动圈式模拟检波器接收到的数据在自然频率以下的低频成分被大幅度衰减,这种相当于物理滤波的低频衰减可用传递函数做数学描述。从确定型号检波器的特性参数(如自然频率、阻尼、灵敏度等),易得检波器系统的传递函数(频率效应),再通过"检波器反褶积"补偿此低频衰减。该补偿会受到检波器允差和"非检波器振动系统输出噪声"两因素的影响。研究表明:对于目前广泛采用的10Hz自然频率动圈式模拟检波器(如20DX),在当前地震勘探背景(多次覆盖、强噪声、耦合条件差异大且极弱信号识别能力有限)下,上述两个因素对反褶积效果(表现为信噪比)影响较小;通过检波器反褶积可将动圈式检波器损失的低频数据恢复到与MEMS数字检波器(无低频衰减)相当的水平;对所有通过模拟检波器采集的以往地震数据(现场施加低截滤波的除外)做检波器反褶积,可提高采集数据中低频分量的占比,为后续处理、解释提供更宽频的高质量基础数据。
Abstract
Data acquired by coiled geophones lacks components of which the frequency is lower than the natural frequency. These low-frequency components are very useful in many fields, such as FWI, velocity analysis, deep target imaging, etc. Low-frequency attenuation similar to physical filtering process can be described as a mathematical transfer function. Since geophone specifications(natural frequency, damp, sensitivity, etc) are known, its transfer function can be obtained. Theoretically, low-frequency attenuation can be compensated by geophone deconvolution. Tolerances of geophone specifications and noises other than geophone mechanical vibration system output are two factors which affect the compensation. According to our simulation, for widely used geophones(20DX), these two factors have very little effect on geophone deconvolution with seismic survey background(multi-coverage, strong noise, poor coupling), and the deconvolution can be accomplished with nominal value of geophone specifications. Thus with this "geophone deconvolution", low-frequency components lost at geophones during the acquisition can be recovered as digital sensors acquire. Seismic data previously collected by geophones can be enhanced with low-frequency components with the proposed approach.
关键词
检波器反褶积 /
低频衰减 /
允差 /
模拟检波器 /
数字检波器 /
非机械振动系统输出噪声 /
机电比
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Key words
geophone deconvolution /
low-frequency attenuation /
tolerance /
analog geophone /
digital sensor /
noise other than geophone mechanical vibration system output /
mechanical vibration to ground noise ratio
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中图分类号：
P631
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