子波延迟对逆时偏移成像精度的影响
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摘要
共炮集数据叠前逆时偏移成像需要在深度方向对震源波场和接收波场分别进行正向和反向延拓,对于成像值的提取,传统的做法是两种波场延拓到所有时间相同时刻都要进行互相关,不同时刻互相关值叠加在一起就是所提取的成像值。通常假设下行波是脉冲波或最小相位子波时,都能得到准确的成像,但是对于实际地震资料,同相轴的拾取一般都追踪子波波峰,它相对于初始时间有一个短延续长度,因此采用互相关成像条件的叠前逆时偏移,其成像位置有一定误差。为此,利用有限元法波动方程叠前逆时偏移程序模拟地震记录并进行逆时偏移,讨论震源波场及接收波场中子波延迟对成像精度的影响。数值模拟试验表明,子波对成像位置误差与2种波场中子波相对延迟时间长短和反射点周围速度大小及子波延续长度有关。
Aiming at the imaging problems of common shot data with prestack reverse time migration method,the source wave-field forward continuation and the receiver wave-field backward continuation in depth direction were needed at the same time.In order to obtain imaging value,the conventional method was that the two wave-fields were used to implement cross correlation at the same time and stack the different cross correlation values at all the same time.It was assumed that the seismic wavelet was impulse or minimum phase,the stacked value of cross correlation was the accurate imaging of the real reflection point,but for the real seismic data,the event picked up was generally the peak of seismic wavelet,which had a short delay related to the wavelet initial time,therefore it resulted in imaging position error in cross correlation method.Theoretical seismic data are simulated and migrated by wave equation finite element prestack reverse time migration program with cross correlation imaging conditions.The influence of wavelet delay both in source wave-field and wave-field of receiver on the imaging accuracy is discussed.Numerical experiment demonstrates that the influence of wavelet delay on the position error is decided by the wavelet relative delay length in the two wave-fields and the seismic velocity around the reflection point and the length of wavelet delay,which provides theoretical reference for selecting seismic wavelet for cross correlation imaging conditions in prestack reverse time migration.
引文
[1]Parkes G E,Hatton L.Towards a systematic understanding of the effects of velocity model errors on depth and time migration of seis-mic data[A].1984SEG Annual Meeting[C].Atlanta,1984-12-2~6.
    [2]Zhu Jinming,Lines L,Gray S.Smiles and frowns in migration velocity analysis[J].Geophysics,1998,63(4):1200~1209.
    [3]Liu Zhenyue,Bleistein N.Migration velocity analysis:Theory and an iterative algorithm[J].Geophysics,1995,60(1):142.
    [4]Claerbout J F.Toward a unified theory of reflection mapping[J].Geophysics,1971,36(3):467~481.
    [5]Claerbout J F.Imaging the Earth's Interior[M].Oxford:Blackwell Scientific Publications,1985.
    [6]薛东川,王尚旭.起伏地表复杂介质波动方程有限元数值模拟方法[J].地球物理学进展,2007,22(2):522~529.
    [7]薛东川,王尚旭.波动方程有限元叠前逆时偏移[J].石油地球物理勘探,2008,43(1):17~21.
    [8]Jrg S,JesséC C,Amélia N.A comparison of imaging conditions for wave-equation shot-profile migration[J].Geophysics,2008,73(6):219~227.
    [9]Chattopadhyay S,McMechan G A.Imaging conditions for prestack reverse-time migration[J].Geophysics,2008,73(3):81~89.

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