Application of EMD in downhole near drill bit weak SNR signal extraction

In practical, the signal to noise ratio (SNR) for the near bit signals is extremely low. To address this problem, empirical mode decomposition (EMD) is proposed to be applied to the extraction of weak SNR signals from downhole near bits. EMD detects the local extremes of the signals iteratively, interpolates the neighboring extremes to get the accurate upper and lower envelopes, and then takes the mean value of the upper and lower envelopes and subtracts them from the original signals to get a set of eigen values that meet specific conditions. Intrinsic mode function (IMF) is the set of eigen values, and then will be properly selected for reconstruction to finally realize the extraction of effective signals. Through simulation tests, it is verified that the measurement error of tool face angle is within ±1.0°, and the measurement error of inclination angle is within ±0.5°.