沁水盆地太原组-山西组页岩孔隙分形特征

Fractal Characteristics of Shale Pores From Taiyuan Formation toShanxi Formation in Qinshui Basin

基于沁水盆地太原组—山西组页岩样品的总有机碳含量、镜质体反射率和矿物组成分析资料,利用高压压汞实验进行测试,获取孔隙直径、孔隙体积、比表面积、孔隙度等孔隙结构参数,并在此基础上利用Sierpinski地毯模型对页岩孔隙结构进行分形处理。结果表明,太原组—山西组页岩样品压汞分形曲线可以分为AB段、BC段和CD段,其中BC段对应的孔隙直径为21~6035 nm;利用Sierpinski地毯模型进行分形处理时,BC段孔隙结构表征性最好;在21~6035 nm孔隙直径范围内,黏土矿物含量越高的页岩,其孔隙结构的非均质性越强,孔隙结构的复杂程度也越高;孔隙体积、比表面积和孔隙度与分形维数均呈负相关关系,三者之中孔隙体积和孔隙度与分形维数相关性较好,可以作为间接判断孔隙结构复杂程度的依据。

Based on the data of shale samples,including TOC,vitrinite reflectance and mineral composition,and through high⁃pressure mer⁃cury intrusion experiment,the pore structure parameters such as pore diameter,pore volume,specific surface area and porosity were ob⁃tained from the Taiyuan formation to the Shanxi formation in the Qinshui basin,and then fractal analysis was performed on the shale pore structure with a Sierpinski carpet model.The results show that the fractal mercury intrusion curve of the shale samples from the Taiyuan for⁃mation to the Shanxi formation can be divided into 3 sections such as AB,BC and CD.The pore diameter corresponding to the BC section is 21 to 6,035 nm.When performing fractal processing on a Sierpinski model,the pore structure of the BC section has the best characterization.In the range from 21 to 6,035 nm,the higher the clay mineral content,the stronger the heterogeneity and the more complicated of the pore structure.Pore volume,specific surface area and porosity are all negatively correlated with fractal dimension.Among them,pore volume and porosity have a good correlation with fractal dimension,and can be used as an indirect criterion for judging the complexity of pore structure.