HTI介质中PP与PS波方位各向异性数值模拟与分析(英文)
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摘要
通过数值模拟研究了HTI介质中利用宽方位多分量地震数据进行各向异性分析时会影响结果的几种因素,模拟了PP与PS波的方位各向异性响应,分析了利用PP与PS波随方位变化的地震属性进行裂缝检测的可行性。结果显示:针对HTI介质的椭圆方位各向异性分析对地震数据的炮检距分布范围有限制,并且PS波数据适合于椭圆方位各向异性分析的炮检距范围要明显大于PP波数据,其显示出的方位各向异性特征也比PP波更加明显。PS波方位振幅拟合的椭圆长轴方向垂直于裂缝方向,而PP波方位振幅拟合的椭圆长轴平行于裂缝方向。与PP波类似,PS波R分量的层间旅行时也具有椭圆方位各向异性特征,其长轴方向垂直于裂缝方向。PS波R分量与PP波的方位振幅属性与层间旅行时属性均显示了与裂缝密度的相关性,当数据的炮检距范围合适时,拟合椭圆的长短轴之比可以用于刻画裂缝的相对密度。
This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP- and PS-wave data in HTI media,with the aim of using the modeling results as guidance in real seismic data application.Our results reveal that there is an offset limitation for both PP- and PS-waves in elliptical anisotropy fitting,and that PS-waves show a wider applicable offset range and larger observable azimuthal anisotropy than PP-waves.The major axis of the elliptical fit to the amplitudes of the R-component is perpendicular to the fracture strike,which is opposite to that in PP-wave analysis.The azimuthal interval travel time of PS-waves shows a nearly elliptical distribution and the major axis of the fit ellipse is perpendicular to the fracture strike,which is same as that in PP-wave analysis.For data within the applicable offset range,the anisotropic magnitude obtained from amplitude and travel time attributes of PP- and PS-waves exhibits a dependence on fracture density,and the major to minor axis ratio of the fit ellipse may be used to infer the relative distribution of fracture densities.
This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP- and PS-wave data in HTI media,with the aim of using the modeling results as guidance in real seismic data application.Our results reveal that there is an offset limitation for both PP- and PS-waves in elliptical anisotropy fitting,and that PS-waves show a wider applicable offset range and larger observable azimuthal anisotropy than PP-waves.The major axis of the elliptical fit to the amplitudes of the R-component is perpendicular to the fracture strike,which is opposite to that in PP-wave analysis.The azimuthal interval travel time of PS-waves shows a nearly elliptical distribution and the major axis of the fit ellipse is perpendicular to the fracture strike,which is same as that in PP-wave analysis.For data within the applicable offset range,the anisotropic magnitude obtained from amplitude and travel time attributes of PP- and PS-waves exhibits a dependence on fracture density,and the major to minor axis ratio of the fit ellipse may be used to infer the relative distribution of fracture densities.
引文
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Liu,Y J.,2003,Analysis of P-wave Seismic Reflection Data for Azimuthal Anisotropy.PhD thesis,University of Edinburgh.
R(u|¨)ger,A.,1998,Variations of P-wave reflectivity with offset and azimuth in anisotropic media:Geophysics,63, 935 - 947.
Sayers,C.M.,and Ebrom,D.A.,1997,Seismic traveltime analysis for azimuthally anisotropic media:Theory and experiment:Geophysics,36,1570- 1582
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Grechka,V.,and Tsvankin,I.,1997,Inversion of nonhyperbolicmoveout in transversely isotropic media: 67~(st) Ann.Internat.Mtg.,Expanded Abstracts,Soc.of Expl.Geophys,1685-1688.
Grechka,V.,and Tsvankin,I.,1998,3-D description of normal moveout in anisotropic inhomogeneous media: Geophysics,63,1079 - 1092.
Hudson,J.A.,1981,Wave speeds and attenuation of elastic waves in material containing cracks.Geophysical Journal Royal Astronaut Society,64,133 - 150.
Li,X.Y.,1998,Fracture detection using P-P and P-S wave in multicomponent sea floor data:68th Ann.Internat. Mtg.,Expanded Abstracts,Soc.of Expl.Geophys,2056 -2059.
Li,X.Y.,1999,Fracture detection using azimuthal variation of P-wave moveout from orthogonal seismic survey lines:Geophysics,64,1193 - 1201.
Liu,E.,Hudson,J.A.,and Pointer,T.,2000.Equivalent medium representation of fractured rock:Journal of Geophysical Research,105,2981 - 3000.
Liu,Y J.,2003,Analysis of P-wave Seismic Reflection Data for Azimuthal Anisotropy.PhD thesis,University of Edinburgh.
R(u|¨)ger,A.,1998,Variations of P-wave reflectivity with offset and azimuth in anisotropic media:Geophysics,63, 935 - 947.
Sayers,C.M.,and Ebrom,D.A.,1997,Seismic traveltime analysis for azimuthally anisotropic media:Theory and experiment:Geophysics,36,1570- 1582
Sena,A.G.,1991,Seismic travel time equations for azimuthally anisotropic and isotropic media.Estimation of interval elastic properties.Geophysics,56,2090 - 2101.
Taylor,D.B.,2001,ANISEIS manual with appendix for releases to 5.3 to 5.6.Macroc limited,UK.
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