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While-drilling mud impulse signal noise reduction method based on optimal wavelet packet decomposition tree

An optimal wavelet packet and mud pulse technology, applied in the direction of earthwork drilling, measurement, borehole/well components, etc., can solve the problems of indistinguishability, information distortion, etc., achieve small mean square error, large energy ratio, and improve time- The effect of frequency resolution

Inactive Publication Date: 2017-02-22
718TH RES INST OF CHINA SHIPBUILDING INDAL CORP
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Problems solved by technology

These noises sometimes drown out the mud pulse signal and are almost indistinguishable
[0003] At present, in the noise reduction method of mud pulse signal while drilling based on wavelet transform, only the low frequency component of mud pulse signal while drilling is decomposed, and the high frequency component of mud pulse signal Much useful signal information will distort the information after noise reduction

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  • While-drilling mud impulse signal noise reduction method based on optimal wavelet packet decomposition tree
  • While-drilling mud impulse signal noise reduction method based on optimal wavelet packet decomposition tree
  • While-drilling mud impulse signal noise reduction method based on optimal wavelet packet decomposition tree

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Embodiment Construction

[0017] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0018] The signal model of mud while drilling with noise can be expressed as: g i =f i +σ·e i , i=0,1,2,…n-1; among them, g i is the noise-containing mud pulse signal, f i is a useful signal, e i is the noise, σ is the noise intensity;

[0019] The noise reduction method based on the optimal wavelet packet decomposition tree performs noise reduction on the noise-containing mud pulse signal while drilling described in this implementation. The specific steps for noise reduction are as follows:

[0020] Step 1. Decompose the wavelet packet of the mud pulse signal, and obtain the complete decomposition tree of the wavelet packet

[0021] 1.1 Selection of wavelet base: db4 wavelet function has symmetry and regularity, its support width is 7, and the order of vanishing moment is 4; since the mud pulse signal not only contains useful signals, bu...

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Abstract

The invention relates to a while-drilling mud impulse signal noise reduction method based on an optimal wavelet packet decomposition tree and belongs to the field of well logging technology. According to the while-drilling mud impulse signal noise reduction method, a wavelet basis and decomposing layers are selected to conduct a wavelet packet decomposition on a mud impulse signal; then logarithm energy entropy is selected as an information cost function to calculate an entropy value of every node; the principle of the minimum entropy value is adopted to build the optimal wavelet packet decomposition tree; a wavelet packet coefficient corresponding to a node of the optimal wavelet packet decomposition tree is subjected to threshold value quantization; at last, the wavelet packet coefficient after the threshold value quantization is subject to signal rebuilding; a signal is obtained after the noise reduction of the optimal wavelet packet decomposition tree. According to the while-drilling mud impulse signal noise reduction method, the while-drilling mud impulse signal after the noise reduction has a large signal-to-noise ratio, a large energy ratio and a small mean square error, useful signals can be separated from noise effectively and good noise reduction effect is provided.

Description

technical field [0001] The invention relates to a noise reduction method for mud pulse signals while drilling based on an optimal wavelet packet decomposition tree, and belongs to the technical field of well logging. Background technique [0002] In the wireless measurement-while-drilling system, affected by the on-site measurement conditions, the signal collected by the standpipe pressure sensor includes not only the mud pulse signal, but also the noise generated by the pressure fluctuation of the mud pump and the pressure fluctuation caused by the rotation of the mud motor. And electromagnetic interference and the noise of the sensor itself. These noises sometimes drown out the mud pulse signal, making it almost impossible to discern. [0003] At present, in the noise reduction method of mud pulse signal while drilling based on wavelet transform, only the low frequency component of mud pulse signal while drilling is decomposed, and the high frequency component of mud puls...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): E21B47/18
CPCE21B47/18
Inventor 林坤马朝选董桂鹏彭晓光李军科亢楠楠
Owner 718TH RES INST OF CHINA SHIPBUILDING INDAL CORP
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