Fahliyan Formation Research Articles

Microfacies and Sedimentary Environments of the Fahliyan Formation from the Southwest of Iran (Shiraz, Zagros)

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.

Sedimentological Studies and Reservoir Potential of the Fahliyan Formation in the Marun Oil Field, North Dezful Embayment, Zagros Basin, Southwest Iran

Considering all different formations in Zagros Basin, the Cretaceous column has a remarkable position. Fahliyan Carbonate Formation with the age of Neocomian (Lower Cretaceous) is a main reservoir of Khami Group and is extended in whole Zagros Basin. Considering Fahliyan performance as a high-quality reservoir and Marun Oil Field as one of the top biggest oil fields in Dezful Embayment, southwest Iran, a detailed study looked quite necessary in this area. This research was mainly done based on petrographic methods. Moreover, well logs were used as a subsidiary tool to assess the reservoir potential of microfacies. After recognition of microfacies and evaluation of lateral and vertical variations (using Walter's law), the depositional model of Fahliyan Formation was proposed. At the final stage, compartments with more reservoir potential were proposed. Generally speaking, the main tasks done through this study are study of different kinds of microfacies, study of diagenetic processes, study of depositional environment, and assessment of microfacies with reservoir potential using thin sections and well logs.

Determination of a rock physics model for the carbonate Fahliyan Formation in two oil wells in southwestern Iran

Geophysical methods, especially seismic inversion, have improved considerably in recent years. The prediction of elastic behaviour is important to decrease risk in mining operations. The investigation of rock physics is a way to predict rock behaviours, especially reservoir geomechanical parameters. The first step in rock physics studies is to diagnose and introduce a suitable rock physics model. In this paper, we review rock physics models, such as the Rymer–Greenberg–Castagna model, and we compare them with real data trends in two oil wells of a carbonate reservoir (the Fahliyan Formation) in the Zagros Basin of southwestern Iran using sonic, density and porosity logs. After omitting the effect of water saturation and clay content, the best model for clean carbonate of the Fahliyan Formation was developed in two oil wells (A1 and A2).

Application of the spectral decomposition technique for characterizing reservoir extensional system in the Abadan Plain, southwestern Iran

The Abadan plain in southwestern Iran has important petroleum reservoir potential but poorly defined structural setting. It is located at the Mesopotamian foredeep basin, bounded by the Arabian plate and the Dezful Embayment. The main reservoir in this field is the Fahliyan formation, composed of reef carbonates. Most of the Abadan area is flat and covered by recent alluvial deposits with no outcrops. Studies of the structures in this area have provided information about the structural history and allowed better reservoir and drilling management. Seismic spectral decomposition techniques have been utilized as a quick and effective interpretation tool. Fast Fourier transform (FFT) and continuous wavelet transforms (CWT) have been used to convert time to frequency domain, and have been applied to detect fault systems in the reservoir. Application of the Fast Fourier transform (FFT) and continuous wavelet transforms (CWT) indicate that the Abadan reservoir consists normal extensional system of the reservoir which display paralleling of contour common depth in two sides of extensional system in some regions and large displacement between two sides of contours indicate that system is normal in which hanging wall moved over footwall. Various displacements between sides indicate parallel strike-slip movements which are associated with reverse faulting and inversion tectonics.

Facies characteristic and paleoenvironmental reconstruction of the Fahliyan Formation, Lower Cretaceous, in the Kuh-e Siah area, Zagros Basin, southern Iran

The Lower Cretaceous Fahliyan Formation, part of the Khami Group, unconformably overlies the Hith Formation and is conformably overlain by the Gadvan Formation in the study area in southern Iran. The Fahliyan Formation 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 Siah Anticline in Boushehr Province. Petrographic studies led to the recognition of 25 microfacies that were deposited in four facies belts: tidal flat, lagoon, and shoal in inner ramp and shallow open-marine in mid-ramp environment. An absence of turbidite deposits, reefal facies, and gradual facies changes indicate that the Fahliyan Formation was deposited on a carbonate ramp. Calcareous algae and benthic foraminifera are abundant in the shallow marine carbonates of the Fahliyan Formation. These skeletal grains have been studied in order to increase the understanding of their distributions in time and space. A total of ten genera belonging to different groups of calcareous algae and 16 genera of benthic foraminifera are recognized from the Fahliyan Formation at Kuh-e Siah section.

Depositional environment, sequence stratigraphy and geochemistry of Lower Cretaceous carbonates (Fahliyan Formation), south-west Iran

The Fahliyan Formation is a carbonate sequence of Lower Cretaceous (Berriasian–Hauterivian) age and was deposited in the Zagros sedimentary basin, Iran. In this investigation, the Fahliyan Formation at the type section and in the subsurface has been studied. Facies analysis and petrographic studies led to the recognition of 10 microfacies that were deposited in three facies belts: lagoon, shoal and open marine. The observed facies patterns indicate a carbonate rimmed-shelf depositional environment. Based on field observations, microfacies analysis and sequence stratigraphic concepts, two-third-order sequences in the type section and three-third-order sequences in the subsurface section were identified. The transgressive deposits display a predominance of deep subtidal facies, while highstand deposits show shallow subtidal facies. Some petrographic evidence such as an abundance of aragonite skeletal and non-skeletal components shows that this formation was deposited in a sub-tropical environment with original aragonite mineralogy. Geochemical evidence such as high Sr/Na ratios also support original aragonite mineralogy. δ 18O and δ 13C values suggests that alteration occurred during burial diagenesis, in a closed system, with low water/rock interaction. Palaeotemperature calculation, based on the heaviest oxygen isotope value in micritic samples of the Fahliyan limestone, shows that ambient water temperature was around 24 °C during the deposition of this formation.

Calcareous algae, foraminifera and sequence stratigraphy of the Fahliyan Formation at Kuh-e-Surmeh (Zagros Basin, SW of Iran)

Palaeontological, environmental and sequence stratigraphic studies were carried out on the shallow carbonate platform facies of the Berriasian – Hauterivian, Fahliyan Formation and the lower part of the Gadvan Formation, at Kuh-e-Surmeh. The studies were based on calcareous green algae (mainly Dasycladales) and accompanying benthic foraminifera, focusing on revision of the considerable, pioneering work of GOLLESTANEH (1965, 1979), initially undertaken on behalf of the National Iranian Oil Company (NIOC). Thirty two species of calcareous green algae and thirty four species of benthic foraminifera were identified from the Fahliyan Formation and from the lower part of the Gadvan Formation. A number of the recognized calcareous green algae were previously given different names by other authors working in SW Iran. Additional taxa were also recorded for the first time in the Zagros basin, including Clypeina dragastani, C. estevezii, C. solkani, C. parasolkani, Holosporella arabica, Otternstella lemmensis, Salpingoporella circassa, S. istriana and S. katzeri. Salpingoporella circassa is quite common and apparently recorded for the first time from Southern Tethys. Also Salpingoporella ? inopinata n. sp., (originally named Iranella inopinata by GOLLESTANEH, a nomen nudum) appears to be quite common in the Fahliyan Formation, although apparently endemic to SW Iran. Three main depositional environments were recognized based on the faunal/floral association, lithological and sedimentological characteristics: inner ramp/restricted platform, mid ramp/margin to open platform, and outer ramp/platform slope, with water depths ranging from about 5m to 20m, rarely reaching 40m. Facies changes facilitated the recognition of three large scale sequences throughout the studied succession, bringing interesting relationships with the sequence bundles identified in the Arabian Plate.

THERMAL HISTORY RECONSTRUCTION IN THE SOROOSH AND NOWROOZ FIELDS, PERSIAN GULF, BASED ON APATITE FISSION TRACK ANALYSIS AND VITRINITE REFLECTANCE DATA

The thermal history of the sedimentary successions at the Soroosh‐17, Soroosh‐02 and Nowrooz‐16 wells in the northern Persian Gulf have been studied using apatite fission track analysis and vitrinite reflectance data. These data were used to identify and quantify episodes of heating and cooling which have affected the sections penetrated by these wells. This information was synthesised to provide a thermal history framework for the wells, within which the history of hydrocarbon generation, as well as regional structural development, can be understood. Preliminary hydrocarbon generation histories are presented for the Soroosh and Nowrooz oilfields and nearby areas.Modelling of hydrocarbon generation histories based on the AFTA‐ and VR‐derived thermal histories, assuming a dominant Type III kerogen for possible Albian Kazhdumi Formation source rocks and a dominant Type II kerogen for possible Neocomian Fahliyan (Lower Ratawi) Formation source rock, suggest that local sourcing of oil from the Kazhdumi Formation is unlikely. The most likely source rock for oil in the Burgan Formation reservoir at Soroosh‐17 and Nowrooz‐16 is interpreted to be the Fahliyan Formation based on the available data. On the other hand, speculative modelling of the Hendijan‐I well down‐dip from the Nowrooz field does allow some oil to be generated from the Kazhdumi sequence at that location, and this might be available for migration to the Nowrooz field.