被动式超低频电磁探测数据采集与处理方法研究

The research of the data collection and processing in the passive supper low frequency(SLF) electromagnetic exploration

由于被动式超低频电磁探测仪具有便携易用、野外布线简单、受地形影响小并且对低阻体、高阻体均有反映的特点,因此在能源勘探、资源勘察和地质构造探测中展现出良好的性能与开发潜力,接收来自地下深部的天然源超低频电磁信号的勘探技术,已成为国内外近些年来的研究热点。文中首先介绍了被动式超低频电磁探测技术最近几年的野外试验情况及超低频磁场传感器的主要技术指标水平,认为目前BD-6型被动式超低频电磁探测仪无论在频谱分辨率、信噪比,还是在探测效率方面都得到了极大提高;其次,分析了场源效应、频深转换公式、分辨率因素对数据采集、处理过程的影响;提出场源效应导致的随机噪声可以通过多次采集数据叠加平均方法加以降低,利用已知地质和钻井资料修正后的频深转换公式更适用于某种勘探目标(煤层气、地下水等)和某个地区探测数据的解释;采用适当的线性(谱分析法)和非线性(分数维法)分析方法,可以为探测数据的处理与解释提供新的方法和技术途径。

The research of receiving the electromagnetic waves in Super Low Frequency （SLF） from the depth of the Earth has become a hot international issue in recent years.This paper introduces the field experiments and applications of the passive-exploration technology of SLF.Owing to its portability,simple surveying line arrangement,being little affected by the terrain and being sensitive both to low resistance and high resistance bodies,the passive SLF explorer presents a good performance and great development potential in the resource explorations.In this paper,the field experiments of passive SLF and the level of the technical specifications of SLF sensor are introduced first.From the introduction,we can see that the BD-6 type of passive SLF electromagnetic detector has been improved greatly,such as the spectral resolution,SNR,the detection efficiency,etc.Furthermore,the influence of the source effects,the frequency-depth conversion and the resolution in the data acquisition and processing are also analyzed.Based on those analyses,we propose that the random noise caused by the source can be reduced by means of averaging the data,that the frequency depth conversion algorithm revised by the known geological and drilling data is more applicable to the data interpretation of some regions or targets,such as the coal-bed methane,the groundwater,etc.,and that the use of linear or non-linear method （spectral analysis method or the fractal dimension method） is a new way for the data processing and interpretation.