The BZ 26-6 oil and gas field, a newly discovered billion-ton-scale buried-hill bedrock reservoir in Bohai Sea, is characterized by a large-scale reservoir system dominated by a weathering-crust hydrocarbon storage zone. By integrating drilling, seismic, logging, and laboratory analysis data, this study elucidates the development characteristics of the buried-hill bedrock reservoir and identifies the main controlling factors governing weathering-crust formation. The results indicate that the metamorphic buried-hill reservoir is primarily composed of metamorphic granites, with dissolution pores and structural fractures serving as the main reservoir spaces. Vertically, the reservoir can be divided into three zones:a weathered sandstone zone, a weathered fracture zone, and a bedrock fracture zone. The formation and distribution of the buried-hill weathering crust reservoir are jointly controlled by lithology, tectonics, weathering-leaching processes, and paleogeomorphology. About 90% of the reservoir consists of felsic-rich metamorphic granites, providing a favorable material basis for weathering-crust development. Multiphase tectonic movements generated extensive fractures within the buried hill, which not only contributed directly to reservoir space but also enhanced deep-seated dissolution through fluid migration. Weathering-leaching played a critical role, with weathering intensity decreasing downward and optimal reservoir quality occurring within 300 m of the buried-hill top surface. Paleogeomorphology further influenced weathering crust thickness and distribution. High-elevation areas experienced strong weathering but poor preservation, with thin weathered sandstone zones and moderately thick weathered fracture zones. Steep slopes developed moderate fracture zones, while gentle slopes and low-lying areas provided favorable conditions for the preservation of thick weathered sandstone and fracture zones.