[en] A field study of a gas-bearing shaly sandstone is presented. Based on the log response a range in shale types can be observed just above the formation. Using the density, neutron, acoustic and gamma ray logs a shale type has been determined for each layer separately in the reservoir. Five distinct shale points resulted. The procedure of using five shale points instead of one yields more accurate values of the reservoir properties. The calculated lithology, porosity and shale volume gave an improved correlation with the core data. The hydrocarbon saturation decreased with about 10% compared to the evaluation with one average shale type