井中近源三分量波场调查试验与数据分析

Test and analysis on borehole near-source three-component wavefield survey

(1中国石油化工集团公司胜利石油管理局地球物理勘探开发公司，山东东营257100;2CNPC东方地球物理公司，河北涿州072751;3中国石油大学（华东），山东青岛266555)

Geophysical Exploration and Development Company,Shengli Petroleum Administration，SINOPEC,Dongying 257100,China

近地表介质具有低速度、高吸收等特性，对地震波场会产生较大的影响，三分量检波器有利于记录全波场信息。选择在灰岩区，利用三分量检波器进行了近源地震数据采集，开展了近地表介质对波场影响的研究。基于三分量资料进行了纵波波场合成，通过对比分析合成纵波记录的频谱特征和能量特征，结合吸收系数特征，得出灰岩区吸收强烈、近地表滤波作用明显的结论。基于合成纵波记录拾取了初至信息，对地表速度的分布特征进行了分析。

Near surface medium has significant effect on wave field because of its characteristics such as low velocity and strong absorption.Three-component geophone is beneficial for recording the information of full wavefield.Therefore,three-component geophone is adopted for near-source seismic data acquisition at limestone area.Meanwhile,the impact of near surface medium on wavefield is studied.P-wave wavefield is synthesized based on three-component data.By comparing and analyzing the spectrum characteristics and energy characteristics of synthetic P-wave record,combing with absorption coefficient characteristics,the conclusion can be obtained that the absorption is strong and near surface filtering is obvious at limestone area.The first break is picked up from synthetic P-wave record,and the distribution of surface velocity is analyzed.