Key techniques of seismic data processing for bedrock buried hills in Bohai Bay Basin

The weathering crust at the top of the bedrock buried hills and the internal fault zones in the Bohai Bay Basin represent a new type of hydrocarbon enrichment zone. The bedrock buried hills are lithologically composed of granites and metamorphic rocks. Owing to their chaotic seismic reflections, it is difficult to accurately image the internal structures of these buried hills, for reliable structure interpretation and reservoir prediction, by using conventional processing techniques for sedimentary rocks. Weak signal enhancement, velocity modeling, and metamorphic reservoir imaging are the key problems in data processing. Our study shows that weak signals within metamorphic buried hills can be effectively enhanced through high-dimensional filtering and five-dimensional data regularization. According to the data characteristics and velocity distribution patterns of Paleogene, Neogene, and Archean strata, a segmented velocity modeling method is developed to establish an accurate velocity field for the bedrock buried hills. Reflection angle tomography improves the accuracy of velocity modeling. Q reverse time migration improves the imaging of the top weathering crust, and scattered wave stacking clearly images the fracture-cavity units within the weathering crust and the internal fault system. Field data processing results show that the proposed methods significantly improve the imaging quality of buried hill interiors and thus provide effective technical means for the exploration of buried-hill reservoirs in similar areas.