基于正则化下延方法的视磁化强度全空间反演

发布时间：2018-12-10 10:20

【摘要】：视磁化强度反演,是利用在观测面采集的实际磁力数据来反推地下异常体的磁性参数以及空间赋存状态的一种地球物理手段,它是地球物理勘探的重要手段之一,由于反演得到的磁化强度是相对值,而非地下异常体的磁化强度真实值,因此称之为“视”磁化强度反演。这种方法的基本思想就是对地下待反演地质体进行网格剖分,通过不停的反演迭代直至达到精度要求,来计算出所有剖分网格单元的视磁化强度。这种计算方法的主要问题就是反演多解性严重:第一、观测磁异常是地下的空间体积效应;第二、采集的数据是离散的而不是连续的。因此,如何降低反演多解性的影响,提高反演成像的精度,一直以来都是视磁化强度反演问题中的重中之重。针对磁反演的多解性问题,本文提出了基于正则化下延方法的视磁化强度全空间反演。其核心思想是通过对观测面磁异常场进行正则化向下延拓,得到不同深度的磁场分布,通过结合观测场和下延场的异常数据,来增大反演原始数据量;此外,当场源埋深较大时,在地表观测到的异常信号较弱,而通过正则化下延所得到的下延磁异常场,可以在深度上更接近异常体赋存位置,有利于突出异常信号。该方法的关键是保证观测磁异常场的正则化下延精度,重点是反演目标函数的构建。理论模型试验结果表明,利用本文提出的方法所进行的视磁化强度反演,其反演精度要明显高于仅用观测场数据进行反演而得到的结果。尤其在存在多个不等深场源体情况下,其反演得到的异常体位置较传统方法相比更接近异常体的真实赋存位置,这说明该方法在纵向分辨能力上有显著提高。对北三台地区实际资料进行了处理,反演得到研究区的视磁化强度三维空间分布,并对火成岩进行圈定,结果与实际钻井资料基本吻合,进一步验证了方法的实用性。
[Abstract]:The inversion of apparent magnetization is a geophysical method which uses the actual magnetic data collected on the observational plane to push back the magnetic parameters and the spatial occurrence state of the underground anomalous body. It is one of the important means of geophysical exploration. Because the magnetization obtained by inversion is a relative value, but not the true value of the magnetization of an underground anomaly, it is called "apparent" magnetization inversion. The basic idea of this method is to mesh the geological bodies to be retrieved, and to calculate the apparent magnetization of all the meshes by continuous inversion iteration until the precision is reached. The main problem of this method is that the inversion multi-solution is serious: first, the observed magnetic anomaly is the volume effect of underground space; second, the collected data is discrete rather than continuous. Therefore, how to reduce the influence of inversion multi-solution and improve the accuracy of inversion imaging has always been the most important problem in the inversion of apparent magnetization. Aiming at the multi-solution problem of magnetic inversion, this paper presents a full-space inversion of apparent magnetization based on regularized downscaling method. The core idea is to obtain the magnetic field distribution of different depths by regularizing the anomalous magnetic field of the observation surface, and to increase the original data by combining the anomaly data of the observation field and the downgoing field. In addition, the anomalous signals observed on the surface of the earth are weaker when the depth of the source is larger on the spot, and the anomalous magnetic field obtained by regularizing the downward continuation can be closer to the location of the anomalous body in depth, which is advantageous to outburst the abnormal signal. The key point of this method is to ensure the regularization and downscaling accuracy of the observed magnetic anomaly field, with emphasis on the construction of the inversion objective function. The experimental results of theoretical model show that the inversion accuracy of apparent magnetization inversion based on the method proposed in this paper is obviously higher than that obtained by only using the observational field data. Especially in the case of multiple source bodies with unequal depth, the position of anomalous bodies obtained by inversion is closer to the real location of anomalous bodies than that of traditional methods, which indicates that the vertical resolution of this method is improved significantly. The actual data of Beisantai area are processed and the 3-D spatial distribution of apparent magnetization is obtained by inversion. The igneous rocks are delineated. The results are in good agreement with the actual drilling data, which further verifies the practicability of the method.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631

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