摘要
大地电磁法(MT)是重要的深部地球物理探测手段,在油气、地热勘探,深部探测等领域有着广泛的应用。传统的MT数据处理通常假定地下介质无磁性,仅对介质的电阻率参数进行反演。本文以国家自然科学基金重大项目为依托,在分析计算岩石磁化率参数对大地电磁数据影响的基础上,提出了由MT数据同时反演介质电阻率和磁化率参数分布的方法,并用所发展的方法技术成功地进行了实测资料的处理。论文的主要内容与成果如下:
(1) 推导了电阻率和磁化率同为参数时的二维大地电磁正演计算公式。利用Madden和Mackie等所提出的基于传输网络的有限差分算法,实现了其正演计算,并详细地阐述了电阻率和磁化率对大地电磁响应的影响,证实了磁化率主要是影响磁场信号的同相分量,而对磁场信号的异相分量和电场信号的影响比较弱。当磁化率k≥0.01SI时,在某些低频点处视电阻率值可以增加5Ωm左右,并且随着磁化率的增加,这种增加的幅度显著增大;而阻抗相位的变化则比较小。通过对比研究,认为在大地电磁勘探中,起决定作用的是岩石的电阻率;但是在高磁性物质存在的地区进行大地电磁观测时,还必需重视磁化率的影响。
(2) 提出了由大地电磁实测数据同时反演电阻率和磁化率分布的方法技术。考虑电阻率和磁化率同为参数变量,推导了由MT数据同时反演电阻率和磁化率参数分布的反演计算公式。在同时反演过程中,观测数据和物性参数之间以及电阻率和磁化率物性参数本身之间是一种复杂的非线性关系。本文对电阻率和磁化率之间的非线性关系利用一个线性函数来处理,重点是采用了Rodi和Mackie所发展的非线性共轭梯度算法来处理观测数据和物性参数之间的非线性关系,完成了新反演方法的程序代码编写。
(3) 推导了二维大地电磁法中TM和TE两种极化模式的观测数据关于模型参数的灵敏度表达式。利用Mora提出的计算灵敏度的思想,根据Rodi、Mackie和Madden发展的算法,给出了观测数据关于模型参数灵敏度的计算表达式和求解过程。
(4) 通过数值实验和实际观测资料实验,证明了本文研究发展的算法和计算程序的正确性与价值。使用所研发的由MT数据同时反演电阻率和磁化率参数分布的方法技术对内蒙古大杨树盆地9条MT测线的观测资料进行了重新处理,厘定了电阻率分布图像,并新获得了磁化率的分布图像。反演结果表明,在火山岩分布地区,由MT数据获得的磁化率分布信息更有助于推断火山岩的分布,并能为在火成岩覆盖地区寻找沉积岩的分布提供一种新的依据。利用新发展的方法技术同时还可以解决在某些大地电磁观测数据中出现负的同相分量值问题,使得这些出现在低频段的负的同相分量值不再是一种“污染源”,而是作为一种提供磁化率分布很重要的信息源。
The MT has been a powerful geophysical tool in exploring the interior of the earth and widely applied in the oil and gas prospecting, geothermal prospecting and deep survey. It is assumed in traditional MT data processing that underground media is not magnetism, in which only the resistivity parameter. Sponsored by NSFC, we calculated and analyzed the effect of rock susceptibility on geoelectric and geomagnetic observations and proposed a new method to invert resistivity and susceptibility distribution simultaneously from the MT data. The application of this method in observed data processing is successful. The main contents and achievements of the thesis are as follows:(1) The 2-D forward modeling formula of the resistivity and susceptibility as model parameters is deduced. By use of the finite difference method, which is based on transmission network proposed by Madden and Mackie, we completed forward calculation and demonstrated in detail the effect of resistivity and susceptibility on MT response. It is conformed that the susceptibility mainly affects the in-phase components of magnetic signal, but a little effect on the quadrature components of magnetic and electrical signal. When the susceptibility is k≥0.01SI, the apparent resistivity amplitude may increase about 5Ωm at some low frequency, and the orders of change increase observably as increase of magnetic susceptibility. But, impedance phase is quite small. So in the MT survey, the resistivity of rock is the decisive factor. However in the region with high susceptibility, the susceptibility must be taken into account.(2) A new method to inverse the resistivity and susceptibility simultaneously from the MT data is proposed. In this inversion method, both resistivity and susceptibility are parameters. The relationship between the observed data and physical parameters of rock and physical parameters of rock themselves are nonlinear. We use a linear function to depict the nonlinear relationship between resistivity and susceptibility, and use the nonlinear conjugate gradient method proposed by Rodi and Mackie to deal with the nonlinear relationship between observed data and physical parameters. We accomplished the program codes of the new method.(3) The expression of observed data with model parameters under the condition of TM and TE polarization in 2-D MT sounding is given. Using the idea of calculation sensitivity proposed by Mora and the algorithm developed by Rodi, Mackie and Madden, we gave the expression of calculating sensitivity and the resolving procedures.(4) By numerical experiments and observation data experiments, the results show that it is feasible to inverse the resistivity ant susceptibility distribution simultaneously and that the program is right. Using this program, We processed the observed data from DaYangShu basin, and the results show that the output of resistivity and susceptibility can gave more information about the distribution of the lava and then can gave new information about sediment. Using this method we can solve the negative in-phase problem as well so that the negative in-phase component can also be used as valuable information.
引文
[1] 曹俊兴,李学民,贺振华,考虑磁参数的MT反演 第六届中国国际地球电磁学术讨论会论文集,2003,5~8
[2] 曹俊兴,非均匀介质电磁成像,四川科学技术出版社,2000
[3] 李学民,曹俊兴,何哓燕,王兴建.用格子玻尔兹曼方法模拟非均匀介质中的电场响应,地球物理学报,2004(2):349~353
[4] 李学民,曹俊兴.磁化率对大地电磁响应的影响.地球物理学报,2005第4期(待刊)
[5] 李学民,曹俊兴,贺桃娥.断层构造的大地电磁响应曲线变化特征的研究,天然气工业,2004(7):42~44
[6] 李学民,曹俊兴,刘百红.分形理论在提取大地电磁资料构造信息中的应用,石油物探,2004(3):245~247
[7] 贺振华,李正文,勘查技术工程学,成都理工大学,2001
[8] 陈乐寿,王光锷,大地电磁测深法,地质出版社,1990
[9] 陈乐寿,王光锷,构造电法勘探,中国地质大学出版社,1991
[10] 刘国栋,邓前辉,电磁方法研究与勘探,地震出版社,1993
[11] 刘国栋,陈乐寿,大地电磁测深研究,地震出版社,1984
[12] 王家映,石油电法勘探,石油工业出版社,1992
[13] 石应骏,刘国栋,王家映等,大地电磁测深法教程,地震出版社,1985
[14] 朴化荣,电磁测深法原理,地质出版社,1990
[15] 王家映,地球物理反演理论,高等教育出版社,2002
[16] 汤吉,刘铁胜,江钊等,长白山天池火山区大地电磁测深初步观测,地震地质,1997(19):164~170
[17] 杨子建,大地电磁法在火山岩覆盖区的应用,石油地球物理勘探,1997(32):165~194
[18] 晋光文,孙洁,王继军,地形对大地电磁测深资料的影响,地震地质,1997(191:363~369
[19] 李丽清,余钦范,李辉,大地电磁资料的分形特征,物探化探计算技术,1997(19):312~316
[20] 石应骏,寸树苍,陈华玢等,桐乡—平湖拗陷大地电磁研究,成都理工学院学报,1996(23):109~112
[21] 赵国泽,汤吉,刘铁胜等,山西阳高~河北容城剖面大地电磁资料的初步解释:阻抗张量分解技术以及应用.地震地质,1996(18):66~76
[22] 安四喜,陈秀儒,大地电磁测深法的现状、作用及发展趋势,石油地球物理勘探,1998(33):164~167
[23] 朱仁学,周云轩,孟令顺等,大地电磁测深资料解释的新方法,长春科技大学学报,2000(30):271~274
[24] 罗静兰,邵红梅,张成立,火山岩油气藏研究方法与勘探技术综述,石油学报,2003(24):31~38
[25] 赵国泽,刘铁胜,江钊等,山西阳高—河北容城剖面大地电磁资料的二维反演解释,地球物理学报,1997(40):38~46
[26] 魏文博,我国大地电磁测深新进展及展望,地球物理学进展,2002(17):245~254
[27] 范典高,段本春,岩浆岩储层的形成及油气藏类型,2000(30):321~326
[28] 杨生,大地电磁测深法环境噪声抑制研究及其应用,中南大学博士论文,2004
[29] 陈小斌,大地电磁正反演新算法研究及资料处理与解释的可视化集成系统开发,中国地震局地质研究所博士论文,2003
[30] 严家斌,大地电磁信号处理理论及其方法研究,中南大学博士论文,2003
[31] Thomas, L. Electromagnetic sounding with susceptibility among the model parameter, Geophysics. 1977(42): 92~96.
[32] Telford, W.M., Geldart, L, P., and Sheriff, R.E. Applied geophysics, 2nd Ed, Cambridge Univ. 1990
[33] Goldstein.N.E, and Ward.S.H. The separation of remnant from induced magnetism in situ Geophysics, 1966(31): 779~796
[34] Ryu, J., Morrison, H.F and Ward, S.H. Electromagnetic fields about a loop source of current. Geophysics, 1970(35): 862~896
[35] Rodi, W. and Mackie, R.L.Nonlinear conjugate gradients algorithm for 2-D magneto telluric inversion, Geophysics, 2001(66): 174~187
[36] Newman, G.A., and Alumbaugh, D.L. Three-dimensional magnetotelluric inversion using non-linear conjugate gradients, Geophysics. 2000(140): 410~424
[37] Farquharson, C.G and Oldenburg, D.W et al., Simultaneous one-dimensional of loop-loop electromagnetic data for magnetic susceptibility and electric conductivity, Draft, 2003,1~42
[38] Farquharson, C.G., and D.W.Oldenburg. Inversion of time-domain electromagnetic data for a horizontally layered Earth, Geophysics Journal International, 1993(114): 433~442
[39] Farquharson, C.G., and D.W.Oldenburg. Approximate sensitivities for the electromagnetic inverse problem, Geophysics Journal International, 1996(126): 235~252
[40] Farquharson, C.G., and D.W.Oldenburg. A comparison of L-curve and GCV techniques for estimating the regularization parameter in nonlinear inverse problem, Geophysics Journal International, 2004(3): 411~422
[41] Huang, H., and D.C.Fraser. Magnetic permeability and electrical resistivity mapping with a multi frequency airborne EM system, Exploration Geophysics, 1998(29): 249~253
[42] Huang, H., and D.C.Fraser. Airborne resistivity and susceptibility mapping in magnetically polarizable areas, Geophysics, 2000(65): 502~511
[43] Li, Y., and D.W, Oldenburg. Fast inversion of large-scale magnetic data using wavelet transforms and a logarithmic barrier method, Geophysical Journal International, 2003(152): 251~265
[44] McGillivray, P.R., and D.W.Oldenburg. Methods for calculating Frechet derivatives and sensitivities for the nonlinear inverse problem: a comparative study, Geophysical Prospecting, 1990(38): 499~524
[45] Zhdanov, M.S., and D.A.Pavlov, Analysis and interpretation of anomalous conductivity and magnetic permeability effects in time domain electromagnetic data, Journal of Applied Geophysics, 2001(46): 235~248
[46] Beard, L.P., and Nyquist, J.E. Inversion of airborne electromagnetic data for magnetic permeability: the 67th Ann. Internat.Mtg.Soc.Expl.Geophys.Expanded Abstracts, 1996,940~943
[47] Fraser, D.C. Magnetite ore tonnage estimates from an aerial electromagnetic survey: Geoexploratio, 1973(11): 97~105
[48] Habashy, T.M., Chew, W.C., and Chow, E.Y. Simultaneous reconstruction of permittivity and conductivity profiles in a radially inhomogeneous slab: Radio Sci., 1986(21): 635~645
[49] Qian, W., Gamey, J., Lo, B., and Holladay, J.S. AEM apparent resistivity and magnetic susceptibility calculation: the 67th Ann. Internat.Mtg.Soc.Expl.Geophys.Expanded Abstracts, 1996, 1282~1285
[50] Sena,A.G., and Toksoz, M.N. Simultaneous reconstruction of permittivity and conductivity for cross hole geometry, Geophysics, 55,1302~1311 (1990)
[51] Ward, S. Unique determination of conductivity, susceptibility, size, and depth in multi frequency electromagnetic exploration, Geophysics, 1959(24): 531~546
[52] Zhang, Z. Reconstruction of conductivity and susceptibility from the inversion of EM data, Ph.D Thesis, Univ. of British Columbia, 1997
[53] Zhang, Z., and Oldenburg, D.W. The inversion of AEM data to recover magnetic susceptibility structure in a 1-D environment, at the 66th Ann. Internat. Mtg., Soc. Expl. Geophys, Expanded Abstracts, 1995, 235~238
[54] Zhang, Z., and Oldenburg, D.W. Simultaneous reconstruction of 1-D susceptibility and conductivity from EM data, at the 67th Ann. Internet. Mtg., Soc. Expl. Geophys, Expanded Abstracts, 1996a, 241~244
[55] Zhang, Z., and Oldenburg, D.W. Reconstruction of 1-D conductivity from coaxial, coplanar, vertical coplanar and perpendicular EM data, at the 67th Ann. Internat. Mtg., Soc. Expl. Geophys, Expanded Abstracts, 1995, 1294~1297
[56] Zhang, Z., and Oldenburg, D.W. Recovering magnetic susceptibility from electromagnetic data over a 1-D earth, Geophysical Journal International, 1997(130): 422~434
[57] Doll, W.E., Helm, J.M., and Beard, L.P. Airborne detection of magnetic anomalies associated with soils on the Oak Ridge Reservation, Tennessee, Symposium on the Application of Geophysics to Engineering and Environmental problems. Proceedings, 1995, 619~626
[58] Fraser, D.C. Magnetite mapping with a multi coil airborne electromagnetic system, Geophysics, 1981 (46): 1579~1593
[59] Walker, P. Inversion of HEM data for resistivity and susceptibility, Presented at the 54th Annual Meeting, Eur. Assn. Geophysics, Abstracts, 1992, 710~711
[60] Ward, S.H. The electromagnetic response of a magnetic in deposit, Geophysics Prospecting, 1961(9): 191~202
[61] Bhattacharyya, B.K. A generalized multi body model for inversion of magnetic anomalies, Geophysics, 1980(45): 255~270
[62] Guillen, A., and Menichetti, V. Gravity and magnetic inversion with minimization of a special functional, Geophysics, 1984(49): 1354~1360
[63] Li, Y., and Oldenburg, D.W. 3-D inversion of magnetic data, Geophysics, 1996(62): 394~408
[64] Wang, X., and Hansen, R.O. Inversion for magnetic anomalies of arbitrary three-dimension bodies, Geophysics, 1970(35): 862~896
[65] Zeyen, H., and Pous, J. A new 3-D inversion algorithm for magnetic total field anomalies, Geophysics Journal International, 1991 (104): 583~591
[66] Constable, S.C., Parker, R.L., and Constable, C.G. Occam's inversion: A practical algorithm for generation smooth models from electromagnetic sounding data, Geophysics, 1987(52): 289~300
[67] DeGroot-Hedlin, C., and Constable, S. Oecam's inversion to generate smooth two-dimensional models from magnetotelluric data, Geophysics, 1990(55): 1613~1624
[68] McGilliviray, P.R., and Oldenburg D.W. Methods for calculating Frechet derivatives and sensitivities for the non-linear inverse problem: a comparative study, Geophysical Prospecting, 1990(28): 499~524
[69] Fraquharson, C.G., and Oldenburg D.W. Approximate sensitivities for the electromagnetic inverse problem, Geophys.J.Int, 1996(126): 235~252
[70] McGillivray, P.R., and Oldenburg D.W. etc. Calculation of sensitivities for the frequency-domain electromagnetic problem, Geophys.J.Int, 1994(116): 1~4
[71] Rodi, W.L. A technique for improving the accuracy of finite element solutions for MT data, Geophys.J.R.astr.Soc. 1976(44): 483~506
[72] Jupp, D.L.B. and Vozoff, K. Two-dimensional magnetotelluric inversion, Geophys.J.R.astr.Soc., 1976(50): 333~352
[73] Weidelt, P. Inversion of two-dimensional conductivity structures, Phys. Earth planet. Inter., 1975(10): 282~291
[74] Park, S.K. Inversion of magnetotelluric data for multi-dimensional structure. Inst. Geophys. Planet. Phys., Rep. 87/6, University of California.San Diego, CA
[75] Madden, T.R. and Mackie, R.L. Three-dimensional magnetotelluric modeling and inversion. Proc. Inst. Electron. Electric. Eng., 1989(77): 318~333
[76] Madden, T.R. Inversion of low frequency electromagnetic data, in Oceanographic and Geophysical Topography, 1990, 379~408
[77] Coggon, J.H. Electromagnetic and electrical modeling by the finite element method, Geophysics, 1971(36): 132~155
[78] Jones, F.W. and Pascoe, L.J. A general computer program to determine the perturbation of alternating electric currents in a two-dimensional model of a region of uniform conductivity with an embedded in homogeneity, Geophys.J.R.astr.soc. 1971 (24): 3~30
[79] Porstendorfer.G. Principles of Magnetotelluric Prospecting, Gebruder Borntraeger, 1975
[80] Pascoe, L.T. and Jones, F.W. Boundary conditions and calculation of surface values for the general two-dimensional electromagnetic induction problem, Geophys.J.R.astr.soc., 1972(27): 179~193
[81] Reddy, I.K. and Rankin, D. Magnetotelluric response of a two-dimensional sloping contact by the finite element method, pure and appl, Geophys, 105, 847~857(1973)
[82] Silvester, P. and Haslam, C.R.S. Magnetotelluric modeling by the finite element method, Geophys.Prospect., 1972(20): 872~891
[83] Swith, C.M.Jr. Theoretical magnetotelluric and Turam response from two-dimensional in homogeneities, Geophysics, 1971 (36): 38~52
[84] Madden, T.R.. Transmission systems and network analogies to geophysical forward and inversion problem: ONR Technical Report 1972, 72~73
[85] Randall Mackie, Shirley Rieven and William Rodi. Users manual and software documentation for two-dimensional inversion of magnetotelluric data, 1997
[86] Jupp, D.L.B. and VozoFF, K. Two-dimensional magnetotellurie inversion. Geophysical Journal of the Royal Astronomical Society 1977(50): 333~352
[87] Randall L. Mackie and Theodore R.Madden. Three-dimensional magnetotelluric inversion using conjugate gradients. Geophys.J.int, 1993(115): 215~229
[88] Mackie.R.L and Madden.T.R. Conjugate gradient relaxation, Geophysics, 1993(58): 1052~1057
[89] Mora, P.R. Nonlinear two dimensional elastic inversion of multionffset seismic data, Geophysics, 1987(52): 1211~1228
[90] Smith, J.T. and Booker, J.R. Rapid inversion of two-and three-dimensional magnetotelluric data, J.geophys.Res. 1991(96): 3905~3922
[91] Ellis, R.G, Farquharson, C.G and Oldenburg, D.W. Approximate inverse mapping inversion of the COPROD2 data, J.Geomag Geoelectr. 1993(45): 1001~1012
[92] Kazunobu Yamane, Shinji Takasugi and Ki Ha Lee. A new magentotelluric inversion scheme using generalized RRI. J of App.Gephy, 1996(35): 209~213
[93] Fillous, J.H. Techniques and instrumentation for study of natural electromagnetic induction at sea, Phys.Earth planet. Int. 1973(7): 323~338
[94] Fillous, J.H. Ocean floor magnetotellufic sounding over north-central pacific, Nature, 1977(269): 297~301
[95] Fillous, J.H. Magnetotelluric soundings over the northeast Pacific may reveal spatial dependence of depth and conductance of the asthenosphere, Earth planet Sci. Lett. 1980(46): 244~252
[96] Vozoff, K. The magnetotelluric method in the exploration of sedimentary basins, Geophysics, 1972(37): 450~462
[97] Wannamaker, P.E. Hohmann, G.W. and Ward, S.H. Magnetotelluric response of three-dimensional bodies in layered earths, Geophysics, 1984(49)
[98] Denghai Bai, Maxwell A. Meju and Zhijie Liao. Magnetotelluric images of deep crustal structure of the Rehai geothermal field near Tengehong,, southern China. Geophys.J.Int, 2002(148): 1~16
[99] Uchida, T. Smooth two dimensional inversion for magnetotellruie data based on statistical criterion ABIC, Journal of Geomagnetism and Geoelectricity, 1993(45): 841~858
[100] Jie Zhang, Randall L. Mackie and Theodore R.Madden. Three dimensional resistivity forward modeling and inversion using conjugate gradients. Geophysics, 1995(60): 1313~1325
[101] Zhiyi Zhang and Oldenburg.D.W. Recovering magnetic susceptibility from electromagnetic data over a one-dimensional earth. Geophys.J.Int. 1997(130): 422~434
[102] Jones A.G. Static shift of magneto telluric data and its removal in a sedimentary basin environment. Geophysics, 1988(53): 967~978
[103] H.Grandis, M.Menvielle and M.Roussignol. Bayesian inversion with Markov chains—Ⅰ. The magnetotellurie one-dimensional case. Geophys.J.Int. 1999(138): 757~768
[104] John A. Scales, Martin L. Smith and Sven Treitel. Introductory geophysical inverse theory. Samizdat Press. 1997
[105] Pamela Lezaeta, Miguel Munoz and Heinrich Brasse. Magnetotellruic image of the crust and upper mantle in the backer of the northwestern Argentinean Andes. Geophys.J.Int. 2000(142): 841~854
[106] Masahiro Ichiki, Masaaki Mishina and Tadanori Goto, etc. Magnetotelluric investigations for the seismically active area in Northern Miyagi Prefecture, northeastern Japan. Earth Planets Space. 1999(51): 351~361
[107] Ma Xiaobing, Kong Xiangru and Yu Sheng. Magnetotelluric sounding in westem Tibet. Chinese Science Bulletin. 1997(42): 678~681
[108] Klaus Spitzer. Magnetotelluric static shift and direct current sensitivity. Geophys.J.Int.2001 (144): 289~299
[109] Yuji Mitsuhata, Koichi Matsuo and Masato Minegishi. Magnetotelluric survey for exploration of a volcanic rock reservoir in the Yurihara oil and gas field, Japan. Geophysical Processing, 1999(47): 195~218
[110] Griffel, D.H, Applied functional analysis. Eillis Horwood Limited, 1981
[111] Zeidler, E, Nonlinear functional analysis and its applications Ⅲ-Varitional Methods and Optimization. Springer-Verlag, Inc. 1985
[112] Jackson, D.D, Interpretation of inaccurate insufficient and inconsistent data. Geophysical Journal of the Royal Astronomical Society, 1972(28): 97~110
[113] Winggins, R.A, The general linear inverse problem: Implication of surface waves and free oscillations for Earth structure. Reviews of Geophysics and Space Physics, 1972(10): 251~285
[114] Jupp, D.L.B and Vozzoff, K, Stable iterative methods for the inversion of geophysical data. Geophysical Journal of the Royal Astronomical Society. 1975(42): 957~976
[115] Jupp, D.L.B and Vozzoff, K, Two-dimensional magnetotelluric inversion. Geophysical Journal of the Royal Astronomical Society. 1977(50): 333~352
[116] Menke, W. Geophysical data analysis: Discrete inverse theory. Academic press, Inc. 1984
[117] Oristaglio, M.L and Worthington, M.H. Inversion of surface and borehole electromagnetic data for two-dimensional electrical conductivity models. Geophysical prospecting. 1980(28): 633~657
[118] Brayton, R.K and Spence, R. Sensitivity and Optimization. Elsevier Science Publishing Co. 1980
[119] Vemuri, V, Dracup, J.A, Erdmann, R.C.etc. Sensitivity analysis method of system indentification and its potential in hydrologic research. Water Resources Research. 1969(5): 341~349
[120] Mcelwee, C.D. Sensitivity analysis and the ground water inverse problem. Ground Water. 1982(20): 723~735
[121] Townle, L.R and Wilson, J.L. Computationally efficient algorithms for parameter estimation and uncertainty propagation in numerical models of groundwater flow. Water Resources Research. 1985(21): 1851~1860
[122] Tarantula, A. Linearized inversion of seismic reflection data. Geophysical Prospecting.