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接收器的排列长度是在数据采集之前必须选好的最重要的野外参数之一.通常,越想增加探测深度,就得越趋向于采用大炮检距.但这受到均方根(RMS)的限制,因为人们不能把不符合均方根假设的数据都包括到速度分析或CDP叠加中去(因为传播角度太大),否则,在那种情况下记录数据就失去其意义了。有几种确定最大炮检距值的约定,例如,最大炮检距不得大于目的层的深度等。然而,在过去的一年中,至少出现了三种不同的方法可让物探工作者根据不符合RMS假设的广角波至取得层速度信息。广角法即波场延拓法(克莱顿,1981),陶萨姆反演法(迪博尔德和斯托发,1981)及UNRAVEL法,它们虽可用来直接估算层速度,但不能凭推理用来估算均方根速度,可以证明,当用大炮检距时,利用某个广角法(如UNRAVEL)进行的速度分析对剖面前一部分的数据格外有效,这意味着广角波至的存在大大地有助于提高该法的灵敏度.事实上,对那些新方法而言,大于反射层深度的炮检距要比那些通常用于均方根速度分析的炮检距更有用.这种大炮检距能记录临界反射能量和临界折射能量,与采用小炮检距相比,从根本上讲,这些反、折射能量包含更多的层速度信息。RMS速度分析不可利用广角波至来进行。即使对浅层地震勘探,在确定大炮检距极限时也应该考虑到:根据某一种可用的广角法所能提高的速度精度与分辨率。确实,在地震勘探中采用大炮检距时,现在可以达到的高速度分辨率就可比采用常规炮检距时分辨出更深的地震剖面。尽管目前还没有能使广角波至成像的可行方法,但当前人们能取得速度精度的提高对将来采用大于“正常”炮检距的勘探设计提供了有力的证据.当物探工作者要借助地震方法来确定和评价难以捉摸的地层油气藏时,上述这些速度估算的新方法会变得格外有用。
The permutation length of the receiver is one of the most important field parameters that must be selected before data acquisition. Generally, the more you want to increase the depth of the probe, the more it tends to adopt large offsets, but this is affected by root mean square Because people can not include data that does not fit the root-mean-square assumptions into speed analysis or CDP overlays (because of the spread of perspective), otherwise recording data in that case loses its meaning. There are several conventions that determine the maximum offset, for example, the maximum offset can not be greater than the depth of the target. However, in the past year at least three different approaches emerged that allow geophysical workers to obtain layer velocity information based on wide-angle waves that do not meet RMS’s assumptions. The wide-angle method, the wave continuation method (Clayton, 1981), the Taosam inversion method (Debord and Stowe, 1981) and the UNRAVEL method, although they can be used to directly estimate the layer velocity, The reasoning used to estimate the root mean square velocity proves that the speed analysis using a wide-angle method (such as UNRAVEL) is particularly valid for the data in the previous section of the profile when using large offsets, which means that the presence of wide-angle waves is significantly greater In fact, for those new methods, offsets greater than the depth of the reflector are more useful than those normally used for root mean square velocity analysis. Since the critical refraction energy and the critical refraction energy can be recorded, these antireflection energies fundamentally contain more information about the layer velocity. RMS speed analysis is not available with wide-angle waves. Even for shallow seismic surveys, the speed accuracy and resolution that can be increased by one of the available wide-angle methods should be taken into account when determining the large offsets. Indeed, with large offsets used in seismic exploration, the high-resolution now achievable can resolve deeper seismic profiles than with conventional offsets. Although there are currently no feasible methods for wide-angle wave imaging, the current increase in velocity accuracy provides strong evidence that future use of exploration designs greater than “normal” offset can occur.When geophysical workers rely on seismic methods These new methods of velocity estimation become particularly useful when determining and evaluating elusive reservoir stratigraphy.