Burial History Reconstruction and Thermal Modelling at Kuh-E Mond, SW Iran.

Abstract

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 DehramGroup while heavy oil has been discovered in the Cretaceous Sarvak and Eocene JahrumFormations. In this paper, we use data from six exploration wells and from nearby surfaceexposures to reconstruct the burial history at Kuh-e Mond. Regional observations showthat the thick sedimentary fill in this part of the Zagros Basin was subjected to intensetectonism during the Zagros Orogeny, with a paroxysmal phase during the late Mioceneand Pliocene. Thermal modelling and geochemical data from Kuh-e Mond and adjacentfields allows possible hydrocarbon generation and migration mechanisms to be identified.Maturities predicted using Lopatin?s TTI model are in accordance with maturities obtainedfrom 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 theoil window in the Mond wells. Moreover, their organic carbon content is very low as theywere deposited in oxic, shallow-water settings. Underlying units (including the Ordovicianand Cambrian) could have reached the gas window but contain little organic matter.Silurian shales (Sarchahan Formation), which generate gas at Kuh-e Gahkum andKuh-e Faraghan (north of Bandar Abbas) and in Saudi Arabia and elsewhere in theMiddle East, are absent from the Mond structure.The absence of source rocks suggests that the gas and heavy oil accumulations at Kuh-eMond and at nearby fields have most probably undergone long-distance lateral migrationfrom distant source kitchens.