TEM方法中磁场垂直分量Bz强度特征研究  

Study on the intensity characteristics of magnetic field vertical component in transient electromagnetic method

作　　者：康慧敏 荣亮亮 王光杰[1,2,3] 王若[1,2,3] 李彦恒 李奇霖[1,2,3] 裴易峰 KANG HuiMin;RONG LiangLiang;WANG GuangJie;WANG Ruo;LI YanHeng;LI QiLin;PEI YiFeng(Institute of Geology and Geophysics,Chinese Academy of Sciences,Institute of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;State Key Laboratory of Functional Materials for Informatics,Shanghai Institute of Microsystem and Information Technology(SIMIT),Chinese Academy of Sciences(CAS),Shanghai 200050,China;Rocket Force Engineering and Design Institute PLA,Beijing 100011,China)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院地球科学研究院,北京100029 [2]中国科学院大学,北京100049 [3]中国科学院页岩气与地质工程重点实验室,北京100029 [4]信息功能材料国家重点实验室中国科学院上海微系统与信息技术研究所,上海200050 [5]火箭军工程设计研究院,北京100011

出　　处：《地球物理学进展》2021年第1期170-177,共8页Progress in Geophysics

基　　金：国家重点研发计划课题(2016YFC0600507)资助。

摘　　要：瞬变电磁法由于其高效、轻便等诸多优点成为现今应用较为广泛的地球物理勘探手段.但由于二次场随时间衰减较快,TEM方法在勘探深度上受到一定的限制.近几年,低温SQUID(Superconducting Quantum Interference Device)磁传感器硬件已经研发成熟,可以应用到TEM方法中,用于磁场强度探测.本文提出了均匀半空间TEM磁场分量Bz的显式表达式,并借助正弦数值滤波变换,得到了层状介质的磁场时间域计算公式.针对均匀半空间地层,分别进行了不同收发距、不同电阻率条件下的Bz响应特征计算.此外,对于层状介质模型,针对不同层厚的两层介质、低阻薄层和高阻薄层的三层介质,均进行了Bz正演结果.最后,对1 km长偶极的TEM磁场响应在地表空间分布情况进行讨论.结果表明,Bz作为TEM测量手段,对深部低阻薄层的探测灵敏度优于高阻薄层;且相对于传统TEM方法中测量磁场变化量,直接测量磁场Bz可以明显地提高探测方法的优势,增大勘探深度,并且电偶极其测量空间范围更大,效率更高.Transient electromagnetic method has become a widely used geophysical exploration method due to its advantages of high efficiency, high resolution and portability. However, the secondary field decays rapidly with time, TEM method is limited in exploration depth. In recent years, low temperature SQUID(Superconducting Quantum Interference Device) magnetic sensor has been developed. It can be applied to TEM magnetic field intensity detection. In this paper, an explicit expression of TEM field Bz in uniform half-space is presented. By means of sinusoidal numerical filter transformation, the Bz formula in the time domain for layered media is derived. Firstly, the characteristics of TEM response for half-space formation under the condition of different resistivity and transmitter-receiver distance are calculated. In addition, for the layered medium model, the magnetic field modeling results are obtained for the two-layer medium with different thickness. The result is consistent with the reality well. The Bz modeling is also performed on three layers of medium with low and high resistance thin layers. Finally, the spatial distribution characteristics of the magnetic field response on the surface for 1 km long dipole are also calculated. The calculation of the ground space distribution of the electric dipole’s magnetic field shows that the vertical component of the magnetic field within the angle of ±75° in the vertical direction of the electric dipole can be effectively measured. The results show that Bz is more sensitive to low resistivity thin layer than high resistivity for deep detection as TEM measurement. Compared with the traditional TEM measurement, the direct detection of magnetic field Bz can obviously improve the advantages of TEM and increase the exploration depth. In other word, this method can improve the advantages of detection method and increase the exploration depth significantly. Moreover,the measurement space scope is larger and the measurement efficiency is higher.

关 键 词：瞬变电磁法 SQUID 磁场强度 正演 

分 类 号：P631[天文地球—地质矿产勘探]