PECT Analytical Modeling Fast Calculation Method of Multilayer Ferromagnetic Casings

Pulsed eddy current testing (PECT) is an effective approach for the nondestructive evaluation of downhole multilayer ferromagnetic casings. However, the time overhead of conventional analytical modeling is undesirable for casing parameter inversion. To improve the time overhead, this article proposed an analytical modeling fast calculation method based on the complex-frequency-domain expression of the PECT and a numerical inverse Laplace transform algorithm. Specifically, the numerical inverse Laplace transform method fixed-Talbot algorithm (FTA) is implemented in the calculation, which computes the inverse Laplace transform rapidly and accurately. The proposed FTA enables the fast analytical modeling calculation of both single-casing and multilayer casings. Numerical and practical experiments are conducted to validate the efficiency and accuracy of the proposed FTA-based analytical modeling. The experimental results indicate that the time overhead of the FTA-based modeling is improved compared with the conventional residue theorem (RT)-based analytical modeling, and the theoretical data obtained with the proposed modeling also show good consistency with the experimental data.