大地电磁测深静态位移数据的反演方法研究
发布时间：2018-07-28 18:04
【摘要】：大地电磁测深法(MT)中观测信号的频谱范围较宽,其勘探深度可以由数十米直至上百公里,因而被广泛应用于深部地质结构调查、油气资源调查、深部矿产勘查以及工程勘察等领域,成为应用最为广泛的电磁勘探方法。近年来,随着大数据集三维MT探测工作的陆续开展,标志着高精度和三维化的数据处理技术开始提上大地电磁勘探的日程。与此同时,随着计算机等相关学科的飞速发展,以三维正、反演技术为代表的MT数据处理与解释技术也得到了快速发展。然而实际工作在处理解释方面的技术需求不仅仅体现在三维化方面,同时也对大数据集反演的计算效率和解释模型的精确程度提出了较高的要求,这成为制约大地电磁实际勘探效果的技术瓶颈。其中,在复杂地质和地球物理模型中,由地表不均匀电性体引起的静态位移更是成为MT数据处理解释中的主要技术难题之一。针对大地电磁静态位移问题,以及目前以空间滤波方法为代表的主流校正方法在技术上的缺陷,提出了利用阻抗相位受静态位移影响较小的特性,以三维正、反演为技术基础,研究MT静态位移数据的直接反演解释方法,以期为MT数据的静态位移处理提供更为合理的技术手段。上述MT静位移数据的反演研究对于提高MT方法在实际勘探工作中的应用效果具有积极意义。正演问题是大地电磁方法理论研究的核心内容,大地电磁的正演研究可以为后续的静态位移数值模拟以及静态位移数据的反演研究提供技术支撑。本文以麦克斯韦方程组为控制方程,分析了三维MT问题的边界条件,以此完成了三维大地电磁边值问题研究。开展了对伽辽金方法的原理研究,在此基础上结合三维大地电磁的边值问题,完成了基于伽辽金方法的三维大地电磁加权余量方程的推导。根据现有网格剖分方法的特性,选择六面体单元剖分作为模型离散化的手段,实现了对研究区域的网格剖分,引入矢量形函数并且结合三维大地电磁的伽辽金方程,从而完成了单元的矢量有限元分析,得到了单元内的刚度矩阵。由于三维MT模型离散化以后具有大量的棱边(或节点),因此在进行全区域的刚度矩阵累加时必须考虑到节省存储和计算空间。基于以上技术考量,分析了刚度矩阵元素的叠加规律,完成了压缩条件下刚度矩阵的按行叠加计算,并对其施以按行标准压缩存储(CSR)。在总体刚度矩阵组装完成的基础上,实现了基于不完全LU分解预条件的稳定双共轭梯度求解器(BICGSTAB)。利用上述线性方程组求解器完成主场值求解以后,利用差分的方法实现了辅助场的计算。在此基础上,推导了三维介质中大地电磁响应函数的计算公式,包括大地电磁阻抗张量、视电阻率、阻抗相位、倾子振幅和倾子相位等,并最终完成了三维大地电磁矢量有限元正演程序。采用三维正演程序验算了一维水平层状模型和MT正演研究领域公认的三维地点模型。将上述模型的模拟结果与解析解或者已得到承认并公开发表的模拟结果进行了对比,上述对比分析表明本文研究的三维MT矢量有限元正演程序计算结果正确,并具有较好的计算精度。对大地电磁静态位移原理的研究有助于认识静态效应影响下的各种大地电磁响应函数的变化规律和特征。从MT的电、磁场与传输函数(阻抗张量)之间的关系出发,研究二、三维条件下大地电磁静态位移的产生机理,对于认识MT静态效应对观测资料的影响特征具有重要意义。在此基础上,对理论模型的静态位移畸变进行了二、三维数值模拟,深入分析了大地电磁视电阻率和阻抗相位在静态效应中的响应特性。上述MT静态位移理论研究和数值模拟结果表明,当区域电性结构对MT观测数据维数特征的影响降低到一定程度时,大地电磁阻抗相位具有受静态位移影响较小的特性。这为提出基于阻抗相位的大地电磁静态位移估算和反演奠定了理论基础。考虑静态位移的大地电磁反演方法研究,包括静态位移估算方法和位移估算值在反演中的应用策略两部分内容,二者可以通过高维反演(二、三维反演)中的模型约束有机地结合起来。在本论文中,首先利用阻抗相位受静态位移影响较小这一特性,基于阻抗相位构建估算目标函数。在此基础上,根据静态位移对MT反演影响的特征(主要表现为在垂向电性异常带的反演解释中具有较强多解性,而对其它区域的反演相对可靠),提出以常规反演模型作为位移估算的模型基础。以三维大地电磁正演为技术基础,采用一维线性搜索的方法可以实现大地电磁静位移的快速估算方法。将位移估算值应用到反演初始模型(通常由低维反演获得)的修正中,在此模型的约束下采用原始数据开展二、三维大地电磁反演,可以在保证反演模型深部结构客观可靠的基础上,实现对模型中、浅部结构的快速修正,最终为大地电磁数据解释提供更为可靠的反演解释模型。利用上述研究成果对理论模型和实际工作中的AMT数据进行了验算,验算结果表明本文提出的静态位移快速估算方法得到的静位移估算结果比较客观和准确。在此基础上将其应用于反演模型的约束中,基于上述模型对原始数据进行反演可以较好的逼近真实模型的电性结构。
[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.
【学位授予单位】：成都理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.325
本文编号：2151164
[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.
【学位授予单位】：成都理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.325
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