矿井瞬变电磁法电阻率偏低原因分析与校正方法
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摘要
矿井瞬变电磁法由于采用多匝小回线工作装置进行发射和接收,实测视电阻率与大地中实际岩层电阻率相比存在严重偏低问题,给资料解释带来困难,探测深度也随之降低。通过数值模拟和现场试验,分别研究了半空间和矿井全空间条件下瞬变电磁法偶极装置观测信号随收发距的变化规律,发现收发距在20 m内变化二次场信号变化很小;随收发距增大,实测信号在双对数坐标系中呈线性衰减。理论分析表明,实测信号主要为发射线圈与接收线圈之间的互感信号和大地中感应二次场的叠加,其中互感信号强度远大于大地中感应的二次场,是造成电阻率偏低的主要原因。然后,基于互感电动势随收发距变化的规律,考虑到二次场信号在20 m收发距内变化很小,提出了利用两次不同收发距观测数据进行互感消除和二次场提取方法,推导了相关计算公式,实现了偶极装置矿井瞬变电磁法实测视电阻率偏低的校正。最后,通过半空间和全空间探测实例应用,验证了方法的有效性。
Mine transient electromagnetic method has a low resistivity problem for using minor transmitter and receiver loops,which leads to data interpretation difficulties and decreases detection depth.Firstly,this paper studied the variation of secondary field with transmitter-receiver distance through numerical simulation and field test,and found that the simulant secondary field was almost unchanged with transmitter-receiver distance within 20 m while measured data decreases linearly in logarithm coordinate system.Theoretical analysis shows that the mutual induced electromotive force is the main component of measured data,which leads to low resistivity problem.Furthermore,the paper proposed a resistivity correction method based on the different properties of secondary field and mutual induced electromotive force.The method eliminates the mutual induced electromotive force by using two measured data with different transmitter-receiver distances.Finally,the proposed method was successfully used in a half-space field case and a whole-space field case to demonstrate its practical usefulness.
Mine transient electromagnetic method has a low resistivity problem for using minor transmitter and receiver loops,which leads to data interpretation difficulties and decreases detection depth.Firstly,this paper studied the variation of secondary field with transmitter-receiver distance through numerical simulation and field test,and found that the simulant secondary field was almost unchanged with transmitter-receiver distance within 20 m while measured data decreases linearly in logarithm coordinate system.Theoretical analysis shows that the mutual induced electromotive force is the main component of measured data,which leads to low resistivity problem.Furthermore,the paper proposed a resistivity correction method based on the different properties of secondary field and mutual induced electromotive force.The method eliminates the mutual induced electromotive force by using two measured data with different transmitter-receiver distances.Finally,the proposed method was successfully used in a half-space field case and a whole-space field case to demonstrate its practical usefulness.
引文
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[14]陈玉玲.地下垂直磁偶极子源电磁场响应模拟[D].长春:吉林大学,2010.CHEN Yuling.Simulating electromagnetic responses from buried magnetic dipole[D].Changchun:Jilin University,2010.
[15]白登海,MAXWELL A Meju,卢健,等.时间域瞬变电磁法中心方式全程视电阻率的数值计算[J].地球物理学报,2003,46(5):697-704.BAI Denghai,MAXWELL A Meju,LU Jian,et al.Numerical calculation of all-time apparent resistivity for the central loop transient electromagnetic method[J].Chinese J.Geophys.,2003,46(5):697-704.
[16]姜国庆,程久龙,孙晓云,等.全空间瞬变电磁全区视电阻率优化二分搜索算法[J].煤炭学报,2014,39(12):2482-2488.JIANG Guoqing,CHENG Jiulong,SUN Xiaoyun,et al.Optimized binary search algorithm of full space transient electromagnetic method all-time apparent resistivity[J].Journal of China Coal Society,2014,39(12):2482-2488.
[2]孙怀风.隧道含水构造三维瞬变电磁场响应特征及突水灾害源预报研究[D].济南:山东大学,2013.SUN Huaifeng.Three-dimensional transient electromagnetic responses of water bearing structures in tunnels and prediction of water inrush sources[D].Shandong:Shandong University,2013.
[3]薛国强,于景邨.瞬变电磁法在煤炭领域的研究与应用新进展[J].地球物理学进展,2017,32(1):319-326.XUE Guoqiang,YU Jingcun.New development of TEM research and application in coal mine exploration[J].Progress in Geophysics,2017,32(1):319-326.
[4]于景邨.矿井瞬变电磁法勘探[M].徐州:中国矿业大学出版社,2007.
[5]杨海燕,岳建华.矿井瞬变电磁法理论与技术研究[M].北京:科学出版社,2015.
[6]刘志新,岳建华,刘仰光.扇形探测技术在超前探测中的应用研究[J].中国矿业大学学报,2007,36(6):822-825.LIU Zhixin,YUE Jianhua,LIU Yangguang.Application of sector detection technology in advanced detection[J].Journal of China University of Mining and Technology,2007,36(6):822-825.
[7]郭纯,刘白宙,白登海.地下全空间瞬变电磁技术在煤矿掘进头的连续跟踪超前探测[J].地震地质,2006,28(3):456-462.GUO Chun,LIU Baizhou,BAI Denghai.Prediction of water disasters ahead of tunneling in coal mine using continuous detection by UW TEM[J].Seismology and Geology,2006,28(3):456-462.
[8]程久龙,邱浩,叶云涛,等.矿井瞬变电磁法波场变换与数据处理方法研究[J].煤炭学报,2013,38(9):1646-1650.CHENG Jiulong,QIU Hao,YE Yuntao,et al.Research on wavefield transformation and data processing of the mine transient electromagnetic method[J].Journal of China Coal Society,2013,38(9):1646-1650.
[9]CHENG Jiulong,LI Fei,PENG Suping,et al.Joint inversion of TEM and DC in roadway advanced detection based on particle swarm optimization[J].Journal of Applied Geophysics,2015,123:30-35.
[10]程建远,李博凡,范涛,等.基于趋势面分析的瞬变电磁弱异常提取方法[J].煤炭学报,2015,40(12):2856-2864.CENG Jianyuan,LI Bofan,FAN Tao,et al.TEM weak anomalies extracting method based on trend surface analysis[J].Journal of China Coal Society,2015,40(12):2856-2864.
[11]岳建华,薛国强.中国煤炭电法勘探36年发展回顾[J].地球物理学进展,2016,31(4):1716-1724.YUE Jianhua,XUE Guoqiang.Review on the development of Chinese coal electric and electromagnetic prospecting during past 36years[J].Progress in Geophysics,2016,31(4):1716-1724.
[12]牛之琏.时间域电磁法原理[M].长沙:中南大学出版社,2007.
[13]李建平,李桐林,赵雪峰,等.层状介质任意形状回线源瞬变电磁全区视电阻率的研究[J].地球物理学进展,2007,22(6):1777-1780.LI Jianping,LI Tonglin,ZHAO Xuefeng,et al.Study on the TEM all-time apparent resistivity of arbitrary shape loop source over the layered medium[J].Progress in Geophysics,2007,22(6):1777-1780.
[14]陈玉玲.地下垂直磁偶极子源电磁场响应模拟[D].长春:吉林大学,2010.CHEN Yuling.Simulating electromagnetic responses from buried magnetic dipole[D].Changchun:Jilin University,2010.
[15]白登海,MAXWELL A Meju,卢健,等.时间域瞬变电磁法中心方式全程视电阻率的数值计算[J].地球物理学报,2003,46(5):697-704.BAI Denghai,MAXWELL A Meju,LU Jian,et al.Numerical calculation of all-time apparent resistivity for the central loop transient electromagnetic method[J].Chinese J.Geophys.,2003,46(5):697-704.
[16]姜国庆,程久龙,孙晓云,等.全空间瞬变电磁全区视电阻率优化二分搜索算法[J].煤炭学报,2014,39(12):2482-2488.JIANG Guoqing,CHENG Jiulong,SUN Xiaoyun,et al.Optimized binary search algorithm of full space transient electromagnetic method all-time apparent resistivity[J].Journal of China Coal Society,2014,39(12):2482-2488.
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