M. R. Kamali1 and M. R. Rezaee2

1 Research Institute of Petroleum Industry, NIOC, kamalim@ripi.ir

2 Tehran University, Faculty of Science, Geology Dept., mrezaee@khayam.ut.ac.ir

At the Kuh-e Mond anticline (Fars Province, SW Iran) and in nearby offshore structures, large volumes of natural gas are reservoired in the Permian -- Early Triassic Dehram Group while heavy oil has been discovered in the Cretaceous Sarvak and Eocene Jahrum Formations. In this paper, we use data from seven exploration wells and from nearby surface exposures to reconstruct the burial history of the Kuh-e Mond field. Regional observations show that the thick sedimentary fill in this part of the Zagros Basin was subjected to intense tectonism during the Zagros Orogeny, with a paroxysmal phase during the late Miocene and Pliocene. Thermal modelling and geochemical data from Kuh-e Mond and adjacent fields allows possible hydrocarbon generation and migration mechanisms to be identified. Maturities predicted using Lopatinís TTI model are in accordance with maturities obtained from vitrinite reflectance measurements.

We show that formations which have source potential in the nearby Dezful Embayment (including the Pabdeh, Gurpi, Gadvan and Kazhdumi Formations) have not reached the oil window in the Mond wells. Moreover, their organic carbon content is very low as they were deposited in oxic, shallow-water settings. Underlying units (including the Ordovician and Cambrian) could have reached the gas window but contain little organic matter. Silurian shales (Sarchahan Formation), which generate gas at Kuh-e Gahkum and Kuh-e Faraghan (north of Bandar Abbas) and in Saudi Arabia and elsewhere in the Middle East, are absent from the Mond structure.

The absence of source rocks suggests that the gas and heavy oil accumulations at Kuh-e Mond and at nearby fields have most probably undergone long-distance lateral migration from distant source kitchens.

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