【摘要】：多道瞬變電磁法(MTEM)是一種近年來(lái)備受關(guān)注的電磁勘探方法。它采用接地導(dǎo)線源、發(fā)送偽隨機(jī)編碼、與地震勘探類似的陣列式多道觀測(cè)方式,接收的脈沖響應(yīng)數(shù)據(jù)可以像地震數(shù)據(jù)一樣被處理,可實(shí)現(xiàn)地下數(shù)千米深目標(biāo)體的探查。目前,MTEM方法仍是一種正在發(fā)展的電磁勘探方法,在其系統(tǒng)設(shè)計(jì)、數(shù)據(jù)處理等方面還有大量的工作可做。本文在參考前人和研究組前期工作的基礎(chǔ)上,主要針對(duì)以下問(wèn)題進(jìn)行了研究:(1)根據(jù)發(fā)射波形的頻譜特征和MTEM響應(yīng)對(duì)其探測(cè)深度和抗噪能力進(jìn)行分析,從而給出MTEM發(fā)射波形和系統(tǒng)參數(shù)的選取原則;(2)研究MTEM數(shù)據(jù)的基本處理方法。針對(duì)反褶積的不適定性給出MTEM響應(yīng)提取的穩(wěn)定方法,并在分析原有MTEM視電阻率定義缺陷的基礎(chǔ)上,研究更適合MTEM數(shù)據(jù)處理的全域視電阻率定義方法;(3)在MTEM數(shù)據(jù)處理中引入波場(chǎng)變換技術(shù),研究將擴(kuò)散場(chǎng)數(shù)據(jù)變換到波場(chǎng)的穩(wěn)定算法,以通過(guò)波場(chǎng)解釋方法提高M(jìn)TEM解釋工作的分辨率;(4)在變換得到波場(chǎng)數(shù)據(jù)后,利用克西霍夫積分偏移實(shí)現(xiàn)地下電性分布的快速成像,結(jié)合MTEM發(fā)射波形的特點(diǎn),研究“疊前”偏移成像方法。與傳統(tǒng)的TEM方法不同的是,MTEM一般采用特定的發(fā)射波形(如偽隨機(jī)二值序列)進(jìn)行發(fā)射,并同時(shí)記錄發(fā)射信號(hào)和大地的全期響應(yīng),通過(guò)反褶積的方法獲取大地脈沖響應(yīng)。由于無(wú)需僅僅在脈沖間歇期間觀測(cè),無(wú)需等待前一次激發(fā)二次場(chǎng)消失殆盡即可進(jìn)行下一次發(fā)射,使得同樣時(shí)間間隔內(nèi)發(fā)射次數(shù)大為增加。不同的發(fā)射波形具有不同的能量分布,對(duì)噪聲的抑制能力也有所不同。文章將首先給出利用數(shù)值濾波和褶積技術(shù)計(jì)算MTEM系統(tǒng)在層狀大地模型上響應(yīng)的方法,在此基礎(chǔ)上,根據(jù)發(fā)射波形的頻譜特征對(duì)其探測(cè)深度和抗噪能力進(jìn)行分析,從而給出MTEM系統(tǒng)參數(shù)的選取原則。隨后,文章將介紹MTEM數(shù)據(jù)的一些基本處理技術(shù)。傳統(tǒng)的MTEM資料處理一般是利用反褶積方法提取地層的脈沖響應(yīng),然后利用沖激時(shí)刻進(jìn)行視電阻率定義,最后形成視電阻率-偏移距剖面作為勘探的基本成果。這種方法定義的視電阻率很難體現(xiàn)深部地層的電阻率變化,同時(shí),也浪費(fèi)了大量采集到的數(shù)據(jù)。本文將從反函數(shù)的定義出發(fā),給出一種全域視電阻率定義方法,并以此為基礎(chǔ)提出對(duì)MTEM系統(tǒng)的改進(jìn)方法。將滿足擴(kuò)散方程的MTEM數(shù)據(jù)轉(zhuǎn)換到波場(chǎng),采用地震勘探的成熟技術(shù)進(jìn)行資料處理,能夠大大提高電磁法勘探的分辨率。然而,波場(chǎng)變換是一個(gè)不適定的過(guò)程,波場(chǎng)變換矩陣具有非常大的條件數(shù)。本文將討論利用平衡法等技術(shù)降低條件數(shù)的方法,在此基礎(chǔ)上討論波場(chǎng)變換的正則化方法和奇異值分解方法。然后在汲取和發(fā)展前人成果的基礎(chǔ)上,給出一種新的穩(wěn)定波場(chǎng)變換算法——掃時(shí)波場(chǎng)變換。將MTEM數(shù)據(jù)變換到波場(chǎng)后,即可引入偏移成像方法獲得地下電性分界面的幾何形態(tài)。本文首先討論了基于克西霍夫積分的反射波場(chǎng)逆時(shí)“歸位”方法,在此基礎(chǔ)上給出利用克西霍夫偏移法獲得地下介質(zhì)分界面幾何形態(tài)的偏移方法,進(jìn)行了簡(jiǎn)單模型的試算。然后,通過(guò)設(shè)計(jì)較為復(fù)雜的模型進(jìn)行模型測(cè)試,驗(yàn)證了本文在MTEM數(shù)據(jù)處理中引入的波場(chǎng)變換和偏移成像技術(shù)的正確性和穩(wěn)定性。最后,研究了MTEM“疊前”偏移成像的實(shí)現(xiàn)方法,并和前文提出的偏移成像方法進(jìn)行了對(duì)比。
[Abstract]:Multi-channel transient electromagnetic method (MTEM) is a kind of electromagnetic exploration method that has attracted much attention in recent years. The method adopts an array type multi-channel observation mode similar to the seismic exploration, and the received impulse response data can be processed like the seismic data, so that the exploration of the underground thousands of meters of deep target bodies can be realized. At present, the MTEM method is still a developing electromagnetic exploration method, and a lot of work can be done in its system design, data processing and so on. Based on the previous work of the predecessors and the research group, this paper mainly studies the following problems: (1) the detection depth and the anti-noise capability of the transmission waveform are analyzed according to the spectral characteristics and the MTEM responses of the emission waveform, so as to give the selection principle of the transmission waveform and the system parameters of the MTEM; (2) The basic processing method of the MTEM data is studied. In this paper, the stability of MTEM response extraction is given for the discomforts of deconvolution, and on the basis of analyzing the defects of the original MTEM apparent resistivity, the global apparent resistivity definition method for the MTEM data processing is studied. (3) The wave field transformation technique is introduced in the MTEM data processing. The stability of the diffusion field data to the wave field is studied, the resolution of the MTEM interpretation is improved by the wave field interpretation method, and (4) after the wave field data is transformed, the rapid imaging of the underground electrical distribution is realized by using the Ksihov integral offset, and the characteristic of the MTEM emission waveform is combined. Study the 鈥減restack鈥，

本文編號(hào)：2356604