Qigu oilfield is located in the southern margin of Junggar basin with complex terrain and high-steep structures, in which Kara-may formation of Triassic belongs to lacustrine shoal-bar sand body sediments with wide distribution area, big thickness and some poten-tials for hydrocarbon exploration. Because the strata are relatively old and deep-buried in geologic history periods, they have strong diagen-esis and compaction, being characterized by seldom primary porosity and developed secondary porosity and fractures. The study shows that the Karamay formation belongs to a porous medium reservoir with super-low porosity and ultra-low permeability, smaller pore throat and high displacement pressure. And it is concluded that this reservoir belongs to a non-conventional and tight sandstone reservoir.