Weighted stacking for rock property estimation and detection of gas
Weighted stacking for rock property estimation and detection of gas
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DOI：
10.1111/j.1365-2478.1987.tb00856.x
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发表时间：
1987-11
影响因子：
2.6
通讯作者：
G. Smith;P. M. Gidlow
中科院分区：
文献类型：
--
作者：
G. Smith;P. M. Gidlow
振幅对偏移概念可用于生成加权叠加方案（这里称为地质叠加），其可用于另外的标准地震数据处理序列中以显示关于岩石性质的信息。Zoeppritz方程可以被简化，并且在文献中出现了几种不同的近似。它们描述了P波反射系数随P波入射角的变化，作为P波速度、S波速度和界面上、下密度的函数。使用平滑的、有代表性的层速度模型（来自钻孔或速度分析）并且假设没有倾角，可以通过迭代射线追踪来找到作为时间和偏移的函数的入射角。特别地，可以针对正常时差校正的CMP道集中的每个样本计算入射角。近似的Zoeppritz方程然后可以被拟合到道集的每个时间样本处的所有道的振幅，并且可以估计某些岩石性质。岩石性质的估计是通过在叠加之前对数据样本应用时变和偏移变权重来实现的。地质叠加可以显示的属性有：P波反射率（或真零炮检距反射率）、S波反射率以及P波速度除以S波速度的反射率（或“伪泊松比反射率”）。如果对含水碎屑硅酸盐岩石的P波速度和S波速度之间的关系进行假设，则可以创建突出显示气体存在的显示。
Amplitude versus offset concepts can be used to generate weighted stacking schemes (here called geo-stack) which can be used in an otherwise standard seismic data processing sequence to display information about rock properties. The Zoeppritz equations can be simplified and several different approximations appear in the literature. They describe the variation of P-wave reflection coefficients with the angle of incidence of a P-wave as a function of the P-wave velocities, the S-wave velocities and the densities above and below an interface. Using a smooth, representative interval velocity model (from boreholes or velocity analyses) and assuming no dip, the angle of incidence can be found as a function of time and offset by iterative ray tracing. In particular, the angle of incidence can be computed for each sample in a normal moveout corrected CMP gather. The approximated Zoeppritz equation can then be fitted to the amplitudes of all the traces at each time sample of the gather, and certain rock properties can be estimated. The estimation of the rock properties is achieved by the application of time- and offset-variant weights to the data samples before stacking. The properties which can be displayed by geo-stack are: P-wave reflectivity (or true zero-offset reflectivity), S-wave reflectivity, and the reflectivity of P-wave velocity divided by S-wave velocity (or ‘pseudo-Poisson's ratio reflectivity’). If assumptions are made about the relation between P-wave velocity and S-wave velocity for water-bearing clastic silicate rocks, then it is possible to create a display which highlights the presence of gas.