MWD drilling mud signal de-noising and signal extraction research based on the pulse-code information

Mud pulse telemetry is a method used for Measurement-While-Drilling (MWD) in the oil industry. Information (tool face orientation, temperature, pressure, tilt, azimuth, etc.) which is modulated by means of pulse positioning modulation (PPM) is sent from the bottom of the well to the surface by means of pressure waves in the drilling fluid(the drilling mud). Due to external disturbances, the noise removal before decoding is of great importance for real-time monitoring of bottom hole. Wavelet transform has been used widely in signal de-noising. In this paper, a wavelet based de-noising technique is used to isolate the signals from the noise, and waveform shaping and signal extraction based on the pulse-code information are processed to restore pulse signal more fully and to improve the SNR. Results showed that the effect of the wavelet transform on signal de-noising suppression is good. While waveform reshaping and the signal extraction based on pulse-code information can be more accurate in restoring the pulse signal to facilitate future decoding.