利用叠前地震资料提取地层相对吸收系数
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摘要
本文在衰减介质地震波正演模拟的基础上,依据Gu等推导的峰值频率两侧对称频率处的振幅值与地层吸收参数之间的关系,利用S变换计算表征地层吸收属性的相对吸收系数;根据吸收系数与品质因子Q值之间的关系,建立相对吸收系数与炮检距之间的关系式;采用多道拟合的方法消除炮检距影响,得到了更为可靠的零炮检距地层相对吸收系数表达式;通过建立理论模型,利用衰减介质单程波动方程非零炮检距数值模拟方法得到叠前CMP道集,并由此提取地层相对吸收系数。文中利用小、中、大角度角道集地震资料提取的地层相对吸收系数进行拟合,得到叠前地震资料相对吸收系数剖面,消除了叠后地震资料相对吸收系数剖面中上覆盖层和含水层处出现的相对吸收系数高值,与单角度域地层相对吸收系数剖面相比,进一步压制了上覆盖层的强反射引起的虚假强衰减,得到了更可靠的油气指示信息,提高了储层预测的精度。理论数据和实际资料均验证了文中方法的可行性。
Based on seismic forward-modeling of attenuation medium,we estimate the relative absorption coefficient,one of the absorption parameters,by S transform,according to the relationship between the amplitude in the frequencies which is symmetric about the peak frequency.In the light of the relationship between the absorption coefficient and quality factor Q,we derive what the relative absorption coefficient have to do with offset.And then,a more reliable relative absorption coefficient is calculated,which is independent of offset through multi-channel fitting method.Finally,a model is established to estimate the relative absorption coefficient from the synthesis CMP gathers in attenuation medium based on non-zero offset one-way wave equation.We also apply this method to pre-stack seismic data in angle domain.Relative absorption coefficient is estimated from near,middle and far angle gathers and fitted.In this way,the high relative absorption coefficient indicating cap rock and reservoir filled with water on post-stack seismic data are eliminated on pre-stack seismic data.Compared with that coming from single angle seismic data,relative absorption coefficient obtained from pre-stack seismic data in angle domain can suppress the illusive high relative absorption coefficient caused by strong reflection of cap rock.As a result,more reliable oil and gas indication,and a more accurate reservoir prediction are achieved.Both synthesis data and real data examples show the effectiveness of the method.
Based on seismic forward-modeling of attenuation medium,we estimate the relative absorption coefficient,one of the absorption parameters,by S transform,according to the relationship between the amplitude in the frequencies which is symmetric about the peak frequency.In the light of the relationship between the absorption coefficient and quality factor Q,we derive what the relative absorption coefficient have to do with offset.And then,a more reliable relative absorption coefficient is calculated,which is independent of offset through multi-channel fitting method.Finally,a model is established to estimate the relative absorption coefficient from the synthesis CMP gathers in attenuation medium based on non-zero offset one-way wave equation.We also apply this method to pre-stack seismic data in angle domain.Relative absorption coefficient is estimated from near,middle and far angle gathers and fitted.In this way,the high relative absorption coefficient indicating cap rock and reservoir filled with water on post-stack seismic data are eliminated on pre-stack seismic data.Compared with that coming from single angle seismic data,relative absorption coefficient obtained from pre-stack seismic data in angle domain can suppress the illusive high relative absorption coefficient caused by strong reflection of cap rock.As a result,more reliable oil and gas indication,and a more accurate reservoir prediction are achieved.Both synthesis data and real data examples show the effectiveness of the method.
引文
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[3]高静怀,杨森林.利用零偏移VSP资料估计介质品质因子方法研究.地球物理学报,2007,50(4):1198～1209Gao Jinghuai,Yang Senlin.On the method of qualityfactor estimation from zero-offset VSP data.ChineseJournal of Geophysics,2007,50(4):1198～1209
[4]刘喜武,年静波,刘洪.基于广义S变换的地震波能量衰减分析.勘探地球物理进展,2006,29(1):20～24Liu Xiwu.Nian Jingbo,Liu Hong.Generalized S-transform based seismic attenuation analysis.Pro-gress in Exploration Geophysics,2006,29(1):20～24
[5]徐峰,冯诗齐.基于时频分析的地层吸收系数计算方法.海洋石油,2007,27(4):1～8Xu Feng,Feng Shiqi.A method for calculating layerabsorption coefficient based on time-frequency analy-sis.Offshore Oil,2007,27(4):1～8
[6]Zhang Changjun and Tadeusz J Ulrych.Estimation ofquality factors from CMP records.Geophysics,2002,67(5):1542～1547
[7]Zhang Changjun.Seismic Absorption Estimation andCompensation[D].The University of British Colum-bia,2008
[8]Gu Hanming,Robert R Stewart.Calculation of rela-tive seismic attenuation from the reflection time-fre-quency differences in a carbonate reservoir.CREWES Research Report,2006
[9]Stockwell R G,Mansinha L and Lowe R P.Localiza-tion of the complex spectrum:The S transform.IEEE Transactions on Signal Processing,1996,44(4):998～1001
[10]何兵红,吴国忱等.黏弹性介质单程波法非零炮检距地震数值模拟与偏移.地球物理学进展,2009,24(4):1299～1312He Binghong,Wu Guochen et al.Viscoelastic medi-um numerical simulation and migration of non-zerooffset seismic wave by one-way wave equation.Pro-gress in Geophysics,2009,24(4):1299～1312
[11]白晓寅.基于地震波衰减理论的地层吸收系数提取方法研究[硕士学位论文].山东东营:中国石油大学(华东),2008
[2]李宏兵,赵文智,曹宏等.小波尺度域含气储层地震波衰减特征.地球物理学报,2004,47(5):892～898Li Hongbing,Zhao Wenzhi,Cao Hong et al.Charac-teristics of seismic attenuation of gas reservoirs inwavelet domain.Chinese Journal of Geophysics,2004,47(5):892～898
[3]高静怀,杨森林.利用零偏移VSP资料估计介质品质因子方法研究.地球物理学报,2007,50(4):1198～1209Gao Jinghuai,Yang Senlin.On the method of qualityfactor estimation from zero-offset VSP data.ChineseJournal of Geophysics,2007,50(4):1198～1209
[4]刘喜武,年静波,刘洪.基于广义S变换的地震波能量衰减分析.勘探地球物理进展,2006,29(1):20～24Liu Xiwu.Nian Jingbo,Liu Hong.Generalized S-transform based seismic attenuation analysis.Pro-gress in Exploration Geophysics,2006,29(1):20～24
[5]徐峰,冯诗齐.基于时频分析的地层吸收系数计算方法.海洋石油,2007,27(4):1～8Xu Feng,Feng Shiqi.A method for calculating layerabsorption coefficient based on time-frequency analy-sis.Offshore Oil,2007,27(4):1～8
[6]Zhang Changjun and Tadeusz J Ulrych.Estimation ofquality factors from CMP records.Geophysics,2002,67(5):1542～1547
[7]Zhang Changjun.Seismic Absorption Estimation andCompensation[D].The University of British Colum-bia,2008
[8]Gu Hanming,Robert R Stewart.Calculation of rela-tive seismic attenuation from the reflection time-fre-quency differences in a carbonate reservoir.CREWES Research Report,2006
[9]Stockwell R G,Mansinha L and Lowe R P.Localiza-tion of the complex spectrum:The S transform.IEEE Transactions on Signal Processing,1996,44(4):998～1001
[10]何兵红,吴国忱等.黏弹性介质单程波法非零炮检距地震数值模拟与偏移.地球物理学进展,2009,24(4):1299～1312He Binghong,Wu Guochen et al.Viscoelastic medi-um numerical simulation and migration of non-zerooffset seismic wave by one-way wave equation.Pro-gress in Geophysics,2009,24(4):1299～1312
[11]白晓寅.基于地震波衰减理论的地层吸收系数提取方法研究[硕士学位论文].山东东营:中国石油大学(华东),2008
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