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Hydrocarbon volumetric calculation needs accurate petrophysical properties data to be populated across the field; they are porosity, net reservoir thickness and water/hydrocarbon saturation. Those properties usually are taken from the well log interpretation, and calibrated to core data to reduce the uncertainty. Porosity can be directly compared and calibrated to core measurement data, but water saturation needs to be predicted using saturation height function. The saturation height function required permeability data. Therefore, optimum saturation height function and accurate permeability determination are needed for hydrocarbon saturation calculation. There are many permeability equations ranging from the simple method of single porosity-permeability relationship to the complex equation using silt and clay volume. The simple method usually is not applicable for multi-well data since the permeability is not only functioned of porosity but also affected by other rock properties such as shale volume. On the other hand, complex method needs to use a sand-silt-clay model in the lithology interpretation, and this interpretation is not accurate in the gas reservoir since the density-neutron logs are affected by gas. Therefore, it is necessary to have a robust permeability equation which only requires simple input data and uncomplicated lithology interpretation. This study will propose new permeability equation, which only required simple input data and sand-shale lithology interpretation. The development of the permeability equation is based on Revil and Cathles clean sand equation, and the shale effect will be added as an exponent of the porosity. Two parameters will be available to control the relationship between shale volume and permeability. The result of the analysis shows that the permeability calculated using proposed equation have good matched with core data and permeability calculated using complex equation. After permeability has been calculated, water saturation can be estimated by using saturation height function. There are several saturation height functions available with different degree of freedom (variable). The equation with highest degree of freedom is expected to provide the best water saturation but also require additional work. Therefore, it is necessary to find the optimum saturation height function which can provide reasonably accurate water saturation with adequate effort. Three equations with different degree of freedom will be investigated by comparing their results to log derived water saturation. The study found that the equation with three degree of freedom is the optimum equation for Casino Field data. The proposed permeability equation and the optimum saturation height function need to be further evaluated using data set from other fields to confirm the finding of this study.