SOTEM深部探测关键问题分析

The key problems of SOTEM used in deep detection

利用阶跃电流源激发可以有效地将一次场和二次场在时间上进行分离,通过时域电磁场近源测深可获得较强的信号和较大的探测深度.基于以往研究基础,作者提出了电性源短偏移瞬变电磁法(SOTEM),并指出需要研究SOTEM深部探测理论、方法和技术等方面的关键问题.根据时变点电荷栽流微元积分理论,推导出SOTEM响应的精确表达式;通过分析SOTEM电场、磁场各分量的响应及分布特征,以及各分量与地层之间的相互作用特点,对高、低阻层的敏感度等,研究SOTEM深部探测能力;研究SOTEM的记录点规则,以及场源复印和阴影效应等附加效应的影响规律及校正方法;通过对模拟及实测数据的分析,研究SOTEM信号受噪声的影响程度以及各种去除噪声的方法;采用曲线精细拟合技术,提高定量反演精度;总结经验并最终形成一套适用于SOTEM的野外工作规程.

The primary and secondary field can be seperated sequencely if excited by step-current,the stronger signal and deeper depth can be achived by collecting pure induced field data nearby source wire.Based on the former study,the authors propose the method of grounded-wire short-offset transient electromagnetic（named SOTEM by authors）.The several key problems,such as theory,methodology and technology will be conducted in this paper.Based on the theoretical study of the infinitesimal integration of current carrying point charge,the exact formula of SOTEM response will be derived.The study of SOTEM deteting abilty will be finished after the analysis to EM field components distribution and response of SOTEM,the coupling effect of EM field with the layered earth,as well as the sensitivity to conductive and resistive target.SOTEM recording rule and source-print effect will be conducted;By comparing the simulated and field data,the influnce of noise and the methods of removing noise will be studied.Using curve fitting techniques to improve the quantitative inversion accuracy;A set of suitable SOTEM field work rules will be summed at last.