Free surface multiple imaging technology of shallow water based on reverse time migration

In shallow water environment, multiples are widely developed but difficult to suppress. How to deal with the shallow free surface multiples is an important part of marine seismic data processing. Compared with the primary effective wave, the multiples have advantages of small reflection angle, wide illumination range, long propagation path, and high resolution. We improved the traditional suppression practice in which multiples are treated as noise. First, based on the deterministic water layer multiple suppression (DWD) technology and free surface multiple suppression (SRME) technology, shallow water free surface multiples and effective reflected waves could be well separated. Secondly, multiple waves of different orders could be predicted using separated effective waves in the feedback loop theory. Finally, based on the reverse time migration imaging technology with higher imaging accuracy, the imaging of multiples of different orders could be achieved. Our trial processing results of model data and actual data show that the combined separation method could well separate multiples from reflected waves at shallow water free surface. The fractional imaging not only avoided the influence of crosstalk noise in the imaging process, but also expanded the imaging illumination range and improved the imaging quality of seismic data in shallow water areas. Therefore, the effective use of shallow-water free surface multiples is realized.