非规则干扰信噪比分析
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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。
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.
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.
引文
1 李庆忠.走向精确勘探的道路,石油工业出版社,1993
2 俞寿朋.高分辨率地震勘探,石油工业出版社,1993
3 凌云,郭向宇.非地表一致性干扰压制方法.石油地球物理勘探,1992,27(1):13～28
4 凌云.大地吸收衰减分析.石油地球物理勘探,2001,36(1):1～8
5 凌云,张汝杰,高军,吴伟康.方形排列干扰波调查方法研究.石油地球物理勘探,2000,35(2):175～184
6 凌云,周熙襄.自适应可控震源地表一致性反褶积.石油地球物理勘探,1994,29(3):306～315,356
7 凌云,俞寿朋,周熙襄.零相位同态反褶积.石油地球物理勘探,1995,30(3):299～309
8 凌云,吴伟康.三维叠后零相位同态反褶积.石油地球物理勘探,1995,30(6):749～756
9 凌云,俞寿朋,周熙襄.瞬时吸收率检测与高频噪声剔除.石油地球物理勘探,1995,30(6):775～787,796
10 高军,凌云,周兴元,牟永光.时频域球面发散与吸收补偿.石油地球物理勘探,1996,31(6):856～866,905
11 凌云,高军,张汝杰.基于一维弹性阻尼波动理论的沙丘吸收补偿.石油地球物理勘探,1997,32(6):795～803,841
12 凌云,高军,张汝杰.地表一致性预测变步长反褶积与沙丘鸣震的压制.石油地球物理勘探,1998,33(1):23～31
2 俞寿朋.高分辨率地震勘探,石油工业出版社,1993
3 凌云,郭向宇.非地表一致性干扰压制方法.石油地球物理勘探,1992,27(1):13～28
4 凌云.大地吸收衰减分析.石油地球物理勘探,2001,36(1):1～8
5 凌云,张汝杰,高军,吴伟康.方形排列干扰波调查方法研究.石油地球物理勘探,2000,35(2):175～184
6 凌云,周熙襄.自适应可控震源地表一致性反褶积.石油地球物理勘探,1994,29(3):306～315,356
7 凌云,俞寿朋,周熙襄.零相位同态反褶积.石油地球物理勘探,1995,30(3):299～309
8 凌云,吴伟康.三维叠后零相位同态反褶积.石油地球物理勘探,1995,30(6):749～756
9 凌云,俞寿朋,周熙襄.瞬时吸收率检测与高频噪声剔除.石油地球物理勘探,1995,30(6):775～787,796
10 高军,凌云,周兴元,牟永光.时频域球面发散与吸收补偿.石油地球物理勘探,1996,31(6):856～866,905
11 凌云,高军,张汝杰.基于一维弹性阻尼波动理论的沙丘吸收补偿.石油地球物理勘探,1997,32(6):795～803,841
12 凌云,高军,张汝杰.地表一致性预测变步长反褶积与沙丘鸣震的压制.石油地球物理勘探,1998,33(1):23～31
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