Research On Channel And Synchronization Of Drilling Mud Pulse Telemetry System

Logging technology is adapt to the rapid development of industry needs,of which Measurement while drilling system has gradually become the mainstream.The technology uses the motor control fixed rotor controlling the mud generates pressure wave signal from the bottom of the well to the ground.Ground data acquisition system collects the signal,and transmits the sampling data to the real-time demodulation system,using digital signal processing methods to complete decoding.Channel transmission characteristics and channel model are the basis of communi-cation system research,and are the key to follow-up theoretical research.Therefore,the subject conducts a systematic study of the mud channel and analyzes the frequency re-sponse characteristics of the real mud channel.I use the correlation method of channel estimation,estimating the channel roughly and obtaining the channel length.So,there is a basic understanding of the mud channel.The core of the complete set of drilling mud pulse telemetry system is signal modula-tion and demodulation,and synchronization is an important step in the demodulation pro-cess for obtaining the signal arrival time.This paper uses the chirp and m sequence which have better autocorrelation to complete the synchronization scheme design.However,there are a lot of difficulties in the synchronization process during the actual drilling experiment,including that the fixed threshold detection scheme can not meet the adaptive requirements,modulation characteristics caused by pressure wave bottom pressure changes,a variety of factors affect the signal waveform distortion,frequency-selective attenuation of chirp due to channel characteristics.Synchronization accuracy is not enough for many reasons.This thesis uses threshold detection algorithm to ensure that the threshold set to meet the engi-neering requirements.The signal-processed chirp of the mud well is intercepted as a local source-related match signal and adjust the m sequence window size to solve the synchro-nization accuracy problem,set up a check program for multi-channel decoding to take the optimal solution.This thesis aims to form a set of independent development of drilling mud pulse telemetry system products,prepared based on C language modulation and demodulation system programming.The software can choose two modulation methods,two kinds of noise reduction methods,and complete filtering,synchronization,matched filtering,equal-ization decisions and other functions.In order to achieve the requirements of real-time decoding output,the principle and engineering verification experiments were carried out.