Reservoir characteristics and comprehensive evaluation of Triassic clastic reservoir in southern Qilian Basin

On the basis of thin section,scanning electron microscopy,physical property analysis and mercury injection analysis,the reservoir characteristics and main control factors of Triassic clastic reservoir in Southern Qilian Basin were studied.The results indicate that the clastic reservoir sandstone is mainly composed of medium to fine grained feldspar sandstone and the textural and compositional maturation of the reservoir is low.The main reservoir space types are interstitial content pores,dissolution pores and fractures.In additional,the reservoir pore structure is characterized by mini pore throat,poor sorting,poor connectedness and poor infiltrating ability.The reservoir physical properties are poor,with low porosity and low permeability.Moreover,the development of reservoir is mainly controlled by sedimentation,diagenism and favorable tectonic condition.Comprehensively considering above analysis,the Triassic clastic reservoirs have been divided into type Ⅴ,type Ⅵ and type Ⅶ,overall belonging to tight reservoirs with ultra-low porosity and permeability.