关键词: 页岩油, 差异聚集, 细粒沉积岩相, 储层“甜点”, 夹层型页岩层系, 混积型页岩层系, 页岩型页岩层系

Abstract: The oil in continental shale formations is a critical component of China’s petroleum production replacement over the next decade. Its pronounced heterogeneity leads to significant differences in hydrocarbon occurrence and accumulation, posing a key scientific challenge for efficient exploration and development. This study focuses on three typical types of continental shale formations (interlayered-type, mixed-type, and shale-type continental shale formations), and systematically investigates their differential accumulation mechanisms and enrichment patterns through integrated approaches such as fine-grained lithofacies description, hydrocarbon occurrence characterization, petrophysical response, and resource assessment. The main findings are as follows. (1) The source-reservoir configurations and differential accumulation mechanisms controlled by distinct lithofacies were clarified. Among them, the interlayered-type shale formation is characterized by source-reservoir separation, near-source accumulation and short-distance hydrocarbon migration, the mixed-type shale formation is characterized by source-reservoir coexistence, proximal accumulation and microscale hydrocarbon migration, and the shale-type shale formation is characterized by source-reservoir integration and in-situ hydrocarbon retention. (2) The occurrence mechanism of hydrocarbons within micrometer- to nanometer-scale pore spaces in the source rocks was elucidated as a sequential process from swelling, adsorption to free states, and an enrichment model evolving from in-situ retention to large-scale migration was established. (3) A comprehensive petrophysical volumetric model was developed, which integrates multiple mineral components, pore types and laminar structures, and petrophysical templates for “sweet spot” identification were established based on differentially sensitive elastic parameters. (4) A parameter system and methodological workflow for resource evaluation of continental shale formations were preliminarily established, with clearly defined lower bounds and classification criteria for key parameters including porosity, oil saturation, pyrolysis free hydrocarbon content, total organic carbon content, and formation pressure coefficient. These phased advances in differential accumulation mechanisms and evaluation methods in continental shale formations provide systematic scientific foundations and methodological supports for the evaluation and optimization of “sweet spot” zones/intervals, resource potential assessment, and efficient development.

Key words: shale oil, differential accumulation, fine-grained sedimentary lithofacies, reservoir “sweet spot”, interlayered-type shale formation, mixed-type shale formation, shale-type shale formation