黏滞介质吸收补偿叠前时间偏移的倾角道集孔径优选

黏滞介质吸收补偿叠前偏移是提高地震成像分辨率的合理方法,考虑了地震波传播过程的高频损失,但在补偿地震高频能量的同时也放大了噪声,如何有效压制偏移噪声是实现高分辨率成像必须解决的问题。为此,基于稳相原理,提出了黏滞介质吸收补偿叠前时间偏移过程中生成倾角道集及自动拾取菲涅耳带的方法,认为倾角道集的同相轴以稳相点为中心向两侧上翘,存在明显的道集时差和振幅变化,同相轴集中弯曲的顶点为稳相点,稳相点邻域的同相轴近平直部分为菲涅耳带,即为最佳偏移孔径。经对拾取结果检查、修改、插值,形成时、空变偏移孔径。实际数据处理结果表明,与常规叠前时间偏移相比,变偏移孔径与黏滞介质吸收补偿叠前时间偏移相结合,具有保证陡倾反射成像、压制偏移噪声、改善成像分辨率和提高偏移计算效率的优势。

Optimization of variable migration aperture in dip-angle gathers for prestack time migration with absorption compensation in viscous elastic media

Prestack time migration with absorption compensation of viscous elastic media is one of the efficient methods to improve seismic imaging resolution. However the compensation of high frequency energy will increase noise. So migration noise suppression is an essential way to achieve high resolution imaging. We propose here optimization of variable migration aperture in dip-angle gathers for prestack time migration with absorption compensation in viscous elastic media. Based on the stationary phase theory, dip-angle gathers are generated and Fresnel zone are automatically picked during the prestack time migration. When events of dip-angle gathers are warped on the both sides at the stationary phase point, there are moveouts and amplitude changes. The vertex of bended events is considered as stationary phase point, straight part of events of stationary phase point neighborhood as Fresnel zone, which is the best migration aperture. Optimized variable aperture with time and space is constructed after checking, modifying and interpolating the picked results. Real data processing results show that the proposed approach improves imaging resolution, dip reflection imaging, migration noise suppression, and migration calculation compared with conventional prestack time migration.