Influential Factors and Characteristics of Chang 8 Oil Reservoir of Triassic Yanchang Formation in Western Nanliang area,Ordos Basin

To study the characteristics and control factors of Chang 8 Reservoir of Western Nanliang area,and direct scientific and effective exploitation.Through collection,arrangement and analysis of cast slices,scanning electron microscope images,mercury injection test,well logging and oil testing,the article researches the physical property and its controls of Chang 8 Formation of Yanchang in Western Nanliang Area,Ordos Basin.Chang 8 Formation mainly contains of lithic-arkose and feldsparthic litharenite.Irregular pores provide major reservoir space and additional space is provided by dissolution pores and micro pores.The reservoir with medium displacement pressure and medium throat is low porosity,low permeability and heterogeneity.Subaqueous distributary channel deposits of delta front form most part of reservoirs.The characteristics of reservoir are controlled by diagenesis.The porosity was reduced by compaction,pressure solution and cementation.Chlorite membrane which forme during stage A of early diagenesis and the two stages of dissolution in Chang 8 period are advantages for reservoir pore evolution.