Abstract:This paper introduces petrophysical evaluation on multi-layers sandstone reservoirs in GU area by logging data QC and data preprocessing, multi-mineral model selection, saturation model selection and cutoff determination. Actual data analysis suggests that cross-plots and frequency graphs are very useful in data QC and cutoff determination. Dues to lack of core analyzed saturation data in the work area, in this paper we focus on the comparison between the water saturation calculated by resistivity model and that derived by J-function. Based on the universally-adopted workflow of thickness division, the thicknesses of gross sand, net sand and net pay are reasonably divided using cutoff of clay volume, porosity and water saturation.