瞬变电磁法深度探测正演模拟研究

Forward modeling of prospecting depth for TEM

针对当前瞬变电磁法探测能力有限的问题,利用一次磁场理论公式,分析相同磁矩下、不同发射线圈一次磁场分布及衰减规律,从而确定其信号深度影响范围;对水平层状介质相同磁矩下、不同发射线圈的二次场进行数值模拟,采用Guptasarma和Singh滤波算法及余弦变换法,利用均匀半空间解析公式进行验证,并对不同正演模型结果进行分析,总结发射磁矩决定探测深度大小。对磁矩相同条件下产生的结果数据进行拟合,得出有效探测深度与线圈边长2倍相当的结论,可为野外矿井生产与工程勘探提供施工布置与定量解释的指导依据,从而提高野外工作效率。

Aimed at the limits of prospecting ability for transient electromagnetic method（TEM）, through theoretical calculation formula of the primary electromagnetic field, the distribution and attenuation of the primary electromagnetic field in different size of emission coil but in the same source moment are analyzed to determinate the limited depth of the primary electromagnetic field signal. Besides, the numerical simulation is carried out for the secondary induced electromagnetic field in horizontal layered medium with different size of emission coil. In addition, using the theory formula of homogeneous half-space medium to verify those numerical simulation results come from Guptasarma and Singh filtering algorithm and the cosine transform method. As well as the analysis of different forward modeling results. Finally, the conclusion is obtained that the source moment is determined to the prospecting depth, and the result data in the same magnetic moment are fitted,founding the effective prospecting depth twice as large as the coil length, which will provide a theoretical guidance for the construction design and quantitative interpretation in mine production, engineering detection and environmental exploration to enhance work efficiency.