灰岩裸露区地震波接收影响因素分析  

Analysis of Factors Affecting Seismic Wave Reception in Limestone Bare Area

作　　者：常鉴[1] CHANG Jian(SINOPEC Geophysical Research Institute,Nanjing 211103,China)

机构地区：[1]中国石油化工股份有限公司石油物探技术研究院,南京211103

出　　处：《科学技术与工程》2020年第5期1740-1746,共7页Science Technology and Engineering

基　　金：国家重点研发计划(2016YFC060110602)。

摘　　要：在复杂山地、山前带地震采集中,相同激发条件下的灰岩裸露地表接收的地震记录信噪比明显低于覆盖有低降速层的砂泥岩区,其原因一直是许多地震勘探工作者关心的问题。利用物理学振动原理、弹性力学理论及数值模拟方法,对弹性波在不同阻抗介质中质点运动的速度、加速度振幅分析表明,使用接收质点运动信息的检波器接收地震波时,灰岩介质的高阻抗导致质点运动振幅小,表现出接收到的地震波能量弱;同时,物理正演模拟和野外试验资料分析表明,灰岩裸露区近地表的非均质性导致了该类地区散射、耦合噪声等更加发育。由于原始地震数据的信噪比是由反射信号的强度与噪声水平的相对关系决定,所以灰岩裸露区地震接收资料质量差的原因是灰岩介质的高阻抗导致接收的地震信号弱,并且灰岩裸露地表特有的表层结构导致噪声强,两种因素的综合作用降低了该类地区地震资料信噪比。改善灰岩裸露区地震数据质量应采取的措施是合理使用压噪技术并避免因检波器与地表耦合不佳而导致的噪声的出现。In seismic acquisition of complex mountain areas and piedmont zone,the signal noise ratio(SNR)of seismic records received on the limestone exposed areas is significantly lower than that of the sand-shale area covered with the low-velocity layers,under the same excitation conditions.Finding the cause of the problem is important for seismic exploration,therefore the problem in two perspectives were analyzed.The principles of physics vibration,elastic mechanics theory,and numerical simulation method were used to analyze the velocity and acceleration amplitude of elastic waves in different impedance media.Results show that the high impedance of limestone medium causes the amplitude of particle motion to be small and the received seismic wave energy is weak.Forward modeling and field data analysis show that the heterogeneity of near-surface structure of limestone exposed areas causes strong scattering and coupling noise in such areas.So the weak seismic waves and strong noise lead to the low SNR of seismic records received on the limestone exposed areas.To improve the quality of seismic data in limestone exposed area,effective noise suppression technology should be used,and the noise caused by poor coupling between geophones and surface should be avoided.

关 键 词：灰岩裸露 介质阻抗 质点运动 近地表结构 非均质性 噪声 

分 类 号：P631.413[天文地球—地质矿产勘探]