【摘要】 微观孔隙结构特征是致密砂岩储层研究中的一个重点,对进一步认识储层和后期开发有着重要的意义。对鄂尔多斯盆地中部长4+5储层22块密闭取芯样品进行了薄片鉴定、扫描电镜分析、X射线衍射和压汞测试,对储层微观孔隙结构的分形特征进行了系统研究。利用毛管压力和湿相饱和度的双对数回归曲线可以计算出分形维数。结果显示,本区长4+5储层存在统一的分形特征。平均孔喉半径与分形维数存在正相关关系,说明随着平均孔喉半径的增大,孔喉半径之间差异变大,储层的非均质性增强。分析认为由于受到成岩作用的影响,孔隙较大的储层受到的溶蚀作用更强,导致孔隙尺寸差别较大,孔隙结构复杂;而孔隙较小的储层的喉道半径变化不大,分布较为均匀。储层的物性和分形维数呈正相关,其主要原因为储层物性主要受到孔喉大小的影响。根据矿物含量与分形维数的关系可得出,石英和绿泥石会使孔隙结构的复杂性降低,而长石和伊利石则会增加储层孔隙结构的复杂性和非均质性。更多还原

【Abstract】 The microscopic pore structure is a key point in the study of tight sandstone reservoirs, which is of great significance for further understanding of reservoirs and later development. The mercury pressure test, cast thin section, scanning electron microscope and X-diffraction were carried out on 22 sealed core samples of chang 4+5 reservoir in the middle of the Ordos Basin, and fractal characteristics of microscopic pore structure were studied. By using the logarithmic regression curve of capillary pressure and wet phase saturation, the fractal dimension was calculated. It is found that the Chang 4+5 reservoir in this area has uniform fractal characteristics. The average radius of pore-throat exists positive correlation with the fractal dimension, which reflects that with the increase of the average pore-throat radius, the difference between pore and throat radius is larger and the heterogeneity of reservoir is larger. Results show that under the influence of diagenesis, reservoirs with larger pores are subjected to stronger dissolution, resulting in large difference in pore size and complex pore-throat structure, while the reservoirs with smaller pore-throat has little change in the radius of pore and throat and is more evenly distributed. The physical properties of the reservoir is positively correlated with fractal dimension, the main reason is that the physical property of the reservoir is mainly affected by the size of pore throat. The relationship between mineral content and fractal dimension shows that quartz and chlorite reduce the complexity of pore structure, while feldspar and illite increase the complexity and heterogeneity of pore structure.更多还原