Mass density, due to its linear relationship with porosity, has long been recognized as a potential seismic indicator of fluid saturation. Given its dependence on mineral composition, density can also be diagnostic for lithology. In this paper we discuss some key aspects of a wide-angle processing and density inversion workflow, and apply it to a bitumen reservoir in Canada for imaging reservoir heterogeneities, such as shales, that can potentially act as permeability baffles. In this field, intrareservoir shales typically have higher densities than surrounding reservoir sands. This wide-angle workflow yields stable density estimates, from reflected P-waves alone, at a resolution suitable for mapping the intrareservoir shales.