Research On Detection Technology Of Signal In Wireless Measurement While Drilling

In the current wireless measurement while drilling (MWD) system which use mud pulse to transmit signal, the channel transmission of drilling fluid pressure,well depth and pump pressure have serious effect on the signal, so the sampled signal in the measurement while drilling system contains various noises which would affect the useful signal measurement precision and the reliability.How to denoise the mud pulse signal,and detect useful signals submerged in unfixed noise has always been much concerned in mud channel MWD.The thesis centers on detection and extraction of mud pulse signal.First,the transmission characteristics of mud pulse and the niose characteristics in signal have been analyzed deeply,and then a method based on traditional wavelet denoising is raised,it determines denoise effect via correlation coefficients according to average denoising effects as reference standards, simulation experiments verify that correlation coefficient method can be a efficient way to select the best wavelet and the processing results are reliable.Then correlation detection of pulse signal is researched in detail,and simulation experiments verify that correlation detection method of pulse signal can gain useful signals even under low input signal-to-noise-ratio.Finally,a detection algorithm of mud pulse signal based on wavelet multi rasolution analysis and correlation detection is raised,the method has reached a new height in theory, processing results of mud pulse signal verify that this method can remove the noise effectively and gain useful signal without visible distortion especially when the signal is very weak.The performance of this method precedes traditional wavelet threshold denoising way and increases output signal-to-noise-ratio obviously,the original signal is restored primely and this detection algorithm can be realized simply,this method also has high calculation speed and is convenient for engineering application,so this method has a broad application prospect in mud pulse signal processing field.