Sixty-three orogenically controlled oil and gas fields, mostly giant, multi-reservoir accumulations producing from fractured carbonate pay zones ranging in age from Permo-Triassic to Oligo-Miocene. The most prolific oil-producing zones are the Asmari Formation (Oligo-Miocene) and the Bangestan Group (Upper Cretaceous). The available geochemical evidence indicates that the major source of the oil is the underlying Albian Kazhdumi Formation. The Kazhdumi source rock was not buried to the depth required for hydrocarbon generation until the Eocene; no significant oil expulsion took place until the Miocene. Entry of oil into the reservoirs postdates the late Miocene-Holocene Zagros orogeny that resulted in the formation of the present structural traps. Development of growth structures during the Late Cretaceous and Paleogene could have contributed to some hydrocarbon localization prior to the formation of the late Tertiary traps.--Modified journal abstract.

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