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虚速度测井应用地震振幅和反射曲线两种资料,试图确定地下速度随深度而变化。严格的理论方法包括: a)将地震道反褶积,以消除地层和仪器的滤波效应。 b)用带有发散规则的完全的反合成处理(desynthesization)对反褶积过的道去除多次波。 c)计算速度, 将这个方法用于合成记录的例子时,并不能普遍用于野外情况,原因之一是对出现的噪声反合成不大可靠。现在这个方法是在严格的和现实的处理方法之间的一种妥协;不进行完全的反合成处理,反褶积和反多次是更典型的应用真振幅技术;确定了的绝对速度既适合反射系数又适合均方根速度。这就得出结论,即虚速度测井是足以正确地显示岩性的变化,经平滑后足以保存讯噪比。例子显示了地中海深海区2500米深处记录的软管激发(Flexichoc)的剖面。虚速度测井显示了1000米处覆于中新世蒸发岩之上的上新—更新世泥灰岩速度随深度而增加的资料。从蒸发岩内的高速和低速层的夹层似乎可看出垂直相变。与确定岩性的其他处理相联系的虚速度测井应成为深海勘探的一种地质工具。
Virtual velocity logging uses both seismic amplitude and reflection curves to try to determine how the subsurface velocity varies with depth. The rigorous theoretical methods include: a) Deconvolution of the seismic traces to eliminate the filtering effects of the formation and instrumentation. b) Remove multiple waves from deconvolved tract using complete desynthesization with divergence rules. c) One of the reasons for calculating velocity, when using this method for synthetic recording examples, is not universally applicable to the field, for one reason is the less reliable inversion of the noise present. Now this approach is a compromise between rigorous and realistic approaches; without complete anti-aliasing, deconvolution and anti-multiple are more typical applications of true amplitude techniques; the absolute speed determined is appropriate Reflection coefficient is suitable for root mean square speed. This concludes that the virtual velocity log is sufficient to correctly show the change in lithology and is smoothed enough to preserve the signal-to-noise ratio. The example shows a section of the hose excitation (Flexichoc) recorded at a depth of 2500 meters in the deep Mediterranean Sea. Velocity logging shows that the velocity of the Neo-Pleistocene marl, which overlies the Miocene evaporites, increases with depth at 1000 m. Vertical phase change appears to be evident from the intercalation of the high-velocity and low-velocity layers within the evaporite. Virtual velocity logging associated with other processes for lithology identification should be a geologic tool for deep sea exploration.