井间地震反射波成像频率变化特征研究

Study on characteristics of imaging frequency variation in cross-hole seismic reflection.

与常规地面地震剖面相比 ,井间地震剖面具有一定的特殊性 ,其中剖面浅部低频化是其基本特征之一。本文利用成像原理对井间地震反射剖面的浅部频率变低问题进行了研究 ,导出了频率变化因子。研究结果表明 ,观测井段浅部出现低频化现象 ,主要是由于成像过程的“拉伸”作用所致 ,其规律是由深向浅、由两井中间向两旁频率逐渐变低 ,低频化现象并不反映该部位地层反射的真实频率特征。因此 ,在资料反演和解释过程中必须引起重视 ,否则会导致错误的解释结果。

Cross-hole seismic sections have some speciality in comparison with ordinary surface seismic sections,among which the low frequency in shallow parts of section is one of its basic characters.The paper studied the issue of low frequency in shallow parts of cross-hole seismic reflection sections using imaging principle and deduced frequency variation factor.The studied results showed that the phenomenon of low frequency in shallow parts of observed well mainly resulted from 'stretching' in imaging processing.The rule of variation is that the frequency gradually changed toward the low frequency direction from deep parts to shallow parts and from middle parts of two wells to both sides of two wells.These low-frequency components don't reflect the true frequency character of reflection in that parts of layers,to which it must pay more attention in a process of data inversion and interpretation,otherwise,it can lead to mistaken interpretation results.