沿射线路径的波动方程延拓吸收与衰减补偿方法
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摘要
地层的吸收与衰减效应使地震波的振幅被衰减,相位被改变。在地震资料处理流程中,反褶积处理假设地震信号是平稳的,即地震子波的波形不随时间变化(或变化较小),这时用地震道自相关函数代替子波自相关函数才比较可靠;而地震成像也要求炮集与炮集之间、道与道之间的地震波能量一致,否则成像结果不保幅,因此必须对地震波进行吸收与衰减补偿。但是,对地震波吸收与衰减的补偿通常是针对自激自收单道记录的。事实上,地层对地震波的吸收与衰减是沿着波的传播路径发生的,因此,补偿应该与叠前深度偏移成像一样在反向波传播过程中进行。为此,提出了一种沿射线路径波动方程延拓的吸收与衰减补偿(Q值)方法。其基本原理是:用非递归波场延拓代替递归波场延拓,用等效Q值代替分层Q值,用平面波传播思想实现对叠前数据沿波传播路径的吸收与衰减(Q值)补偿。这种方法适合于局部水平层状介质假设的情况。数值试验表明该方法是有效的,补偿后子波波形的一致性得到了改善,衰减的振幅得到了恢复。
Seismic wave dispersion and dissipation distort the shape of the wavelet and attenuate the energy of seismic reflections.In seismic data processing,the de-convolution is based on the assumption that the signal is stationary the waveform does not change with time. Only when this condition is satisfied,will the substitution of the record's self-correlation for the wavelet's self-correlation be relia- ble.Imaging also requires the consistency of energy among shot gathers and among traces,and if not,the imaging amplitude can- not be well preserved.So,it is necessary to compensate the energy of absorptions and attenuations.However,the commonly used compensation methods only aim at the traces in zero-offset profile. Actually,it is along the ray path that the strata absorbs and atten- uates the seismic energy.Therefore,a compensation method was proposed using wave eguation continuation along the ray path of seismic wave propagation.The basic principles are that 1)the re- cursion wave field continuation is substituted by non-recursive wave field continuation,2)the layering Q is substituted by equivalent Q,and 3) the plane wave propagation theory is used to realize the compensation of absorption and attenuation from pre-stack data a- long ray path.The method is suitable for the assumption of partial horizontal layer medium.Numerical test indicate that the method is effective and the conformity of wavelet shape is improved after compensation,and the attenuation amplitude recovered.
Seismic wave dispersion and dissipation distort the shape of the wavelet and attenuate the energy of seismic reflections.In seismic data processing,the de-convolution is based on the assumption that the signal is stationary the waveform does not change with time. Only when this condition is satisfied,will the substitution of the record's self-correlation for the wavelet's self-correlation be relia- ble.Imaging also requires the consistency of energy among shot gathers and among traces,and if not,the imaging amplitude can- not be well preserved.So,it is necessary to compensate the energy of absorptions and attenuations.However,the commonly used compensation methods only aim at the traces in zero-offset profile. Actually,it is along the ray path that the strata absorbs and atten- uates the seismic energy.Therefore,a compensation method was proposed using wave eguation continuation along the ray path of seismic wave propagation.The basic principles are that 1)the re- cursion wave field continuation is substituted by non-recursive wave field continuation,2)the layering Q is substituted by equivalent Q,and 3) the plane wave propagation theory is used to realize the compensation of absorption and attenuation from pre-stack data a- long ray path.The method is suitable for the assumption of partial horizontal layer medium.Numerical test indicate that the method is effective and the conformity of wavelet shape is improved after compensation,and the attenuation amplitude recovered.
引文
1张关泉．声波的上行波方程和下行波方程及其应用[A]．见：地球物理学学报编辑委员会．八十年代中国地球物理学进展——纪念付承义教授八十寿辰[C]．北京：学术出版社，1988．410～419
2 Ursin B,Toverud T.Comparison of seismic disper- sion and attenuation models[EB/OL].CWP408.http:// www.cwp.mines.edu/meetings/project02/cwp408.pdf
3 Kjartansson E.Constant Q-wave propagation and at- tenuation[J].Joural of Geophysics Research,1979,84 (B9):4737～4748
4 Bickel S H,Natarajan R R.Plane-wave Q deconvolu- tion[J].Geophysics,1985,50(9):1426～1439
5 Hargreaves N D.Calvert A J.Inverse Q filtering by Fou- rier transform[J].Geophysics,1991,56(4):519～527
6 McCarley I A.An antoregressive filter model for con- stant Q attenuation [J].Geophysics,1985,50(5): 749～758
7 Wang Y H.A stable and efficient approach of inverse Q filtering[J].Geophysics,2002,67(2):657～663
8 Wang Y H.Inverse Q-filter for seismic resolution en- hancement[J].Geophysics,2006,71(3):V51～V60
2 Ursin B,Toverud T.Comparison of seismic disper- sion and attenuation models[EB/OL].CWP408.http:// www.cwp.mines.edu/meetings/project02/cwp408.pdf
3 Kjartansson E.Constant Q-wave propagation and at- tenuation[J].Joural of Geophysics Research,1979,84 (B9):4737～4748
4 Bickel S H,Natarajan R R.Plane-wave Q deconvolu- tion[J].Geophysics,1985,50(9):1426～1439
5 Hargreaves N D.Calvert A J.Inverse Q filtering by Fou- rier transform[J].Geophysics,1991,56(4):519～527
6 McCarley I A.An antoregressive filter model for con- stant Q attenuation [J].Geophysics,1985,50(5): 749～758
7 Wang Y H.A stable and efficient approach of inverse Q filtering[J].Geophysics,2002,67(2):657～663
8 Wang Y H.Inverse Q-filter for seismic resolution en- hancement[J].Geophysics,2006,71(3):V51～V60
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