电性源短偏移瞬变电磁探测深度分析与应用
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摘要
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.
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.
引文
[1]程志平.电法勘探教程[M].北京:冶金工业出版社,2007.
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[4]Spies B R.Depth of investigation in electromagnetic sounding methods[J].Geophysics,1989,54(7):872-888.
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[6]薛国强.论瞬变电磁测深法的探测深度[J].石油地球物理勘探,2004,39(5):575-578.
[7]闫述,石显新,陈明生.瞬变电磁法的探测深度问题[J].地球物理学报,2009,52(6):1538-1591.
[8]薛国强,陈卫营,周楠楠,等.接地源瞬变电磁短偏移深部探测技术[J].地球物理学报,2013,56(1):255-261.
[9]陈卫营,薛国强,崔江伟,等.SOTEM响应特性分析与最佳观测区域研究[J].地球物理学报,2016,59(2):739-748.
[10]Eaton P A,Hohmann G W.A rapid inversion technique for transient electromagnetic soundings[J].Physics of the Earth and Planetary Interiors,1989,53:384-404.
[2]底青云,王若.可控源音频大地电磁数据正反演及方法应用[M].北京:科学出版社,2008.
[3]牛之琏.时间域电磁法原理[M].长沙:中南工业大学出版社,1992.
[4]Spies B R.Depth of investigation in electromagnetic sounding methods[J].Geophysics,1989,54(7):872-888.
[5]殷长春.瞬变电磁测深法的研究深度[J].长春地质学院学报,1992,22(1):103-107.
[6]薛国强.论瞬变电磁测深法的探测深度[J].石油地球物理勘探,2004,39(5):575-578.
[7]闫述,石显新,陈明生.瞬变电磁法的探测深度问题[J].地球物理学报,2009,52(6):1538-1591.
[8]薛国强,陈卫营,周楠楠,等.接地源瞬变电磁短偏移深部探测技术[J].地球物理学报,2013,56(1):255-261.
[9]陈卫营,薛国强,崔江伟,等.SOTEM响应特性分析与最佳观测区域研究[J].地球物理学报,2016,59(2):739-748.
[10]Eaton P A,Hohmann G W.A rapid inversion technique for transient electromagnetic soundings[J].Physics of the Earth and Planetary Interiors,1989,53:384-404.