零偏VSP反演Q值CFS方法及影响因素研究
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摘要
当地震波在地层中传播时,能量的衰减是传播介质非弹性性质的反映.这种介质所固有的衰减特性通常用品质因子(Quality Factor,Q)来描述.本文基于地震波在传播过程中主频降低的衰减特性,利用质心频率偏移法(Centrold Frequency Shift,简称CFS)对零偏VSP正演模型进行Q值计算,分析薄层、上下行波场、频带宽度、反演波速、震源位置等因素的影响.模型结果显示:CFS法比频谱比法、振幅衰减法能更加准确识别薄层界面,可准确反演出厚度10m的地层;上行波场的加入降低反演结果准确度,尤其对高Q值层;当有效波频带增宽时,高频部分衰减明显,Q值反演结果接近理论值;反演波速误差对反演准确性影响很大.最后,利用CFS对实际井旁地面地震资料进行Q值反演,反Q滤波后其主频由25Hz提高到35Hz,分辨率得到改善,证明了CFS方法的实用性.
Energy attenuation is the reflection of non-elastic property when seismic wave propagates in the medium, which is usually represented by Quality Factor,Q for short.As higher frequency attenuates more quickly than lower one,based on the centroid frequency receding in the propagation,the Centroid Frequency Shift method (CFS for short ) is used to inverse the Q value on the forward zero-offset VSP geological model.Some factors that influence this method s application results are discussed,including the thin layer,down-going wave and up-going wave,frequency bandwidth,velocity to inverse and locations of sources.The calculations of several models show that the CFS method is much more accurate in inversion of the Q value and can reveal boundaries of thin layers,even a layer of 10m thickness.The joined up-going wave influences the inverse effect,especially to high Q layers.And the broadening of bandwidth can apply more space to attenuate higher frequency,so it ought to improve the accuracy,up to the theoretical value of Q.The deviation of velocity used to inversion can greatly bring in errors,which should attract attention.While,in order to check the effect of CFS method on the field material,zero-offset VSP data and its nearby ground seismic data are chosen.After the inverse Q-filtering,its main frequency ascends from 25Hz to 35Hz and the resolution of section is ameliorated,which can illustrate CFS method s utility somewhat.
Energy attenuation is the reflection of non-elastic property when seismic wave propagates in the medium, which is usually represented by Quality Factor,Q for short.As higher frequency attenuates more quickly than lower one,based on the centroid frequency receding in the propagation,the Centroid Frequency Shift method (CFS for short ) is used to inverse the Q value on the forward zero-offset VSP geological model.Some factors that influence this method s application results are discussed,including the thin layer,down-going wave and up-going wave,frequency bandwidth,velocity to inverse and locations of sources.The calculations of several models show that the CFS method is much more accurate in inversion of the Q value and can reveal boundaries of thin layers,even a layer of 10m thickness.The joined up-going wave influences the inverse effect,especially to high Q layers.And the broadening of bandwidth can apply more space to attenuate higher frequency,so it ought to improve the accuracy,up to the theoretical value of Q.The deviation of velocity used to inversion can greatly bring in errors,which should attract attention.While,in order to check the effect of CFS method on the field material,zero-offset VSP data and its nearby ground seismic data are chosen.After the inverse Q-filtering,its main frequency ascends from 25Hz to 35Hz and the resolution of section is ameliorated,which can illustrate CFS method s utility somewhat.
引文
[1] 马昭军,刘洋.地震波衰减反演研究综述[J].地球物理学进展,2005,20(4) :1074～1082． Ma Z J,Liu Y.A summary of research on seismic attenuation[J].Progress in Geophysics(in Chinese),2005,20(4) :1074～1082．
[2] Rainer T.The determination of the seismic quality factor Q from VSP data.A comparison of different computational methods[J].Geophysical Prospecting,1991,39:1～27．
[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[J].地球物理学报,2007,50(4) :1198～1209． Gao J H,Yang S L.On the method of quality factors estimation from zero-offset VSP data[J].Chinese J.Geophys.(in Chinese),2007,50(4) :1198～1209．
[4] 赵伟,戈艳.利用零偏移距VSP资料在小波域计算介质Q值[J].地球物理学报,2008,51(4) :1202～1208． Zhao W,Ge Y.Estimation of Q from VSP data with zerooffset in wavelet domain[J].Chinese J.Geophys(in Chinese),2008,54(4) :1202～1208．
[5] Quan Y L,Jerry M H.Seismic attenuation tomography using the frequency shift method[J].Geophysics,1997,62(3) :895～905．
[6] 严又生,宜明理,魏新,等.井间地震速度和Q值联合层析成像及应用[J].石油地球物理勘探,2001,36(1) :9～17． Yan Y S,Yi M L,Wei X,et al.Joint tomographic imaging for cross-hole seismic velocity and Q value[J].OGP(in Chinese),2001,36(1) :9～17．
[7] 王辉,常旭,高峰.井间地震波衰减成像的几种方法[J].地球物理学进展,2001,16(1) :104～109． Wang H,Chang X,Gao F.Seveal methods of crosswell seismic attenuation tomography[J].Progress in Geophysics(in Chinese),2001,16(1) :104～109．
[8] 朱定,闵小刚,顾汉明.基于主频偏移反演地层的吸收系数[J].勘探地球物理进展,2006,29(1) :30～33． Zhu D,Min X G,Gu H M.Inversion of attention coefficient based on frequency shift[J].Progress in Exploration Geophysics(in Chinese),2006,29(1) :30～33．
[9] 刘冰,王德利,巩向博,等.基于VSP资料进行的吸收系数Q值反演[J].吉林大学学报(地球科学版),2007,37:22～26． Liu B,Wang D L,Gong X B.Absorption Coefficient Quality Factor(Q)Inversion[J].Journal of Jilin University(Earth Science Edition),2007,37:22～26．
[10] 朱光明.垂直地震剖面方法[M].北京:石油工业出版社,1988,177～191． Zhu G M.The vertical seismic profiling methods in Chinese[M].Beijing:Petroleum Industry Press,1988,177～191．
[11] 高静怀,王玉贵.制作包括吸收和波散效应的VSP合成记录[J].西安地质学院学报,1991,13(2) :78～87． Gao J H,Wang Y G.Synthetic seismogram with attenuation and wave-scattering effect[J].Journal of Xi'an College of Geology,(in Chinese),1991,13(2) :78～87．
[12] Sams M,Goldberg D.The validity of Q estimates from borehole data using spectral ratios[J].Geophysics,1990,55(1) :97～101．
[13] 朱定,闵小刚,顾汉明.基于主频偏移反演地层的吸收系数[J].勘探地球物理进展,2006,29(1) :30～33． Zhu D,Min X G.Gu M H.Inverse the attenuation coefficient based on centroid frequency shift method[J].Progress in Exploration Geophysics(in Chinese),2006,29(1) :30～33．
[14] Alessandra R,Jean V.Asymptotic theory for imaging the attenuation factor Q[J].Geophysics,1998,63(5) :1767～1778．
[15] James R.Integrated estimation of interval-attenuation profiles[J].Geophysics,2006,71(4) :19～23．
[16] Li H B,Zhao W Z,Cao H.Measures of scale based on the wavelet scalogram with applications to seismic attenuation[J].Geophysics,2006,71(5) :111～118．
[17] 安慧,黄德济,赵宪生.VSP资料的程变反Q滤波[J].物探化探计算技术,1998,20(1) :19～24． An H,Huang J D,Zhao X S.Distance-varying inverse Q filtering in VSP[J].Techniques for Geophysical and Geochemical Exploration(in Chinese),1998,20(1) :19～24．
[18] Tommy T,Bjorn U.Comparion of seismic attenuation models using zero-offset seismic profiling(VSP)data[J].Geophysics,2005．
[19] Wang Y H,A stable and efficient approach to inverse Q filtering[J].Geophysics,2002,67(2) :657～663．
[20] Wang Y H.Inverse Q-filter for seismic resolution enhancement[J].Geophysics,2006,71(3) :51～60．
[21] 李子顺.地震波衰减规律及其恢复方法[J].地球物理学进展,2007,22(5) :1545～1551． Li Z S.Seismic wave attenuation and recovering method[J].Progress in Geophysics(in Chinese),2007,22(5) :1545～1551．
[22] 钟磊.地层吸收补偿方法研究[D].中国石油大学,2008． Zhong L.Methodology and research on compensation for strata absorption[D].China University of Petroleum,2008．
[23] 王珺,杨长春,乔玉雷。用稳定高效的反Q滤波技术提高地震资料分辨率[J].地球物理学进展,2008,23(2) :456～463． Wang J,Yang C C,Qiao Y L.Improve the seismic resolution with a stable and efficient inverse Q filter[J].Progress in Geophysics,2008,23(2) :456～463．
[2] Rainer T.The determination of the seismic quality factor Q from VSP data.A comparison of different computational methods[J].Geophysical Prospecting,1991,39:1～27．
[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[J].地球物理学报,2007,50(4) :1198～1209． Gao J H,Yang S L.On the method of quality factors estimation from zero-offset VSP data[J].Chinese J.Geophys.(in Chinese),2007,50(4) :1198～1209．
[4] 赵伟,戈艳.利用零偏移距VSP资料在小波域计算介质Q值[J].地球物理学报,2008,51(4) :1202～1208． Zhao W,Ge Y.Estimation of Q from VSP data with zerooffset in wavelet domain[J].Chinese J.Geophys(in Chinese),2008,54(4) :1202～1208．
[5] Quan Y L,Jerry M H.Seismic attenuation tomography using the frequency shift method[J].Geophysics,1997,62(3) :895～905．
[6] 严又生,宜明理,魏新,等.井间地震速度和Q值联合层析成像及应用[J].石油地球物理勘探,2001,36(1) :9～17． Yan Y S,Yi M L,Wei X,et al.Joint tomographic imaging for cross-hole seismic velocity and Q value[J].OGP(in Chinese),2001,36(1) :9～17．
[7] 王辉,常旭,高峰.井间地震波衰减成像的几种方法[J].地球物理学进展,2001,16(1) :104～109． Wang H,Chang X,Gao F.Seveal methods of crosswell seismic attenuation tomography[J].Progress in Geophysics(in Chinese),2001,16(1) :104～109．
[8] 朱定,闵小刚,顾汉明.基于主频偏移反演地层的吸收系数[J].勘探地球物理进展,2006,29(1) :30～33． Zhu D,Min X G,Gu H M.Inversion of attention coefficient based on frequency shift[J].Progress in Exploration Geophysics(in Chinese),2006,29(1) :30～33．
[9] 刘冰,王德利,巩向博,等.基于VSP资料进行的吸收系数Q值反演[J].吉林大学学报(地球科学版),2007,37:22～26． Liu B,Wang D L,Gong X B.Absorption Coefficient Quality Factor(Q)Inversion[J].Journal of Jilin University(Earth Science Edition),2007,37:22～26．
[10] 朱光明.垂直地震剖面方法[M].北京:石油工业出版社,1988,177～191． Zhu G M.The vertical seismic profiling methods in Chinese[M].Beijing:Petroleum Industry Press,1988,177～191．
[11] 高静怀,王玉贵.制作包括吸收和波散效应的VSP合成记录[J].西安地质学院学报,1991,13(2) :78～87． Gao J H,Wang Y G.Synthetic seismogram with attenuation and wave-scattering effect[J].Journal of Xi'an College of Geology,(in Chinese),1991,13(2) :78～87．
[12] Sams M,Goldberg D.The validity of Q estimates from borehole data using spectral ratios[J].Geophysics,1990,55(1) :97～101．
[13] 朱定,闵小刚,顾汉明.基于主频偏移反演地层的吸收系数[J].勘探地球物理进展,2006,29(1) :30～33． Zhu D,Min X G.Gu M H.Inverse the attenuation coefficient based on centroid frequency shift method[J].Progress in Exploration Geophysics(in Chinese),2006,29(1) :30～33．
[14] Alessandra R,Jean V.Asymptotic theory for imaging the attenuation factor Q[J].Geophysics,1998,63(5) :1767～1778．
[15] James R.Integrated estimation of interval-attenuation profiles[J].Geophysics,2006,71(4) :19～23．
[16] Li H B,Zhao W Z,Cao H.Measures of scale based on the wavelet scalogram with applications to seismic attenuation[J].Geophysics,2006,71(5) :111～118．
[17] 安慧,黄德济,赵宪生.VSP资料的程变反Q滤波[J].物探化探计算技术,1998,20(1) :19～24． An H,Huang J D,Zhao X S.Distance-varying inverse Q filtering in VSP[J].Techniques for Geophysical and Geochemical Exploration(in Chinese),1998,20(1) :19～24．
[18] Tommy T,Bjorn U.Comparion of seismic attenuation models using zero-offset seismic profiling(VSP)data[J].Geophysics,2005．
[19] Wang Y H,A stable and efficient approach to inverse Q filtering[J].Geophysics,2002,67(2) :657～663．
[20] Wang Y H.Inverse Q-filter for seismic resolution enhancement[J].Geophysics,2006,71(3) :51～60．
[21] 李子顺.地震波衰减规律及其恢复方法[J].地球物理学进展,2007,22(5) :1545～1551． Li Z S.Seismic wave attenuation and recovering method[J].Progress in Geophysics(in Chinese),2007,22(5) :1545～1551．
[22] 钟磊.地层吸收补偿方法研究[D].中国石油大学,2008． Zhong L.Methodology and research on compensation for strata absorption[D].China University of Petroleum,2008．
[23] 王珺,杨长春,乔玉雷。用稳定高效的反Q滤波技术提高地震资料分辨率[J].地球物理学进展,2008,23(2) :456～463． Wang J,Yang C C,Qiao Y L.Improve the seismic resolution with a stable and efficient inverse Q filter[J].Progress in Geophysics,2008,23(2) :456～463．
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