The Research On Measurement While Drilling Mud Pulse Signal Recognition

Measurement while drilling is a new well logging technology developed in recent years,and it can measure the parameters under the well automatically and continuously and transmits the signal to the ground.It can improve the ability of engineering control and formation evaluation of the large displacement wells and difficult horizontal wells.And it can improve the drilling rate.In the technology of Measurement While Drilling(MWD),because the transmission of mud pulse signal in the drill pipe is affected by kinds of noises,and long distance transmission caused large attenuation,leading to the mud pulse signal on wellhead is weak and noisy.How to detective the mud pulse and distinguish correctly from the strong background noise whose frequency is not fixed,become a key issue in the technology of MWD.The current research on MWD technology exist these problems: such as data transmission rate is low,the method to processing noises is not perfect,and the accuracy rate of the recognition about mud pulse signal is low.Based on the analysis of the methods of Discrete Short-Time Fourier Transform and the optimum receiver,to solve the problem of low accuracy rate of the recognition,this thesis applies the methods of Discrete Short-Time Fourier Transform and the optimum receiver to the recognition of MWD mud pulse signal.According to the results of the CRC,the new method corrects the wrong bits in certain circumstances,achieving the purpose of correction.The simulation result indicates that the new method can improve the accuracy rate of the recognition effectively when the SNR is relatively large.