Microfacies and sedimentary environments of Dalan Formation at Surmeh Mountain, Folded Zagros Zone, southwestern Iran (original) (raw)
Related papers
Gadvan and Darian formations are in the upper part of Khami group that has been deposited in the highland Zagros zone and the southern Margin of Neotethys. These formations outcrop in the south of Semirom (Agh-Dagh Mountain) consist of Orbi-tolina limestones and marly limestones with a Late Barremian-Aptian age and thickness of 520 meters. Based on field characteristics, petrographic and texture of facies, these rocks consist of Oregonian facies (Urgonian facies) with 12 carbonate microfa-cies which are deposited in Lagoon, barrier and shallow open marine. The absence of loss and flows of turbidities indicates that carbonate platform of Gadvan and Darian formations in the studied area are (Hmoklinal) platform type. Abundance of rudist (bivalves) and Peloid markers show that there is a Photozoan collection in tropical climates. In the above sedimentary succession, from a sequence stratigraphic perspective , three sedimentary cycles were recognized which deposited in a platform model. The Gadvan Formation overlies on Fahliyan Formation disconformable and is covered by Darian Formation gradual with reducing the amount of marl and increase of limestone. The Kazhdumi Formation is exposed disconformably with he-matite nodules and oxidized sediments over the Darian Formation. On the basis of petrographic studies, diagenetic process of Gadvan and Darian formations in the study area includes cementation, the physical and chemical density and replacement processes such as pyritation, ironies and silica. Porosity observed in the study area is mainly inter-granular porosity type, modular and vaggy.
Open Journal of Geology, 2013
The Fahliyan Formation is a carbonate sequence of Lower Cretaceous (Berriasian-Hauterivian) in age and was deposited in the Zagros sedimentary basin. This formation is a part of Khami Group and is a reservoir rock in Zagros Basin. This formation was investigated by a detailed petrographic analysis in order to clarify the depositional facies and sedimentary environment in the Kuh-e-Gadvan in Fars Province. Petrographic studies led to the recognition of nine microfacies that were deposited in four facies belts: tidal flat, lagoon, and barrier and shallow open-marine. An absence of turbidite deposits, reefal facies, and gradual facies changes indicate that the Fahliyan Formation was deposited on a carbonate ramp.
Open Journal of Geology, 2016
Dalan Formation is one of the most important gas reservoirs of south and southwest Iran which it belongs to Dehram Group and its age is Middle to Late Permian. The Dalan formation is interpreted as reflecting a major tectono-eustatic event related to the onset of rapid thermal subsidence of the early Neo-Tethys passive margin in Arabia and Iran, and the drowning of its rift shoulders. The Dalan formation consists mainly of medium to thick-bedded oolitic to micritic shallow-marine carbonate, with intercalations of evaporates. This formation overlies the Faraghan formation and extends up into the Lower Triassic kangan formation. The current paper is focused on the facies, sedimentary environment and sequence Stratigraphy study of the Middle to Upper Permian Dalan formation in the West Assaluyeh gas field the subsurface section of well ASL-A. Based on microfacies analysis and significant founa and flora, nineteen major facies in five facies associations including Tidal flat (A), Lagoon (B), Shoal (C), Open marine (D) and Mid ramp (E) were recognized in the Dalan formation. Facies analysis and those comparisons with modern and ancient environments indicated that the Dalan formation was deposited inner to mid parts of a homoclinal ramp. The sequence stratigraphy studies on the Dalan formation in this gas field led to assessment of seven main sedimentary sequences of the third-order in the Assaluyeh field, well ASL-A. The boundary between the third-order sequences with the Faraghan formation and between the Nar and Upper Dalan members are Subaerial Unconformity (SU) and the boundaries between the third-order sequences with each other and also with the Kangan formation are Correlative Conformity (CC). The main diagenetic processes in this formation are dolomitization, dissolution, anhydritization, cementation and compaction which played a significant role in improving reservoir quality. The shoal ooid grainstone facies with intergranular and oomoldic porosity * Corresponding author. N. Rezavand et al. 945 comprise the main reservoir facies of the Dalan formation.
Himalayan Geology
The Fahliyan and Gadvan formationsof Lower Cretaceous age (Neocomian-Early Aptian) exposed on Kuh-e-Surmeh section were studied in order to evaluate microfacies, depositional environment and sequence stratigraphy. Petrographic study led to recognition of 18 microfacies deposited in five subenvironment : pelagic, hemipelagic, middle shelf, inner shelf, coastal plain. Sequence stratigraphy assessment of these deposits revealed three depositional sequence of third order of which the two lower ones belong to the Fahliyan Formation and the third one related to the Gadvan Formation. Except for the lower boundary of the sequence, the other boundaries are type 2
GeoArabia, 2007
The late Oligocene-early Miocene Qom Formation in the Central Iran Basin contains oil and gas in the Alborz and Sarajeh fields. Organic geochemical analyses in previous studies indicated that the hydrocarbons migrated from deeper source rocks, likely of Jurassic age. In the Central Iran Basin, the Qom Formation is 1,200 m thick and is bounded by the Oligocene Lower Red Formation and the middle Miocene Upper Red Formation. In previous studies, the Qom Formation was divided into nine members designated from oldest to youngest: a, b, c 1 to c 4 , d, e and f, of which "e" is 300 m thick and constitutes the main reservoir. Our study focused on a Qom section located in the Gooreh Berenji region of central Iran which is 294 m thick. The lower part of the formation was not deposited, and only the following four members of early Miocene age (Aquitanian and Burdigalian) were identified between the Lower and Upper Red formations: "c 2 "? (mainly greyish to greenish gypsiferous marls); "d" (thin-to thick-bedded anhydrite with intercalation of thin-bedded sandstone); "e" (argillaceous or sandy limestone); and "f" (fine-grained coral and bryozoan boundstone). In contrast to the Central Iran Basin, the "e" member in Gooreh Berenji is only 15 m thick and does not have a good reservoir potential. A detailed petrographic analysis of the Gooreh Berenji section resulted in the identification of 13 microfacies (MF) that were interpreted in terms of their depositional environments according to the following categories: MF1 (sabkha), MF2 (intertidal river channel), MF3 (lower intertidal), MF4 (peritidal), MF5 (supratidal), MF6 and MF7 (shallow restricted lagoon), MF8 and MF10 (proximal open-marine), MF9 (leeward lagoon), MF11 (shoal), MF12 (reef and patch reef formed within lagoon), and MF13 (open-marine). The Qom Formation constitutes a regional transgressive-regressive sequence that is bounded by two continental units (Lower and Upper Red formations). The transgression started from the south in the late Oligocene and by the early Miocene the sea covered all of central Iran. In the Gooreh Berenji area, carbonate deposition occurred on a shallow-marine ramp. The presence of a wide range of lagoonal facies indicates that reefal facies ("f") developed in a narrow elongated strip away from the shoreline.
Iranian Journal of Earth Sciences, 2018
In the present research Kuh-e Siah Section in the Northeast of Shiraz in the Interior Fars, was investigated to study microfacies, sequence stratigraphy, facies analysis and sedimentary environment of Fahliyan Formation. Generally, 345 meters of these sediments were studied by investigating 240 thin sections. In this study, the indicator microfacies were accurately identified which include Mudstone, Wackestone, Packstone and Grainstone. Besides, skeletal and non-skeletal grains of these microfacies are Intraclast, Bioclast, Exteraclast and Peloid. According to lithostratigraphic study, underneath limit of Fahliyan Formation with the Surmeh Formation and its upper contact with Gadvan Formation were in the gradual form (SB2) and included (TST-LST-Early HST-Late HST) system tracts. In general, there were two second-degree sequences in this section., According to the analysis of the sedimentary environment, the The lowermost of the Fahliyan Formaion is comprised of the Inner shelf depos...
Journal of …, 2009
Sarvak Formation, a thick carbonate succession with the age of Middle Cretaceous, is one of the most significant hydrocarbon reservoirs in the Zagros basin. The Tang-e Solak section of the Sarvak Formation in the Bangestan anticline with a total thickness of about 850 m has been studied, in order to determinate its microfacies types, depositional setting model and depositional sequences. Detailed textural and petrographic analysis led to the identification of 11 microfacies that arranged in three facies associations: inner ramp, mid-ramp, outer ramp and basin. Examination of vertical and lateral facies changes indicated these sediments were deposited in a carbonate ramp depositional system. Frequency analysis of facies indicated outer ramp and basin facies associations are the most frequent facies. Sea level fluctuations during in deposition of Sarvak successions led to formation of two depositional sequences. These depositional sequences are composed of transgressive systems tract and highstand systems tract. The highstand systems tract can be separated into Early HST and Late HST. Stacking pattern in Early HST part is aggradational and in Late HST is progradational.
In the present study the Pabdeh Formation (late Paleocene-early Oligocene) was investigated in the Zagros Basin (W Iran). The main goal of this research was elucidating the depositional environments of this formation. This research was performed based on field observations and measurements, thin section petrography, trace fossil studies and OM (TOC % and kerogen type) measurements, from which seven microfacies assemblages were recognized. The Pabdeh Formation comprises alternation of thin to thick limestones and dark to light gray shale beds, rich in planktonic microfauna. These facies are interpreted as pelagic facies in the Zagros Basin and consist of mudstone (md), wackestone (wk), packstone (pk) and shale beds. Based on systematic study of the ichnofossil content of these facies, five ichnogenera grouped in two separate assemblages were recognized. The first assemblage present a relatively high ichnodiversity (Arenicolites, Chondrites, Planolites and Neonerites) and occurs in md-wk-pk facies. This assemblage represents the Cruziana ichnofacies, formed in relatively moderate-energy conditions. The second assemblage with lower ichnodiversity (Zoophycos and Chondrites) is found in shale, wk, md and pk beds and represents the Zoophycos ichnofacies which were formed in low energy and deeper conditions. Vertical stacking of these facies suggest a shallowing-up ward trend with these facies deposited in a distally steepend carbonate ramp, where the depositional settings evolved from an outer ramp with pelagic and turbidite facies (Microfacies 4B and 4C) and reducing condition to oxygen depleted waters (TOC> 2.5%; kerogens type , and less amount ) that gradually changed into a middle ramp where marine currents (e.g. turbidity currents) had an important impact on sediment reworking and resedimentation.
Reservoir facies controlling factors in the Upper Permian Dalan Formation, SW Iran
The Upper Permian Dalan Formation is an economically significant gas and condensate reservoir in the Fars region of southwest Iran. It is composed mainly of limestone and dolostone. Facies analyses, depositional environments and diagenetic processes of the Dalan Formation at eight drilled wells and reference section at the Surmeh anticline were studied. Field and petrographic studies combined with wireline well logs analyses and available seismic images resulted in recognition of various carbonate facies related to tidal flat, lagoon, shoal, basinal facies tracts, siliciclastic and evaporitic facies deposited on a carbonate ramp. Petrographic investigations and facies analyses of the Dalan Formation, led to the recognition of aragonite mineralogy and diagenetic environments of the Dalan Formation, which resulted in recognition of controlling factors of reservoir facies. Grainstone facies deposited on paleohighs have marine cements with isopachous and fibrous fabrics, which leaching of grains created porous intervals. On the other hand, grainstone facies deposited in places with lower palaeogeographic positions, not only show limited distribution but also have been affected much more by deep burial cements and diagenetic processes, which resulted in loosing their reservoir properties. This study suggests that paleohighs had played main role in the diagenetic sequences and reservoir facies distribution.