Revisiting the fold discontinuity after ACCP binning
Xinxiang Li, Han-xing Lu
In converted wave seismic data processing, common conversion point (CCP) binning and stacking is commonly used to transform the converted wave data into a different domain where many conventional pure-mode seismic data processing procedures can be more conveniently applied. However, because CCP binning requires velocity information, which is often not available with desired accuracy, a simplified method called asymptotic common conversion point (ACCP) binning is often used. The ACCP binning process usually requires only a value of the P-wave and S-wave velocity ratio. It is noticed that, after ACCP binning with the original CMP spacing as in pure-mode data processing, the CCP fold distribution often has periodical discontinuities. This discontinuity may result in spatial inconsistency on the CCP stacked sections, and then influences the quality of final migration and interpretation.
Starting from analysing the CMP and CCP fold distributions of single-shot acquisition geometry, the reasons of the CCP fold discontinuity are revisited in this paper. The main reason of CCP fold discontinuity can be explained as that the CCP coverage of each one-shot-multi-receiver experiment is larger than the CMP coverage. According to this fold discontinuity problem, the optimum bin-width concept is also involved. The optimum bin-width is not only dependent to the acquisition geometry, it also depends on the effective P-wave and S-wave velocity ratio used for the ACCP binning. The optimum bin-width is usually larger than the CMP spacing, which is determined directly by the acquisition geometry. Some practical approaches to overcome the fold-discontinuity problem are also discussed.