本文關鍵詞：基于EMD和小波變換的核磁測井回波信號去噪研究　出處：《東北石油大學》2014年碩士論文　論文類型：學位論文

  更多相關文章： 核磁共振測井 小波變換 經(jīng)驗模態(tài)分解 端點效應 去噪

【摘要】：核磁共振測井技術能夠測得豐富的巖層信息，從而對地層進行準確的評價。但是核磁共振測井產(chǎn)生的回波信號是非常微弱的，伴隨著大量的噪聲干擾，導致回波信號的信噪比較低。因此，研究回波信號的去噪，提取更多的有用信息是核磁共振測井中非常重要的步驟。本文的主要工作如下： 首先，詳細介紹了小波去噪的理論，應用MATLAB工具對仿真信號進行小波閾值去噪，分別研究了小波閾值去噪中閾值函數(shù)的選取，小波基函數(shù)的選取和小波軟閾值、硬閾值的選取對去噪效果的影響。分析了信號和噪聲的模極大值在尺度間的傳播特性，用信號仿真對最大分解層次進行了分析，討論了小波閾值去噪和小波模極大值去噪的優(yōu)缺點。并運用小波去噪方法對現(xiàn)場采集的核磁共振回波信號進行去噪研究。 其次，研究了經(jīng)驗模態(tài)分解基本理論和基于經(jīng)驗模態(tài)分解算法的去噪過程。針對經(jīng)驗模態(tài)分解過程產(chǎn)生端點效應問題，提出了本文基于局部極值延拓和端點判斷的方法。通過仿真實驗證明了該方法能夠有效的抑制端點效應，并將基于該方法的經(jīng)驗模態(tài)分解應用在回波信號的去噪中，得到了較好的效果。 最后，研究了核磁共振測井中回波信號噪聲產(chǎn)生的因素。根據(jù)小波去噪理論中閾值和小波基函數(shù)選取問題，經(jīng)驗模態(tài)分解去噪粗糙，丟失有用信息等問題，結(jié)合兩者的優(yōu)點，提出了基于經(jīng)驗模態(tài)分解和小波變換的聯(lián)合去噪方法，通過對現(xiàn)場采集的原始回波信號，應用小波閾值法，經(jīng)驗模態(tài)分解算法和聯(lián)合去噪方法的結(jié)果進行對比分析，，得到融合的算法獲取的信息更多，去噪效果更好，進一步提高了核磁共振測井中回波信號的有用信息含量。
[Abstract]:Nuclear Magnetic Resonance logging (NMR) technology can obtain abundant information of strata and evaluate the formation accurately, but the echo signal generated by NMR logging is very weak, accompanied by a large number of noise interference. Therefore, it is very important to study the denoising of echo signal and extract more useful information. The main work of this paper is as follows: Firstly, the theory of wavelet de-noising is introduced in detail, and the wavelet threshold denoising of simulation signal is carried out by using MATLAB tool, and the selection of threshold function in wavelet threshold de-noising is studied respectively. The influence of wavelet basis function selection and wavelet soft threshold and hard threshold selection on the denoising effect is analyzed. The propagation characteristics of the modulus maximum of signal and noise between scales are analyzed. The maximum decomposition level is analyzed by signal simulation. The advantages and disadvantages of wavelet threshold denoising and wavelet modulus maximum de-noising are discussed. Secondly, the basic theory of empirical mode decomposition and the denoising process based on empirical mode decomposition algorithm are studied. A method based on local extremum continuation and endpoint judgment is proposed in this paper. The simulation results show that the method can effectively suppress the endpoint effect. The empirical mode decomposition based on this method is applied to the denoising of echo signal, and good results are obtained. Finally, the factors of echo signal noise in NMR logging are studied. According to wavelet denoising theory, the selection of threshold and wavelet basis function, the rough denoising by empirical mode decomposition, the loss of useful information and so on. Combining the advantages of the two methods, a combined denoising method based on empirical mode decomposition and wavelet transform is proposed. The wavelet threshold method is applied to the original echo signal collected in the field. The results of empirical mode decomposition algorithm and joint denoising method are compared and analyzed. The fusion algorithm can get more information and better denoising effect. The useful information content of echo signal in NMR logging is further improved.
【學位授予單位】：東北石油大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：P631.81;TN911.4

【參考文獻】

中國期刊全文數(shù)據(jù)庫 前7條

1 池越;周亞同;;基于小波變換的數(shù)字水印算法研究與實現(xiàn)[J];電子制作;2013年05期

2 秦亞輝;馮景輝;陳立定;;基于小波變換的信號去噪方法研究[J];信息技術;2010年01期

3 管玲玲;柳忠校;張善心;;基于小波的信號分析[J];計算機與現(xiàn)代化;2011年03期

4 傅婷;陳瑩;;核磁共振測井技術現(xiàn)狀[J];礦物學報;2013年S2期

5 唐玲;程建;;小波變換在語音信號處理上的應用[J];四川理工學院學報(自然科學版);2012年01期

6 王文圣,丁晶,向紅蓮;小波分析在水文學中的應用研究及展望[J];水科學進展;2002年04期

7 張照煌;丁顯;劉曼;曾菊瑛;;基于小波變換的風電機組傳動系統(tǒng)故障診斷與分析[J];應用基礎與工程科學學報;2011年S1期

中國博士學位論文全文數(shù)據(jù)庫 前1條

1 王婷;EMD算法研究及其在信號去噪中的應用[D];哈爾濱工程大學;2010年

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