潜水波胖射线走时层析速度反演及其在深度偏移速度建模中的应用

Diving wave tomography velocity inversion using fat ray in prestack depth migration

探讨了潜水波胖射线走时层析速度反演的方法原理、处理流程以及关键步骤、关键参数和影响因素,给出了基于该技术建立深度偏移初始速度模型的方法。潜水波胖射线走时层析速度反演技术针对既定的观测系统,通过拓宽射线路径,降低了层析反演矩阵的稀疏性,提高了速度模型反演的稳定性,较常规折射波层析反演获得的近地表速度模型深度更大,将其与深层速度模型进行合理拼接,可以为深度偏移提供更为准确的初始速度模型。实际资料处理结果表明:采用该方法建立初始速度模型,可以明显改善深度偏移成像品质,消除浅层速度剧烈变化引起的构造假象,提高地震剖面的信噪比,降低井震误差。

This paper introduces a diving wave traveltime tomographic velocity inversion technology based on the natural pixel fat ray tech nique,namely, its principle, processing flow, main steps, key parameters, influencing factors, and application to the initial velocity model building of depth migration.This inversion technology could reduce the sparsity of the tomographic inversion matrix, thus improving the stability of the velocity inversion by broadening the ray path for the established observed system.The technology could build a nearsurface velocity model that is deeper than that obtained using conventional refraction tomography inversion, thus providing a better initial velocity model for depth migration by merging with the deep velocity model reasonably.The field data processing results showed that the proposed technology could eliminate the structure imaging artifacts caused by strong lateral velocity variations in the shallows and improve the sig nal-to-noise ratio of seismic imaging, thus reducing seismic-well depth deviation.