The Upper Jurrasic Arab Formation in the Satah Field is composed of two major rock units, i.e. shallow marine carbonates and cyclic carbonates-anhydrite sequence. The former is defined as the Arab D zone, while the latter is divided into three zones, i.e. Arab A, B and C in descending order. The Arab C and D zones comprise hydrocarbon bearing formations in the field.

The Arab D reservoir is characterized by upward shallowing sequence. Its lower and middle portions are dominated by mud supported facies deposited on a shallow shelf, while its upper part is composed of various lithology types resulting from upward shallowing system. Total eight lithology types were identified within the Arab D reservoir. The petrophysical characteristics of the Arab D sequence is determined by the original sedimentary fabrics and by various diagenetic processes. Leaching and dolomitization can enhance both porosity and permeability, whereas bitumen fills associated with paleo O.W.C. and matrix cementation related to paleo acquifer reduce the reservoir quality. In general, below "Bitumen Mat" both porosity and permeability deteriorate rapidly. In other word, the Arab D reservoir is considered to be bottom sealed reservoir. According to the lithological and petrophysical variations, the Arab D reservoir was subdivided into fifteen reservoir layers.

On the other hand, the Arab C zone is made up of alternated carbonates and anhydrite and was accumulated under the various depositional environments ranging from supratidal-sabkha to subtidal conditions. The carbonates are dominated by grain-supported facies and divided into six lithology types. The original fabrics of the sediments play an important role on the reservoir quality, as well as several diagenetic events. Good reservoir characteristics are distributed where the secondary pores by leaching and dolomitization are connected with the primary pore networks. Major porosity reduction as observed in the Arab D reservoir is not recognized.

Such geological analysis is considered to be not only essential but helpful for the reservoir layering scheme and simulation study.

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