电性源短偏移瞬变电磁探测深度分析与应用

Analysis and application of the detection depth of electrical source Short-offset TEM

瞬变电磁法中有多种深度概念,包括扩散深度、极限探测深度、有效探测深度和视探测深度等。本文以电性源短偏移距瞬变电磁法(SOTEM)为例,针对上述几种深度概念展开了分析、计算与应用研究。扩散深度表征了地下涡流场的扩散;极限探测深度和有效探测深度揭示了SOTEM的探深能力。计算结果表明:当偏移距等于0.7~1倍目标体埋深时可获得最大探测深度;视探测深度可对给定时刻的实际探测深度做出估算,对野外施工参数设计具有重要意义。文章通过理论模型和野外探测实例验证了视探测深度的适用性。

There are several concepts of depth in transient electromagnetic method,including diffusion depth,limit detection depth,effective detection depth and apparent detection depth.In this paper,we conducted the calculation,analysis and application to these different depths based on the method of SOTEM.The diffusion depth represent the diffusion and propagation of the underground transient EM field,the limit detection depth reveals the detectability of SOTEM and the results indicate that the greatest depth will be obtained when the offset approximately equal to the 0.7~1 times of buried depth of targets,and the apparent detection depth can give a estimation of the actual detection depth for a given recording time which have a significant meaning to the field work designing.At last,we proposed a synthetic model and a filed example to verify the feasibility and accuracy of using apparent detection depth to estimate the actual detection depth of SOTEM.