The giant fields of the Zagros fold belt of southwestern Iran fall within the greater context of the Arabian-Iraq-Persian basin and contain cumulative recoverable reserves estimated at 87 billion barrels of oil and 514 trillion cubic feet of gas.

The regional geology of the area comprises a wedge of Paleozoic to Holocene sediments, 10-15 km (6-9 mi) or more in thickness, supported on a mobile Eocambrian salt economic basement. Forming a classic carbon-evaporite sequence, the succession contains prolific source-reservoir combinations and effective seals of integrity. Located on the eastern subducting boundary of the Arabian plate, hydrocarbon generation has been largely controlled by the Neogene Zagros orogenic event. A number of potential source sequences have been recognized. With one exception, all are typically of an organic-rich, argillaceous, lime-mudstone litho-textural type.

Most of the giant oil accumulations in Asmari (Oligocene-Miocene) and Bangestan Group (Upper Cretaceous) reservoirs have a common provenance in the Kazhdumi Formation of Early Cretaceous (Albian) age. The Pabdeh (Paleogene), lower Garau-Gadvan (Lower Cretaceous, Neocomian), and Sargelu (Middle Jurassic) formations contribute less to overall reserves, having been the source for selected subordinate Asmari, Bangestan, and Khami Group (Upper Jurassic-Lower Cretaceous) reservoirs only. Gas in Permian-Triassic reservoirs has a provenance in Ordovician-Silurian siliciclastics.

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