Abstract:The Lower Cambrian black shale is a set of favorable shale gas reservoirs. In the selection of typical shale gas wells in different sedimentary- structural units, comparative analysis of shale gas reservoir characteristics of Niutitang Formation have been done by means of organic geochemistry testing, mineral X- ray diffraction, field emission scanning electron microscopy and nuclear magnetic resonance. The research shows that the mineral composition of shale is obviously controlled by sedimentary facies, and is characterized by “low silicon and high calcium” in shallow shelf region, and by “high silicon and low calcium” in the basin facies area. With the increase of sedimentary water from Yichang to Zhangjiajie, the lithofacies types of shale changed from calcareous shale and mixed shale to siliceous shale. Correspondingly, the brittleness index of shale reservoir increases and the rock compressibility improved. There is a good positive correlation between organic carbon content and porosity, especially in the organic- rich shale with organic carbon content more than 2.0%, which indicates that the enrichment of organic matter in shale has an important contribution to the porosity. In addition, nanopores are well developed in shale reservoir, and the Niutitang Formation shale in Yichang area with relatively low maturity and burial depth has larger pore size and higher surface porosity. The nano- pores of shale is dominated by micropores (0~10 nm) and small pores (10~100 nm) in well YY1, while the small pores are abundant in well ZD1, and the pore volume of shale is mainly provided by small pores less than 100 nm. In the longitudinal direction, the pore structure of shale will improve near the organic enrichment layer with the increase of porosity.