The Albian - Turonian Sarvak Formation, the second major reservoir formation in south and southwest Iran is composed of mainly carbonate rocks. In this study, the upper part of Sarvak Formation in Siri Oil Fields was studied to determine facies, depositional environments, diagenetic processes and sequence stratigraphy analysis. The facies analysis led to the recognition of 12 microfacies in 5 facies associations, which deposited in a homoclinal carbonate ramp environment. The main diagenetic processes affected carbonates of this formation are bioturbation, micritization, cementation, dissolution, dolomitization, stylolitization, pyritization and fracturing. The most important cements in this formation are fine equant calcite cement, drusy mosaic calcite cement, coarse blocky calcite cement and syntaxial calcite overgrowth cement. Three third order sequences recognized in sequence stratigraphic studies for the upper part of Sarvak Formation taking into account of facies and diagenetic events in a sequence stratigraphic framework.