Petrography, sedimentary environment, and sequence stratigraphy of Tale-Zang oilfield in Southwest Iran. (English)

In order to study microfacies, diagenetic processes, sedimentary environment, and sequence stratigraphy of the Tele Zang Formation in the Lab Sefid oil field, two wells (No. 1 and 5) were analyzed. Based on the study of 250 thin sections prepared from cuttings, 8 microfacies were identified and deposited in an homoclinal carbonate ramp. On a larger scale and considering the stratigraphic equivalence of the Paleocene-Eocene sediments in the studied area, a carbonate shelf sedimentary environment can also be proposed for the Tele Zang Formation. The major diagenesis processes that have affected the Tel Zang Formation include micritization, neomorphism, dolomitization, dissolution, cementation, compaction, pyritization, hematitization, and fracture. The identified diagenetic processes are the product of shallow marine to deep marine diagenesis. According to lithological changes, gamma log changes, and vertical changes of microfacies, the sequence stratigraphy of Tele Zang formation in well No. 1 of the studied field was evaluated, and one complete third depositional sequence was recognized. In well number 5, a typical third depositional sequence with Pabdeh Formation was detected, such that the closed sedimentary facies group TST is the pelagic facies of Pabdeh Formation with high gamma log values and low resistivity and the closed sedimentary facies group HST is thin to thick limestone layers of the formation. It includes bell traps with low log gamma values and medium to high resistivity. In general, the transgressive systems tract in the studied sequence is characterized by a slight increase in the log gamma value in the sequence, and a decrease or constant log gamma values characterize the highstand systems tract during the thickness of the segregated depositional sequence. The critical point about this systems tract is the equivalence of this systems tract with the increase of reservoir potential along the length of the reservoir. The expansion of the supporting grain facies affected by the depositional environment and diagenetic processes such as dissolution, dolomitization, and fractures is one factor in the high reservoir potential in the HST facies category. [ABSTRACT FROM AUTHOR]

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