相控电磁法观测系统初探  

Preliminary study on phased controlled electromagnetic method

作　　者：李帝铨 LI DiQuan(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University),Ministry of Education,Changsha 410083,China;Key Laboratory of Non-Ferrous and Geological Hazard Detection,Changsha 410083,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,China)

机构地区：[1]有色金属成矿预测与地质环境监测教育部重点实验室(中南大学),长沙410083 [2]有色资源与地质灾害探测湖南省重点实验室,长沙410083 [3]中南大学地球科学与信息物理学院,长沙410083

出　　处：《地球物理学进展》2024年第3期1193-1205,共13页Progress in Geophysics

基　　金：国家重点研发计划(2022YFC2903704)资助。

摘　　要：电磁波具有动力学(振幅)和运动学(相位)性质,传统可控源电磁法场源研究中,主要利用了动力学性质,存在3个局限:(1)单源激发存在场的弱区甚至零值带;(2)采用双源或多源激发时,改变源与源之间的夹角,只利用电磁波的动力学性质,实现某些方向的信号增强,但低值带仍然存在;(3)双源或多源同相位激发时的电磁场简单叠加不能实现宽方位测量.在实际工作中,无论是单源还是多源系统,可测量角度范围并无变化,无法扩展测量方位角.本文基于均匀半空间模型,讨论理想情况下综合利用电磁波的动力学和运动学性质,尝试采用双源实现可控源电磁法的宽方位测量:(1)改变源与源之间的夹角和发射电流相位差,消除信号弱区,实现电磁波分布在更宽广的区域上,或实现电磁波在某个特定方向上同相叠加,提高信噪比;(2)综合主射方向、主叶宽度、振幅变化特征等场的方向图特征信息,建立双源系统的宽方位测量区,实现360°全方位测量.相控电磁法可实现大面积测量,提高勘探效率,降低勘探成本,也可以提高某方向上的电磁场场强和信噪比,为城市等强干扰区的电磁探测开辟新路.Electromagnetic wave has both dynamic(amplitude) and kinematic(phase) properties.There were 3 main limitations in the excitation source research of Controlled Source Electromagnetic(CSEM),(1) Single source was widely used,and there was weak and zero zones,was unable to measure.(2) When used dual-source or multi-source excitation,only the dynamic property was used,by change the angle between the sources,achieve signal enhancement in some directions,but weak and zero zone still exists.(3) When the dual-source or multi-source excitation in-phase,the electromagnetic field was simply superposed,and it cannot meet the needs of omnidirectional measurement.In practical,there was no mater single source or multi-source,the measurement angle range cannot be expanded,and the measurement area cannot be extended.These problems could be solved by the following methods,(1) Change the angle between the sources,and change the sources current phase,make full use of kinematic and dynamic properties of the electromagnetic wave,eliminate the weak signal area,make electromagnetic wave distribution in wide-azimuth,or to achieve the electromagnetic wave in a certain direction superposition,improve the signal-to-noise ratio.(2) Make full understanding to the characteristics of electromagnetic field pattern,comprehensive utilization the mainlobe direction,half-power angle and amplitude change,established the wide-azimuth measurement system with dual-source,achieve omnidirectional measurement.Phase controlled electromagnetic method can realize wide-azimuthmeasurement,improve the exploration efficiency andreduce the exploration cost.

关 键 词：可控源电磁法 相位控制 场源 方向图 全方位测量 

分 类 号：P631[天文地球—地质矿产勘探]