基于微观孔喉结构及渗流特征建立致密储层分类评价标准——以鄂尔多斯盆地陇东地区长7储层为例

以鄂尔多斯盆地陇东地区长7致密储层为例，通过物性分析、铸体薄片、扫描电镜、CT扫描、高压压汞、恒速压汞等实验对微观孔喉特征进行分析，结合核磁共振、可视化多相渗流实验分析流体渗流特征，选择合理的评价参数对致密储层进行分类评价。陇东地区长7致密储层平均孔隙度、渗透率分别为9.33%和0.18×10-3 μm2；孔隙类型以长石溶孔、粒间孔为主，平均面孔率为1.89%，孔喉半径主要分布在小于1 μm的范围内，其储集能力较强，但连通性差；主要受细小孔喉控制，可动流体饱和度及驱油效率较低，非均质性对驱油效率也有一定影响。选择孔隙度、渗透率、面孔率、平均孔喉半径、均值系数、排驱压力、可动流体饱和度、驱油效率作为评价参数，利用多元分类系数法进行分类并建立致密储层评价标准，将储层由好到差依次分为Ⅰ、Ⅱ、Ⅲ和Ⅳ类。 

Establishment of classification and evaluation criteria for tight reservoirs based on characteristics of microscopic pore throat structure and percolation: a case study of Chang 7 reservoir in Longdong area,Ordos Basin

Taking the Chang 7 reservoir in the Longdong area of the Ordos Basin as an example, the microscopic pore throat characteristics were comprehensively analyzed through physical analysis, casting thin section, scanning electron microscope, CT scanning, high pressure mercury injection and constant rate mercury injection experiments. Fluid seepage was analyzed by NMR and visualized multiphase seepage experiments. Some reasonable evaluation parameters were selected to classify and evaluate tight reservoirs. The average porosity and permeability of the Chang 7 tight reservoir in the Longdong area are 9.33% and 0.18×10-3 μm2, respectively. The main pore types are feldspar dissolved pore and intergranular pore, with an average plane porosity of 1.89%. The pore throat radius is small, mainly distributed in the range of less than 1 μm. Its reservoir capacity is strong, but its connectivity is poor. The movable fluid saturation and oil displacement efficiency are mainly controlled by the fine pore throat, and the heterogeneity also has a certain influence on the oil displacement efficiency. Porosity, permeability, plane porosity, average pore throat radius, mean value coefficient, displacement pressure, movable fluid saturation and oil displacement efficiency are selected as evaluation parameters, and a multi-classification coefficient method is used to classify and establish an evaluation criteria for tight reservoirs, which are divided into Ⅰ, Ⅱ, Ⅲ and IV from good to bad.