Detailed studies of sedimentology and petrology of oil fields, especially oil fields located in the seas, play avery important role in reducing the risk of danger, increasing harvest, and reducing the amount of environmentalpollution. The South Pars gas field in the waters of the Persian Gulf on the joint border line of Iran and Qatar andon the south coast of Iran has been used as a comprehensive model for this type of study. In these studies, thesedimentary environment and sequential stratigraphy of the Scorpion and Sarvak Formations in the South Parsgas field in wells 1 and 3 have been investigated. Microscopic studies and analysis of gamma-ray and acousticdiagrams of these formations have led to the identification of 9 facies in three facies belts related to wetland,dam, and open sea. Dam facies have been identified only in Sarvak formation. This study shows that the faciesbelts of the abovementioned formations in a ramp platform are also sloping. Sequence stratigraphy of Kazhdomiand Sarvak Formations in the study wells shows that Kazhdomi Formation has one sedimentary sequence (thirdcategory cycle) and Sarvak Formation has two sedimentary sequences. The lower boundaries of sequences 1 and2 and the upper boundary of sequence 3 have type 1 (SB1) discontinuities, and the boundary between sequences2 and 3 has type 2 (SB2) discontinuities.