We recently introduced new petrophysical and compositional methods for joint interpretation of multiple conventional well logs. These inversion-based methods are suited for petrophysical interpretation of rock formations that exhibit complex solid composition, include thin beds, and are subject to mud-filtrate invasion. They combine nuclear and resistivity logs to assess porosity and volumetric/weight concentrations of mineral and fluid constituents, and are ideal for the quantitative interpretation of carbonate formations. We document the successful application of the newly introduced inversion-based interpretation methods to three carbonate formations. Interpretation results are compared to those obtained with commercial software and core/X-ray diffraction (XRD) data whenever available. For two of the carbonate field examples where XRD data are available, nonlinear joint inversion of well logs improves the assessment of porosity by more than 30% and up to 100% in the presence of thin beds when compared to conventional interpretation methods.