Petroleum geochemistry of the Albian-Turonian Sarvak reservoir in one of the Oil fields of Southwest Iran

Document Type: Research Paper

Authors

1 School of Geology, College of Science, University of Tehran, Tehran, Iran

2 Institute of Petroleum Engineering (IPE), Petroleum Engineering Dept. School of Chemical Engineering, Univeristy of Tehran

3 School of Geology, College of Science, University of Tehran, Iran

10.22078/jpst.2020.4094.1662

Abstract

Organic geochemical investigations using thin layer chromatography (TLC-FID), Gas Chromatography (GC), Gas Chromatography-Mass Spectrometer (GC-MS), API gravimetry, elemental analysis and isotope-ratio mass spectrometry (IR-MS) were carried out on eleven oil samples from the Albian-Turonian Sarvak reservoir in Abadan plain (SW Iran). Determination of oil chemical composition, source, thermal maturity, age, lithology and depositional environment of the source rock of these oils are main purpose of this study. Sarvak oils are mainly naphthenic and paraffinic type with an API degree between 16.2 and 20.14 and also, the sulfur content about of 4.6% which indicate heavy and sulfur-rich oil. The results of the study biomarkers, stable carbon isotope composition, trace elements, aromatic and sulfur content indicated that all oil samples related to a marine-carbonate source rock with strongly anoxic conditions. According to the absence of oleanane in all oil samples, variation of Pr/Ph against the carbon isotope ratio (δ13C) of whole oil, also C28/C29 steranes against geological age, it is proved that these oils related to older than the upper Cretaceous. Distribution of n-paraffins, calculation of Rc (%) from aromatic compounds, CPI (Carbon Preference Index) from gas chromatograms and index maturity biomarkers indicated that the Sarvak oils are mature. Although the Sarvak oils are heavy, these indicate approximately high level of thermal maturation that this represents a challenge in this study. We guess that the high sulfur content, low API° in the Sarvak reservoir oils are due to the presence of sulfur-rich organic matter (type IIS kerogen) in the source rock

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