深层地震速度分析的不确定性研究
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摘要
在深层三维地震勘探中,速度的精度直接关系到地震数据的叠加及偏移的质量。本文针对深层地震资料反射能量弱、信噪比低、分辨率低、基底反射不清的特点,根据地震勘探的基本理论对深层地震速度分析的不确定性因素进行了探讨。认为在深层条件下必须将各向同性层状介质看成是垂直各向异性(VTI)介质,在大炮检距获得的时距曲线已经不是双曲线,而是高次曲线。因此在进行速度分析时不能使用常规速度分析方法,而必须使用新的速度分析方法。文中推荐VTI介质P波非双曲线速度分析及量板法两种方法,得到了较为实用、稳定的结果。
The precision of velocity is directly relative to the quality of stack and migration of seismic data in 3D deep seismic exploration. Faced with the characteristics of weak reflected energy, poor S/N ratio , lower resolution and smeared base reflections in deep seismic data,the paper discussed the uncertain factors in analysis of deep seismic velocity according to basic theory of seismic exploration. It is considered that it must consider the isotropic medium as VTI medium in a deep condition and the time-distance curves at larger offsets are no longer the hyperbolic curves but high-order curves contrarily. Therefore, the common-used velocity analysis method is no longer used and new velocity analysis method is needed when carrying out velocity analysis. The paper recommended two methods for velocity analysis in VTI medium:non-hyperbolic P-wave velocity analysis and template method,which achieved practical and stable effects.
The precision of velocity is directly relative to the quality of stack and migration of seismic data in 3D deep seismic exploration. Faced with the characteristics of weak reflected energy, poor S/N ratio , lower resolution and smeared base reflections in deep seismic data,the paper discussed the uncertain factors in analysis of deep seismic velocity according to basic theory of seismic exploration. It is considered that it must consider the isotropic medium as VTI medium in a deep condition and the time-distance curves at larger offsets are no longer the hyperbolic curves but high-order curves contrarily. Therefore, the common-used velocity analysis method is no longer used and new velocity analysis method is needed when carrying out velocity analysis. The paper recommended two methods for velocity analysis in VTI medium:non-hyperbolic P-wave velocity analysis and template method,which achieved practical and stable effects.
引文
[1] Taner M T et al. Velocity spectra-digital computer derivation and applications of velocity functions. Geophysics, 1969,34(6):859-881
[2] Hubral P and Krey T. Inteval velocities from seismic reflection time measurements. [USA] Tulsa:SEG, 1980,341-344
[3] Tsvankin et al. Nonhyperbolic reflection moveout in anisotropic media. Geophysics,1994,59(8):1290-1304
[4] Alkhalifah T et al. Velocity analysis for transversely isotropic media. Geophysics,1995,60(5):1550-1566
[5] Alkhalifah T. Velocity analysis using nonhyperbolic moveout in transversely isotropic media. Geophysics, 1997,62(6):1839-1854
[6]徐常练等.速度随炮检距变化(VVO)分析.石油地球 物理勘探,1998,33(6):733-741
[2] Hubral P and Krey T. Inteval velocities from seismic reflection time measurements. [USA] Tulsa:SEG, 1980,341-344
[3] Tsvankin et al. Nonhyperbolic reflection moveout in anisotropic media. Geophysics,1994,59(8):1290-1304
[4] Alkhalifah T et al. Velocity analysis for transversely isotropic media. Geophysics,1995,60(5):1550-1566
[5] Alkhalifah T. Velocity analysis using nonhyperbolic moveout in transversely isotropic media. Geophysics, 1997,62(6):1839-1854
[6]徐常练等.速度随炮检距变化(VVO)分析.石油地球 物理勘探,1998,33(6):733-741
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