关键词: 裂缝, 脉冲涡流, 套管, 油管, 有限元

Abstract: Transverse cracks are great menace to casing safety due to their high probability to cause fracture. Transverse crack detection in casing through tubing with transverse probe using pulsed eddy current method is studied by finite element simulations and experiments. Distributions and variations of the eddy currents and magnetic fields in pipes and voltages of the receiving coil in different detection setups are given in the simulations. Simulation results show that highest eddy current intensity in casing wall does not appear in the zone which the transverse probe directly faces against but the zone which the axis of the transverse probe is parallel to. The greatest disturbance in the eddy current distribution is caused when the crack is parallel to the axis of the transverse probe. The properties of the magnetic field in the pipe are similar to those of the eddy current field. Thus it is explained why higher detection sensitivity is obtained when the axis of the transverse probe is parallel to the transverse crack rather than perpendicular to the crack. The experimental results agree well with the simulations and show that the detection sensitivity of the transverse probe to transverse crack is much higher when the axis of the probe is parallel to the crack than perpendicular to the crack.

Key words: casing, crack, finite element, pulsed eddy current, tubing