The BZ 26-6 oil and gas field, a recently discovered billion-ton-scale buried-hill bedrock reservoir in the Bohai Sea, is characterized by its large-scale reservoir system, with the weathering crust serving as the primary hydrocarbon storage space. By integrating drilling, seismic, logging, and laboratory analysis data, this study clarifies the developmental characteristics of the bedrock buried-hill reservoir and investigates the main controlling factors of weathering crust reservoir formation. The results indicate that the metamorphic rock buried-hill reservoir in the study area is dominated by metamorphic granites, with dissolution pores and structural fractures as the main reservoir spaces. Vertically, the reservoir can be divided into a weathered sandstone zone, weathered fracture zone, and bedrock fracture zone. The development of the buried-hill weathering crust reservoir is jointly controlled by lithology, tectonics, weathering-leaching processes, and paleogeomorphology.（1）Approximately 90% of the reservoir comprises metamorphic granites rich in felsic minerals, providing the material basis for weathering crust formation.（2）Multiphase tectonic movements generated extensive fractures within the buried hill, directly contributing to reservoir space and acting as conduits for fluid migration, enhancing deep-seated rock dissolution.（3）Weathering-leaching is critical to weathering crust development, with the intensity of weathering decreasing downward, and reservoir quality being optimal within 300 m of the buried-hill top surface.（4）Paleogeomorphology controls weathering crust thickness and distribution. In high-elevation areas, intense weathering leads to limited preservation of the weathering crust, with thin weathered sandstone zones and moderately thick weathered fracture zones. Steep slopes are characterized by negligible weathered sandstone development but moderate weathered fracture zones. In contrast, gentle slopes and low-lying areas exhibit favorable preservation conditions, supporting thick weathered sandstone and fracture zones. This systematic analysis highlights the interplay of lithological composition, structural evolution, weathering dynamics, and paleotopography in shaping high-quality reservoirs within the BZ 26-6 field.