The upper part of Surmeh Formation (Arab Member) with the Late Jurassic age, is the oldest Formation of Khami Group. In this study, Biostratigraphy and Depositional environments of Arab Member of the Surmeh Formation in well #2 in Balal oil field have been studied. Lithology of Arab Member in this studied section, with 96 meters thickness consists of Limestone, fine to medium crystal Dolomite, anhydrite layers of fine crystal.It is overline byHith Formation and overlying the Diayb Formation. According to the study of 200 thin sections of drill cutting ,Based on the assemblage of algal remains and also benthic foraminifera, 2 biozones were identified include of Clypeina jurassic Zone, Kurnubia Jurassica Interval Zone based of these biozones Arab Member is Late Jurassic number 12 Microfacies Supratidal,Intertidal, Lagoon and Schoal was detected. This indicates that the depositional Environment of the Arab Member of Surmeh Formation was carbonate ramp platform.

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