红海玄武岩覆盖区拖缆地震采集技术
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摘要
本文从玄武岩体的地质、地球物理特征分析出发,研究了拓展并加强有效波低频分量的拖缆地震采集技术,有效地改善了玄武岩下伏地层的成像品质。通过对红海地区玄武岩覆盖区的拖缆地震资料采集试验,得到如下认识:①提升气枪的容量和增加气枪的数量可提高气枪的激发强度,加强了玄武岩下伏地层的地震波反射能量,并有效地改善了地震资料的信噪比;②适当加大拖缆和气枪的沉放深度,可使低频端的虚反射响应曲线变陡,截频点向低频方向移动,更多的低频分量被释放,丰富了低频分量,同时也使得海上拖缆作业的两种主要干扰——膨胀波噪声和波浪噪声得到削弱,从而提高了低频端的信噪比。
Starting from analyzing the geologic and geophysical characters of basalt body,the paper studied the technology of streamer seismic data acquisition for broadening and strengthening low-frequency components of useful waves,which effectively improved the imaging quality of basalt-overlaid strata.The following knowledge resulted from the test of seismic data acquisition by streamer in basalt-overlaid area,Red Sea:①increasing volume and number of airgun can improve the shooting strength of airgun,strengthen the energy of seismic reflections in basalt-overlaid strata and effectively improve the S/N ratio of seismic data;②increasing sink depth of airgun and streamer adequately can make ghost response curve at the lowfrequency end become steep and cutoff frequency move toward low-frequency direction,which releases more low-frequency components,richens lowfrequency components and makes two kinds of major interference-dilatational wave noise and sea noise-be weakened at the same time,improving S/N ratio of data at the low-frequency end as a result.
Starting from analyzing the geologic and geophysical characters of basalt body,the paper studied the technology of streamer seismic data acquisition for broadening and strengthening low-frequency components of useful waves,which effectively improved the imaging quality of basalt-overlaid strata.The following knowledge resulted from the test of seismic data acquisition by streamer in basalt-overlaid area,Red Sea:①increasing volume and number of airgun can improve the shooting strength of airgun,strengthen the energy of seismic reflections in basalt-overlaid strata and effectively improve the S/N ratio of seismic data;②increasing sink depth of airgun and streamer adequately can make ghost response curve at the lowfrequency end become steep and cutoff frequency move toward low-frequency direction,which releases more low-frequency components,richens lowfrequency components and makes two kinds of major interference-dilatational wave noise and sea noise-be weakened at the same time,improving S/N ratio of data at the low-frequency end as a result.
引文
[1]Fliedner M M et al.Seismic velocity structure of basalt flows.SEG SP4.5,1998,1178～1181
[2]余德平等．应用低频信号提高高速玄武岩下的成像质量．应用地球物理(英文版)，2006，(2)
[3]Richardson K R et al.Crustal structure east of the Faroe Islands:mapping sub-basalt sediments using wide-angle seismic data.Petroleum Geoscience,1999,5:161～172
[4]Van Mastrigt et al.Improvements in 3-D marine acquisi- tion using continuous long offset(CLO).The Leading Edge,2002,21(4):394～395
[5]Hanssen Petal.Converted waves for sub-basalt imaging? Expanded Abstracts of 70th SEG Mtg,2000,1174～1177
[6]William H D.Air-gun array specs:A tutorial.Geophys- ics,The Leading Edge of Exploration,1990,24～33
[2]余德平等．应用低频信号提高高速玄武岩下的成像质量．应用地球物理(英文版)，2006，(2)
[3]Richardson K R et al.Crustal structure east of the Faroe Islands:mapping sub-basalt sediments using wide-angle seismic data.Petroleum Geoscience,1999,5:161～172
[4]Van Mastrigt et al.Improvements in 3-D marine acquisi- tion using continuous long offset(CLO).The Leading Edge,2002,21(4):394～395
[5]Hanssen Petal.Converted waves for sub-basalt imaging? Expanded Abstracts of 70th SEG Mtg,2000,1174～1177
[6]William H D.Air-gun array specs:A tutorial.Geophys- ics,The Leading Edge of Exploration,1990,24～33
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