3-D prestack migration of common-azimuth data

被引:55
作者
Biondi, B
Palacharla, G
机构
[1] Stanford Exploration Project, 360 Mitchell Building, Stanford
[2] Schlumberger Geco-Prakla, Houston, TX 77077
关键词
D O I
10.1190/1.1444098
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
In principle, downward continuation of 3-D prestack data should be carried out in the 5-D space of full 3-D prestack geometry (recording time, source surface location, and receiver surface location), even when the data sets to be migrated have fewer dimensions, as in the case of common-azimuth data sets that are only four dimensional. This increase in dimensionality of the computational space causes a severe increase in the amount of computations required for migrating the data. Unless this computational efficiency issue is solved, 3-D prestack migration methods based on downward continuation cannot compete with Kirchhoff methods. We address this problem by presenting a method for downward continuing common-azimuth data in the original 4-D space of the common-azimuth data geometry. The method is based on a new common-azimuth downward-continuation operator derived by a stationary-phase approximation of the full 3-D prestack downward-continuation operator expressed in the frequency-wavenumber domain. Although the new common-azimuth operator is exact only for constant velocity, a ray-theoretical interpretation of the stationary-phase approximation enables us to derive an accurate generalization of the method to media with both vertical and lateral velocity variations. The proposed migration method successfully imaged a synthetic data set that was generated assuming strong lateral and vertical velocity gradients. The common-azimuth downward-continuation theory also can be applied to the derivation of a computationally efficient constant-velocity Stolt migration of common-azimuth data, The Stolt migration formulation leads to the important theoretical result that constant-velocity common-azimuth migration can be split into two exact sequential migration processes: 2-D prestack migration along the inline direction, followed by 2-D zero-offset migration along the cross-line direction.
引用
收藏
页码:1822 / 1832
页数:11
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