Hydrocarbon Vertical Continuity Evaluation in the Cretaceous Reservoirs of Azadegan Oilfield, Southwest of Iran: Implications for Reservoir Geochemistry

Abstract

A collection of data obtained from analytical methods in geochemistry along with the reservoir engineering and geologic data were used to investigate the reservoir continuity in the Cretaceous Fahliyan, Gadavan, Kazhdumi and Sarvak reservoirs of the super‐giant Azadegan oilfield, SW Iran. The geochemical data indicate that the oil samples, with medium to high level of thermal maturity, have been generated from the anoxic marine marl/carbonate source rock(s). The Sargelu (Jurassic) and Garau (Cretaceous) formations are introduced as the main source rocks for the studied oils. The dendrogram obtained from the cluster analysis of high‐resolution gas chromatography data introduces two main oil groups including Fahliyan reservoir, and Kazhdumi along with Sarvak/Gadvan reservoirs. This is confirmed by C7 Halpern star diagram, indicating that, the light oil fraction from Fahliyan reservoir is distinct from the others. Also, different pressure gradient of the Fahliyan Formation (over‐pressured) relative to other reservoirs (normally‐pressured) show the presence of compartments. The relation between toluene/n‐heptane and n‐heptane/methylcyclohexane represents the compartmentalization due to maturation/evaporative fractionation for Fahliyan and water washing for other studied reservoirs. Also, the impermeable upper part of the Fahliyan Formation and thin interbedded shaly layers in the Kazhdumi, Sarvak and Gadvan formations have controlled reservoir compartmentalization.

Petroleum Systems Analysis of the Eastern Arabian Plate: Chemometrics Based on a Review of the Geochemical Characteristics of Oils in Jurassic – Cenozoic Reservoirs

“…LMW hydrocarbon data for samples from the Azadegan and Foroozan oil fields (AZ and FR, Fig. 1; Hassanzadeh et al, 2018;Alizadeh et al, 2020b) point to even higher thermal maturities.…”

“…Data for oils from the Dezful Embayment, SW Iran, was compiled from Alizadeh et al (2007), Alizadeh et al (2012), Asadi Mehmandosti et al (2015, Ghorbani et al (2016), Alizadeh et al (2018aAlizadeh et al ( , 2018b, Sadouni and Rabbani (2018), Alizadeh et al (2020a), , and . Publications by Alizadeh et al (2016) and Alizadeh et al (2020b) as well as Kobraei et al (2019aand 2019b) and Asadi Mehmandoosti et al (2022 were used to compile a dataset for oils from the Abadan Plain, SW Iran. The dataset for oils from the Iranian sector of the Persian Gulf was from Rabbani et al (2014), Alizadeh et al (2017), Baniasad et al (2017), Hosseiny et al (2017) and Hassanzadeh et al (2018); and that for the Summan area in northeastern Saudi Arabia was from Arouri et al (2018).…”

“…Rabbani et al, 2014;El Diasty et al, 2016;Arouri et al, 2018) and at different oil fields (e.g. Al-Khafaji, 2015;Hassanzadeh et al, 2018;Alizadeh et al, 2020b), no regional study has previously been published at the scale of the entire eastern Arabian Plate. Such a regional geochemical study may help to elucidate the relationships between the discovered oils in different parts of this area and migration pathways from kitchen areas to reservoirs and traps.…”

Impacts of Depositional Facies and Diagenesis on Reservoir Quality: A Case Study from the Rudist‐bearing Sarvak Formation, Abadan Plain, SW Iran

“…The late Albian-early Turonian Sarvak Formation is the second most important oil reservoir in the Zagros Basin of Iran (James and Wynd, 1965;Al-Husseini, 2007). This formation and its equivalent units in the Arabian Plate, i.e., the Mauddud, Ahmadi, Rumaila, Khatiyah, Mishrif and Natih formations, have been extensively studied from different geological and petrophysical aspects including facies analysis and depositional environment (van Buchem et al, 2002;Sadooni, 2005;Ghabeishavi et al, 2010;Hajikazemi et al, 2010;Rahimpour-Bonab et al, 2012;Mahdi et al, 2013;Assadi et al, 2016;Mahdi and Aqrawi 2018;Gholami Zadeh et al, 2019;Mehrabi et al, 2020;Bagherpour et al, 2021), biostratigraphy (Omidvar et al, 2014;Navidtalab et al, 2019;Mohajer et al, 2021), diagenesis and geochemistry interpretation (Hajikazemi et al, 2010(Hajikazemi et al, , 2017Hollis, 2011;Vincent et al, 2015;Navidtalab et al, 2016;de Periere et al, 2017;Boschetti et al, 2020), organic geochemistry (Hosseiny et al, 2016(Hosseiny et al, , 2017Alizadeh et al, 2020) sequence stratigraphy (Taghavi et al, 2006;Razin et al, 2010;Sharp et al, 2010;Aqrawi, 2014, 2018;Assadi et al, 2016;Kadkhodaie and Rezaee, 2017;Mohseni and Javanmard, 2020), fracturing (Kosari et al, 2017;Ezati et al, 2018), and reservoir characterization and rock typing…”