深反射地震资料的偏移处理

Migration of the deep reflection seismic data

本文在对偏移理论和相关算法进行概括性的梳理和总结之外,主要针对深反射地震资料叠前偏移方法进行介绍,对初始数据的规则化、偏移孔径、去假频因子以及速度模型等关键参数进行详细的测试和深入地探讨.适当的规则化处理能提高深反射地震资料中反射信号的连续性和剖面整体能量的均一性;合理的偏移孔径能让波场能量很好地收敛、陡倾角反射层能够准确归位以及岩石圈中、深部的精细结构能较好地成像,同时又不至于引入严重的偏移噪音;通过选择适当的去假频因子来减少剖面上的高频干扰,使得整个剖面的高、低频能量分布适中;精确的速度模型是影响偏移结果的关键性因素,通过对速度模型的不断迭代优化,能显著地提高深反射地震剖面的中、深部偏移成像的精度和准确性,为后续深反射地震资料的综合解释打下良好基础.

In this paper both the migration theories and some algorithms have been briefly summarized. The paper are focus on studying the prestack migration method of deep reflection seismic data and discussing on the input data processing procedure and migration parameters in detail, that is, input data regularization, migration aperture width, anti-aliasing factor and velocity model. A proper data regularization procedure being used for the input data before prestack migration can enhance the continuities of reflection events and improve the uniformity of energy in the final migrated section. An appropriate migration aperture width should be chosen during prestack migration to make sure the energy of wavefield is properly converged and steep-dipping reflectors are clearly imaged without improving noise in the final section. A proper anti-aliasing factor should be used during prestack migration to make sure the high frequency noise can be depressed and the dominant frequency bandwidth of the entire section is in a reasonable range. An accurate velocity model is a key point for prestack migration. It can improve the accuracy of imaging in the migrated section with an iterative velocity updating procedure during the prestack migration of the deep reflection seismic data, which is very important for generating a clear and accurate image of the lithosphere and the basis of the subsequent interpretation of the migrated section.