摘要
为了选择最佳的石灰岩出露区地震资料的采集参数，我们在川东高院构造石灰岩出露区作了近源地震波频谱测试及资料采集试验。其方法是将地震加速度传感器分别置于井下和地表，测试来自不同激发条件（井深、药量及岩性）的近源地震波激发频谱，并与用地震检波器同时接收的地震信号进行对比，以验证其结果的精度。试验结果表明：①山区的低速带，不仅限于表土，而且岩石露头也存在约10m厚的低速带，②受这10m度低速带的影响，在井下和地表测试的激发频谱存在着显著的差异；③三种岩性对高频成分吸收的程度明显不同，其中央岩最严重，砂岩次之，泥岩最弱；④延迟组会爆炸对降低激发频谱、减轻地震波能量的衰减具有明显作用；⑤受低速带的影响，地震波旅行时间、振幅、频率及相位都要发生很大变化。最后指出，要想提高石灰岩出露区原始资料的信噪比，不仅应选择合理的激发参数，而且也要重视接收条件的改善，必要时应考虑将检波器置于井下接收。
In order to choose optimum seismic acquisition parameters for 1imestone cropping area,we conducted both data acquisition test and frequency spectrum determi-nation for near source seismic waves in the steep limestone structure cropping areain east Sichuan. Acceleration sensors were planted in borehole and on surface to de-termine the frequency spectra of near-source seismic waves which were generatedfrom different shot conditions (depth, charge and lithology). The frequency spectrawere compared with the seismic signals received by seismic geophones so as tocheck the results. The field test led to the conclusion: ① low velocity layer inmountainous region appears as both surface soil and weathered cropping (10 m orso); ② downhole frequency spectrum and surface frequency spectrum differ greatlydue to the influence of low velocity layer 10m thicki ③ limestone,sandstone andmudstone have very different absorptions to high frequency contents, their absorptions decreasing in the order；④ directional- delayed shots play obvious role in decreasing frequency spectrum and seismic wave attenuation；⑤ influenced by the lowvelocity layer, seismic wave varies greatly in their travel time, amplitude, frequency and phase. In order to improve S/N ratio of seismic data in limestone croppingarea, we must choose reasonable shot parameters, pay more attention to improvingthe receiving conditions, and use downhole receiving when it is necessary.
出处
《石油地球物理勘探》
EI
CSCD
北大核心
1994年第1期75-83,共9页
Oil Geophysical Prospecting
关键词
地震数据采集
地震波
频谱分析
seismic data acquisition, limestone, near-source seismic wave,frequency spectrum analysis, shot condition, receiving condition
