考虑激电效应的瞬变电磁三维正演研究

发布时间：2018-07-18 13:12

【摘要】：瞬变电磁法属于时间域电磁法,它利用电性源或者磁性源向地下发送一次脉冲分量,在其一次脉冲激发下,地下地质体因为导电性和导磁性的差异,将产生随时间变化的感应二次场。因为是在关断一次场后测量纯二次场,不存在一次场干扰,从而得到了迅速的发展,其中在观测二次场中,场源通过多次激发,并通过不同时间窗口观测,可以获得不同的地电结构信息,又因为在噪声源方面的重要区别,使得和频率域电磁法相比有很多的优点。瞬变电磁法工作装置灵活多样,包括同点回线、大回线、电偶源、航空、井中等工作装置;其具有对低阻体反应灵敏、纵横向分辨率高、施工方便效率高等很多优点,因此是在能源、矿产、工程、环境等领域广泛应用的物探方法。本文分别采用垂直磁偶极源和水平电偶极源作为场源,在三维正演中,从麦克斯韦方程组出发,把电磁场分解为一次场和二次场,利用汉克尔变换计算一次场,采用交错采样网格有限差分法计算频率域中二次场,然后加入考虑激电效应的Cole Cole模型,最后把得到的频率域结果通过时频转换到时间域中,对比不同的极化率、频率相关系数、时间常数所得到的时间域响应结果,进行分析并作出结论。本文采用Fortran编程语言编写程序,采用Matlab语言对结果进行可视化。
[Abstract]:The transient electromagnetic method belongs to the time domain electromagnetic method. It uses electrical or magnetic sources to send a single pulse component to the underground. Under the excitation of its first pulse, the underground geological body is caused by the difference between conductivity and magnetic conductivity. The induced quadratic field will change with time. Because the pure quadratic field is measured after the primary field is turned off, and there is no single field interference, it has been developed rapidly. In the observation of the secondary field, the field source is excited many times and observed through different time windows. Different geoelectric structure information can be obtained, and because of the important differences in noise sources, there are many advantages compared with frequency domain electromagnetic method. The transient electromagnetic method has a variety of flexible working devices, including the same point loop line, large loop line, electric couple source, aviation, well, etc. It has many advantages, such as sensitive response to low resistance body, high vertical and horizontal resolution, high construction convenience and efficiency, etc. Therefore, it is widely used in the fields of energy, mineral, engineering, environment and so on. In this paper, the vertical magnetic dipole source and the horizontal electric dipole source are used as the field sources respectively. In the three-dimensional forward modeling, the electromagnetic field is decomposed into the primary field and the quadratic field from Maxwell's equations, and the primary field is calculated by the Hankel transform. Using the staggered sampling grid finite difference method to calculate the quadratic field in the frequency domain, then adding the Cole Cole model considering the induced electric effect. Finally, the obtained frequency domain results are converted to the time domain by time-frequency, and the different polarizabilities are compared. The frequency correlation coefficient and time constant are analyzed and the results of time domain response are analyzed and concluded. In this paper, Fortran programming language is used to program and Matlab language is used to visualize the results.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.325

【共引文献】