Influence of undulating terrain on three-dimensional controlled-source electromagnetic response
SHANG Xiaorong1,2, YUE Mingxin1,2,3, YANG Xiaodong1,2, WU Xiaoping1,2, LI Yong3
1. School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China; 2. Anhui Mengcheng National Geophysical Observatory, University of Science and Technology of China, Mengcheng, Anhui 233500, China; 3. Key Laboratory of Geophysical Electromagnetic Probing Technologies of Ministry of Natural Resources, Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang, Hebei 065000, China
Abstract：The controlled-source electromagnetic (CSEM) method is one of the important means for oil, gas, and mineral resource exploration. At present, the conventional interpretation of CSEM data is usually based on the assumption of flat terrain, which leads to the distortion of the positions and shapes of inversion anomalies and even false anomalies. To explore the influence of undulating terrain on the propagation of the three-dimensional (3D) CSEM field and enhance data processing and interpretation, this paper applies the vector finite element algorithm based on unstructured grids to carry out numerical simulation of the 3D CSEM field under undulating terrain and discusses the influence of terrain on each component of the CSEM field. For this purpose, a layered medium model and a simple anomaly model are constructed for digital simulation, and the results prove the correctness and timeliness of the algorithm. Then, the effects of undulating terrain on each component of the CSEM field are discussed in detail with multiple 3D undulating terrain models. Finally, the electromagnetic response characteristics of the metal mine model under actual complex terrain are analyzed, which proves the practicability of the proposed algorithm.
MUTTON A J.The application of geophysics during evaluation of the Century zinc deposit[J].Geophy-sics, 2000, 65(6):1946-1960.
[3]
BARTEL L C, JACOBSON R D.Results of a controlled-source audio-frequency magnetotelluric survey at the Puhimau thermal area, Kilauea Volcano, Hawaii[J].Geophysics, 1987, 52(5):665-677.
[4]
柳建新, 麻昌英, 孙丽影, 等.可控源音频大地电磁测深法在地热勘探中的应用[J].工程地球物理学报, 2014, 11(3):319-325.LIU Jianxin, MA Changying, SUN Liying, et al.The application of CSAMT to the geothermal exploration[J].Chinese Journal of Engineering Geophysics, 2014, 11(3):319-325.
[5]
底青云, 伍法权, 王光杰, 等.地球物理综合勘探技术在南水北调西线工程深埋长隧洞勘察中的应用[J].岩石力学与工程学报, 2005, 24(20):3631-3638.DI Qingyun, WU Faquan, WANG Guangjie, et al.Geo-physical exploration over long deep tunnel for west route of south-to-north water transfer project[J].Chinese Journal of Rock Mechanics and Engineering,2005, 24(20):3631-3638.
[6]
JING J E, ZHAO Q X, DENG M, et al.A study on natural gas hydrates and their forming model using marine controlled-source electromagnetic survey in the Qiongdongnan Basin[J].Chinese Journal of Geophysics, 2018, 61(11):4677-4689.
[7]
吕国印.瞬变电磁法的现状与发展趋势[J].物探化探计算技术, 2007, 29(增刊1):111-115.LYU Guoyin.Current status and development trend of transient EM method[J].Computing Techniques for Geophysical and Geochemical Exploration, 2007, 29(S1):111-115.
[8]
薛国强, 李貅, 底青云.瞬变电磁法理论与应用研究进展[J].地球物理学进展, 2007, 22(4):1195-1200.XUE Guoqiang, LI Xiu, DI Qingyun.The progress of TEM in theory and application[J].Progress in Geophysics, 2007, 22(4):1195-1200.
[9]
MILLER C, ROUTH P, DONALDSON P, et al.Electrical conductivity imaging using controlled source electromagnetics for subsurface fluid flow characte-rization[C].SEG Technical Program Expanded Abstracts, 2004, 23:1171-1174.
[10]
林昌洪, 谭捍东, 舒晴, 等.可控源音频大地电磁三维共轭梯度反演研究[J].地球物理学报, 2012, 55(11):3829-3838.LIN Changhong, TAN Handong, SHU Qing, et al.Three-dimensional conjugate gradient inversion of CSAMT data[J].Chinese Journal of Geophysics, 2012, 55(11):3829-3838.
[11]
刘云鹤, 殷长春.三维频率域航空电磁反演研究[J].地球物理学报, 2013, 56(12):4278-4287.LIU Yunhe, YIN Changchun.3D inversion for frequency-domain HEM data[J].Chinese Journal of Geophysics, 2013, 56(12):4278-4287.
[12]
WANG G, WEI Y, QIAO S, et al.Generalized Inverses:Theory and Computations[M].Springer, Singapore, 2018.
[13]
MEJU M A, MACKIE R L, MIORELLI F, et al.Structurally tailored 3D anisotropic controlled-source electromagnetic resistivity inversion with cross-gradient criterion and simultaneous model calibration[J].Geophysics, 2019, 84(6):E387-E402.
[14]
朱成, 李桐林, 杨海斌, 等.带地形频率域可控源电磁法三维反演研究[J].石油地球物理勘探, 2016, 51(5):1031-1039.ZHU Cheng, LI Tonglin, YANG Haibin, et al.3D controlled source electromagnetic inversion with topography in the frequency domain[J].Oil Geophysical Prospecting, 2016, 51(5):1031-1039.
[15]
MIENSOPUST M P.Application of 3-D electromagnetic inversion in practice:challenges, pitfalls and solution approaches[J].Surveys in Geophysics, 2017, 38(5):869-933.
[16]
XIONG Z.Electromagnetic modeling of 3-D structures by the method of system iteration using integral equations[J].Geophysics, 1992, 57(12):1556-1561.
[17]
ZHDANOV M S, FANG S.Quasi-linear approximation in 3-D electromagnetic modeling[J].Geophy-sics, 1996, 61(3):646-665.
[18]
汤井田, 周峰, 任政勇, 等.复杂地下异常体的可控源电磁法积分方程正演[J].地球物理学报, 2018, 61(4):1549-1562.TANG Jingtian, ZHOU Feng, REN Zhengyong, et al.Three-dimensional forward modeling of the controlled-source electromagnetic problem based on the integral equation method with an unstructured grid[J].Chinese Journal of Geophysics, 2018, 61(4):1549-1562.
[19]
MACKIE R L, SMITH J T, MADDEN T R.Three-dimensional electromagnetic modeling using finite difference equations:The magnetotelluric example[J].Radio Science, 1994, 29(4):923-935.
[20]
殷长春, 贲放, 刘云鹤, 等.三维任意各向异性介质中海洋可控源电磁法正演研究[J].地球物理学报, 2014, 57(12):4110-4122.YIN Changchun, BEN Fang, LIU Yunhe, et al.MCSEM 3D modeling for arbitrarily anisotropic media[J].Chinese Journal of Geophysics, 2014, 57(12):4110-4122.
[21]
HABER E, ASCHER U M.Fast finite volume simulation of 3D electromagnetic problems with highly discontinuous coefficients[J].SIAM Journal on Scientific Computing, 2001, 22(6):1943-1961.
[22]
韩波, 胡祥云, Adam SCHULTZ, 等.复杂场源形态的海洋可控源电磁三维正演[J].地球物理学报, 2015, 58(3):1059-1071.HAN Bo, HU Xiangyun, SCHULTZ A, et al.Three-dimensional forward modeling of the marine controlled-source electromagnetic field with complex source geometries[J].Chinese Journal of Geophy-sics, 2015, 58(3):1059-1071.
[23]
COGGON J H.Electromagnetic and electrical mode-ling by the finite element method[J].Geophysics, 1971, 36(1):132-155.
[24]
BASTOS J P A, SADOWSKI N.Electromagnetic Mode-ling by Finite Element Methods[M].CRC Press, 2003.
[25]
MUKHERJEE S, EVERETT M E.3D controlled-source electromagnetic edge-based finite element mo-deling of conductive and permeable heterogeneities[J].Geophysics, 2011, 76(4):F215-F226.
[26]
李勇, 吴小平, 林品荣, 等.电导率任意各向异性海洋可控源电磁三维矢量有限元数值模拟[J].地球物理学报, 2017, 60(5):1955-1978.LI Yong, WU Xiaoping, LIN Pinrong, et al.Three-dimensional modeling of marine controlled-source electromagnetism using the vector finite element method for arbitrary anisotropic media[J].Chinese Journal of Geophysics, 2017, 60(5):1955-1978.
[27]
任政勇, 汤井田.基于局部加密非结构化网格的三维电阻率法有限元数值模拟[J].地球物理学报, 2009, 52(10):2627-2634.REN Zhengyong, TANG Jingtian.Finite element modeling of 3-D DC resistivity using locally refined unstructured meshes[J].Chinese Journal of Geophy-sics, 2009, 52(10):2627-2634.
[28]
PUZYREV V, KOLDAN J, DE LA PUENTE J, et al.A parallel finite-element method for three-dimensional controlled-source electromagnetic forward modelling[J].Geophysical Journal International, 2013, 193(2):678-693.
[29]
蔡红柱, 熊彬, MICHAEL Zhdanov.电导率各向异性的海洋电磁三维有限单元法正演[J].地球物理学报, 2015, 58(8):2839-2850.CAI Hongzhu, XIONG Bin, MICHAEL Zhdanov.Three-dimensional marine controlled-source electromagnetic modelling in anisotropic medium using finite element method[J].Chinese Journal of Geophysics, 2015, 58(8):2839-2850.
[30]
汤文武, 柳建新, 叶益信, 等.基于节点有限元与矢量有限元的可控源电磁三维正演对比[J].石油地球物理勘探, 2018, 53(3):617-624.TANG Wenwu, LIU Jianxin, YE Yixin, et al.Comparison of 3D controlled-source electromagnetic forward modeling based on the nodal finite element and the edge-based finite element[J].Oil Geophysical Prospecting, 2018, 53(3):617-624.
[31]
HE G, XIAO T, WANG Y, et al.3D CSAMT modelling in anisotropic media using edge-based finite-element method[J].Exploration Geophysics, 2019, 50(1):42-56.
[32]
NAM M J, KIM H J, SONG Y, et al.3D magnetotelluric modelling including surface topography[J].Geo-physical Prospecting, 2007, 55(2):277-287.
[33]
LIN C, ZHONG S, AUKEN E, et al.The effects of 3D topography on controlled-source audio-frequency magnetotelluric responses[J].Geophysics, 2018, 83(2):WB97-WB108.
[34]
殷长春, 惠哲剑, 张博, 等.起伏海底地形时间域海洋电磁三维自适应正演模拟[J].地球物理学报, 2019, 62(5):1942-1953.YIN Changchun, HUI Zejian, ZHANG Bo, et al.3D adaptive forward modeling for time-domain marine CSEM over topographic seafloor[J].Chinese Journal of Geophysics, 2019, 62(5):1942-1953.
[35]
ANSARI S, FARQUHARSON C G.3D finite-element forward modeling of electromagnetic data using vector and scalar potentials and unstructured grids[J].Geophysics, 2014, 79(4):E149-E165.
[36]
SCHWARZBACH C, BÖRNER R U, SPITZER K.Three-dimensional adaptive higher order finite element simulation for geo-electromagnetics:a marine CSEM example[J].Geophysical Journal Internatio-nal, 2011, 187(1):63-74.
[37]
杨军, 刘颖, 吴小平.海洋可控源电磁三维非结构矢量有限元数值模拟[J].地球物理学报, 2015, 58(8):2827-2838.YANG Jun, LIU Ying, WU Xiaoping.3D simulation of marine CSEM using vector finite element method on unstructured grids[J].Chinese Journal of Geophysics, 2015, 58(8):2827-2838.
[38]
CAI H, HU X, LI J, et al.Parallelized 3D CSEM mo-deling using edge-based finite element with total field formulation and unstructured mesh[J].Computers & Geosciences, 2017, 99:125-134.
[39]
周峰, 张志勇, 陈煌, 等.基于非结构网格的三种CSEM有限元三维正演系统分析[J].石油地球物理勘探, 2021, 56(5):1190-1202.ZHOU Feng, ZHANG Zhiyong, CHEN Huang, et al.Analysis of 3D finite-element forward modeling of CSEM data using three different formulas and unstructured grids[J].Oil Geophysical Prospecting, 2021, 56(5):1190-1202.
[40]
KEY K.1D inversion of multicomponent, multi-frequency marine CSEM data:Methodology and synthe-tic studies for resolving thin resistive layers[J].Geophysics, 2009, 74(2):F9-F20.
