叠前逆时深度偏移低频噪声压制策略研究

摘要

Low wavenumber noise severely affects the migration results of prestack reverse-time depth migration (RTM).One of most important aspects of RTM is to select the right noise suppression method.In this paper,we firstly analyze the essence of the low wavenumber noise in RTM.Then,according to the mechanism of the low wavenumber noise,noise suppression methods are analyzed and classified into two kinds:one with the key aspect of avoiding back-scattered reflection,the other with the key aspect of selectively imaging.Finally,by reasonably rearranging variety of noise suppression methods,an optimal noise suppression strategy is given under different practical environments and imaging requirements for RTM.By testing and comparing several schemes with numerical examples,the results have shown high signal-to-noise ratio RTM images can be obtained by reasonably rearranging different noise suppression methods.%低波数噪音严重影响了逆时偏移的成像质量,选择合适的低波数噪音压制方法是进行逆时偏移时必然涉及到的一个重要方面.本文首先详细分析了逆时偏移中低波数噪音产生的本质原因,然后根据噪音的产生机制对目前各类低波数噪音压制方法进行了分析和归类:第一类低波数噪音压制策略的核心是在构建波场中避免发生背向反射；第二类低波数噪音压制策略的核心是进行选择性成像.最后通过对压噪方法进行合理的选择和搭配,构建了在不同实现条件和成像需求情况下逆时偏移去噪方法的最佳抉择策略.结合数值算例对几种压噪方案进行了测试和比较,实例表明了对噪音压制方法进行合理的搭配可以获得高信噪比逆时偏移成像结果.