Processing method for multichannel mid-to-far offset seismic data of shallow water strong-shielding layer in the South Yellow Sea Basin

The seismic imaging quality of the Mesozoic–Paleozoic strata in the Laoshan Uplift of the South Yellow Sea has long faced significant challenges. The core constraining factor is that the coupling effect of seismic-geological conditions in shallow water areas and the strong shielding properties of internal stratigraphic media significantly reduces the signal-to-noise ratio of deep seismic data. Moreover, during data processing, the effective utilization of mid-to-far offset information from long-offset seismic data has not been achieved. Therefore, we systematically analyzed the mechanism by which shallow water environments and strong shielding layers affect the mid-to-far offset data. In response to wide-angle multiple interference generated by shallow-water sources and low-velocity coherent noise induced by strong shielding layers, we developed a multi-scale denoising strategy. In addition, by enhancing the signal-to-noise ratio of mid-to-far offset data, we significantly improved the accuracy of velocity analysis and the resolution of seismic profiles, laying the foundation for obtaining high-quality prestack migration results. In practice, our seismic data processing demonstrated that the proposed joint processing technique for mid-to-far offset data effectively enhanced the imaging quality of the target Mesozoic–Paleozoic strata; the unconformity between the Sinian and Cambrian Systems beneath the strong shielding layer was clearly revealed, providing a robust geophysical data support for further research into the tectonic-sedimentary evolution of the lower Paleozoic in the South Yellow Sea.