微地震信号传播特性分析  

Analysis of propagation characteristics of micro-seismic signals

作　　者：苗永康[1] 

机构地区：[1]中国石油化工股份有限公司胜利油田分公司物探研究院,东营257022

出　　处：《地球物理学进展》2016年第3期1139-1144,共6页Progress in Geophysics

基　　金：国家高技术研究发展计划(863)(2011AA060300)资助

摘　　要：本文基于层状介质模型比较了地面激发深部接收信号与深部激发地表接收信号的差异,研究表明地震信号从高速层或者低速层入射时,当入射角不同时都会存在透射系数绝对值大于1的情况;法向入射时,上方入射和下方入射的透射波的振幅传递系数的绝对值不相等;相对于浅层炮点的情况,炮点位于深层时接收到的VSP记录信号更强记录更清晰;微地震事件井中和地表监测的信噪比依赖于许多因素,如几何扩散、衰减效应、噪声水平、信号频率、接收器数目、近地表放大效应以及阻抗对比效应等,本文只考虑井中检波器阵列与微地震震源之间距离的影响,随着距离的增大地面阵列的叠加信号信噪比相对于VSP记录会有明显的提高;阻抗差异和自由表面边界情况会导致入射P波的强度增强,这种效果能够补偿表面增加的噪声造成的影响,使得我们可以在地表通过相对较少的检波器监测微地震信号.This paper compares the differences between signals received on the ground with underground excitation and signals received underground with excitation on the surface based on layered medium model. Studies show that for seismic signals from high speed or low speed layer, the absolute value of transmission coefficient is greater than 1 in some cases when the incident angle is changing. When the signal is normal incident,the absolute value of the amplitude transmission coefficient of the transmitted wave incident from the above and the bottom are not equal. Contrast with record using source near the surface,the VSP record is more clearly when the shot point is located in the deep layer. The SNR of microseismic monitored both in the borehole and on the surface depends on many factors,such as the geometrical spreading,attenuation effect,noise level,signal frequency,the number of receivers,the near-surface contrast amplification and impedance effects. This article only considering the influence of the distance between borehole geophone array and source,with the increasing of this distance, the SNR of ground array signal will have obvious improvement relative to VSP records. The impedance differences and the free surface boundary situation will lead to the incident Pwave enhance,this effect can be used to compensate for the noise caused by the surface,making it possible for us at the surface monitoring micro-seismic signals using relatively less seismometer.

关 键 词：微地震 地面监测 井中监测 层状介质模型 信噪比 

分 类 号：P631[天文地球—地质矿产勘探]