关键词: 扎格罗斯前陆盆地, 大油气田, 含油气系统, 形成条件, 分布特征

Abstract: Oil and gas resources are rich in Zagros Foreland Basin. The research on giant oil and gas fi elds in Zagros Foreland Basin will enrich petroleum geology theory of foreland basins, and can also provide reference basis for oil and gas exploration in foreland basins. Based on the data of discovered 60 giant oil and gas fi elds in Zagros Foreland Basin, this paper applies the concept and analytical method of petroleum system, dissects giant oil and gas fi elds one by one, and probes into the formation and distribution of giant oil and gas fi elds in the basin. The study shows that the source rocks of giant oil and gas fi elds are Lower Silurian Gahkum Formation, Lower Cretaceous Garau Formation, Middle Cretaceous Kazhdumi Formation, Palaeocene and Eocene Pabdeh Formation. The reservoir rocks of giant oil and gas fi elds are limestone of Oligocene and Lower Miocene Asmari Formation, limestone of Middle Cretaceous Albian and Turonian Bangestan Group, limestone of Triassic Dashtak Formation and Kangan Formation, and limestone of Permian Dalan Formation. Giant oil and gas fi elds are controlled by Miocene Gachasaran Formation evaporite rock seal and Upper Cretaceous Gurpi Formation mudstone. They accumulate in folded anticlinal trap. Giant oil and gas fi elds are mainly distributed in Iran, Iraq and Syria. Big discoveries were made from 1960 to 1979. Oil and gas are rich in the layer of Mesozoic and Cenozoic. The lithology of reservoir is mainly carbonate rock which is buried at a depth less than 3km, and the reserves are less than 1×1010bbl. The factors controlling the distribution of giant oil and gas fi elds are the formation and evolution history of basin and the evolution history before basining, the organic type of source rock, the thermal evolution and distribution, the favorable reservoiring conditions, the high-quality region and direct cap rock, and the folded anticlinal traps favorable for hydrocarbon accumulation and the fracturing pathway favorable for vertical hydrocarbon migration that formed in the process of Neocene orogenic activity and folding. These factors control the distribution area and the accumulation layer of oil and gas.