Downhole Mwd Data Coding And Ground Signal Identification

The MWD technology is developed for transmitting the downhole data to the ground,monitoring the well trajectory,guiding directional drilling.Mud pressure continuous wave method can effectively improve downhole data transmission rate and has a good development prospects.Based on the previous research on this technology,this paper analyzes the compression performance of binary Huffman coding method and Manchester coding method for the downhole drilling data.According to the data characteristics of downhole parameters,this paper proposes that using the quadratic Huffman coding method to compress the downhole data,and the compression ratio is higher than the binary coding method.Considering the generating principle of mud pressure continuous wave signal,this paper proposes a modulation method combining the FSK-PSK,and gives the four-different waveform,which can satisfy the requirement of quadratic coding method.It also can overcome the disadvantage of strong noise of mud channel and the difficulty of signal recognition.According to the source of the noise in the signal detected by the pressure sensor on the ground,this paper analyzes the characteristics of the noise from different sources.Using NLMS adaptive denoising algorithms to filter the mud pump noise and wavelet packet denoising algorithms to filter the noise from the downhole motors,the rotation of the drill string,the drill bit cutting rock,etc.About identification of the after-denoising signal,distinguish the single-bit by the peak and trough of the signal.According to the phase and frequency characteristics,codewords can be confirmed in a single-bit,so we can recover the downhole data.