航空瞬变电磁CDI方法及分析

发布时间：2018-04-09 17:07

本文选题：航空瞬变电磁法　切入点：电导率深度成像　出处：《成都理工大学》2015年硕士论文

【摘要】：由于航空瞬变电磁法具有成本较低、勘探效率高、可大面积勘查等优点,所以该方法已经在矿产资源勘查、地下水调查、地质填图和环境监测等领域获得了广泛的应用。尽管航空瞬变电磁反演已经获得了大量研究,但是由于航空瞬变电磁数据量较大、反演耗时较高,所以反演解释已经阻碍了该方法的推广。为此,作为一种快速成像方法,电导率深度成像(CDI)方法已经成为航空瞬变电磁法实用化的关键技术之一。本文分别对基于查询表和基于水平薄板模型的CDI方法进行研究并编程实现,同时分析这些方法的特点。具体来说,主要研究内容如下:(1)航空瞬变电磁一维正演方法。首先,通过麦克斯韦方程组得到扩散方程,并推导出中心回线航空瞬变电磁的一维正演模拟公式;然后,运用G-S变换和汉克尔积分变换对正演公式进行计算,其中G-S变换采用12个系数,汉克尔积分变换采用120个的零阶滤波系数和140个的一阶滤波系数。上述的正演计算公式为后续的查询表的建立奠定了理论基础。(2)基于一维正演查询表的电导率深度成像方法。首先,分别建立假层均匀半空间查询表和时间序列?(?)查询表;然后,通过三次样条插值法对查询表进行插值并根据待成像的电磁响应值实现电导率查询;最后,分别采用不同的视深度计算公式得到视深度,从而获得电导率深度成像结果。同时,分析了上述两种查询表方法在一维、准二维地电模型中的成像结果。(3)基于水平薄板模型电导率深度成像方法。首先,分析研究了水平薄板模型电磁正演响应,并通过正演响应公式进行了基于水平薄板模型电导率深度成像方法原理推导;然后,采用Maxwell软件的2.5维航空瞬变电磁正演程序获得电磁模拟数据;最后,对电磁模拟数据进行成像并对成像结果进行分析。(4)实测航空瞬变电磁数据的成像结果与分析。首先,利用本研究组所研制的吊舱式直升机时间域航空电磁数据处理及解释软件系统对实测数据进行预处理,获得航空瞬变电磁剖面数据;然后,分别使用基于假层均匀半空间的CDI方法和基于水平薄板模型的CDI方法对实测的电磁剖面数据进行成像;最后,对成像结果进行分析,验证上述成像方法的有效性和正确性。
[Abstract]:Because the aeronautical transient electromagnetic method has the advantages of low cost, high exploration efficiency and large area exploration, it has been widely used in mineral resources exploration, groundwater survey, geological mapping and environmental monitoring.Although a great deal of research has been done on aeronautical transient electromagnetic inversion, because of the large amount of aeronautical transient electromagnetic data and the high time consuming of the inversion, the inversion interpretation has hindered the popularization of this method.Therefore, as a rapid imaging method, the conductivity depth imaging (CDI) method has become one of the key technologies in the application of aeronautical transient electromagnetic method.In this paper, CDI methods based on query table and horizontal thin plate model are studied and implemented, and the characteristics of these methods are analyzed.Specifically, the main research contents are as follows: 1) one-dimensional forward modeling method of aeronautical transient electromagnetic.First, the diffusion equation is obtained by Maxwell's equations, and the one-dimensional forward simulation formula of aeronautical transient electromagnetic in the central loop is derived, and then the forward formula is calculated by using G-S transform and Hankel integral transform.Among them, G-S transform uses 12 coefficients, Hankel integral transform uses 120 zero-order filter coefficients and 140 first-order filtering coefficients.The above forward calculation formula lays a theoretical foundation for the subsequent establishment of the look-up table. (2) the conductivity depth imaging method based on the one-dimensional forward lookup table.Firstly, a pseudo-layer uniform half-space query table and a time series are established respectively.The look-up table is then interpolated by cubic spline interpolation method and the electrical conductivity query is realized according to the electromagnetic response value of the imaging. Finally, the apparent depth is obtained by using different formulas for calculating the apparent depth.The results of electrical conductivity depth imaging are obtained.At the same time, the imaging results of the above two look-up table methods in one-dimensional and quasi-two-dimensional geoelectric models are analyzed. The results are based on the conductivity depth imaging method of the horizontal thin plate model.Firstly, the electromagnetic forward response of horizontal thin plate model is analyzed and studied, and the principle of conductivity depth imaging method based on horizontal thin plate model is deduced by forward response formula.The electromagnetic simulation data are obtained by the 2.5-D aeronautical transient electromagnetic forward modeling program of Maxwell software. Finally, the electromagnetic simulation data are imaged and the imaging results are analyzed. 4) the imaging results and analysis of the measured aeronautical transient electromagnetic data are analyzed.Firstly, the time-domain aero-electromagnetic data processing and interpretation software system of the podded helicopter developed by this research group is used to preprocess the measured data to obtain the aeronautical transient electromagnetic profile data.The CDI method based on pseudo-layer uniform half-space and the CDI method based on horizontal thin plate model are used to image the measured electromagnetic profile data respectively. Finally, the imaging results are analyzed to verify the validity and correctness of the above imaging methods.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.326

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