A real-time correction method for baseline wander of transient electromagnetic logging signals

摘要

The empirical mode decomposition method can eliminate the baseline wander caused by the changes in the downhole environment, but it is difficult to achieve real-time segmentation processing due to the influence of the end effect. Aiming at this problem, this paper proposed a real-time correction method for baseline wander of transient electromagnetic logging signals based on mirror continuation method. In this method, by locating the position of the coupling in the original signal, and taking the middle position of the two couplings as the end point, the logging signal is extracted and corrected in real time and in sections. First, the original signal at the endpoint is extracted and its mirror image is extended. Then the extended signal is decomposed by empirical mode and the high-order intrinsic mode function is removed. On this basis, the corresponding continuation point is truncated according to the depth of the original signal endpoint and then the signal is reconstructed. Finally, the next segment of the original signal is reselected to eliminate the baseline wander and the corrected signals are successively spliced to finally realize the real-time segmented correction of the log signal baseline wander. The processing and analysis of field measured data show that the method studied in this paper can effectively solve the problem of transient electromagnetic logging signal baseline wander caused by downhole temperature, and has the advantages of real-time, high efficiency and accuracy.