<p>The Miocene-aged fluvio-deltaic Bhuban Formation in the Bengal Basin is generally regarded as a poor hydrocarbon producer due to the dominance of low-quality reservoir facies. This study investigates the occurrence and characteristics of higher-quality reservoir facies within the formation, leading to the identification of sand-filled incised valleys in outcrop. In addition to this valley-fill sandstone (RF-III), alternating sandstone and shale layers (RF-I), and fine-grained channel sandstones (RF-II) were identified through detailed fieldwork. Petrographic, X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses indicate that RF-III possesses the most favorable reservoir properties, with coarser grains and high porosity observed in thin section. By contrast, RF-I represents the poorest reservoir quality, while RF-II has moderate potential that becomes significant when multiple units are stacked. Seismic data from the adjacent Srikail gas field were interpreted to map incised valleys within the Bhuban Formation and used for volumetric modeling. Results suggest that a single sand-filled incised valley could contain up to 40 BCF of Gas Initially In Place (GIIP), with substantially greater volumes possible if the valley and field dimensions are larger. These findings demonstrate, for the first time, the quantitative reservoir potential of sand-filled incised valleys in the Bhuban Formation, highlighting them as promising but underexplored exploration targets in the Bengal Basin.</p>