<p>Bangladesh’s increasing energy demand and declining natural gas reserves necessitate the reassessment of existing hydrocarbon fields to ensure sustainable energy production. The Kailashtila Gas Field, one of the major gas-producing fields in Bangladesh, has reached a mature stage, requiring detailed geological and petrophysical re-evaluation to optimize future exploration and development strategies. This study characterizes the gas-bearing reservoirs and evaluates hydrocarbon reserves in the Kailashtila field through petrophysical analysis using geophysical well logs, 2D seismic data, and vertical seismic profiles. Three key gas sand intervals - upper, middle, and lower - were identified, exhibiting effective porosity between 13% and 28%, permeability ranging from 10 mD to 400 mD, and hydrocarbon saturation levels of 59% to 91%. Well-to-seismic correlation enabled the mapping of three major horizons, which were converted into depth structure maps using velocity data. Reserves were estimated using map based volumetric analysis using the reservoir top and gas water contact/lowest known depth of gas. The total estimated Gas Initially in Place (GIIP) is 2,552 BCF, with a recoverable reserve of 1,785.2 BCF, assuming a 70% recovery factor. The estimated reserves are higher than the previously estimated reserves. This underscores the importance of the integration of updated petrophysical modeling with more well data and improved data integration techniques. This study provides a framework for petrophysical analysis and reserve re-estimation and can be applied to similar gas fields in Bangladesh to ensure efficient and sustainable hydrocarbon production.</p>