各向异性克希霍夫叠前深度偏移
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摘要
随着地震勘探精度的提高,各向异性对于常规克希霍夫叠前深度偏移效果的影响已不容忽视。研究了利用P波非双曲旅行时求取各向异性参数的方法,当道集的排列长度远大于勘探目的层深度时,P波走时资料包含的信息可以用来确定VTI介质的各向异性参数。利用VTI介质的CMP道集,研究了二步法提取η参数的方法,即先利用短排列地震数据求取均方根动校正速度,再利用长排列数据和水平速度扫描法得到水平速度,通过转换得到各向异性η参数;采用基于声学近似的VTI介质程函方程,通过各向异性射线追踪计算旅行时。模型及实际资料处理结果表明,利用上述方法提取各向异性参数,进行VTI介质各向异性克希霍夫叠前深度偏移,使成像精度和质量得到了明显提高。
Along with the improvement of seismic exploration accuracy,the effect of anisotropy on conventional Kirchhoff pre-stack depth migration can't be ignored any more.Therefore,we studied the method of obtaining anisotropic parameters by using P-wave non-hyperbolic traveltime.The results show that P-wave traveltime information can be used to identify the anisotropic parameters of VTI media when seismic array length is much longer than the depth of the exploration target.Based on the CMP gathers from VTI media,we probed the two-step method for extracting the parameter.The first step is striking RMS NMO correction velocity by using short-array seismic data,and then applyin ghorizontal velocity scanning on long-array seismic data to get horizontal velocity,followed by conversion to get the anisotropy parameters.The second step is calculating travel time by anisotropic ray tracing based on the VTI media eikonal equation with acoustic approximation.Model and field data tests show that,the proposed method is workable to extract the anisotropy parameters,and is effective to improve the accuracy & quality of VTI anisotropic Kirchhoff pre-stack depth migration.
Along with the improvement of seismic exploration accuracy,the effect of anisotropy on conventional Kirchhoff pre-stack depth migration can't be ignored any more.Therefore,we studied the method of obtaining anisotropic parameters by using P-wave non-hyperbolic traveltime.The results show that P-wave traveltime information can be used to identify the anisotropic parameters of VTI media when seismic array length is much longer than the depth of the exploration target.Based on the CMP gathers from VTI media,we probed the two-step method for extracting the parameter.The first step is striking RMS NMO correction velocity by using short-array seismic data,and then applyin ghorizontal velocity scanning on long-array seismic data to get horizontal velocity,followed by conversion to get the anisotropy parameters.The second step is calculating travel time by anisotropic ray tracing based on the VTI media eikonal equation with acoustic approximation.Model and field data tests show that,the proposed method is workable to extract the anisotropy parameters,and is effective to improve the accuracy & quality of VTI anisotropic Kirchhoff pre-stack depth migration.
引文
[1]Alkhalifah T.An acoustic wave equation for anisotropicmedia[J].Geophysics,2000,65(4):1239-1250
[2]Zhu T,Gray S H,Wang D.Kinematic and dynamicray tracing in anisotropic media:Theory and applica-tion[J].Expanded Abstracts of 75th Annual InternatSEG Mtg,2005,96-99
[3]Lawton D C,Isaac J H,Vestrum R W,et al.Slip-slidin away-some practical implications of seismic veloc-ity anisotropy on depth imaging[J].The LeadingEdge,2001,20(1):70-73
[4]段鹏飞,程玖兵.TI介质射线追踪与局部角度域叠前深度偏移[J].SPG/SEG深圳2011国际地球物理会议论文集,2011,940-945Duan P F,Cheng J B.Ray tracing in TI media andlocal angle domain Kirchhoff prestack depth migra-tion[J].SPG/SEG Shenzhen 2011International Ge-ophysical Conference Symposium,2011,940-945
[5]Tsvankin I,Thomsen L.Inversion of reflection trav-eltimes for transverse anisotropy[J].Geophysics1995,60(4):1095-1107
[6]Thomsen L A.Weak elastic anisotropy[J].Geo-physics,1986,51(10):1954-1966
[7]Alkhalifah T.Velocity analysis using nonhyperbolicmoveout in transversely isotropic media[J].Geo-physics,1997,62(6):1839-1854
[8]Alkhalifah T,Tsvankin I.Velocity analysis in trans-versely isotropic media[J].Geophysics,1995,60(5):1550-1566
[9]Grechka V,Tsvankin I.Feasibility of nonhyperbolicmoveout inversion in transversely isotropic media[J].Geophysics,1998,63(3):957-969
[10]Grechka V,Pech A,Tsvankin I,et al.Velocity anal-ysis for tilted transversely isotropic media,aphysicalmodelling example[J].Geophysics,2001,66(3):904-910
[11]Le Stunff Y,Grechka V,Tsvankin I.Depth domainvelocity analysis in VTI media using surface P-wavedata,is it feasible?[J].Geophysics,2001,66(3):897-903
[2]Zhu T,Gray S H,Wang D.Kinematic and dynamicray tracing in anisotropic media:Theory and applica-tion[J].Expanded Abstracts of 75th Annual InternatSEG Mtg,2005,96-99
[3]Lawton D C,Isaac J H,Vestrum R W,et al.Slip-slidin away-some practical implications of seismic veloc-ity anisotropy on depth imaging[J].The LeadingEdge,2001,20(1):70-73
[4]段鹏飞,程玖兵.TI介质射线追踪与局部角度域叠前深度偏移[J].SPG/SEG深圳2011国际地球物理会议论文集,2011,940-945Duan P F,Cheng J B.Ray tracing in TI media andlocal angle domain Kirchhoff prestack depth migra-tion[J].SPG/SEG Shenzhen 2011International Ge-ophysical Conference Symposium,2011,940-945
[5]Tsvankin I,Thomsen L.Inversion of reflection trav-eltimes for transverse anisotropy[J].Geophysics1995,60(4):1095-1107
[6]Thomsen L A.Weak elastic anisotropy[J].Geo-physics,1986,51(10):1954-1966
[7]Alkhalifah T.Velocity analysis using nonhyperbolicmoveout in transversely isotropic media[J].Geo-physics,1997,62(6):1839-1854
[8]Alkhalifah T,Tsvankin I.Velocity analysis in trans-versely isotropic media[J].Geophysics,1995,60(5):1550-1566
[9]Grechka V,Tsvankin I.Feasibility of nonhyperbolicmoveout inversion in transversely isotropic media[J].Geophysics,1998,63(3):957-969
[10]Grechka V,Pech A,Tsvankin I,et al.Velocity anal-ysis for tilted transversely isotropic media,aphysicalmodelling example[J].Geophysics,2001,66(3):904-910
[11]Le Stunff Y,Grechka V,Tsvankin I.Depth domainvelocity analysis in VTI media using surface P-wavedata,is it feasible?[J].Geophysics,2001,66(3):897-903
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