METHOD AND DEVICE FOR ELECTROMAGNETIC FLAW DETECTION-THICKNESS MEASUREMENT OF FERROMAGNETIC METAL PIPES IN MULTI-COLUMN WELLS Russian patent published in 2022 - IPC G01N27/82 

FIELD: measuring technology.

SUBSTANCE: invention relates to flaw detection of metal pipes coaxially located in wells, including steel drill, casing and tubing pipes. The essence of the invention lies in the fact that the excitation of non-stationary electromagnetic fields in the metal columns of the well is carried out by generator coils in probes of different lengths when a current pulse T, selected from the condition T = ah, passes simultaneously through all generator coils, then, starting from the shortest probe, they are sequentially disconnected from the generator with an interval T_i and EMF measurement (E) as a function of time E(t_j,) induced in the receiving coils by eddy currents flowing in the metal pipes under study, at the same time, in probes of different lengths along the perimeter of each receiving coil, hereinafter referred to as the main receiving coil, additional receiving coils with an inductance equal to the inductance of the main receiving coil are placed on magnetic cores whose axes are parallel to the axis of the probe, and for each probe, starting with the shortest probe, the EMF (E) ratios are recorded as time functions E(t_j,) measured by each main and additional receiving coils: in this case, the azimuthal inhomogeneity of the pipe is determined by the magnitude of the excess of the specified ratio over one, the greater the excess, the more pronounced the azimuthal inhomogeneity of the pipe, where E(t_j)main is the EMF measured on the main receiving coil, mV, E(t_j)add is the EMF measured on the additional coil, mV, T is the duration of the current pulse, s, T_i is the current cut-off interval, s, t_j is the step of the EMF measurement interval in the interval T_i, s, τ is the decay constant, 1/s, E is the measured EMF, mV, a is the proportionality coefficient, s/mm, h is the total thickness of the columns, mm.

EFFECT: increasing the accuracy of determining metal loss in local pipe defects in multi-column wells through the use of azimuthal and radial measurements.

2 cl, 8 dwg