3D seismic acoustic impedance inversion was performed for a Permo-Carboniferous sandstone reservoir interval based on limited well control. The impedance volume was then depth converted and used to target development well locations. The drilling campaign yielded mixed results; some areas of the field showed a high correlation between impedance computed from the wells and that derived from seismic, and other areas showed a low correlation. This difference in correlation presented a challenge when using the impedance model to condition the porosity model. Changes to the impedance volume would be needed in areas of low confidence in the seismic data. To address this problem, the depth-converted impedance volume was rebuilt using a 3D intensity function. This technique assigns appropriate weights to the seismic data in different areas of the field, based on confidence in the seismic data quality. Using this technique produced a more realistic porosity model, when conditioned by the revised impedance model. The subsequent construction of an object-based facies model also used intensity functions to locate seed positions of the sand dune objects, which were then tied to specific impedance ranges in the updated impedance model. Paleosol and sheet-sand facies, unrestricted to specific porosity ranges, were constructed separately using probabilities of occurrence from each well. The separate models were then merged together to produce the final facies model.