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.