Status quo, advances, and prospects of shale oil exploration in the Bohai Bay Basin

With the transition of the global energy supply/demand landscape, shale oil exploration and exploitation have emerged as a significant developmental direction in the energy sector. Based on constant extensive research for over a decade and a summary of onshore shale oil exploration in the Shengli and Dagang oilfields, coupled with the sedimentary background of the Bohai Bay Basin, we categorize the offshore shale oil reservoirs in the basin into matrix, lamina, and sandwich types. The lamina and sandwich types, among others, are further divided into sandy lamina, mixed lamina, sandy sandwich, and mixed sandwich subtypes. Using this classification, we assess the types, distributions, and resource potential of shale oil reservoirs in the Laizhou Bay, Huanghekou, and Liaozhong sags. New technological and theoretical advances are achieved in four aspects: the hydrocarbon generation and expulsion mechanisms and assessment methods of source rocks, the characterization of reservoirs of fine-grained sedimentary rocks, mechanisms of differential shale oil enrichment, and criteria for sweet spot evaluation. Nevertheless, shale oil exploration in the Bohai Bay Basin still faces multiple challenges imposed by complex geological structures, diverse sequences, and insufficient accuracy in pore structure characterization. In the future, it is necessary to intensify digital basin modeling, construct a comprehensive and unified standard system for reservoir characterization, innovate experimental and simulation methods, and promote the in-depth integration of geology, geochemistry, and engineering technology. Furthermore, it is recommended to prioritize key issues including mechanisms underlying shale oil enrichment, the identification of shale oil sweet spots, and large-scale shale oil production. This will help comprehensively enhance the understanding of unconventional hydrocarbon resources, as well as their exploration and exploitation efficiency.