内蒙古海拉尔盆地乌尔逊及贝尔凹陷南屯组致密砂岩储层微观结构表征

为了明确海拉尔盆地南屯组致密砂岩储层微观孔隙结构与储层物性的相关关系,本次研究通过铸体薄片观察、物性测试及恒速压汞实验,明确储层微观特征及孔隙结构参数,包括孔隙及喉道类型、大小、分布、连通性,并讨论了储层微观孔隙结构与储层物性的相关关系。研究结果表明:南屯组储层主要矿物颗粒为石英、长石、火山碎屑岩及凝灰岩岩屑,压实作用较强烈,颗粒排列紧密,胶结类型多为接触式胶结及镶嵌胶结,并以长石溶蚀现象最为普遍。储层多发育溶蚀孔,同含有少量粒间孔,喉道多为片状、管束状及缩颈型喉道。储层孔隙半径大多分布在110~170μm,孔径分布曲线形态呈单峰态,孔隙半径与孔隙度、渗透率无明显相关性;喉道半径分布在0.508~4.069μm。受控于孔隙结构的差异,孔喉半径比与渗透率呈一定相关性。综上所述,南屯组致密砂岩储层孔隙结构是其物性差异的主控因素,决定流体渗流能力。

Microstructure characterization of tight sandstone reservoirs in the Nantun Formation of Wuerxun and Beier Depresses in Hailaer Basin,Inner Mongolia

In order to define the hailaer basin south tuen set of tight sandstone reservoir microscopic pore structure and the relation between reservoir physical property, the study by the casting thin sections observation and physical property test and constant speed mercury injection experiment, clear reservoir microscopic characteristics and pore structure parameters, including the type of pore and throat, size, distribution, connectivity, and discusses the reservoir microscopic pore structure and the relationship between the reservoir property. The results show that the main mineral particles in nantun formation are quartz, feldspar, pyroclastic rock and tuff debris, with strong compaction, compact particle arrangement, contact cementation and Mosaic cementation, and feldspar dissolution is the most common phenomenon. There are many dissolution pores in the reservoir, and there are also a few intergranular pores. The pore radius of the reservoir is mostly distributed between 110-170um, and the shape of the pore diameter distribution curve is unimodal. There is no obvious correlation between the pore radius and porosity and permeability. The throat radius is between 0.508 and 4.069um. Controlled by the difference of pore structure, the ratio of pore-throat radius is correlated with permeability. In conclusion, pore structure of tight sandstone reservoir in nantun formation is the main controlling factor of physical property difference and determines fluid seepage capacity.