【摘要】 在一个地区开展地震勘探之前 ,勘探工作者首先要考虑的问题是 ,在勘探目的层处是否可以获得预期的地震成像分辨率 ?要弄清这一实际勘探问题有一定难度 ,因为有多种因素影响地震勘探成像分辨率 ,主要有大地吸收衰减 (包括近地表吸收和储层上覆地层吸收衰减 )和近地表干扰波(包括非规则干扰和规则干扰 )。前者引起反射波信息随传播时间逐步减弱 ;后者为不随时间吸收衰减变化 (或随时间吸收衰减变化较慢 )的干扰波。二者的变化关系制约着地震勘探的信噪比临界门限值。在该信噪比临界门限值上采集数据 ,通常可以获得较好的反射成像分辨率 ;反之 ,则难以获得。但在实际中如何确定信噪比临界门限值仍是需要研究的问题。基于多道统计分析 ,文中用时频域、频时域信噪比统计分析来确定时间域和频率域统计信噪比临界门限值 ,该信噪比临界门限值可以指示出数据信噪比小于 1时的时间和频率 ,为实际勘探采集、处理和解释提供了重要的分析依据。更多还原

【Abstract】 The question first needed to consider for exploration worker before conducting seismic exploration in a area are whether desired resolution in seismic imaging for exploration target can be obtained.Because major factors affected resolution in seismic imaging are various, mainly including attenuation by earth absorption(attenuation by absorption in near-surface and by absorption in overburden of reservoir) and near-surface interference (irregular and regular interference),it is difficult to clarify the practical exploration question.The former is reflection information which has gradually weakened with propagation time caused by attenuation by absorption;the latter is interference which is no change with time or which attenuation by absorption has slowly variation with time.The changing relation between the two restricts the threshold value of signal-to-noise ratio for seismic prospecting.A good resolution in reflection imaging can be usually obtained in acquisition data at the threshold of signal-to-noise ratio,otherwise, there is difficult to get it.But how to define the threshold of signal-to-noise ratio in practice there is a problem that still needs to study. Based on multi-trace statistical analysis,the paper defines critical threshold value of statistical signal-to-noise ratio in time-domain and in frequency domain,the threshold can indicate the time and the frequency when data signal-to-noise ratio is less than 1,providing a important analysis basis for acquisition,processing and interpretation in real prospecting.更多还原