时间域航空电磁系统仿真与关键技术研究

发布时间：2018-01-02 22:26

本文关键词：时间域航空电磁系统仿真与关键技术研究　出处：《吉林大学》2016年博士论文　论文类型：学位论文

【摘要】：航空电磁法(Airborne Electromagnetic Method,简称AEM)是一种感应类电磁勘探方法。由于采用移动平台,较传统地面电磁法具有方便、快速、无需地面人员接近等显著优点,适合复杂地形条件,特别适合在无人区(高山、沙漠、沼泽、湖泊、森林覆盖等)进行大面积油气、矿产、地下水和地热资源及环境与工程勘查。近年来,时间域航空电磁法因其分辨率高和勘探深度大等优点已成为电磁法勘探研究的热点。目前时间域航空电磁数据处理的一维成像和反演方法已十分成熟,但是其只能处理off-time段的数据,无法解译信息丰富的on-time段数据,而且基于一维模型的成像或反演无法准确的反映地下三维目标体信息。此外,由于实际地层经常呈现出各向异性特征,如用各向同性模型来解释各向异性地区测得的时间域航空电磁资料会产生较大偏差。因此,为了提高时间域航空电磁数据的处理水平,本文开展各向异性介质中三维时间域航空电磁响应仿真研究,并对时间域航空电磁法几个关键技术进行分析。本文首先开展一维时间域航空电磁全时响应仿真技术研究。利用快速汉克尔积分数值滤波算法实现垂直磁偶极子源(Vertical Magnetic Dipole,简称VMD)的频率域全空间电磁场各分量响应计算,通过快速傅里叶变换将频率域电磁响应转换到时间域,得到时间域全空间电磁场响应;鉴于时间域脉冲响应早期的不稳定性,提出利用阶跃波与实际发射波形进行褶积的计算方法,实现任意发射波形时间域电磁场全时响应模拟。通过理论计算表明,本算法计算精确、稳定,很好地展现出磁场B与磁感应d B/dt的一致性,为研究复杂三维地电模型的全时电磁响应奠定良好的基础。本文研究任意各向异性的三维时间域航空电磁仿真技术。通过欧拉旋转得到任意各向异性介质的电导率张量,并利用广义变分原理推导出任意各向异性介质的频率域航空电磁二次场控制方程;采用六面体对求解区域进行离散,并用矢量线性插值基函数进行有限单元分析,实现对控制方程的离散;将离散单元进行总体合成,形成大型稀疏线性方程组,并采用高性能MUMPS直接求解器对方程组进行求解;最后采用时-频转换计算方法和褶积算法实现任意波形的三维时间域航空电磁各向异性正演模拟。通过与解析解对比和典型各向同性三维介质的模拟,验证算法的准确性和可行性。同时,本文还重点分析任意各向异性对三维时间域航空电磁法的影响特征。本文对时间域航空电磁法中一些关键技术进行了探讨。首先对不同发射波形(半正弦波、梯形波、三角波、方波、多波)的三维时间域航空电磁法全时响应进行数值分析,比较各单一波形在断电后的响应情况,并阐明多波在浅层地表的勘探效果;同时给出两种基频下不同发射装置各单一波形不同场分量的勘探效果。其次,研究飞行高度对时间域航空电磁响应的影响,分析不同高度对理论数据产生的误差;并对树冠和落叶层下的均匀半空间模型及异常体模型进行数值分析。最后在均匀半空间模型中,对发射和接收装置任意姿态变化的时间域航空电磁全时响应进行数值分析。结果显示,在航空电磁实际勘探中,为提高勘探效果,应合理选择波形及设定测量参数,尽可能采用多波发射实现全时采样,并精确记录发射和接收线圈的高程及姿态变化。本文的研究成果可为时间域航空电磁法的系统研制或航空电磁观测参数设计及数据反演提供参考和依据,同时能够提高时间域航空电磁数据的解释水平,具有一定的理论和实际意义。
[Abstract]:Airborne electromagnetic method (Airborne Electromagnetic Method, referred to as AEM) is a kind of induction type electromagnetic exploration method. Due to the use of mobile platform, compared with the traditional ground electromagnetic method has the advantages of convenient, fast, no significant advantage of near ground personnel, suitable for complex terrain, especially in uninhabited areas (mountains, deserts, swamps, lakes, forest cover) a large area of oil and gas, mineral resources, groundwater and geothermal resources and environment and engineering exploration. In recent years, the time domain airborne electromagnetic method has become a research hotspot of electromagnetic exploration because of its advantages of high resolution and great exploration depth. The time domain airborne electromagnetic data processing of one-dimensional imaging and inversion methods have been very mature, but it can only deal with off-time data, cannot decipher the abundant information of on-time data, and the one-dimensional model inversion based on imaging or can not accurately reflect the underground three-dimensional target The body of information. In addition, due to the actual formation often exhibit anisotropic characteristics, such as the use of isotropic model to explain the time domain airborne electromagnetic data measured in anisotropic regions will have great errors. Therefore, in order to improve the level of processing in time domain airborne electromagnetic data, this paper carried out in anisotropic medium three-dimensional time domain simulation research on the response of aviation the electromagnetic, and several key technologies of airborne electromagnetic method in time domain analysis. This paper studies the response of the whole simulation technology of one-dimensional time domain airborne electromagnetic. Using Hankel integral numerical filtering algorithm to realize the vertical magnetic dipole source (Vertical Magnetic Dipole, referred to as VMD) to calculate the response of the frequency domain space electromagnetic field, through fast the Fourier transform frequency domain electromagnetic response to the time domain, the time domain response in whole space electromagnetic field; in view of the time domain pulse The early response of instability, the step wave and the actual waveform calculation methods of convolution, arbitrary waveform of time domain electromagnetic full response simulation. Through theoretical calculations show that the algorithm is accurate, stable, good to show consistency of the magnetic field B and magnetic induction D B/dt, research the complex three-dimensional geoelectric model of the entire electromagnetic response to lay a good foundation. This paper studies arbitrary anisotropic 3D time domain airborne electromagnetic simulation technology. The conductivity tensor obtained Euler rotation in arbitrary anisotropic medium, and generalized variational principle are derived for arbitrary anisotropic medium frequency domain airborne electromagnetic field control equation by two times; hexahedral discrete domain, and finite element analysis with vector linear interpolation function, the realization of discrete control equations of the discrete unit in total; The synthesis, the formation of large sparse linear equations, and the use of high performance MUMPS direct solver to solve the equations; finally using time-frequency transform calculation method and realization algorithm of arbitrary waveform fold product of 3D time domain airborne electromagnetic anisotropic modeling. Through simulation and analytical methods and typical three-dimensional isotropic medium the accuracy, and verify the feasibility of the algorithm. At the same time, this paper also focuses on the analysis of arbitrary anisotropic effect on 3D time domain airborne electromagnetic characteristics. This paper discusses some key technologies of time domain airborne electromagnetic method. Firstly, different waveform (half sine wave, trapezoidal wave, triangle wave, square wave, wave) the 3D time domain airborne electromagnetic method response numerical analysis, the response in power after the comparison of each single waveform, and clarify the multiwave in shallow surface exploration results are given at the same time; Two kinds of fundamental frequency under different emission device of the single waveform of different component of the exploration effect. Secondly, the research on influence of flight height time domain airborne electromagnetic response, error analysis of different height of theoretical data; and the homogeneous half space model and canopy under litter and abnormal body model by numerical analysis. Finally, in uniform half space model, the time domain airborne electromagnetic transmitting and receiving device arbitrary attitude change in full response by numerical analysis. The results showed that in the actual airborne electromagnetic exploration, in order to improve the exploration effect, should be a reasonable choice of the waveform and setting of measurement parameters, as far as possible the use of multiwave emission to achieve full sampling, and accurate records and emission the receiving coil height and posture change. The results of this study can provide for system development or airborne electromagnetic observation parameter design and data inversion of time domain airborne electromagnetic method At the same time, it can improve the interpretation level of the time domain aero electromagnetic data, which has some theoretical and practical significance.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.326

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