Abstract: Nanyishan structural reservoir is the biggest reservoir in northwestern Qaidam basin at present. The deep E23 is a condensate gas reservoir and the shallow N2 2 is a conventional oil reservoir. Study and anatomy of such reservoirs with a unique distribution in this area is of significance to its petroleum exploration. It is suggested from comprehensive recognition of oil source in terms of the light hydrocarbon, gas carbon isotopes and biomarkers that the crude oil in the shallow N22 is different from that in the deep E23 . The former comes from the N1 source rocks, while the latter from the E23 source rocks, and pointed out that the oil and gas of Nanyishan structural reservoir are captured from the source rocks in the vicinity, not migrated from the south of Qaidam basin. The shape of deep condensate gas reservoir is controlled by the kerogen type and the maturity.

Key words: Qaidam basin, Nanyishan field, oil-gas origin, reservoir, condensate gas pool