Extracting pulse signals in measurement while drilling using optimum denoising methods based on the ensemble empirical mode decomposition

Abstract

To extract original pulse signals in measurement while drilling (MWD), different low-pass filtering methods were designed based on intrinsic mode functions through the ensemble empirical mode decomposition (EEMD). After shaping square waves, a filtering and shaping algorithm on pulse signals was designed. A judgment criterion of filtering algorithms was established according to the approximation index and relevance index of the algorithm. To simulate pulse signals in measurement while drilling, unit impulse signal, periodic noise signal and Gaussian white noise signal were combined. The denoising effect on the simulated signals was analyzed. The optimum denoising algorithm is composed of the intrinsic mode functions (without the front 4 intrinsic mode functions) and the remainders in EEMD. The approximation index of denoising algorithm is 0.771 9 and relevance index is as high as 0.892 9. The real-time mud signals of MWD was analyzed and discussed with the help of the algorithm, the obtained results were reasonable and effective. Key words: pulse signal, Ensemble Empirical Mode Decomposition (EEMD), low-pass filtering, optimum denoising algorithm