样品粒度对气体吸附实验的影响-以四川长宁龙马溪组及五峰组页岩为例

Influence of Sample Partical Size on Gas Adsorption Experiments——A Case Study of Longmaxi Formation and Wufeng Formation Shales in Changning Region of Sichuan Province

尽管低压气体吸附法已被广泛应用于泥页岩多孔矿物孔隙度的表征,然而到目前为止并没有一个统一的标准来规范样品的粒度。该文以四川长宁地区龙马溪组和五峰组露头页岩样品为例,旨在探究样品颗粒大小对气体吸附实验的影响并尝试提出适合于低压N_(2)和CO_(2)吸附测量的粒径范围。该文通过TOC、Ro、XRD测试以及扫描电镜观察获得了页岩样品的基础岩石学特征和孔隙特征,并对不同粒度样品进行低压CO_(2)和N_(2)吸附实验。结果表明:粒度变化对CO_(2)以及N_(2)吸附实验均存在不同程度的影响。在极端细碎(200目)的情况下,部分原生孔隙结构被破坏,吸附作用明显减弱,总孔隙体积减少,比表面积降低,实验结果误差较大。而140~180目样品孔隙暴露程度最为充分,建议作为CO_(2)和N_(2)吸附实验的最佳粒度范围。高的有机质含量有利于孔隙的发育,相较于五峰组样品,龙马溪组样品TOC含量高,所以气体吸附量更高,比表面积、孔隙体积更大。研究成果对完善气体吸附实验的样品处理标准以及提高页岩孔隙定量表征的精确度有着重要的意义。

Although the low-pressure gas adsorption method has been widely used to characterize the porosity of shale porous minerals,there is no unified standard to regulate the granularity of samples so far.Taking the outcrop shale samples of Longmaxi Formation and Wufeng Formation in Changning region of Sichuan province as an example,this paper aims to explore the influence of sample particle size on gas adsorption experiments and try to propose a particle size range suitable for low-pressure N_(2)and CO_(2)adsorption measurements.In this paper,the basic petrological characteristics and pore characteristics of shale samples were obtained by TOC,RO,XRD tests and scanning electron microscopy.And low-pressure CO_(2)and N_(2)adsorption experiments were carried out on samples with different particle sizes.The results show that the change of particle size has different effects on CO_(2)and N_(2)adsorption experiments.In the case of extremely fine crushing(200 mesh),part of the native pore structure is destroyed,the adsorption is significantly weakened,the total pore volume is reduced,the specific surface area is reduced,and the experimental results have large errors.The pore exposure degree of 140~180 mesh samples is the most sufficient,which is recommended as the optimal particle size range for CO_(2)and N_(2)adsorption experiments.High organic matter content is conducive to the development of pores.Compared with the samples of Wufeng Formation,the samples of Longmaxi Formation have higher TOC content,so the gas adsorption amount is higher,and the specific surface area and pore volume are larger.The above results are of great significance for improving the sample processing standards of gas adsorption experiments and improving the accuracy of quantitative characterization of shale pores.