基于氩离子抛光-SEM和ImageJ软件的页岩储层孔隙结构分析——以中扬子地区陡山沱组为例

Analysis of the pore structure of shale gas reservoirs based on argon-ion milling SEM and ImageJ

为分析页岩储层孔隙结构,分析核磁共振、CT扫描、SEM、压汞法、氮气吸附法等方法,提出基于氩离子抛光SEM技术与ImageJ软件结合的改进的页岩储层孔隙结构分析方法.首先,利用氩离子抛光SEM技术获得中扬子地区陡山沱组页岩孔隙图像,将页岩分为有机质孔隙、粒间孔隙、粒内孔隙和微裂缝等4种孔隙类型;孔隙形态分为不规则多边形孔隙、近圆形孔隙、复杂网状孔隙、脉状或条带状孔隙等4类;然后,利用ImageJ软件定量分析陡山沱组页岩孔隙SEM图像.结果表明：中扬子地区陡山沱组页岩有机质孔最发育,粒间孔次之,粒内孔最不发育;粒间孔和粒内孔的孔隙直径较有机质孔的大;页岩的孔隙率为0.49％～1.21％,总孔隙率为2.86％.该方法实现对页岩储层孔隙结构的定性分析和定量表征,以及对储层的定量评价,研究结论对页岩储层孔隙结构分析具有参考意义.

In order to analyze the pore structure of shale reservoir,comparing the characteristics of nuclear magnetic resonance,CT scanning,SEM,mercury porosimetry,nitrogen adsorption method,we introduced an improvement method for combination of Argon-ion milling-SEM technology and ImageJ software.First,get the shale pore images of the Doushantuo Formation in middle Yangtze area using argon ion polishing-SEM technology,the pore types are divided into organic pore,intragranular pores,intergranular pore and micro cracks;the pore morphology is divided into irregular polygonal pore,suborbicular pore,complex pore network pore,vein or banded pore.Then,quantitative analysis was conducted of the SEM images of Doushantuo Formation shale using ImageJ software.The results show that:organic pore is the most development than intergranular pore and intragranular pore;the diameter of intergranular pore and intragranular pore is larger than organic pore;the porosity of shale is 0.49%~1.21%,the average total porosity is 2.86%.By using this method,we can realize the qualitative analysis and quantitative characterization of shale gas pore structure,as well as the quantitative evaluation of shale reservoirs,this study has great significance in the analysis of shale gas pore structure.