Non-linear relationships for shale volume estimation are designed for a specific area or formation age and most of the time they are optimistic in calculating low shale volume. This study evaluates some petrophysical properties of Late Paleozoic Kati Formation in Seri Iskandar area based on well logs and core plug samples from well CTW-01 drilled within University Teknologi PETRONAS campus. Shale volume is calculated using gamma ray log and calibrated with that obtained by sedimentation method in the lab. Porosity is determined from sonic log and calibrated with that measured in lab using Helium Porosimeter on core plugs. The shale volume equation derived from the lab analysis and well log data is Vsh = 1.0157 (IGR) - 0.0158 and achieved a correlation coefficient, R2, greater than 0.99. Shale volumes estimated from GR log using this model are in good agreement with laboratory measurements. Since the porosity is ranging between 0.5 and 2, the reservoir rocks of the study interval are classified as tight sandstones. © Published under licence by IOP Publishing Ltd.