Document Type : Original Research Paper
Authors
1 Faculty of Petroleum and Natural Gas Engineering, Sahand University of Technology, Tabriz, Iran
2 Department of Geology, National Iranian South Oil Company (NISOC), Ahwaz, Iran
Abstract
Objective of this study is to conduct a geochemical assessment over source candidates in the Garangan oilfield using Rock-Eval pyrolysis and vitrinite reflectance to identify factors contributing to the lack of hydrocarbon reserves in the Middle Cretaceous – Early Oligocene petroleum system. Furthermore, the impact of mineral matrix retention, inert organic material (OM) and maturity were examined, and the results were used to split TOC and S2 parameters into the oil-prone and gas-prone components. Based on results, Pabdeh formation is an immature rich source, exhibiting the highest levels of active OM. Unexpectedly, OM quantity for the Kazhdumi source rocks is fair, for which contribution from inert OM is substantial. Significant inert OM is also confirmed for the oil/gas-prone upper Dariyan shales and gas-prone Gadvan samples. These characteristics seem to be related to the activities of the Khark-Mish paleo-high during the Cretaceous. Moreover, the Cretaceous intervals show a maturity level equivalent to the preliminary stages of main oil generation phase. Finally, owing to the presence of high-quality reservoir and cap strata, the absence of economical reserves in the Asmari and Bangestan reservoirs of the oilfield is possibly related to mediocre OM quantity and quality, and insufficient maturity of the source candidates.
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