基于体积分方程方法的低频近场问题的数值模拟
发布时间：2018-11-08 11:16
【摘要】：作为电磁场方法在地球物理探测领域中的重要应用,电磁随钻测量(Electromagnetic-measurement-while-drilling,EM-MWD)信号无线传输技术是比较典型的低频近场问题。在石油测井以及煤层气探测等现代测井应用中,随钻测量技术担负着监控井下工作,将井下探测数据与地面系统交互,是测井控制系统中不可或缺的一部分。由于地层介质的复杂性,以及电磁波在井下环境中的迅速衰减而被迫用极低频率传输使得EM-MWD的理论研究难以建立精确、可靠的模型。如何实现对EM-MWD系统的精确建模,是当前研究工作的一个重要问题。针对EM-MWD系统的精确数值模型的建立及分析,本文做了以下工作,一共分为6个部分:首先在绪论中介绍了随钻测量技术的主要分类,国内外EM-MWD技术的发展历史与现状、研究意义以及本文的主要内容和组织结构。第二章简要介绍了体面积分方程以及矩量法求解原理,通过几何建模,选取基函数,计算阻抗元素,最终求解线性方程组;重点介绍了数值积分及其奇异性处理和线性方程组迭代求解方法。第三章介绍了多层自适应交叉近似算法的基本原理以及具体流程。MLACA算法有效解决了积分方程矩量法中的大未知量所导致的内存以及迭代时长的问题。第四章是本文的重点研究内容,在考察了几种常用的EM-MWD数值建模方法后,建立了基于体积分方程方法的EM-MWD数值模型。本文选择了间隙电压激励作为EM-MWD的馈电方式,经过理论推导,建立了有限宽度(Finite-Gap)电压源等效模型,并以此为基础对EM-MWD模型进行了数值验证。第五章为数值分析部分,对EM-MWD系统的各个参数进行算例分析,包括地层电导率、钻杆尺寸及频率等因素的变化,并对结果予以解释。
[Abstract]:As an important application of electromagnetic field method in geophysical detection, electromagnetic while drilling measurement (Electromagnetic-measurement-while-drilling,EM-MWD) signal wireless transmission technology is a typical low-frequency near-field problem. In the modern logging applications such as petroleum logging and coalbed methane detection, while drilling and measuring technology is responsible for monitoring and controlling downhole, and it is an indispensable part of logging control system to interact downhole detection data with surface system. Due to the complexity of formation medium and the rapid attenuation of electromagnetic wave in underground environment, it is forced to transmit at very low frequency, which makes it difficult to establish an accurate and reliable model for the theoretical study of EM-MWD. How to realize accurate modeling of EM-MWD system is an important problem in current research work. Aiming at the establishment and analysis of accurate numerical model of EM-MWD system, this paper has done the following work, which is divided into six parts: firstly, in the introduction, it introduces the main classification of measurement technology while drilling, the development history and present situation of EM-MWD technology at home and abroad. The significance of the study and the main content and organizational structure of this paper. In the second chapter, the decent integral equation and the principle of moment method are introduced briefly. Through geometric modeling, selecting the basis function, calculating the impedance element, and finally solving the linear equation group; The numerical integration and its singularity treatment and iterative solution method for linear equations are introduced in detail. In chapter 3, the basic principle and flow chart of multi-layer adaptive crossover approximation algorithm are introduced. MLACA algorithm effectively solves the problem of memory and iteration time caused by large unknown quantity in the method of moment of integral equation. Chapter 4 is the focus of this paper. After investigating several commonly used EM-MWD numerical modeling methods, a EM-MWD numerical model based on the volume fractional equation method is established. In this paper, gap voltage excitation is chosen as the feed mode of EM-MWD. Through theoretical derivation, the equivalent model of finite width (Finite-Gap) voltage source is established, and the EM-MWD model is verified numerically on the basis of this model. The fifth chapter is the numerical analysis part. The numerical examples of the parameters of EM-MWD system are given, including the variation of formation conductivity, drill pipe size and frequency, and the results are explained.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.32
[Abstract]:As an important application of electromagnetic field method in geophysical detection, electromagnetic while drilling measurement (Electromagnetic-measurement-while-drilling,EM-MWD) signal wireless transmission technology is a typical low-frequency near-field problem. In the modern logging applications such as petroleum logging and coalbed methane detection, while drilling and measuring technology is responsible for monitoring and controlling downhole, and it is an indispensable part of logging control system to interact downhole detection data with surface system. Due to the complexity of formation medium and the rapid attenuation of electromagnetic wave in underground environment, it is forced to transmit at very low frequency, which makes it difficult to establish an accurate and reliable model for the theoretical study of EM-MWD. How to realize accurate modeling of EM-MWD system is an important problem in current research work. Aiming at the establishment and analysis of accurate numerical model of EM-MWD system, this paper has done the following work, which is divided into six parts: firstly, in the introduction, it introduces the main classification of measurement technology while drilling, the development history and present situation of EM-MWD technology at home and abroad. The significance of the study and the main content and organizational structure of this paper. In the second chapter, the decent integral equation and the principle of moment method are introduced briefly. Through geometric modeling, selecting the basis function, calculating the impedance element, and finally solving the linear equation group; The numerical integration and its singularity treatment and iterative solution method for linear equations are introduced in detail. In chapter 3, the basic principle and flow chart of multi-layer adaptive crossover approximation algorithm are introduced. MLACA algorithm effectively solves the problem of memory and iteration time caused by large unknown quantity in the method of moment of integral equation. Chapter 4 is the focus of this paper. After investigating several commonly used EM-MWD numerical modeling methods, a EM-MWD numerical model based on the volume fractional equation method is established. In this paper, gap voltage excitation is chosen as the feed mode of EM-MWD. Through theoretical derivation, the equivalent model of finite width (Finite-Gap) voltage source is established, and the EM-MWD model is verified numerically on the basis of this model. The fifth chapter is the numerical analysis part. The numerical examples of the parameters of EM-MWD system are given, including the variation of formation conductivity, drill pipe size and frequency, and the results are explained.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.32
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