The successful development of shale gas and oil in North America has created considerable interest in shale. The analysis of genetic types, the sedimentary environment, and the mudstone development mechanism within sequences is critical for evaluating shale gas and oil exploration prospects, exploration favorable zones, and resource potential. This study focused on the shale of Shahejie Formation in Dongying Depression of Bohai Bay Basin. Shale lithofacies division, geochemical analysis, and well-log analysis were performed for a sedimentary environment and its related elemental response characteristics’ identification. Based on the results, we concluded that the sedimentary environment of the lake basin evolved from the saltwater lake to the ambiguous lake and then the open lake to the delta. In response, we observed gradually decreasing Sr/Ba and Ca/Mg ratios and increasing Rb/Ca and Fe/Mn ratios during the whole process during the reduction of the salinity and the decrease in PH value and sediments’ transport distance. The relationship between ratio elements and high-frequency sequences was initially established within the shale strata. Our results show that ratios of Sr/Ba and Ca/Mg ratios near the sequence boundary are relatively low, and ratios of Fe/Mn and Rb/Ca are relatively high, while ratios of Sr/Ba and Ca/Mg near the flooding surface are relatively high, and ratios of Fe/Mn and Rb/Ca are relatively low. Those features can be used as a marker for high-frequency sequence division of shale strata. Our results provided a new theoretical basis and technical method for shale gas and oil exploration and development.

Clarification of the source of the Eocene sediments filling the Huimin depression provides significant support for current and future oil and gas exploration in the Bohai Bay Basin, China. A comprehensive assessment of sediment provenance based on sandstone petrography, heavy mineral assemblages, seismic reflection data, and distribution of sandstone bodies of the Shahejie Formation (Es²) to the Dongying Formation (Ed) productive interval based on both its macroscopic and microscopic provenance aspects. This method of analysis has the advantages of easy data acquisition, high accuracy, strong flexibility, wide application range, and making the analysis of sedimentary provenances more systematic. Comprehensive analysis of the Huimin depression, Bohai Bay Basin has revealed further that the origin of the Eocene second member of the Shahejie Formation (Es²) to the Dongying Formation (Ed) provenance system was derived from the Linfanjia high, the Chengning uplift, and the Luxi uplift.

The genesis and sedimentary architecture of lacustrine gravity flow deposits include ongoing questions affecting the exploration and development of oil and gas, which require attention and investigation. Based on the core description, logging characteristics, and seismic facies in the third member of Paleogene Shahejie formation from the southern Bohai Bay Basin, this study provides some insights regarding lacustrine gravity flows by analyzing the characteristics, distribution patterns, and sedimentary processes of lacustrine gravity flow deposits. Twenty lithofacies are classified into eight bed types which are caused by cohesive flows, inflated flows, concentrated-density flows, or turbidity currents. The characteristics and distributions of different bed types in five sublacustrine fans with two provenance directions and in a slump olistolith reflect two sedimentary processes influenced by sediment supply, basin structure, and climate, including cohesive flow deposits covered by inflated sandflow deposits transforming into concentrated-density flow deposits into hybrid event beds and finally into turbidity current deposits from inner to outer fan, and cohesive flow deposits transforming into inflated sandflow deposits covered by turbidity current deposits into concentrated-density flow deposits into hybrid event beds finally into turbidity current deposits from proximal to distal lobe. Based on the results, a depositional model of lacustrine gravity flow deposits is established, which highlights the change from superimposed channels to anastomosing channels, the distributions and characteristics of hybrid event beds, and distinctive facies in different elements.

A new method incorporating geophysical analysis and geological analysis is proposed to define the sedimentary characteristics and distributions in basins with few drilling wells to promote the exploration of reservoirs. This method is applied to a study, through which its principles, closed-loop workflow and technologies are introduced in detail and the sedimentary characteristics and distributions of the study area are accurately defined. During the application process of the method, a compatible geological model is established, based on which the seismic data are interpreted and the results derived from the interpretation are further verified via seismic forward modeling. The study results exhibit a successive sand-rich deposition from the retrogradational gully-filling gravity flow deposition including near-shore fans, slope fans and basin-floor fans delimited by different slope break belts in transgressive sequences to the progradational delta deposition in a retrogressive sequence including braided river deltas with a long extension distance and fan deltas developed along a steep slope belt. And the potential reservoirs are located at the point-out sites of sand bodies with lower average P-wave velocities than those of muddy sediments. The proposition and application of this method are of great significance for oil and gas exploration.