| Summary: | Continuous wave mud pulse transmission is the most widely used information transmission technology in measurement while drilling (MWD). The increase in transmission distance will cause the signal attenuation and deformation during transmission, the affecting exploration efficiency. The waveform change law of continuous mud pulse wave in the process of downhole transmission, this paper establishes a mathematical analysis model, focuses on the modulation form of continuous wave signal, physical mud characteristics, and drill pipe characteristics, and discusses the transmission rules of various characteristics on continuous pressure wave. A simulation system of drill pipe transmission pressure wave is constructed. The transmission characteristics of continuous wave signals under different modulation forms are discussed. The positive correlation between the amplitude attenuation and waveform distortion of pulse signals caused by increased gas holdup in the mud under bubbly flow patterns is analyzed. The numerical calculation and simulation analysis results show that the viscosity frequency characteristic of mud is the main factor affecting the attenuation of continuous wave signal. The surface roughness, size and other physical characteristics of drill pipe can affect the transmission speed and attenuation of signals in long-distance transmission. The signal is prone to distortion at the position of modulation phase change.
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