拟真三维投影偏移

Pseudo-true 3-D projective migration

常规三维地震资料处理中常用二步法来实现偏移，但由于三维纵测线或横测线往往不在地质体的真倾角方向上，所以很难实现三维地震数据的正确偏移归位。而真三维地震数据偏移方法，需要较大的计算机内存及计算量，故未能得到广泛应用。为此，本文介绍一种拟真三维投影偏移方法。该方法的实现过程是，首先利用三维叠加数据体的时间切片进行Radon投影，得到一系列径向剖面；然后对每条经向剖面作Radon正、反变换，得到径向偏移剖面；最后在时间切片上作Radon反投影，便能实现真倾角同相轴的偏移归位。该方法能实现三维地震数据体空间归位，明显提高了剖面的信噪比，加强了同相轴的连续性，对各种构造现象均能理想成像，且所需内存和计算量与二步法相当，其分辨率亦与其它偏移方法相当、实际资料的处理结果表明，该方法是一种有效的三维叠后偏移方法。

The ordinary 3-D seismic data migration is often finished by two-step ap-proach. However, correct migration of 3-D seismic data can hardly be achieved be-cause crossline and inline are usually not along true dip direction of geoiogical body.Unfortunately, true 3-D seismic migration has not found its wide application be-cause of big internal storage need and heavy computation. Pseudo-true 3-D projec-tive migration is thus advanced, and it includes following essential steps:. Obtain a series of radial sections by making Radon projection of time slicesof stacked 3-D data volume.. Conduct forward and inversive Radon transforms of each radial section toproduce radial migration section.. Achieve a true-dip migration by doing Radon inverse projection of time slice.The method offers good migration of 3-D data volume,improved signal/noiseratio of seismic section, desirable continuity of seismic events, satisfactory imagesof various geological structures. What is more, it needs as much internal storageand computations as two - step approach does; and it brings the seismic resolutionwhich is equivalent to that other methods creat- It has been shown in practice thatthis method is an effective 3-D poststack migration technique.