To estimate elastic moduli is a challenging task in carbonates due to their complex pore structures in developing the rock physics models. In this study, Fahliyan carbonate formation in an Iranian oil field within Abadan plain is considered to quantify pore shapes using the rock physics model. In this modeling, the aspect ratios of different pore shapes and their volume fractions are calculated using differential effective medium (DEM) theory, taking into account the pore shape effect on the elastic moduli estimation. Different pore shapes together with their aspect ratios and volume fractions are quantified using DEM theory and then used further to predict elastics logs by Xu-Payne modeling. The results indicate that two pore types of reference pores and stiff pores can be characterized as the main pores in Fahliyan carbonate formation, a conclusion that is confirmed by FMI log and core information.