地-井瞬变电磁法线性导体正演及异常响应特征研究
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摘要
地-井瞬变电磁法采用地面发射、井中或巷道接收的方式,距离异常较近,可以提高对异常分辨力和增加探测的深度,为了对深部小异常进行精细探测,基于二维时域有限差分和地面瞬变电磁探测原理,在均匀介质背景条件下,以大定源回线装置作为发射场源,建立不同深度和不同位置的板状、方形导体的多个场电模型;采用地面、钻孔(巷道) 2种观测方式,并进行数值模拟正演分析,对小异常体的垂直磁场强度和及差值EA多测道曲线响应特征进行研究;并利用垂直磁场强度曲线的极值点和EA曲线的交叉点,可对小异常进行准确定位作出解释。研究结果表明:时域有限差分法能够对建立的线性导体场电模型进行有效准确的计算,能够获取小异常的响应曲线特征;地面-钻孔观测方式下基于垂直磁场强度曲线的极值点,能够确定异常的纵向位置和区分多个异常,且幅值随时间增大越来越小;而地面-巷道观测方式下通过EA曲线的交叉点,能够确定异常的横向位置和区分多个异常,且至异常越近EA值越大;以极值点和交叉点对小异常进行准确定位,提高了纵横向分辨力。
The ground-well transient electromagnetic method( TEM) adopts the methods of ground launching and well or roadway receiving,and the distance is too close to the anomaly,which has important research significance for improving resolution and increasing the depth of detection.In order to finely detect deep small anomalies,based on two-dimensional time domain( FDTD) finite difference and ground TEM detection principle,and under the condition of uniform medium,the large fixed source loop device was used as the launch field source to establish multiple field-electric models of plate-like and square-conductors in different depths and different positions; using ground-drilling( tunnel) observation methods for numerical simulation forward analysis,researches were conducted on vertical magnetic field intensity curves of small anomalies and response characteristics of multi-track curves of vertical magnetic field intensity difference value( EA); an interpretation method for accurate localization analysis of small anomalies using the intersection of the extreme point of vertical magnetic field intensity curve and the EA curve was proposed.The results show that the time-domain finite difference method can effectively and accurately calculate the established linear conductor field electric model,and can obtain the characteristics of the small anomaly response curve.The ground-drilling observation mode passes the extreme value of vertical magnetic field intensity curve.The longitudinal position of the anomaly can be determined and the plurality of anomalies can be distinguished,and the amplitude is smaller and smaller with time; the intersection of the EA curve in the ground-tunnel observation mode can determine the lateral position of the anomaly and distinguish the plurality of anomalies,and the closer the distance is,the larger the EA value is; the accurate positioning of small anomalies is realized according to the extreme pointsand intersections,and the vertical and horizontal resolution is improved.
The ground-well transient electromagnetic method( TEM) adopts the methods of ground launching and well or roadway receiving,and the distance is too close to the anomaly,which has important research significance for improving resolution and increasing the depth of detection.In order to finely detect deep small anomalies,based on two-dimensional time domain( FDTD) finite difference and ground TEM detection principle,and under the condition of uniform medium,the large fixed source loop device was used as the launch field source to establish multiple field-electric models of plate-like and square-conductors in different depths and different positions; using ground-drilling( tunnel) observation methods for numerical simulation forward analysis,researches were conducted on vertical magnetic field intensity curves of small anomalies and response characteristics of multi-track curves of vertical magnetic field intensity difference value( EA); an interpretation method for accurate localization analysis of small anomalies using the intersection of the extreme point of vertical magnetic field intensity curve and the EA curve was proposed.The results show that the time-domain finite difference method can effectively and accurately calculate the established linear conductor field electric model,and can obtain the characteristics of the small anomaly response curve.The ground-drilling observation mode passes the extreme value of vertical magnetic field intensity curve.The longitudinal position of the anomaly can be determined and the plurality of anomalies can be distinguished,and the amplitude is smaller and smaller with time; the intersection of the EA curve in the ground-tunnel observation mode can determine the lateral position of the anomaly and distinguish the plurality of anomalies,and the closer the distance is,the larger the EA value is; the accurate positioning of small anomalies is realized according to the extreme pointsand intersections,and the vertical and horizontal resolution is improved.
引文
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[13]苗彬,姜志海,刘树才.矿井地面-巷道瞬变电磁探测系统设计及应用[J].煤炭科学技术,2016,44(12):148-153.MIAO bin,JIANG Zhihai,LIU Shucai.Design and application of mine ground-tunnel transient electromagnetic detection system[J].Coal Science and Technology,2016,44(12):148-153.
[14]范涛.孔巷瞬变电磁动源定接收方法探测采空区试验[J].煤炭学报,2017,42(12):3229-3238.FAN Tao.Test of detecting goaf by fixed receiving method of transient electromagnetic power source in tunnel[J].Journal of China Coal Society,2017,42(12):3229-3238.
[15]李术才,李凯,翟明华,等.矿井地面-井下电性源瞬变电磁探测响应规律分析[J].煤炭学报,2016,41(8):2024-2032.LI Shucai,LI Kai,ZHAI Minghua,et al.Analysis of transient electromagnetic detection response law of surface-underground electrical source in mine[J].Journal of China Coal Society,2016,41(8):2024-2032.
[16]易洪春.地-井瞬变电磁响应特征研究[J].物探与化探,2018,42(5):970-976.YI hongchun.Study on transient electromagnetic response characteristics of ground-well[J].Geophysical and Geochemical Exploration,2018,42(5):970-976.
[17]唐继强,席振铢,王鹤,等.三维体地-井瞬变电磁三分量测量响应规律研究[J].工程地球物理学报,2015,12(3):315-321.TANG Jiqiang,XI Zhenzhu,WANG He,et al.Three-dimensional body-ground-well transient electromagnetic three-component response study[J].Chinese Journal of Engineering Geophysics,2015,12(3):315-321.
[18]葛德彪.电磁波时域有限差分方法[M].西安:西安电子科技大学出版社,2002.
[19]米萨克N.纳比吉安.勘查地球物理电磁法:第1卷[M].赵经祥,王艳君,译.北京:地质出版社,1992.
[20]GREENFIELD R J,WU S T.Electromagnetic wave propaga tionin disrupted coal seams[J].Geophysics,1991,56(10):1571-1577.
[2]WEST R C,WARD S H.The borehole transient electromagnetic response of a three-dimensional fracturezone in a conductive halfspace[J].Geophysics,1988,53(11):1469-1478.
[3]杨海燕,岳建华,徐正玉,等.覆盖层影响下典型地-井模型瞬变电磁法正演[J].吉林大学学报:地球科学版,2016,46(5):1527-1537.YANG Haiyan,YUE Jianhua,XU Zhengyu,et al.Typical groundwell model TEM forward modeling under the influence of overburden[J].Journal of Jilin University:Earth Science Edition,2016,46(5):1527-1537.
[4]武军杰,李貅,智庆全,等.电性源地-井瞬变电磁全域视电阻率定义[J].地球物理学报,2017,60(4):1595-1605.WU Junjie,LI Xiu,ZHI Qingquan,et al.Definition of global apparent resistivity of electrical source-well transient electromagnetism[J].Journal of Geophysics,2017,60(4):1595-1605.
[5]武军杰,李貅,智庆全,等.电性源地-井瞬变电磁异常场响应特征初步分析[J].物探与化探,2017,41(1):129-135.WU Junjie,LI Xiu,ZHI Qingquan,et al.Preliminary analysis of transient electromagnetic anomaly field response characteristics of electrical source-well[J].Geophysical and Geochemical Exploration,2017,41(1):129-135.
[6]武军杰,李貅,智庆全,等.电性源地-井瞬变电磁法三分量响应特征分析[J].地球物理学进展,2017,32(3):1273-1278.WU Junjie,LI Xiu,ZHI Qingquan,et al.Three-component response analysis of electrical source-well transient electromagnetic method[J].Progress in Geophysics,2017,32(3):1273-1278.
[7]徐正玉,杨海燕,邓居智,等.垂直接触带影响下地-井瞬变电磁响应研究[J].地球物理学进展,2015,30(3):1345-1353.XU Zhengyu,YANG Haiyan,DENG Juzhi,et al.Transient electro magnetic response of underground-well under the influence of vertical contact zone[J].Progress in Geophysics,2015,30(3):1345-1353.
[8]徐正玉,杨海燕,邓居智,等.回线源三维地-井瞬变电磁法FDTD数值模拟[J].工程地球物理学报,2015,12(3):327-332.XU Zhengyu,YANG Haiyan,DENG Juzhi,et al.Three-dimensional geo-well transient electromagnetic FDTD numerical simulation with loop source[J].Chinese Journal of Engineering Geophysics,2015,12(3):327-332.
[9]徐正玉,杨海燕,邓居智,等.基于异常场的地-井瞬变电磁法正演研究[J].物探与化探,2015,39(6):1176-1182.XU Zhengyu,YANG Haiyan,DENG Juzhi,et al.Forward modeling of ground-well transient electromagnetic method based on anomalous field[J].Geophysical and Geochemical Exploration,2015,39(6):1176-1182.
[10]孟庆鑫,潘和平.地-井瞬变电磁响应特征数值模拟分析[J].地球物理学报,2012,55(3):1046-1053.MENG Qingxin,PAN Heping.Numerical simulation and analysis of transient electromagnetic response characteristics of groundwell[J].Chinese Journal of Geophysics,2012,55(3):1046-1053.
[11]孟庆鑫,潘和平,牛峥.大地介质影响下地-井瞬变电磁的正演模拟研究[J].中国矿业大学学报,2014,43(6):1113-1119.MENG Qingxin,PAN Heping,NIU Zheng.Forward modeling of ground-well transient electromagnetic(TEM)under influence of geodetic media[J].Journal of China University of Mining&Technology,2014,43(6):1113-1119.
[12]MENG Qingxin,HU Xiangyun,PAN Heping,et al.Mul ticomponent numerical analysis of ground-well transient electromagnetic response[J].Applied Geophysics,2017,14(1):175-186,192.
[13]苗彬,姜志海,刘树才.矿井地面-巷道瞬变电磁探测系统设计及应用[J].煤炭科学技术,2016,44(12):148-153.MIAO bin,JIANG Zhihai,LIU Shucai.Design and application of mine ground-tunnel transient electromagnetic detection system[J].Coal Science and Technology,2016,44(12):148-153.
[14]范涛.孔巷瞬变电磁动源定接收方法探测采空区试验[J].煤炭学报,2017,42(12):3229-3238.FAN Tao.Test of detecting goaf by fixed receiving method of transient electromagnetic power source in tunnel[J].Journal of China Coal Society,2017,42(12):3229-3238.
[15]李术才,李凯,翟明华,等.矿井地面-井下电性源瞬变电磁探测响应规律分析[J].煤炭学报,2016,41(8):2024-2032.LI Shucai,LI Kai,ZHAI Minghua,et al.Analysis of transient electromagnetic detection response law of surface-underground electrical source in mine[J].Journal of China Coal Society,2016,41(8):2024-2032.
[16]易洪春.地-井瞬变电磁响应特征研究[J].物探与化探,2018,42(5):970-976.YI hongchun.Study on transient electromagnetic response characteristics of ground-well[J].Geophysical and Geochemical Exploration,2018,42(5):970-976.
[17]唐继强,席振铢,王鹤,等.三维体地-井瞬变电磁三分量测量响应规律研究[J].工程地球物理学报,2015,12(3):315-321.TANG Jiqiang,XI Zhenzhu,WANG He,et al.Three-dimensional body-ground-well transient electromagnetic three-component response study[J].Chinese Journal of Engineering Geophysics,2015,12(3):315-321.
[18]葛德彪.电磁波时域有限差分方法[M].西安:西安电子科技大学出版社,2002.
[19]米萨克N.纳比吉安.勘查地球物理电磁法:第1卷[M].赵经祥,王艳君,译.北京:地质出版社,1992.
[20]GREENFIELD R J,WU S T.Electromagnetic wave propaga tionin disrupted coal seams[J].Geophysics,1991,56(10):1571-1577.