Abstract:

Based on core observation, grain size analysis, thin section identification, well logging and seismic data interpretation and other methods, the sedimentary characteristics of E₂s13 (the glutenites in the upper section of the Sha 3 member of the Shahejie formation) were studied in Block Tuo 826 in the northern steep slope zone of the Dongying sag in the Bohai Bay basin. The results show that although both the glutenites from the eastern and the western E₂s13 are close to the parent rock, but their compositions, textures and structures are obviously different from each other due to different provenances and transport mechanisms, and as a result, their reservoir physical properties are different too. The eastern glutenite is dominated by tractive current deposits with good sorting and relatively high original porosity, and supported by grains, while the western glutenite is mainly composed of gravity flow deposits with poor sorting and relatively low original porosity, and supported by matrix. The E₂s13 glutenites deposited in fan delta fronts have two sediment transport pathways (one is the eastern Z366 secondary paleo-gulley and the other is the western Z361-Z364 secondary paleo-gulley), and composite lobes with larger differences in lithology and physical properties form, which include 5 microfacies, i.e., debris flow deposit, underwater braided channel, interdistributary bay, mouth bar and sand sheet, among which the underwater braided channel and the sand sheet are developed, and the debris flow deposits are more developed in the western part of the study area. From bottom to top, the fan delta generally show a retrograding to prograding cycle.

Key words: Baohai Bay basin, Jiyang depression, Dongying sag, Sha 3 member, glutenite, sedimentary characteristic, provenance, fan delta