【作者】 杨毅；

【导师】 李桐林；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 基于磁偶源的电磁勘探方法是电法勘探的重要分支,广泛应用于石油,工程,环境等关乎国计民生的各个领域,并且取得了卓越的应用效果。时代的发展,对地球物理勘探提出了新的要求,复杂条件的电磁数据处理就是最主要的问题,解决这个问题,三维多参数正反演的理论研究无疑是行之有效的方法。本文主要针对常见的垂直磁偶极子源进行了三维模型下同时考虑激发极化效应、电磁效应的三维复电阻率电磁场模拟研究,首先根据电磁散射积分方程理论,用Cole-Cole模型来刻画大地中不均匀体,然后对不均匀体进行剖分离散,进而化为多个代数方程组,通过解此方程组求得空间任意点电磁场,实现了磁偶源地面定源观测和动源观测模式下的三维复电阻率电磁场正演模拟,分析和讨论了异常体复电阻率参数对正演结果的影响特征,并总结了响应规律,同时模拟结果表明基于磁性源的激发极化是可行的。更多还原

【Abstract】 Rock electrical conductivity and differences IP is the difference of geological problem to solve electrical prospecting. With complex resistivity characterizations of electricity is more precise and accurate. Using complex resistivity (such as zero frequency resistivity ( ? 0) and polarizability ( m ), time constant (? ), frequency and correlation coefficient ( c ) of abnormal body can be realized) can achieved quantitative evaluation of electrical characteristics. Therefore, based on complex resistivity multi-parameter forward research has important theoretical and practical significance. First this paper divided the underground body which is depicted by the Cole-Cole model,then dispersed it into a series of linear equations, got the value of electromagnetic field at arbitrary point. so as to realize the magnetic dipole, the more one source of much more complex resistivity 3D electromagnetic modeling simulation, according to the different ways of observation divided into moved source and fixed source to discussed, the simulation results show that based on magnetic source of polarization is feasible, conclusions are as follows:(1) Fixing source observation: achieved CSAMT forward based on magnetic source, CSAMT near-source effect is simulated, the abnormal resistance body buried in the homogeneous half-space was carried out by profile observations and sounding observations. The results of abnormal body can very good response. The secondary magnetic field was analyzed when the source above and side abnormal body, then compared the real and complex resistivity field in fixed source, the results show that in magnetic fixed source conditions, magnetic field decreases rapidly, two of the same abnormal body response to the secondary market rate is different, the one that close the source is stronger in response. Through the study of the complex resistivity parameter on second field response, we summarized the result of second field is effected by electromagnetic induction, IP effects and induction IP effects. Zero frequency resistivity ( ? 0) and frequency are main factors which effect second field. Real resistivity quadratic field direction while the complex resistivity changes in high resistance. When frequency is low (< 1Hz), virtual amplitude is larger than real, when frequency is large (> when 10Hz) ,real amplitude is larger than and virtual, and real part change obviously when frequency between 100Hz to 1000Hz. Complex resistivity body makes the amplitude is bigger than real resistivity. Polariability ( m ), time constant (? ), frequency and correlation coefficient ( c ) makes than second field’s amplitude increases with the parameters, but very small.(2) Moving source observation: realized the dipole-dipole profiles forward with different offsets, and even abnormal multi-body existed in the half space. The secondary field response verified through simulated normalized vertical magnetic. We changed offset, then we find with the increase of offsets, the normalized amplitude of magnetic field got strong. Its normalized center - 1/2 transceiver distances corresponds to abnormal body x coordinate location. Then we carried out real and complex resistivity quadratic field contrast in the conditions of moved source, the results show that the 3D complex resistivity electromagnetic response is produced by electromagnetic induction and IP effect. Parameters on real part amplitude influence is more, imaginary part is lesser under the condition of 1Hz (low). Real resistivity response is positive when the zero frequency resistivity is less than the background, and changed when the zero frequency resistivity is larger than the background. Complex resistivity real part response is negative. The amplitude of response reduced with the zero frequency resistivity increase, and virtual part almost changed both the real and complex resistivity. With the increasing rate of polarization, real amplitude decreases, and imaginary part changes small. With the increasing frequency coefficients, the real value increases, the department vice versa. With the increased of time constant the real amplitude of response attenuated.更多还原