influence of the electromagnetic and geometric characteristics of the near magnetic metal tube on the results of measurements at later times in subsequent pipes.

3 dwg