满足叠前偏移要求的三维地震观测系统设计

3D geometry designing for pre-stack migration

常规3D观测系统设计基于水平层状介质假设,其主要目的是得到规则采样的叠加数据体,能够用叠后偏移进行成像。与叠后偏移使用规则的叠加数据体不同,叠前偏移使用相对不规则的炮检对数据。3D观测系统不规则的空间采样很可能导致严重的偏移噪声,从而部分降低叠前偏移的效果。从叠前偏移的需要出发进行观测系统设计,这对于充分发挥叠前偏移技术优势、提高地震成像精度具有重要意义。本文介绍了从叠前偏移成像要求出发的观测系统设计方法,根据采样均匀和面元属性一致性原则设计观测系统模板,获得良好的空间采样,并利用聚焦束、叠前偏移响应、正演模型和波场照明等技术对观测系统逐步优化,得到符合叠前偏移成像要求并能解决地质问题的观测系统。该技术在东濮凹陷QK工区的应用取得了良好效果。

The conventional 3D seismic geometry designing is based on the horizontally stratified medium presumption,its main objective is to obtain regularly sampled stacking dataset,which can be used to image the geological target through post-stack migration.Different from post-stack migration in which the regular post-stack data volume is used,the pre-stack migration uses irregular offset datasets.The irregular spatial sampling of the 3D geometry could probably result in severe migration noise,which then may partially decrease the effect of the pre-stack migration.Designing the 3D geometry which meets the requirement of pre-stack migration has great significance by fully making use of the advantages of the pre-stack migration and raising the imaging accuracy.The new geometry designing method was introduced in this paper,based on the evenly sampling and bin attribute consistence principle the geometry template was designed,good spatial samples were acquired,the designed geometry were gradually optimized by using focus beam,pre-stack migration response,forward modeling,wave field illumination and other techniques,at last the geometry which could meet the requirement of pre-stack migration and could resolve geological problem was obtained.The new method was applied in QK survey in Dongpu Depression and the excellent results were achieved in the survey.