Abstract: The pore structure characteristics of tight sandstone are the core research work of tight oil and gas geological evaluation. Through a variety of experimental analysis methods such as cast thin section, X-ray diffraction, scanning electron microscope, conventional mercury injection, constant velocity mercury injection and gas-water relative permeability, the pore structure characteristics of dense sandstone of Shaximiao Formation in Zhongjiang Gas Field, Western Sichuan are studied, the causes of pore structure differences are discussed, and the influence of pore structure on development is analyzed. The research shows that the tight reservoir rocks of Shaximiao Formation in Zhongjiang Gas Field are lithic arkose, feldspathic lithic sandstone and lithic sandstone; the physical properties of the reservoir are affected by the combination of primary minerals, diagenetic evolution process and their products. The contribution of quartz to the permeability of the reservoir is relatively obvious, but not obvious to the porosity. Clay minerals and calcite have obvious effects on the porosity and permeability, which are negatively correlated; among the pore structure parameters, the pore throat combination relationship and the size of roar determine the reservoir permeability, and the large pore throat contributes the most to the reservoir permeability; pore structure has an obvious impact on productivity and gas well production characteristics. The better the homogeneity of pore structure, the higher the corresponding gas well productivity and average daily gas production. The research results have important theoretical significance for deeply understanding the pore structure of tight sandstone and the difference of gas well development effect, and can provide scientific basis for reasonable development and evaluation of gas reservoir.

Key words: tight sandstone, pore structure, seepage characteristics, development characteristics, Shaximiao Formation of Zhongjiang Gas Field