三维叠后投影时间偏移——兼与牟永光商榷偏移孔径问题

3-D Poststack project time migration-discussion about migration aperture with Mr. Mu Yong-guang.

地震偏移成像是地震资料处理的重要组成部分。笔者和同事从 1994年开始一直致力于投影偏移成像的研究。应用层析成像理论研究了包括三维和二维叠后及叠前投影偏移 (时间域和深度域 )等八种方法。本文主要介绍三维叠后投影偏移的原理及其实现方法。以傅里叶投影定理为基础 ,对三维数据体沿时间轴做水平时间切片 ,并在其上做 Radon投影 ,形成一系列径向线二维剖面 ,尔后进行 Radon插值和反投影 ,完成三维偏移。此法与一步法偏移相比 ,剖面整体的信噪比有所提高 ,局部地段的同相轴连续性和成像清晰度有较为明显的改善。在本文中还讨论了偏移孔径问题。基于层析原理对三维数体做完全观测角投影的偏移方法和基于双平方根算子炮点—偏移距域的叠前偏移等方法都不存在选择偏移孔径的问题。那种认为“一切偏移方法都必需考虑偏移孔径的影响”的观点是不正确的 。

Seismic migration imaging is an important component to seismic data processing. The author and his colleagues have devoted to study project migration imaging since 1994,which includes 3-D (2-D) pre-stack (post-stack) depth (time) domain project migration etc.In this paper we mainly describe the principle and implementation method for post-stack 3-D project time migration. The proposed method is on the basis of famous Fourier projection theorem. After processing of 3-D seismic data volume by making horizontal time slice along time axis and Radon projection,we obtained a series of 2-D radial sections. Using Radon interpolation and then reverse projection for these sections, the purpose of 3-D migration finally can be achieved. Compared with one-pass migration method,the project migration showed a result having improvement in ration of signal to noise for all sections,obviously improving the continuity of events and the accuracy of imaging in local area. This paper also discused about the migration aperture in seismic data processing.The application of some methods,such as project migration method with complete observation angle based on tomography theory and pre-stack migration method with double-square-root operator in source-offset domain,needs not select migration aperture. Author points out that such point of view as 'there is necessary to consider the effect of migration aperture in all migration method.' is not correct,and moreover, this opinion is not of benefit to developing of migration method in the future.