应用黏弹性波动方程模拟地震低频阴影
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摘要
以地震频谱分解为基础的低频阴影提取技术是一项有效的烃类检测方法,但是对于低频阴影的产生机理一直缺少明确的解释。本文通过建立含流体饱和介质的等效地质模型,采用黏弹性波动方程进行正演模拟,对得到的合成地震记录进行频谱分解,探讨低频阴影现象的产生机制。在低频(如15Hz)瞬时频谱剖面中,含油气储层下方表现为强能量团;当频率增加到55Hz以上时,含油气储层下方的能量则比低频瞬时剖面中对应位置的能量要弱得多,这就是典型的低频阴影现象。对低频阴影形成条件的分析结果表明,对于具有低Q值(QP小于90,QS小于70)且达到一定厚度(厚度大于半个地震波长)的储层,低频阴影现象明显,出现在储层下方最先存在波阻抗差异的地层界面处。
Based on the instantaneous spectral analysis(ISA)method,low-frequency shadows(LFSs)have been used as an effective hydrocarbon indicator.But the cause of these shadows is unclear.We try here to find out the cause with numerical simulation method. With equivalent fluid-saturated media models,we perform the forward modeling by visco-elastic wave equation based on the KelvinVoigt model.Then we obtain corresponding ISA sections of different seismograms using time frequency continuous wavelet transform(TFCWT).On low-frequency(e.g.15Hz)ISA sections,the spectral energy of the area under oil-bearing reservoirs is much stronger than that of the same area on high-frequency ISA sections(e.g.>55Hz).Our study reveals that LFS is more apparent if reservoir is thicker(>λ/2)and quality factors are lower(QP<90and QS<70).It is concluded that LFSs will appear around the first interface with impedance difference under reservoirs.
Based on the instantaneous spectral analysis(ISA)method,low-frequency shadows(LFSs)have been used as an effective hydrocarbon indicator.But the cause of these shadows is unclear.We try here to find out the cause with numerical simulation method. With equivalent fluid-saturated media models,we perform the forward modeling by visco-elastic wave equation based on the KelvinVoigt model.Then we obtain corresponding ISA sections of different seismograms using time frequency continuous wavelet transform(TFCWT).On low-frequency(e.g.15Hz)ISA sections,the spectral energy of the area under oil-bearing reservoirs is much stronger than that of the same area on high-frequency ISA sections(e.g.>55Hz).Our study reveals that LFS is more apparent if reservoir is thicker(>λ/2)and quality factors are lower(QP<90and QS<70).It is concluded that LFSs will appear around the first interface with impedance difference under reservoirs.
引文
[1]Taner M T,Koehler F,Sheriff R E.Complex seismic trace analysis.Geophysics,1979,44(6):1041-1063.
[2]Mitchell J T,Derzhi N,Lickman E.Low frequency shadows:The rule,or the exception.SEG Technical Program Expanded Abstracts,1997,16:685-686.
[3]Goloshubin G M,Korneev V A,Vingalov V M.Seismic low-frequency effects from oil-saturated reservoir zones.SEG Technical Program Expanded Abstracts,2002,21:1813-1816.
[4]Goloshubin G M,Korneev V A.Seismic low-frequency effects from fluid-saturated reservoir.SEG Technical Program Expanded Abstracts,2000,19:1671-1674.
[5]Korneev V A,Goloshubin G M,Daley T M et al.Seismic low-frequency effects in monitoring fluid-saturated reservoirs.Geophysics,2004,69(2):522-532.
[6]尹陈,贺振华,黄德济.基于二维黏滞性波动方程的地震波衰减理论研究.物探化探计算技术,2008,30(5):353-356.Yin Chen,He Zhenhua,Huang Deji.The research and the application of the seismic attenuation theory based on the wave equation.Computing Techniques for Geophysical and Geochemical Exploration,2008,30(5):353-356.
[7]尹陈,贺振华,黄德济.基于弥散—黏滞型波动方程的地震波衰减及延迟分析.地球物理学报,2009,52(1):187-192.Yin Chen,He Zhenhua,Huang Deji.The analysis of seismic attenuation and time delay based on the diffusivity-viscosity wave equation.Chinese Journal of Geophysics,2009,52(1):187-192.
[8]陈学华,贺振华,文晓涛等.低频阴影的数值模拟与检测.石油地球物理勘探,2009,44(3):298-303.Chen Xuehua,He Zhenhua,Wen Xiaotao et al.Numeric simulation and detection of low frequency shadow.OGP,2009,44(3):298-303.
[9]陈学华,贺振华,钟文丽.低频阴影与储层特征关系的数值模拟.中国矿业大学学报,2011,40(4):584-591.Chen Xuehua,He Zhenhua,Zhong Wenli.Numeric simulation in the relationship between low frequency shadow and reservoir characteristic.Journal of China University of Mining&Technology,2011,40(4):584-591.
[10]Castagna J P,Sun S,Siegfried R W.Instantaneous spectral analysis:Detection of low-frequency shadows associated with hydrocarbons.The Leading Edge,2003,22(2):120-127.
[11]Ebrom D.The low-frequency gas shadow on seismic sections.The Leading Edge,2004,23(8):772-772.
[12]Tai S,Puryear C,Castagna J P.Local frequency as a direct hydrocarbon indicator.SEG Technical Program Expanded Abstracts,2009,28:2160-2164.
[13]Goloshubin G M,Chabyshova E.A possible explanation of low frequency shadows beneath gas reservoirs.SEG Technical Program Expanded Abstracts,2012.
[14]Li Fangyu,Li Yandong,Lu Wenkai et al.Hydrocarbon detection for cavern carbonate reservoir using low-and-high-frequency anomalies in spectral decomposition.SEG Technical Program Expanded Abstracts,2012.
[15]奚先,姚姚.二维黏弹性随机介质中的波场特征分析.地球物理学进展,2004,19(3):608-615.Xi Xian,Yao Yao.The analysis of the wave field characteristics in 2-D viscoelastic random medium.Progress in Geophysics,2004,19(3):608-615.
[2]Mitchell J T,Derzhi N,Lickman E.Low frequency shadows:The rule,or the exception.SEG Technical Program Expanded Abstracts,1997,16:685-686.
[3]Goloshubin G M,Korneev V A,Vingalov V M.Seismic low-frequency effects from oil-saturated reservoir zones.SEG Technical Program Expanded Abstracts,2002,21:1813-1816.
[4]Goloshubin G M,Korneev V A.Seismic low-frequency effects from fluid-saturated reservoir.SEG Technical Program Expanded Abstracts,2000,19:1671-1674.
[5]Korneev V A,Goloshubin G M,Daley T M et al.Seismic low-frequency effects in monitoring fluid-saturated reservoirs.Geophysics,2004,69(2):522-532.
[6]尹陈,贺振华,黄德济.基于二维黏滞性波动方程的地震波衰减理论研究.物探化探计算技术,2008,30(5):353-356.Yin Chen,He Zhenhua,Huang Deji.The research and the application of the seismic attenuation theory based on the wave equation.Computing Techniques for Geophysical and Geochemical Exploration,2008,30(5):353-356.
[7]尹陈,贺振华,黄德济.基于弥散—黏滞型波动方程的地震波衰减及延迟分析.地球物理学报,2009,52(1):187-192.Yin Chen,He Zhenhua,Huang Deji.The analysis of seismic attenuation and time delay based on the diffusivity-viscosity wave equation.Chinese Journal of Geophysics,2009,52(1):187-192.
[8]陈学华,贺振华,文晓涛等.低频阴影的数值模拟与检测.石油地球物理勘探,2009,44(3):298-303.Chen Xuehua,He Zhenhua,Wen Xiaotao et al.Numeric simulation and detection of low frequency shadow.OGP,2009,44(3):298-303.
[9]陈学华,贺振华,钟文丽.低频阴影与储层特征关系的数值模拟.中国矿业大学学报,2011,40(4):584-591.Chen Xuehua,He Zhenhua,Zhong Wenli.Numeric simulation in the relationship between low frequency shadow and reservoir characteristic.Journal of China University of Mining&Technology,2011,40(4):584-591.
[10]Castagna J P,Sun S,Siegfried R W.Instantaneous spectral analysis:Detection of low-frequency shadows associated with hydrocarbons.The Leading Edge,2003,22(2):120-127.
[11]Ebrom D.The low-frequency gas shadow on seismic sections.The Leading Edge,2004,23(8):772-772.
[12]Tai S,Puryear C,Castagna J P.Local frequency as a direct hydrocarbon indicator.SEG Technical Program Expanded Abstracts,2009,28:2160-2164.
[13]Goloshubin G M,Chabyshova E.A possible explanation of low frequency shadows beneath gas reservoirs.SEG Technical Program Expanded Abstracts,2012.
[14]Li Fangyu,Li Yandong,Lu Wenkai et al.Hydrocarbon detection for cavern carbonate reservoir using low-and-high-frequency anomalies in spectral decomposition.SEG Technical Program Expanded Abstracts,2012.
[15]奚先,姚姚.二维黏弹性随机介质中的波场特征分析.地球物理学进展,2004,19(3):608-615.Xi Xian,Yao Yao.The analysis of the wave field characteristics in 2-D viscoelastic random medium.Progress in Geophysics,2004,19(3):608-615.
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