正交水平磁偶源的电磁场分布规律
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摘要
基于平面波卡尼亚电阻率的电磁测深法应用广泛,从天然源到人工源,由单场源到多场源实现从标量测量到张量测量,是电磁法研究的一个方向和趋势。多场源时的张量测量更适合于复杂的、非层状的二维构造,更符合实际地质情况,且可以实现全方位的观测。
正交水平磁偶源能够有效模拟天然场源,方便实现可控源高频大地电磁张量测量。正交水平磁偶源的电磁场分布规律是野外实际工作方法技术的理论基础。
论文推导了均匀大地模型、一维水平层状模型上水平磁偶源的电磁场各分量表达式,利用场的叠加原理计算了正交水平磁偶源的电磁场分量。通过计算张量阻抗得到张量视电阻率。分析了单个水平磁偶源和正交水平磁偶源的电磁场分量、标量视电阻率、张量视电阻率及其相位的分布规律；研究了收发距、场源角度、地电阻率对张量视电阻率的影响；分析了典型的水平层状模型上的张量视电阻率曲线。通过野外试验和找矿实例来验证理论分析结果。
研究表明,正交水平磁偶源产生的电磁场水平分量在各个象限都有一相对低值带,对应的标量视电阻率形成了高阻畸变带,但张量视电阻率畸变带消失；张量视电阻率曲线显示出近区的低阻、过渡区的高阻隆起和远区趋于真值的规律；根据收发距和地电阻率合理确定远区距离,尽量避免在近区和过渡区测量；低阻覆盖比高阻覆盖时达到远区的距离要大；层状模型时底层高阻和过渡区隆起无法分辨,底层低阻和过渡区隆起可以分辨。同时野外试验结果表明,在远区,场源摆放角度对张量测量结果几乎没有影响,即在远区可以实现全方位张量测量；试验剖面和找矿实例证实了正交水平磁偶源的优越性。最后总结了采用正交水平磁偶源的电磁测深法的工作方法技术。
Electromagnetic method based on the plane wave Cagnird apparent resistivity has been used widely. It is an research direction and trend to realize from scalar measurement to tensor measurement by a single source to multi-source and from natural source to artificial source. Tensor measurement realized with multi-source is more suitable for complex、two dimension structure and more actual geological conditions, and can also realize measurement in any azimuth.
The orthogonal horizontal magnetic dipole source simulates the natural electromagnetic field effectively, and conveniently realizes the tensor survey of controlled source electromagnetic in a high frequency band. The field distribution of orthogonal horizontal magnetic dipole source is the theoretical foundations to determine the field operation method.
This thesis infers the electromagnetic field components expression of horizontal magnetic dipole source on the homogeneous model and one-dimensional horizontal layer model, and calculates the electromagnetic field components of the orthogonal horizontal magnetic dipole source using the principle of superposition. It obtains the tensor apparent resistivity through the computation tensor impedance; It analyzes the electromagnetic field components of the single horizontal magnetic dipole source and the orthogonal horizontal magnetic dipole source, the scalar apparent resistivity, the tensor apparent resistivity and the phase distributed rule; It studies the influence of the separation, the source angle, the earth-resistivity to the tensor apparent resistivity; It analyzes tensor apparent resistivity curve of the typical horizontal layered model. It confirms the theoretical analysis result through the field experiment and the mineral exploration.
The research indicates that:The horizontal components of the electromagnetic field show relatively low value belt in each quadrant, the scalar apparent resistivity show a distortion belt in the same position, while the tensor apparent resistivity doesn't show distortion belt; The tensor apparent resistivity is low in the near zone, and high in the transition region, and tending to the true value in the far zone. According to separation and the earth-resistivity reasonably definited the distance of far zone, as far as possible avoids surveying in the near zone and the transition region; When one-dimensional horizontal layer model, the bottom high-resistance layer and the high-resistance of transition region is unable to distinguish, then the bottom low-resistance layer and the high-resistance of transition region may distinguish. And the field experiment carried out indicates that:In the far zone, the source angle has no effects on the measurement result, namely measurement can be done in any azimuth in the far zone. Through the testing profile and the mineral exploration prove the advantage of the orthogonal horizontal magnetic dipole source. Finally it summarizes the methods and techniques of the electromagnetic sounding method using the orthogonal horizontal magnetic dipole source.
正交水平磁偶源能够有效模拟天然场源,方便实现可控源高频大地电磁张量测量。正交水平磁偶源的电磁场分布规律是野外实际工作方法技术的理论基础。
论文推导了均匀大地模型、一维水平层状模型上水平磁偶源的电磁场各分量表达式,利用场的叠加原理计算了正交水平磁偶源的电磁场分量。通过计算张量阻抗得到张量视电阻率。分析了单个水平磁偶源和正交水平磁偶源的电磁场分量、标量视电阻率、张量视电阻率及其相位的分布规律；研究了收发距、场源角度、地电阻率对张量视电阻率的影响；分析了典型的水平层状模型上的张量视电阻率曲线。通过野外试验和找矿实例来验证理论分析结果。
研究表明,正交水平磁偶源产生的电磁场水平分量在各个象限都有一相对低值带,对应的标量视电阻率形成了高阻畸变带,但张量视电阻率畸变带消失；张量视电阻率曲线显示出近区的低阻、过渡区的高阻隆起和远区趋于真值的规律；根据收发距和地电阻率合理确定远区距离,尽量避免在近区和过渡区测量；低阻覆盖比高阻覆盖时达到远区的距离要大；层状模型时底层高阻和过渡区隆起无法分辨,底层低阻和过渡区隆起可以分辨。同时野外试验结果表明,在远区,场源摆放角度对张量测量结果几乎没有影响,即在远区可以实现全方位张量测量；试验剖面和找矿实例证实了正交水平磁偶源的优越性。最后总结了采用正交水平磁偶源的电磁测深法的工作方法技术。
Electromagnetic method based on the plane wave Cagnird apparent resistivity has been used widely. It is an research direction and trend to realize from scalar measurement to tensor measurement by a single source to multi-source and from natural source to artificial source. Tensor measurement realized with multi-source is more suitable for complex、two dimension structure and more actual geological conditions, and can also realize measurement in any azimuth.
The orthogonal horizontal magnetic dipole source simulates the natural electromagnetic field effectively, and conveniently realizes the tensor survey of controlled source electromagnetic in a high frequency band. The field distribution of orthogonal horizontal magnetic dipole source is the theoretical foundations to determine the field operation method.
This thesis infers the electromagnetic field components expression of horizontal magnetic dipole source on the homogeneous model and one-dimensional horizontal layer model, and calculates the electromagnetic field components of the orthogonal horizontal magnetic dipole source using the principle of superposition. It obtains the tensor apparent resistivity through the computation tensor impedance; It analyzes the electromagnetic field components of the single horizontal magnetic dipole source and the orthogonal horizontal magnetic dipole source, the scalar apparent resistivity, the tensor apparent resistivity and the phase distributed rule; It studies the influence of the separation, the source angle, the earth-resistivity to the tensor apparent resistivity; It analyzes tensor apparent resistivity curve of the typical horizontal layered model. It confirms the theoretical analysis result through the field experiment and the mineral exploration.
The research indicates that:The horizontal components of the electromagnetic field show relatively low value belt in each quadrant, the scalar apparent resistivity show a distortion belt in the same position, while the tensor apparent resistivity doesn't show distortion belt; The tensor apparent resistivity is low in the near zone, and high in the transition region, and tending to the true value in the far zone. According to separation and the earth-resistivity reasonably definited the distance of far zone, as far as possible avoids surveying in the near zone and the transition region; When one-dimensional horizontal layer model, the bottom high-resistance layer and the high-resistance of transition region is unable to distinguish, then the bottom low-resistance layer and the high-resistance of transition region may distinguish. And the field experiment carried out indicates that:In the far zone, the source angle has no effects on the measurement result, namely measurement can be done in any azimuth in the far zone. Through the testing profile and the mineral exploration prove the advantage of the orthogonal horizontal magnetic dipole source. Finally it summarizes the methods and techniques of the electromagnetic sounding method using the orthogonal horizontal magnetic dipole source.
引文
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[31]X. Lu. Inversion of Controlled-Source Audio-Frequency Magnetotelluric Data: [D]. Washington:Washington university,1999
[32]I. EMI ElectroMagnetic Instruments. Operation Manual For Stratagem systems running IMAGEM Ver.2.19.2007
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[2]李金铭.地电场与电法勘探.北京：地质出版社,2005
[3]L. Cagniard. Base theory of the magnetotelluric method of geophysical propeeting. Geophysics,1953,18:605-635
[4]A.A.考夫曼,G.V.凯勒.频率域与时间域电磁测深.北京：地质出版社,1987
[5]刘国栋,陈乐寿.大地电磁测深法研究.北京：地震出版社,1984
[6]石应俊,刘国栋,陈乐寿,等.大地电磁测深法教程.北京：地震出版社,1985
[7]朴化荣.电磁测深法原理.北京：地质出版社,1990
[8]何继善.可控源音频大地电磁法.长沙：中南工业大学出版社,1990
[9]M. A. Goldsteind,D. W. Strangway. Audio-frequency magnetotellurics with a grounded electric dipole source. Geophysics,1975,40(4):669-683
[10]赵国泽,陈小斌,汤吉.中国地球电磁法新进展和发展趋势.地球物理学进展,2007,22(4)：1171-1180
[11]王家映.我国石油电法勘探评述.勘探地球物理进展,2006,29(2)：77-81
[12]P. N. Zhao G Z, Huang Q H. Recent advances of Geo-electromagnetic methods. Chinese J. Geophys,2010,53(3):469-473
[13]S. H.Ward地球物理用电磁理论.北京：地质出版社,1978
[14]M. N. Nabighian勘查地球物理电磁法(第一卷理论).北京：地质出版社,1992
[15]罗延钟,史保连,朴化荣.勘查地球物理勘察地球化学文集(电法专辑)北京：地质出版社,1996
[16]李帝铨,底青云,王光杰,等CSAMT探测断层在北京新区规划中的应用.地球物理学进展,2008,23(6)：1963-1969
[17]雷达.起伏地形下CSAMT二维正反演研究与应用.地球物理学报,2010,53(4)：982-993
[18]P. E. Wannamaker. Tensor CSAMT survey over the Sulphur Springs thermal area,Valles Caldera, New Mexico, U.S.A., Part II:Implications for CSAMT methodology. Geophysics,1997,62(2):466-476
[19]尚通晓.双极源CSAMT一维全区反演：[硕士学位论文].长春：吉林大学,2008
[20]何继善.广域电磁测深法研究.中南大学学报(自然科学版),2010,41(3)：1065-1072
[21]周晋国,李毓茂.磁偶源频率测深解释方法.中国煤田地质,1989,1(3)：48-52
[22]胡清龙.磁偶源频率域电磁法正演模拟及快速成像研究：[硕士学位论文].成都：成都理工大学,2008
[23]A. Dey, S. H. Ward. Inductive souding of a layered earth with a horizontoal magneic dipole.Geophysics,1970,35(4):600-703
[24]A. Kostecki. Electromagnetic field of a horizontal harmonic magnetic dipole immersed in a layered anisotropic half space. Acta Geophysical Polonica, 1975,23(4):337-350
[25]C.H.Stoyer, R.J.Greenfield. Numerical solutions of the response of a two-dimensional earth to an oscillating magnetic dipole source. Geophysics, 1976,41(3):519-530
[26]K.H.Lee, H.F.Morrison. A numerical solution for the electromagnetic scattering by a two-dimensional inhomogeneity. Geophysics,1985,50(3):466-722
[27]X. Li, L. B. Pedersen. Controlled source tensor magnetitellurics. Geophysics, 1991,56(9):1456-1461
[28]X. Li, L. B. Pedersen. The electromagnetic response of an azimuthally anisotropic half space. Geophysics,1991,56(9):1462-1473
[29]X. Li, B. Oskooiz,L. B. Pedersen. Inversion of controlled-source tensor magnetotelluric data for a layered earth with azimuthal anisotropy. Geophysics, 2000,65(2):452-464
[30]N. P. SINGH, T. LAL. Horizontal magnetic dipole over an inhomogeneous earth model with exponential variation of conductivity. Pageoph,1995,144(1): 135-153
[31]X. Lu. Inversion of Controlled-Source Audio-Frequency Magnetotelluric Data: [D]. Washington:Washington university,1999
[32]I. EMI ElectroMagnetic Instruments. Operation Manual For Stratagem systems running IMAGEM Ver.2.19.2007
[33]郭建强,武毅著StratageTM EH-4电导率成像系统简介及应用.物探与化探,1998,22(6)：458-464
[34]陈庆凯,席振铢.EH4电磁成像系统的数据处理过程研究.有色矿冶,2005,21(5)：6-9
[35]M. Bastani. EnviroMT-A new controlled source radioma-gnetotelluric system: [D]. Sweden:Uppsala University,2001
[36]A. Pfaffhuber. Development and test of a controlled source MT method in the frequency range 1 to 50 kHz:[D]. Berlin:Technical University Berlin,2001
[37]N. Ismail. Controlled source radiomagnetotelluric (CSRMT) applications in environmental and resource exploration:[D]. Sweden:Uppsala University, 2009
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