Research On Signal Processing Method For Continuous Wave Mud Pulse

The continuous development of the MWD(Measure While Drilling)and LWD(Logging While Drilling)has contributed to the advancement of drilling technology.As the downhole measurement of data continues to increase,the downhole data transmission rate requirements are getting higher and higher.Continuous wave pulse transmission technology becomes the frontier development direction of the MWD and LWD information transmission with its high transmission rate and strong anti-interference ability.The processing method of weak signal in strong noise background is studied based on continuous pulse signal collected by ground hydraulic cycle experiment.The main works are shown as follows.The current situation of information transmission technology and the research status of data processing of MWD are introduced,indicating that the generation mechanism and transmission characteristics of continuous wave mud pulse signal is described,and the effect of noise on signal detection during continuous wave transmission is discussed.In particular,the research analyzes the principle and characteristics of pump noise,and draws the conclusion that the pump noise cycle is affected by the piston motion rate and the number of cylinders.The ground hydraulic circulation experimental system is briefly introduced,and the continuous wave mud pulse signal processing method based on single pressure sensor and double pressure transmitter acquisition method is discussed respectively.According to the characteristics of the single pressure sensor acquisition and the property that the noise in the two time periods in the frequency domain features unchanged,the collected data are divided into noise-only segments and signal segments with continuous-wave pulses.Under this premise,a time domain denoising method based on pump noise waveform is proposed.A method of frequency filtering is also proposed,which is based on the study of the influence factors of the frequency spectrum distribution of FSK signal.The results of experimental data show that the time domain denoising method and the frequency filtering method have good noise suppression ability.In particular,the frequency filtering method can be used to increase the signal-to-noise ratio of the original signal from less than-20 dB to 6dB,which has high application value.On the basis of further considering the time-varying characteristics of noise,and by using the important feature that the two-way pressure signal characteristics are similar and the main noise is opposite to the useful signal transmission direction,this research analyses the delay differential method denoising principle in detail,establishes a denoising model,and formes a continuous wave mud pulse signal processing method based on double pressure sensor.This method directly suppresses the noise interference by delaying the difference between the twoway pressure signal without considering the noise time domain and the frequency domain timevarying characteristic.Simulation and experimental data processing results show that the method is simple and feasible,and the processing effect is better.