Common‐Angle Gathers Based on Kirchhoff Pre‐Stack Time Migration

Abstract

AbstractIn this paper we present the improved algorithm for common‐angle gathers based on Kirchhoff pre‐stack time migration. The algorithm can calculate relatively true incident angle under three‐dimensional circumstance, while the traditional ray‐parameter method could not gain the incident angle between incident ray and dipping reflector normal. Compared with straight‐ray Kirchhoff angle domain gathers method proposed in recent years, our method is able to extract much wider angle for taking interval velocity and ray bending into account. Moreover, we apply non‐hyperbolic moveout equation to calculate the travel time, thus the commonangle gathers are flatter at large angle than straight ray method. Efficient true‐amplitude weighting function as well as hit‐count correction is beneficial for AVA inversion. The results of synthetic model data have verified that, compared with angle gathers transformed from offset to angle domain with CMP gathers or CRP gathers after migration, common‐angle gathers based on Kirchhoff pre‐stack time migration have following advantages: much more accurate incident angle, the amplitude versus angle (AVA) is robust and clear. The real 3‐D data test shows that angle gathers provided with our method are beneficial for AVA analysis and AVA inversion, and could improve pre‐stack inversion's resolution.