Modeling initial water saturation in transition zones in Carbonate has been a long lasting challenge particularly in heterogeneous reservoirs. The variation of water saturation has a considerable impact on initial volumes estimation, oil recovery prediction as well as the design of field development plans.Log-derived saturation can suffer from interpretation uncertainties particularly in the transition zone associated with the lack of knowledge of Archie exponents and especially n variability related to wettability. Moreover in the transition zone True Formation Resistivity ("Rt") evaluation presents a wide range of uncertainties as Laterolog and Induction Log domains overlap. Therefore there is a strong need for an independent source of water saturation profile.Mercury Injection Capillary Pressure (MICP), Porous Plate and Oil-Displacing-Brine Capillary Pressure measurements on core samples, at reservoir conditions, are used for building a reliable saturation profile for different rock types. In this paper the reconciliation process of water saturation from revised log analysis, laboratory measurements and Water Oil Contact takes into account the uncertainties on each source of data acquisition.The proposed methodology has been applied to a giant carbonate reservoir in Abu Dhabi and has improved the robustness of the water saturation evaluation in the transition zone. Production data are in a good agreement which supports the consistency of the methodology.