基于数字递归陷波的多通道瞬变电磁法周期噪声去除研究  

The removal of MTEM periodic noise based on digital recursive notching

作　　者：张文伟 底青云[3,4,5] 耿启立 雷达 王中兴[3,4,5] 缪佳佳[1,2] ZHANG Wen-Wei;DI Qing-Yun;GENG Qi-Li;LEI Da;WANG Zhong-Xin;MIAO Jia-Jia(China Geological Equipment Research Institute Co.,Ltd.,Beijing 100011,China;China Geological Equipment Group Co.,Ltd.,Beijing100102,China;Key Laboratory of Shale Gas and Geoengineering,CAS,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing100029,China;Institutions of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中地装(北京)科学技术研究院有限公司,北京100011 [2]中国地质装备集团有限公司,北京100102 [3]中国科学院地质与地球物理研究所中国科学院页岩气与地质工程重点实验室,北京100029 [4]中国科学院地球科学研究院,北京100029 [5]中国科学院大学,北京100049

出　　处：《物探与化探》2020年第2期278-289,共12页Geophysical and Geochemical Exploration

基　　金：国家重点研发计划项目“地面探测装备试验与方法示范”(2018YFC0603206);中国科学院战略性先导科技专项(A类)“智能导钻系统集成与试验”(XDA14050100)。

摘　　要：多通道瞬变电磁数据受工频噪声干扰严重,去除周期性的工频噪声是多通道瞬变电磁法实测数据处理面临的重大难题。通过交换发射与接收位置避开电力线从源头上减小工频噪声只适合电力线分布少而简单、地形较平坦的情况,极性反转叠加法更适合阶跃激励电流,观测垂向电场仅适合一维电性结构。数字递归陷波能够相对稳健地压制周期性噪声,并且计算速度快,但是,数字递归陷波法本身也有问题:其一,反褶积前陷波会使大地脉冲响应出现周期性的凹陷;其二,数字递归陷波器本身存在瞬态响应。本文研究了利用数字递归陷波器去除多通道瞬变电磁数据的周期性噪声的几个关键问题。首先,对设计数字递归陷波器的传统零点极点法进行修正,推导了新的计算公式。新的设计方法采用陷波带宽计算滤波系数。陷波带宽具有明确的物理意义,便于分析问题。其次,研究反褶积后陷波,即直接对大地脉冲响应进行处理,并系统地分析了陷波带宽、初始条件、大地脉冲响应波形等因素对数字递归陷波器的瞬态响应及陷波效果的影响。研究表明,选择合适的初始条件可以有效压制数字递归陷波器的瞬态响应,从而消除大地脉冲响应包含的周期噪声。最后,应用反褶积后数字递归陷波方法处理了野外实测数据,得到了合理结果。Multi-channel transient electromagnetic data suffer seriously from cultural noise, and removal of periodic cultural disturbance has been a major problem in the multi-channel transient electromagnetic method. In some cases with only quite a few power lines configured regularly, the power line interference can be reduced by exchanging the receiver and source. The method by reversing source current polarity then stacking them period-by-period works better for step-current source. When only homogeneous earth is considered, the perpendicular electric component, which is in fact noise, can be measured and then subtracted from the in-line electric component. Digital recursive notching is a relatively robust way in which the periodic noise can be suppressed. It is well known that recursive notching is very fast;however, holes resulting from pre-deconvolution notching and transient response of digital recursive notcher has to be highly regarded. In this paper, several key points in removal of periodic power line noise in multi-channel transient electromagnetic data using digital recursive notch are studied. First of all, a modified version of so-called zero-pole digital recursive notcher design method, where filter coefficients are evaluated from notch width that makes significant physical sense and make analysis more clear, is proposed. After that, research on post-deconvolution notching, which directly deals with earth impulse response, is conducted. In addition, factors influencing transient response and notch result, such as notch width, initial conditions, and shape of earth impulse response, are analyzed. The results indicate that appropriate selection of initial conditions can effectively reduce the transient response of digital recursive notcher and thus remove periodic noise in earth impulse. Finally, reasonable result is obtained by applying the post-deconvolution digital recursive notch to real field data.

关 键 词：多通道瞬变电磁法 大地脉冲响应 数字递归陷波 瞬态响应 初始条件 

分 类 号：P631[天文地球—地质矿产勘探]