Processing of Wellbore Anti-collision Signal Based on Empirical Mode Decomposition

The vibration caused by an approaching drill bit can be monitored from the existing well casing and used to pre-alarm the well bore collision of the offshore cluster well. For analyzing the non-stationary drill bit vibration signal under complicated drilling environment, use of conventional discrete Fourier Transform (DFT) has been known to be less efficient. To extract useful information contained in the bit signal, a new extraction method based on empirical mode decomposition (EMD) is presented. In the signal processing, EMD is used to decompose the original drill bit vibration signal into the intrinsic mode functions (IMFs). By analyzing kurtosis and energy spectrum of the IMFs, the first five IMFs are found that contain the characteristic of the drill bit, and the specific frequency band of the bit vibration is determined after power spectrum analyzing. When the drill bit is approaching to the adjacent well, the reconstruction bit signal after band-pass filter changes significantly and agrees well with the on-site situation.