3C-3D VSP: Normal moveout correction and VSPCDP transformation
3C-3D VSP: Normal moveout correction and VSPCDP transformation
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发表时间：
1997
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通讯作者：
J. Gulati;R. Stewart;J. Peron;J. Parkin
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作者：
J. Gulati;R. Stewart;J. Peron;J. Parkin
在本文中，我们解决了与 3C-3D VSP 数据的正常时差校正和 VSPCDP 变换相关的问题。证明表明，在水平层状各向同性地球中，VSP 勘测中记录的信号的走时距离 (t-x) 公式是双曲线的。使用振幅相似分析校正的综合结果表明，事件以显着的准确性校正到正入射时间。 Blackfoot 3C-3D VSP 测量的数据在振幅相似分析后校正为正入射时间，显示与使用光线追踪校正的数据具有良好的相关性。然后使用 Dix 公式根据时差校正期间获得的堆积速度来估计低于井总深度的层速度。时差校正期间获得的叠加速度用于 VSP 数据的近似 VSPCDP 变换。使用近似方法映射的反射点与使用光线追踪方法进行合成的反射点的比较表明，近似方法可以准确地映射反射，以满足所有实际目的。对 Blackfoot 3C-3D VSP 应用相同的近似程序会产生与使用光线追踪方法获得的图像非常相似的 3D 图像。这些针对水平层状各向同性地球开发的方法是在简单地质条件下获取高分辨率 2-D/3-D 地震图像的有效方法。然而，在复杂的地质情况下，它们可以先于更精确的成像方法（例如偏移）来提供有关地质情况的粗略想法。
In this paper, we address issues related to the normal moveout correction and VSPCDP transformation of 3C-3D VSP data. A proof is presented to show that in a horizontally layered isotropic earth the traveltime-distance ( t-x) formulae for signals recorded in a VSP survey is hyperbolic. Synthetics corrected using amplitude semblance analysis show that events are corrected to normal incidence times with remarkable accuracy. Data from the Blackfoot 3C-3D VSP survey corrected to normal incidence time after amplitude semblance analysis show good correlation with that corrected using raytracing. A Dix formula is then used to estimate interval velocities below the total depth of the well from the stacking velocities obtained during the moveout correction. The stacking velocities obtained during the moveout correction are used in an approximate VSPCDP transformation of the VSP data. Comparison of reflection points mapped using the approximate method with those using a raytracing method for synthetics show that the approximate method maps the reflections accurately for all practical purposes. The same approximate procedure applied to the Blackfoot 3C- 3D VSP resulted in a 3-D image very similar to that obtained using a raytracing method. These methods developed for a horizontally layered isotropic earth are an efficient way to obtain high-resolution 2-D/3-D seismic images in simple geologies. In complex geologies, however, they could precede more accurate imaging methods like migration to give a rough idea about the geology.