摘要
分布式声传感(DAS)基于光纤中瑞利散射效应获取地震波振动信号,光纤在探测地震波的同时实现信号的传输,适用于井中地震信号采集,具有成本低、分辨率高、抗电磁干扰强等优点。基于离散光纤瑞利散射干涉模型,在不考虑背景压力、温度和井壁光纤耦合的条件下,采用数值模拟方法模拟了井中DAS系统地震信号特征,详细探讨了震源强度、脉冲宽度以及光纤空间采样间隔对DAS光纤信号波形特征以及信噪比的影响。模拟结果表明:①不同震源强度对DAS光纤信号的影响不同,而且震源强度过大可能导致DAS光纤信号波形畸变或旁瓣增多而影响信号保真度。②较小的脉冲宽度常伴有较强的噪声,较大的脉冲宽度在一定程度上可以压制高频噪声、提高信噪比,但不可避免地降低分辨率。③通过相邻道叠加增大的光纤空间采样间隔有利于提高信噪比,因此选择合适的光纤空间采样间隔可以有效地提高信噪比、提升信号质量;DAS信号频率通常略高于原始地震信号频率,同时附带系统本身的高频噪声。
Owing to the Rayleigh scattering effect,distributed acoustic sensing(DAS)could detect seismic vibrations in optical fibers,which meanwhile also function as the carrier for signal transmission.Thus,this system is suitable for borehole seismic acquisition with low cost,high resolution,and high performance of anti-electromagnetic interference.Based on the discrete Rayleigh scattering interference model,we use numerical simulation to model borehole seismic signals in the DAS system;we also discuss the impacts of source strength,pulse width,and spatial fiber sampling interval on the waveform and signal to noise ratio of DAS signals.In this process,we do not consider the influence of ambient pressure,temperature,and borehole wallfiber coupling.The results show that(1)DAS signals vary with source strength.A strong source may cause waveform distortion or increased side lobes;this may lead to signal distortion;(2)small pulse width is usually associated with strong noises.In contrast,large pulse width may facilitate high-frequency noise suppression and improve signal to noise ratio;but the resolution will be inevitably sacrificed to some extent;(3)increased fiber sampling interval by multi-trace stacking may be useful to the improvement of signal to noise ratio.Thus,we may choose a proper sampling interval to improve signal to noise ratio and signal quality.DAS signals usually exhibit slightly higher frequencies than the original seismic signals;there are also inherent high-frequency noises.
作者
马国旗
曹丹平
尹教建
朱兆林
MA Guoqi;CAO Danping;YIN Jiaojian;ZHU Zhaolin(School of Geosciences,China University of Petroleum(East China),Qingdao,Shandong 266580,China;Functional Laboratory for Marine Mineral Resources Assessment and Prospecting,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266071,China;College of Science,China University of Petroleum(East China),Qingdao,Shandong 266580,China)
出处
《石油地球物理勘探》
EI
CSCD
北大核心
2020年第2期311-320,I0003,I0004,共12页
Oil Geophysical Prospecting
关键词
分布式声传感
瑞利散射
震源强度
脉冲宽度
光纤空间采样间隔
数值模拟
distributed acoustic sensing
Rayleigh scattering
source strength
pulse width
spatial fiber sampling interval
numerical simulation
