瞬变电磁B场参数测试效果

Test and analysis of TEM B field parameter

传统的瞬变电磁信息获取方式大多采用空芯线圈和磁芯线圈形式,用以测量磁场随时间变化率,但是晚期信号往往较弱,不利于分辨异常。笔者开展了直接测量瞬变电磁法磁场参数的模拟和实测效果分析研究。首先通过对B场和d B/dt参数的响应特性分析,认为B场参数在晚期探测方面具有一定的优越性;分别采用澳大利亚产SM24瞬变电磁系统(磁通门磁探头,直接测量B场)和GDP-32仪器(感应线圈,测量感应电压)进行了实测数据的对比,在同样瞬变电磁观测装置情况下,发现采用磁通门传感器所测量B场数据比采用感应线圈测量的二次感应电压数据效果较好,即:磁通门传感器的特征频率相对较低(往往小于1 k Hz),衰减速度慢,磁场B数据与磁场变化率d B/dt场数据的幅值范围较大,受低阻覆盖层影响程度小,有利于晚期测量。研究结果表明开发和使用磁通门传感器是解决瞬变电磁精细探测的突破方向之一。

In normal TEM sounding,the parameter of secondary induced voltage V signal is collected by using magnetic induced coil; however, the late signal is usually too weak to identify deep buried target.In this paper, direct measuring of B field parameters is used to test its practical effect.Firstly, from the response of B field and dB/dt and numerical calculation of different models, we can see that the B field has superiority in late time detection.Then the SM24 TEM system which is used to measure B field and the GDP-32 system which is adopted to measure induced voltage are compared with each other.With the same observation parameters ,B field data are more superior than induced voltage data.The characteristic frequency of fluxgate sensor is relatively low and it decays slow.In addition, the amplitude of B field data is larger than that of dB/dt data.This means is favorable for measurement in late time because the influence of low resistivity covered layer on it is relatively low.The results show that developing and using fluxgate sensor is an important direction to resolve fine TEM exploration.