重磁三维约束反演研究及应用

发布时间：2018-06-15 14:12

本文选题：重磁勘探 + 三维　；参考：《成都理工大学》2015年硕士论文

【摘要】：重磁物性模型构建中,因为不涉及场源复杂的形态变化,并且更容易结合地质等先验信息和约束条件,因此物性反演已成为重磁反演发展的趋势。而反演技术的关键是充分利用约束条件尽量避免多解性。所以,本文深入研究了重磁三维约束反演,对比了不同模型下约束反演的理论效果,并通过处理实际资料验证了约束反演良好效果。首先,在研究了重磁异常基本理论的基础上,重点研究了重磁异常点源法计算方法,得到了点源法的重磁异常正演离散公式,并编制Fortran程序实现了模型的重磁异常正演计算。其次,在熟悉反演基本理论的基础上重点研究了英属哥伦比亚大学的Li和Oldenburg提出了重磁三维光滑约束反演。构建的目标函数既包含了数据拟合函数,又包含了模型函数,其中的正则化因子,用来控制模型函数在目标函数中的权重。并将深度加权函数引入到目标函数中,克服了核函数的自然衰减(即趋肤效应)。推导了粗糙度函数,并将其引入到模型函数中,实现了模型的光滑约束。采用比广义逆法更好的共轭梯度法求解目标函数的最小化。再次,本文以磁异常反演为例,分别设计了一个直立长方体模型、两个长方体模型、五个长方体模型及倾斜板状体模型,运用了深度加权约束、模型加权约束进行反演,并对比分析了有无深度加权、有无模型加权时的反演效果,并得出有约束时恢复的模型更接近真实模型。最后,将约束反演方法用于西藏东巧地区的重磁勘探,取得了较好的效果,验证了方法的有效性。
[Abstract]:In the construction of gravity and magnetic physical properties model, physical inversion has become the trend of gravity and magnetic inversion because it does not involve complex morphological changes of field sources, and it is easier to combine prior information and constraints such as geology. The key of inversion technique is to make full use of constraints to avoid multi-solution. Therefore, in this paper, the gravity and magnetic three-dimensional constrained inversion is deeply studied, and the theoretical results of constrained inversion under different models are compared, and the good results of constrained inversion are verified by processing the actual data. Firstly, on the basis of studying the basic theory of gravity and magnetic anomaly, the calculation method of gravity and magnetic anomaly point source method is studied emphatically, and the forward discrete formula of gravity and magnetic anomaly is obtained, and the Fortran program is compiled to realize the forward calculation of gravity and magnetic anomaly. Secondly, on the basis of the basic theory of inversion, Li and Oldenburg of the University of British Columbia proposed the gravity and magnetic 3D smooth constrained inversion. The constructed objective function includes both the data fitting function and the model function. The regularization factor is used to control the weight of the model function in the objective function. The depth-weighted function is introduced into the objective function to overcome the natural attenuation of the kernel function (i.e. skin effect). The roughness function is derived and introduced into the model function to realize the smooth constraint of the model. The conjugate gradient method, which is better than the generalized inverse method, is used to minimize the objective function. Thirdly, taking the inversion of magnetic anomalies as an example, this paper designs a vertical cuboid model, two cuboid models, five cuboid models and inclined slab model respectively. The inversion results with or without depth weighting and model weighting are compared and analyzed, and it is concluded that the model with constraints is closer to the real model. Finally, the constrained inversion method is applied to gravity and magnetic exploration in Dongqiao area, Tibet, and good results are obtained, and the validity of the method is verified.
【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

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