致密砂岩储层孔隙结构特征及其对开发的影响

致密砂岩孔隙结构特征是致密油气地质评价的核心研究工作。通过铸体薄片、X-射线衍射、扫描电镜、常规压汞、恒速压汞及气水相相对渗透率等多种实验分析手段，研究了川西中江气田沙溪庙组致密砂岩孔隙结构特征，探讨了孔隙结构差异性成因，并分析孔隙结构对开发的影响。研究表明，中江气田沙溪庙组致密储层岩石类型以岩屑长石砂岩、长石岩屑砂岩和岩屑砂岩为主；储层物性受原生矿物组合与成岩演化过程及其产物的影响，其中，石英对储层的渗透率贡献相对明显，对孔隙度影响不明显，黏土矿物、方解石都对孔隙度和渗透率影响明显，均呈负相关；在孔隙结构参数中，孔喉组合关系、喉道大小决定储层渗流能力，以大孔喉对储层渗透能力的贡献最大；孔隙结构对产能及气井生产特征影响明显，孔隙结构均质性越好所对应的气井产能及平均日产气就越高。研究成果对于深入理解致密砂岩孔隙结构及气井开发效果差异性具有重要的理论意义，能为气藏合理开发及评价提供科学依据。

Pore Structure Characteristics of Tight Sandstone Reservoir and Its Influence on Development

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.