Three-dimensional forward modeling using the transient electromagnetic method under complex terrains and the analysis of terrain effects

Authors

QU Shaobo, School of Mines, China University of Mining and Technology, Suzhou 221116, China; Shanxi Ningwu Yushupo Coal Industry Co., Ltd., Xinzhou 036700, ChinaFollow
ZHU Jiao, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
JIANG Zhihai, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
LI Maofei, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
HE Zhilong, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China

Abstract

The ground-based transient electromagnetic method (TEM), with unique advantages, has been extensively applied for hydrogeological exploration in coal mines. However, in field exploration, complex terrains tend to cause variations in geometric shapes of transmitting sources and deviations in signals received, reducing exploration accuracy. Hence, by integrating theoretical analysis and numerical simulations with the analysis of actual terrain data, this study systematically investigated the response characteristics of electrical- and magnetic-source TEM fields under complex terrains. Using the vector finite-element electromagnetic forward modeling technique based on second-order backward Euler discretization, this study delved into the laws of influence of peak and valley terrains as locations of receiving points and transmitting sources on the two source systems. The results show that the electrical-source system suffered signal changes, with responses being enhanced in the case of the source wire position higher than the surrounding terrain and weakened otherwise. In contrast, the magnetic-source system manifested no signal changes but similar response variations. Then, based on measured terrain data, this study established a three-dimensional forward model that highly matched actual terrains using tetrahedral grids. The simulation results indicate that the earlier response curves can distinctly mirror the terrain details, with curve morphologies consistent with terrain features, whereas the later response curves gradually tended to flatten, suggesting the influence of deep structures. The findings of this study will provide theoretical guidance for exploration device arrangement, as well as data acquisition, processing, and interpretations, of the TEM method under complex terrains, thereby holding critical significance for improving the hydrogeological exploration accuracy of coal mines.

Keywords

transient electromagnetic method (TEM), rugged terrain, finite-element forward modeling, numerical simulation, electrical source, magnetic source

DOI

10.12363/issn.1001-1986.23.11.0780

Recommended Citation

QU Shaobo, ZHU Jiao, JIANG Zhihai, et al. (2024) "Three-dimensional forward modeling using the transient electromagnetic method under complex terrains and the analysis of terrain effects," Coal Geology & Exploration: Vol. 52: Iss. 4, Article 15.
DOI: 10.12363/issn.1001-1986.23.11.0780
Available at: https://cge.researchcommons.org/journal/vol52/iss4/15

Reference

[1] 胡雄武,陈人峻,张平松,等. 线圈耦合距对坑道瞬变电磁场的影响与校正方法[J]. 煤炭科学技术,2023,51(2):306−316

HU Xiongwu,CHEN Renjun,ZHANG Pingsong,et al. Effect of coil coupling distance on roadway transient electromagnetic field and its correction method[J]. Coal Science and Technology,2023,51(2):306−316

[2] 杨海燕,刘志新,张华,等. 圆锥型场源瞬变电磁法试验研究[J]. 煤田地质与勘探,2021,49(6):107−112

YANG Haiyan,LIU Zhixin,ZHANG Hua,et al. Experimental study on transient electromagnetic method with a conical source[J]. Coal Geology & Exploration,2021,49(6):107−112

[3] 张莹莹. 电性源瞬变电磁法综述[J]. 物探与化探,2021,45(4):809−823

ZHANG Yingying. Review on the study of ground–source transient electromagnetic method[J]. Geophysical and Geochemical Exploration,2021,45(4):809−823

[4] ZHOU Nannan,XUE Guoqiang,HOU Dongyang,et al. An investigation of the effect of source geometry on grounded–wire TEM surveying with horizontal electric field[J]. Journal of Environmental & Engineering Geophysics,2018,23(1):143−151.

[5] MUDGE S T. Short note:The location of TEM transmitter loops underground and in rugged terrain[J]. Exploration Geophysics,1996,27(2/3):175−177.

[6] 饶丽婷,武欣,党博,等. 大回线源内三维地形对电磁响应影响研究[J]. 地球物理学进展,2021,36(5):2090−2101

RAO Liting,WU Xin,DANG Bo,et al. Effect of topographic relief inside the large loop source on EM response[J]. Progress in Geophysics,2021,36(5):2090−2101

[7] 王新宇，严良俊，毛玉蓉，等. 起伏地形条件下长偏移距瞬变电磁三维正演[J]. 吉林大学学报(地球科学版)，2022，52(3)：754–765.

WANG Xinyu，YAN Liangjun，MAO Yurong，et al. Three–dimensional forward modeling of long–offset transient electromagnetic method over topography[J]. Journal of Jilin University (Earth Science Edition)，2022，52(3)：754–765.

[8] YANG Zhou,PAN Jianwei,LIU Hao,et al. Multi–turn small–loop transient electromagnetic data processing using constraints from borehole and electrical resistivity tomography data[J]. Arabian Journal of Geosciences,2022,15(22):1675.

[9] JI Yanju,ZHAO Yi,DU Shangyu,et al. Topographic correction for the data of SQUID–based TEM using a ground loop[J]. Journal of Environmental & Engineering Geophysics,2019,24(1):111−117.

[10] SASAKI Y,NAKAZATO H. Topographic effects in frequency–domain helicopter–borne electromagnetics[J]. Exploration Geophysics,2003,34:24−28.

[11] HEIMANN D. Wide–area assessment of topographical and meteorological effects on sound propagation by time–domain modeling[J]. Journal of the Acoustical Society of America,2013,133(5):419−425.

[12] HORDT A,MULLER M. Understanding LOTEM data from mountainous terrain[J]. Geophysics,2000,65(4):1113−1123.

[13] 齐彦福,李貅,孙乃泉,等. 电性源短偏移距瞬变电磁地形影响特征分析[J]. 吉林大学学报(地球科学版),2022,52(1):247−260

QI Yanfu,LI Xiu,SUN Naiquan,et al. Analysis of influence characteristics of topography on grounded–source short–offset transient electromagnetic responses[J]. Journal of Jilin University (Earth Science Edition),2022,52(1):247−260

[14] 赵越,李貅,王祎鹏,等. 三维起伏地形条件下航空瞬变电磁响应特征研究[J]. 地球物理学报,2017,60(1):383−402

ZHAO Yue,LI Xiu,WANG Yipeng,et al. Characteristics of terrain effect for 3–D ATEM[J]. Chinese Journal of Geophysics,2017,60(1):383−402

[15] 张博,殷长春,刘云鹤,等. 起伏地表频域/时域航空电磁系统三维正演模拟研究[J]. 地球物理学报,2016,59(4):1506−1520

ZHANG Bo,YIN Changchun,LIU Yunhe,et al. 3D modeling on topographic effect for frequency– /time–domain airborne EM systems[J]. Chinese Journal of Geophysics,2016,59(4):1506−1520

[16] XUE Guoqiang,ZHOU Nannan,CHEN Weiying,et al. Research on the application of a 3–m transmitter loop for TEM surveys in mountainous areas[J]. Journal of Environmental & Engineering Geophysics,2014,19(1):3−12.

[17] 薛国强,闫述,陈卫营. 电磁测深数据地形影响的快速校正[J]. 地球物理学报,2016,59(12):4408−4413

XUE Guoqiang,YAN Shu,CHEN Weiying. A fast topographic correction method for electromagnetic data[J]. Chinese Journal of Geophysics,2016,59(12):4408−4413

[18] QI Yanfu,LI Xiu,YIN Changchun,et al. 3–D time–domain airborne EM inversion for a topographic earth[J]. IEEE Transactions on Geoscience and Remote Sensing,2020,60:2000113.

[19] LIU Yunhe,YIN Changchun,QIU Changkai,et al. 3–D inversion of transient EM data with topography using unstructured tetrahedral grids[J]. Geophysical Journal International,2019,217:301−318.

[20] HABER E,ASCHER U M,ARULIAH D A,et al. Fast simulation of 3D electromagnetic problems using potentials[J]. Journal of Computational Physics,2000,163(1):150−171.

[21] 孙怀凤,李貅,卢绪山,等. 隧道强干扰环境瞬变电磁响应规律与校正方法:以TBM为例[J]. 地球物理学报,2016,59(12):4720−4732

SUN Huaifeng,LI Xiu,LU Xushan,et al. Transient electromagnetic responses in tunnels with strong interferences and the correcting method:A TBM example[J]. Chinese Journal of Geophysics,2016,59(12):4720−4732

[22] PUZYREV V,KOLDAN J,PUENTE J D L,et al. A parallel finite–element method for three–dimensional controlled–source electromagnetic forward modelling[J]. Geophysical Journal International,2013,193(2):678−693.

[23] GRAYVER A V,MARKUS B. Robust and scalable 3–D geo–electromagnetic modelling approach using the finite element method[J]. Geophysical Journal International,2014,198(1):110−125.

[24] NEWMAN G A,ALUMBAUGH D L. Three–dimensional induction logging problems,Part 2:A finite–difference solution[J]. Geophysics,2002,67(2):484−491.

[25] UEDA T,ZHDANOV M S. Fast numerical modeling of multitransmitter electromagnetic data using multigrid quasi–linear approximation[J]. IEEE Transactions on Geoscience and Remote Sensing,2006,44(6):1428−1434.

[26] 程久龙,黄少华,温来福,等. 矿井全空间三维主轴各向异性介质瞬变电磁场响应特征研究[J]. 煤炭学报,2019,44(1):278−286

CHENG Jiulong,HUANG Shaohua,WEN Laifu,et al. Response characteristics of three–dimensional axial anisotropic media for transient electromagnetic method in underground whole–space[J]. Journal of China Coal Society,2019,44(1):278−286

[27] 张永超,李宏杰,邱浩,等. 矿井瞬变电磁法的时域矢量有限元三维正演[J]. 煤炭学报,2019,44(8):2361−2368

ZHANG Yongchao,LI Hongjie,QIU Hao,et al. 3D forward modeling of mine transient electromagnetic by time–domain vector finite element[J]. Journal of China Coal Society,2019,44(8):2361−2368

[28] YANG Hao,CAI Hongzhu,LIU Minghong,et al. Three–dimensional inversion of semi–airborne transient electromagnetic data based on finite element method[J]. Near Surface Geophysics,2022,20:661−678.

[29] 石信肖,王健,孙文潇. 基于四面体模型的地质体三维重建[J]. 煤炭科学技术,2022,50(11):150−155

SHI Xinxiao,WANG Jian,SUN Wenxiao. 3D reconstruction of geological body based on tetrahedron model[J]. Coal Science and Technology,2022,50(11):150−155

[30] 李金铭. 地电场与电法勘探[M]. 北京：地质出版社，2005.

[31] LI Jianhui,FARQUHARSON C G,HU Xiangyun. Three effective inverse Laplace transform algorithms for computing time–domain electromagnetic responses[J]. Geophysics,2016,81(2):113−128.

[32] 李建慧,朱自强,曾思红,等. 瞬变电磁法正演计算进展[J]. 地球物理学进展,2012,27(4):1393−1400

LI Jianhui,ZHU Ziqiang,ZENG Sihong,et al. Progress of forward computation in transient electromagnetic method[J]. Progress in Geophysics,2012,27(4):1393−1400