可控震源高效采集噪声对弱信号的影响及应对方法

Influence of vibroseis high-efficiency acquisition on weak signals and corresponding countermeasures

可控震源高效采集技术通过多组震源不间断扫描提高地震数据采集作业效率,但同时带来了更多的谐波噪声及震源移动产生的机械噪声(以下统称为高效采集噪声)。高效采集噪声的强弱与震源组数、组间距离、激发时间间隔及生产组织方式等因素密切相关。如何在有限的设备投入和保持采集效率的情况下消除或者减弱高效采集噪声是高效采集作业需要解决的问题。从弱信号可记录性的角度确定震源组间距,可以在动态滑动扫描采集作业中通过对震源分组和摆放方式的优化,最大限度地减弱高效采集噪声的影响。通过提取原始资料中不同炮检距弱信号振幅计算相对于高效采集噪声的信噪比,然后以检波器动态范围为阈值,将信噪比大于阈值的炮检距范围作为最大组间距进行震源摆放和野外作业。实际资料应用结果表明,该方法可以大幅降低可控震源高效采集噪声的能量,在对动态滑动扫描地震采集野外作业的可控震源分组、组间距设置和摆放等方面具有定量指导作用。

The high-efficiency acquisition technology using vibroseis increases the efficiency of seismic data acquisition by continuously sweeping multiple groups of sources.However,it also captures more harmonic and mechanical noise generated by the source movement(hereinafter referred to as high-efficiency acquisition noise).The intensity of this noise is closely related to the number of sources,interval of excitation,and production organization.Finding suitable techniques to eliminate or reduce the this noise while ensuring a high acquisition efficiency is critical.In this study,a method was proposed to determine the distance between source fleets based on the recordability of weak signals,to organize the sources in the dynamic sweeping acquisition system and minimize the impact of the high-efficiency acquisition noise.In this method,the weak signal amplitudes associated with different offsets from the original data were extracted to calculate the signal-to-noise ratio(SNR).Afterwards,the dynamic range of the geophones was taken as the threshold value,and the offset range with SNR greater than the threshold value was taken as the maximum group distance requirement for source placement and field operation.Tests on field data showed that this method can considerably reduce the energy of the high-efficiency acquisition noise of vibroseis as well as guide the process of grouping,spacing,and placing vibroseis sources for dynamic sweeping seismic acquisition.