孔隙结构是决定致密砂岩储层物性和油气产量的关键因素，明确孔隙结构特征对油气的勘探开发具有重大意义。以天府气区须家河组须四段致密砂岩储层为例，通过薄片鉴定、扫描电镜观察、核磁共振测试、高压压汞测试以及X衍射等实验，结合分形理论，系统分析了研究区须四段砂岩的孔隙结构特征、分形特征及流体可动性。结果表明：研究区须四段砂岩主要为长石岩屑砂岩，储层类型为特低孔-特低渗孔隙型储层，孔隙类型主要为长石溶孔，喉道类型以片状喉道为主。根据高压压汞曲线形态和核磁共振结果，可将须四段砂岩孔隙结构分为三类，其中Ⅰ类样品储层物性最好，孔喉半径较大，孔喉连通性和分选性好，流体可动性强，储层质量最优。须四段致密砂岩孔隙结构和流体可动性受沉积结构和矿物含量影响较为明显，粒度较粗、分选性较好的储层孔隙结构和流体可动性较好。同时，石英作为砂岩中主要的刚性矿物，具有抗压实的能力，对储层孔隙起到了一定的保护作用，而方解石和黏土矿物会占据孔隙空间，导致储层的孔隙结构和流体可动性变差。

The pore structure is a pivotal determinant of the physical properties of tight sandstone reservoirs, and elucidating its characteristics holds great significance for oil and gas exploration and development. Taking the 4th member of the Xujiahe Formation tight sandstone reservoirs in Tianfu Gas Area as an example, the pore structure characteristics, fractal features, and fluid mobility of the Xu-4 sandstone in the study area were systematically analyzed through thin section identification, scanning electron microscopy observation, nuclear magnetic resonance testing, high-pressure mercury intrusion testing, and X-ray diffraction experiments, combined with fractal theory. The results indicate that the sandstones of the 4th member of the Xujiahe Formation in the study area are predominantly composed of feldspar lithic sandstone, belonging to an ultra-low pore-ultra-low permeability pore type reservoir. The pore type is primarily feldspar-dissolved pores, and the throat type is predominantly sheet throats. According to the morphology of the high-pressure mercury injection curves and nuclear magnetic resonance outcomes, the pore structure of the 4th member of the Xujiahe tight sandstone reservoir is categorized into three distinct types. Among them, the material properties of the I-type samples are the best, with larger pore-throat radii, good connectivity and sorting of pore-throat, strong fluid mobility, and the best reservoir quality. The pore structure and fluid mobility of the fourth member of the Xujiahe tight sandstone reservoir are affected by sedimentary structures and mineral content. Specifically, reservoirs with coarser grain sizes and better sorting demonstrate superior pore structure and fluid mobility. Furthermore, quartz, the primary rigid mineral in sandstones, exhibits resistance to compaction, thereby safeguarding the reservoir pores to a certain extent. However, calcite and clay minerals will occupy pore space, resulting in deterioration of the pore structure and fluid mobility of the reservoir.