【摘要】：大地電磁測(cè)深法(MT)中觀測(cè)信號(hào)的頻譜范圍較寬,其勘探深度可以由數(shù)十米直至上百公里,因而被廣泛應(yīng)用于深部地質(zhì)結(jié)構(gòu)調(diào)查、油氣資源調(diào)查、深部礦產(chǎn)勘查以及工程勘察等領(lǐng)域,成為應(yīng)用最為廣泛的電磁勘探方法。近年來(lái),隨著大數(shù)據(jù)集三維MT探測(cè)工作的陸續(xù)開展,標(biāo)志著高精度和三維化的數(shù)據(jù)處理技術(shù)開始提上大地電磁勘探的日程。與此同時(shí),隨著計(jì)算機(jī)等相關(guān)學(xué)科的飛速發(fā)展,以三維正、反演技術(shù)為代表的MT數(shù)據(jù)處理與解釋技術(shù)也得到了快速發(fā)展。然而實(shí)際工作在處理解釋方面的技術(shù)需求不僅僅體現(xiàn)在三維化方面,同時(shí)也對(duì)大數(shù)據(jù)集反演的計(jì)算效率和解釋模型的精確程度提出了較高的要求,這成為制約大地電磁實(shí)際勘探效果的技術(shù)瓶頸。其中,在復(fù)雜地質(zhì)和地球物理模型中,由地表不均勻電性體引起的靜態(tài)位移更是成為MT數(shù)據(jù)處理解釋中的主要技術(shù)難題之一。針對(duì)大地電磁靜態(tài)位移問(wèn)題,以及目前以空間濾波方法為代表的主流校正方法在技術(shù)上的缺陷,提出了利用阻抗相位受靜態(tài)位移影響較小的特性,以三維正、反演為技術(shù)基礎(chǔ),研究MT靜態(tài)位移數(shù)據(jù)的直接反演解釋方法,以期為MT數(shù)據(jù)的靜態(tài)位移處理提供更為合理的技術(shù)手段。上述MT靜位移數(shù)據(jù)的反演研究對(duì)于提高M(jìn)T方法在實(shí)際勘探工作中的應(yīng)用效果具有積極意義。正演問(wèn)題是大地電磁方法理論研究的核心內(nèi)容,大地電磁的正演研究可以為后續(xù)的靜態(tài)位移數(shù)值模擬以及靜態(tài)位移數(shù)據(jù)的反演研究提供技術(shù)支撐。本文以麥克斯韋方程組為控制方程,分析了三維MT問(wèn)題的邊界條件,以此完成了三維大地電磁邊值問(wèn)題研究。開展了對(duì)伽遼金方法的原理研究,在此基礎(chǔ)上結(jié)合三維大地電磁的邊值問(wèn)題,完成了基于伽遼金方法的三維大地電磁加權(quán)余量方程的推導(dǎo)。根據(jù)現(xiàn)有網(wǎng)格剖分方法的特性,選擇六面體單元剖分作為模型離散化的手段,實(shí)現(xiàn)了對(duì)研究區(qū)域的網(wǎng)格剖分,引入矢量形函數(shù)并且結(jié)合三維大地電磁的伽遼金方程,從而完成了單元的矢量有限元分析,得到了單元內(nèi)的剛度矩陣。由于三維MT模型離散化以后具有大量的棱邊(或節(jié)點(diǎn)),因此在進(jìn)行全區(qū)域的剛度矩陣?yán)奂訒r(shí)必須考慮到節(jié)省存儲(chǔ)和計(jì)算空間�；谝陨霞夹g(shù)考量,分析了剛度矩陣元素的疊加規(guī)律,完成了壓縮條件下剛度矩陣的按行疊加計(jì)算,并對(duì)其施以按行標(biāo)準(zhǔn)壓縮存儲(chǔ)(CSR)。在總體剛度矩陣組裝完成的基礎(chǔ)上,實(shí)現(xiàn)了基于不完全LU分解預(yù)條件的穩(wěn)定雙共軛梯度求解器(BICGSTAB)。利用上述線性方程組求解器完成主場(chǎng)值求解以后,利用差分的方法實(shí)現(xiàn)了輔助場(chǎng)的計(jì)算。在此基礎(chǔ)上,推導(dǎo)了三維介質(zhì)中大地電磁響應(yīng)函數(shù)的計(jì)算公式,包括大地電磁阻抗張量、視電阻率、阻抗相位、傾子振幅和傾子相位等,并最終完成了三維大地電磁矢量有限元正演程序。采用三維正演程序驗(yàn)算了一維水平層狀模型和MT正演研究領(lǐng)域公認(rèn)的三維地點(diǎn)模型。將上述模型的模擬結(jié)果與解析解或者已得到承認(rèn)并公開發(fā)表的模擬結(jié)果進(jìn)行了對(duì)比,上述對(duì)比分析表明本文研究的三維MT矢量有限元正演程序計(jì)算結(jié)果正確,并具有較好的計(jì)算精度。對(duì)大地電磁靜態(tài)位移原理的研究有助于認(rèn)識(shí)靜態(tài)效應(yīng)影響下的各種大地電磁響應(yīng)函數(shù)的變化規(guī)律和特征。從MT的電、磁場(chǎng)與傳輸函數(shù)(阻抗張量)之間的關(guān)系出發(fā),研究二、三維條件下大地電磁靜態(tài)位移的產(chǎn)生機(jī)理,對(duì)于認(rèn)識(shí)MT靜態(tài)效應(yīng)對(duì)觀測(cè)資料的影響特征具有重要意義。在此基礎(chǔ)上,對(duì)理論模型的靜態(tài)位移畸變進(jìn)行了二、三維數(shù)值模擬,深入分析了大地電磁視電阻率和阻抗相位在靜態(tài)效應(yīng)中的響應(yīng)特性。上述MT靜態(tài)位移理論研究和數(shù)值模擬結(jié)果表明,當(dāng)區(qū)域電性結(jié)構(gòu)對(duì)MT觀測(cè)數(shù)據(jù)維數(shù)特征的影響降低到一定程度時(shí),大地電磁阻抗相位具有受靜態(tài)位移影響較小的特性。這為提出基于阻抗相位的大地電磁靜態(tài)位移估算和反演奠定了理論基礎(chǔ)�？紤]靜態(tài)位移的大地電磁反演方法研究,包括靜態(tài)位移估算方法和位移估算值在反演中的應(yīng)用策略兩部分內(nèi)容,二者可以通過(guò)高維反演(二、三維反演)中的模型約束有機(jī)地結(jié)合起來(lái)。在本論文中,首先利用阻抗相位受靜態(tài)位移影響較小這一特性,基于阻抗相位構(gòu)建估算目標(biāo)函數(shù)。在此基礎(chǔ)上,根據(jù)靜態(tài)位移對(duì)MT反演影響的特征(主要表現(xiàn)為在垂向電性異常帶的反演解釋中具有較強(qiáng)多解性,而對(duì)其它區(qū)域的反演相對(duì)可靠),提出以常規(guī)反演模型作為位移估算的模型基礎(chǔ)。以三維大地電磁正演為技術(shù)基礎(chǔ),采用一維線性搜索的方法可以實(shí)現(xiàn)大地電磁靜位移的快速估算方法。將位移估算值應(yīng)用到反演初始模型(通常由低維反演獲得)的修正中,在此模型的約束下采用原始數(shù)據(jù)開展二、三維大地電磁反演,可以在保證反演模型深部結(jié)構(gòu)客觀可靠的基礎(chǔ)上,實(shí)現(xiàn)對(duì)模型中、淺部結(jié)構(gòu)的快速修正,最終為大地電磁數(shù)據(jù)解釋提供更為可靠的反演解釋模型。利用上述研究成果對(duì)理論模型和實(shí)際工作中的AMT數(shù)據(jù)進(jìn)行了驗(yàn)算,驗(yàn)算結(jié)果表明本文提出的靜態(tài)位移快速估算方法得到的靜位移估算結(jié)果比較客觀和準(zhǔn)確。在此基礎(chǔ)上將其應(yīng)用于反演模型的約束中,基于上述模型對(duì)原始數(shù)據(jù)進(jìn)行反演可以較好的逼近真實(shí)模型的電性結(jié)構(gòu)。
[Abstract]:The spectrum range of the magnetotelluric sounding method (MT) is wide, and its exploration depth can be from tens to hundreds of kilometers, so it is widely used in deep geological structure investigation, oil and gas resources investigation, deep mineral exploration and engineering exploration and so on. It has become the most widely used electromagnetic exploration method. In recent years, with large data With the development of the 3D MT detection work, the high precision and three-dimensional data processing technology began to put on the agenda of magnetotelluric exploration. At the same time, with the rapid development of computer related disciplines, the technology of MT data processing and interpretation represented by three dimensional positive and inversion techniques has also developed rapidly. However, the actual work has been done. The technical requirements for processing and interpretation are not only reflected in the three-dimensional aspect, but also of higher requirements for the calculation efficiency of the large data set inversion and the accuracy of the interpretation model. This has become a technical bottleneck to restrict the actual exploration effect of magnetotelluric. The static displacement caused by the body is one of the main technical problems in the MT data processing and interpretation. In view of the magnetotelluric static displacement problem and the technical defects of the mainstream correction method represented by the spatial filtering method at present, the characteristic that the impedance phase is less influenced by the static position shift is proposed, and the three dimensional positive inversion is used. On the basis of technology, the direct inversion interpretation method of MT static displacement data is studied to provide more reasonable technical means for the static displacement processing of MT data. The inversion of the above MT static displacement data is positive for improving the application effect of the MT method in the actual exploration work. The forward problem is the theory of magnetotelluric method The core content of the study is that the forward modeling of magnetotelluric can provide technical support for the subsequent numerical simulation of static displacement and the inversion of static displacement data. In this paper, the boundary conditions of the three dimensional MT problem are analyzed with the Maxwell equation as the control equation. In this way, the three dimensional magnetotelluric boundary value problem is studied. On the basis of the theory of the method of Liao and Jin, based on the boundary value problem of three-dimensional magnetotelluric, the derivation of the three dimensional magnetotelluric weighted residual equation based on Galerkin method is completed. According to the characteristics of the existing mesh generation method, the hexahedral element division is chosen as the method of model discretization, and the grid subdivision of the study area is realized. By introducing the vector shape function and combining the Galerkin equation of three-dimensional magnetotelluric, the vector finite element analysis of the unit is completed and the stiffness matrix in the element is obtained. Since the three-dimensional MT model is discretized with a large number of edges (or nodes), the saving and storage must be taken into account when the stiffness matrix is added to the whole region. Based on the above technical considerations, the superposition law of the stiffness matrix element is analyzed, the stiffness matrix is superimposed under the compression condition, and the storage (CSR) is compressed according to the line standard. On the basis of the assembly of the overall stiffness matrix, the stable Bi conjugate gradient based on the incomplete LU decomposition precondition is realized. BICGSTAB. Using the linear equation solver to solve the home value, the calculation of the auxiliary field is realized by the difference method. On this basis, the calculation formula of the magnetotelluric response function in the three-dimensional medium is derived, including the magnetotelluric impedance tensor, the apparent resistivity, the impedance phase, the dip amplitude and the dip phase, etc. Finally, the three-dimensional magnetotelluric vector finite element forward program is completed. The 3D modeling of the one-dimensional horizontal layered model and the MT forward research field is checked by the three-dimensional forward program. The simulation results of the above model are compared with the analytical solutions or the simulated results which have been recognized and published. The above comparison analysis is made. It shows that the calculation results of the three-dimensional MT vector finite element forward program studied in this paper are correct and have good calculation precision. The study on the principle of magnetotelluric static displacement helps to understand the change laws and characteristics of various magnetotelluric response functions under the influence of static effects. From the electricity of MT, the magnetic field and the transfer function (impedance tensor) The mechanism of magnetotelluric static displacement in two and three dimensional conditions is studied. It is of great significance to understand the influence of the static effect of MT on the observation data. On this basis, the static displacement distortion of the theoretical model is two, three-dimensional numerical simulation, and the magnetotelluric apparent resistivity and impedance phase are analyzed in depth. The response characteristics in the state effect. The above MT static displacement theory and numerical simulation results show that the magnetotelluric impedance phase has a small influence on the static displacement when the influence of the regional electrical structure on the dimension of the MT observational data is reduced to a certain extent. This is a method to estimate the static displacement of the magnetotelluric based on the impedance phase. The calculation and inversion lay a theoretical foundation. The study of magnetotelluric inversion considering static displacement, including the two parts of the static displacement estimation method and the application strategy of the displacement estimation value in the inversion, the two can be organically combined with the model constraints in the high dimensional inversion (two, three dimensional inversion). In this paper, the impedance is first used. The phase is less influenced by the static displacement. Based on the impedance phase construction, the target function is estimated. On this basis, the characteristics of the effect of the static displacement on the MT inversion are based on the strong multi solution in the inversion interpretation of the vertical electrical anomaly zone, and the relative reliability of the inversion to other regions. As the basis of the model of displacement estimation, the method of rapid estimation of magnetotelluric static displacement can be realized by using the method of one-dimensional linear search, which is based on the three-dimensional magnetotelluric forward modeling. The displacement estimation is applied to the correction of the initial model (usually obtained by low dimensional inversion), and the original data is used under the constraint of this model. Two, three dimensional magnetotelluric inversion can ensure the rapid correction of the shallow structure in the model based on the objective reliability of the deep structure of the inversion model, and finally provide a more reliable inversion interpretation model for the magnetotelluric data interpretation. Using the above research results, the theoretical model and the actual work of AMT data are tested. The calculation results show that the static displacement estimation results obtained by the method proposed in this paper are objective and accurate. On this basis, it is applied to the constraints of the inversion model. Based on the above model, the original data can be retrieved well to approximate the real mode electric structure.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P631.325

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本文編號(hào)：2151164