VTI介质P波反射时差分析
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摘要
常规动校正处理方法提供的叠加速度及层速度精度不能满足钻前压力预测的需要。其主要原因在于该方法假定地震波在各向同性层状介质中传播 ,而实际地层却表现为各向异性特征。因此本文以 VTI介质为地下岩层模型 ,采用纵波 (P波 )正演模拟 ,论述了 Alkhalifah方法、含有效各向异性参数的四阶时差分析方法和平移双曲线时差分析技术 ,分别校正了 P波非双曲线反射时差 ;同时与基于各向同性介质模型的四阶时差校正和平移双曲线时差校正结果进行了比较 ;并采用 Thom en(1986 )提供的实际岩样的有效各向异性参数 ,对实际资料进行了校正。结果表明 :VTI介质的时差分析方法同样适用于各向同性介质 ,并可以提供更为精确的地震速度 ;利用 VTI介质有效各向异性参数 η也可以描述各向同性水平层状介质 ;当取有效各向异性参数 η<0 .1时 ,可以较好地反映弱各向异性层的特征 ,在中、近炮检距附近道的校正误差仅为一个采样间隔。本文最后给出两种求取有效动校正速度和有效各向异性参数 η的实用方法
The precision of stack velocity and interval velocity provided by common NMO correction processing method can't meet the need of predicting the pre-drilling press.The key reason is that the method supposed that the seismic wave traveled in isotropic layered medium and the practical layer has anisotropic feature on the contrary.Therefore,taking VTI medium as underground layer model,the paper uses P-wave forward modeling,expounds Alkhalifah method,4-order moveout analysis method containing useful anisotropic parameters and parallel-shifted hyperbolic moveout analysis technique,using these methods to correct the P-wave non-hyperbolic moveout separately;meanwhile,the comparison of above mentioned results with the results of 4-order moveout correction and parallel-shifted hyperbolic moveout correction based on isotropic medium model;The correction for real data is carried out by using useful isotropic parameters of real rock samples presented by Mr. Thmen (1986) .The results showed that the moveout analysis method of VTI medium is also suitable for isotropic medium and can provide precise seismic velocity;using useful anisotropic parameter of VTI medium η can also describe isotropic horizontal layered medium;when the useful anisotropic parameter η is taken as less than 0.1,the characters of weak anisotropic layer can be better reflected,which the errors of trace correction in near and middle offset are only 1 sample interval.Finally,the paper gave two practical methods for calculating useful NMO velocity and useful anisotropic parameter η.
The precision of stack velocity and interval velocity provided by common NMO correction processing method can't meet the need of predicting the pre-drilling press.The key reason is that the method supposed that the seismic wave traveled in isotropic layered medium and the practical layer has anisotropic feature on the contrary.Therefore,taking VTI medium as underground layer model,the paper uses P-wave forward modeling,expounds Alkhalifah method,4-order moveout analysis method containing useful anisotropic parameters and parallel-shifted hyperbolic moveout analysis technique,using these methods to correct the P-wave non-hyperbolic moveout separately;meanwhile,the comparison of above mentioned results with the results of 4-order moveout correction and parallel-shifted hyperbolic moveout correction based on isotropic medium model;The correction for real data is carried out by using useful isotropic parameters of real rock samples presented by Mr. Thmen (1986) .The results showed that the moveout analysis method of VTI medium is also suitable for isotropic medium and can provide precise seismic velocity;using useful anisotropic parameter of VTI medium η can also describe isotropic horizontal layered medium;when the useful anisotropic parameter η is taken as less than 0.1,the characters of weak anisotropic layer can be better reflected,which the errors of trace correction in near and middle offset are only 1 sample interval.Finally,the paper gave two practical methods for calculating useful NMO velocity and useful anisotropic parameter η.
引文
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[3] L eonT.Weak elastic anisotropy.Geophysics,1986,51(10):1954～1966
[4] 薛冈,王良书,胡中平.大偏移距地震资料动校正方法比较.石油地球物理勘探,2003,38(2):151～155
[5] L lyaT andL eonT.Nonhyperbolic reflection m ove-out in anisotropic.Geophysics,1994,59(8):1290～1304
[6] TariqA andL lyaT.Velocity analysis for transverse-ly isotropic media.Geophysics,1996,60(5):1550～1566
[7] TariqA.Velocity analysis using nonhyperbolic m ove-out in transversely isotropic media.Geophysics,1997,62(6):1839～1854
[8] RistoS.Technological leap in time processing focuesthe data throughout anisotropic m edia.FirstBreak,2001,19(11):612～617
[9] RistoS.Anelliptic time processing based on a shiftedhyperbola approach.ExpandedAbstracts of the70 thSEG Mtg,2000
[10] HakeH K H andMesdagC S.Three- termTaylor se-ries for t2- x2- curves ofP- andS- waves over layeredtransversely istropoc ground.GeophysicalProspect-ing,1984,32:828～850
[11] TanerM T andKoehlerF.Velocity spectra- digitalcomputer derivation and application of velocity func-tions.Geophysics,1969,34(6):859～881
[12] CastleR J.A theory of norm al m oveout.Geophysics,1994,59(6):983～999
[2] DuttaN C.Geopressure prediction using seismic da-ta:Current status and the road ahead.Geophysics,2002,67(6):2012～2041
[3] L eonT.Weak elastic anisotropy.Geophysics,1986,51(10):1954～1966
[4] 薛冈,王良书,胡中平.大偏移距地震资料动校正方法比较.石油地球物理勘探,2003,38(2):151～155
[5] L lyaT andL eonT.Nonhyperbolic reflection m ove-out in anisotropic.Geophysics,1994,59(8):1290～1304
[6] TariqA andL lyaT.Velocity analysis for transverse-ly isotropic media.Geophysics,1996,60(5):1550～1566
[7] TariqA.Velocity analysis using nonhyperbolic m ove-out in transversely isotropic media.Geophysics,1997,62(6):1839～1854
[8] RistoS.Technological leap in time processing focuesthe data throughout anisotropic m edia.FirstBreak,2001,19(11):612～617
[9] RistoS.Anelliptic time processing based on a shiftedhyperbola approach.ExpandedAbstracts of the70 thSEG Mtg,2000
[10] HakeH K H andMesdagC S.Three- termTaylor se-ries for t2- x2- curves ofP- andS- waves over layeredtransversely istropoc ground.GeophysicalProspect-ing,1984,32:828～850
[11] TanerM T andKoehlerF.Velocity spectra- digitalcomputer derivation and application of velocity func-tions.Geophysics,1969,34(6):859～881
[12] CastleR J.A theory of norm al m oveout.Geophysics,1994,59(6):983～999
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