EMD-Based Borehole TEM Array Signal Denoising and Baseline Wander Correction for NDT of Downhole Casings

Abstract

Transient electromagnetic (TEM) techniques have been proven to be efficient for nondestructive testing (NDT) operations due to their pulsed eddy-current properties. However, in the field of downhole measurements, harsh environments may significantly influence the NDT performance in downhole casings. In this paper, an empirical mode decomposition (EMD) method based on borehole TEM array signal denoising and baseline wander (BW) correction is proposed to compensate for the bad measurement conditions that affect downhole NDT. Based on the borehole TEM signal model, we investigated the principle of the EMD approach for the borehole TEM response, where the background magnetic noise and temperature drift effects were analyzed by considering the motion measurement and effective permeability. It was found out that although the BW can be effectively removed with the EMD approach, the performance of the signal denoising is closely related to the measurement speed of the downhole NDT sensors. To solve this problem, we proposed an array-based ensemble EMD method to improve the denoising performance of the borehole TEM signals by formulating a three-dimensional borehole TEM data structure, where the generation of the noise-aided data can be more efficient by employing the borehole TEM array. The performance of the proposed method was verified by applying it to a borehole TEM system for the NDTs of oil-well casings. In addition, field experiments were conducted, and the results demonstrated the effectiveness of the proposed method.

Multiple-Transmit Focusing for the Nondestructive Testing of Downhole Casings Based on Borehole Transient Electromagnetic Systems

“…Notably, in the derivation above, although G T (t, d) was unknown, it was not used directly. As an alternative, XzG T (t, d) was involved in (12) and could be obtained from the receiving signal. Therefore, the modification of the LCMV subjection did not influence the realization of the MTF method.…”

“…NDT techniques, the design of eddy-current sensors as well as their signal processing for borehole measurements are strongly restricted by harsh environments, including narrow underground confined spaces [9], the large temperature range [10], and cumbrous metal tool housings against high wellbore pressure [11], which greatly affect the performance of borehole NDTs [12], [13].…”

Uniform Circular-Array-Based Borehole Pulsed Eddy-Current System for Asymmetry Defect Inspection in Downhole Casings

“…Moreover, some previous studies focused on optimizing the PEC probe design for defect detection and revealed that the level of sensitivity of PEC probes can be improved by optimizing the probe design parameters and using magnetic sensors in place of conventional pickup coils [23,24]. Based on this, considering the limited space and high temperatures, approaches for designing PEC sensors and processing signals have been proposed to improve the performance of borehole PEC systems [25][26][27]. In [25,26], a probe with a single transmitter and multiple receivers was designed, and the array output was weighed to eliminate the influence of transmitting-receiving distance and correct the baseline wander caused by the variation in the temperature and motion measurement.…”

“…Based on this, considering the limited space and high temperatures, approaches for designing PEC sensors and processing signals have been proposed to improve the performance of borehole PEC systems [25][26][27]. In [25,26], a probe with a single transmitter and multiple receivers was designed, and the array output was weighed to eliminate the influence of transmitting-receiving distance and correct the baseline wander caused by the variation in the temperature and motion measurement. Authors in [27] employed multiple transmitters to realize the magnetic focusing by weighing the current of each transmitter.…”

Near-And Remote-Field Eddy Current Data Fusion: Wellbore Casing Inspection with Hybrid Neural Networks

“…Wellbore casing electromagnetic (EM) inspection data is well-known in its difficulty in interpretation (Martin et al 2017, Brill et al 2011), especially when directional information of metal loss is required. A variety of factors such as temperature drift, inspection tool movement speed, baseline wander (Dang et al 2020), and the non-uniformity in casing permeability contributes to the perturbations in EM data. In addition, other conductive wellbore components such as collars often greatly affect EM sensor readings (Sun et al 2022).…”