【摘要】 页岩孔隙结构及差异性是页岩含气性和产能评价的基础性问题.针对川东南彭水地区五峰组与龙马溪组页岩的孔隙结构已有若干研究成果,然而在页岩孔隙结构差异性和有机孔定量特征方面还缺乏研究.利用低温低压氮气吸附测定和氩离子抛光-场发射扫描电镜(FE-SEM)技术,对页岩样品纳米孔隙进行了二维观察与统计以及分形特征计算,研究了3nm至几百nm页岩孔径范围的孔隙结构及其差异性.研究区五峰组-龙马溪组页岩有机孔十分发育;氮气吸附测定页岩孔隙形状包含开放型圆筒状、层状结构狭缝状和墨水瓶状等;扫描电镜观察有机孔形态主要有近圆形、椭圆形和多角形等.五峰组和龙马溪组页岩孔隙结构具有明显的差异性,主要体现在孔径大小、形态和数量上.氮气吸附测定表明,五峰组页岩孔隙比表面积和总孔容较龙马溪组大,微孔所占总孔的比例也较高;五峰组页岩孔径相对龙马溪组更细窄.扫描电镜二维图像观察与统计结果表明,五峰组有机孔径以小于35nm为主,形态以多角形为主;龙马溪组有机孔径以小于50nm为主,形态多呈近圆形和椭圆形.五峰组页岩的分形维值大于龙马溪组页岩,说明前者孔隙复杂程度较高.更多还原

【Abstract】 Pore structure and its difference is a basic issue in shale gas content and capacity evaluation.A number of studies have been made on the pore structure of the shale in the Wufeng Formation and Longmaxi Formation in Pengshui area,southeastern Sichuan.However,there is a lack of research on shale pore structure difference and organic pore quantitative characteristics.Using low-temperature and low-pressure N2 adsorption and Ar ion milling field emission scanning electron microscopy(FESEM),for Wufeng and Longmaxi marine shales in Pengshui area of southeastern Sichuan,this paper investigated the pore structure of shale samples with the pore size ranging from 3nm to hundreds nm,and its difference between Wufeng and Long-maxi formations was also analyzed by observing and counting nano-pores in two-dimension,and computing fractal dimension.Results indicate that organic pores from Wufeng and Longmaxi shales in Pengshui area are very developed.Results of N2 adsorption show the shale samples contain open cylindrical-like pores,layered slit-like pores and ink-bottle pores.And observation of scanning electron microscopy reveals organic pore morphology mainly is nearly circular,elliptic and polygon.The obvious difference of pore structure between Wufeng and Longmaxi shales is mainly reflected on the pore size,shape and quantity.N2 adsorption results show that Wufeng shales have higher specific surface area and total pore volume than that of Longmaxi shales,and micropore within Wufeng shales accounts for higher proportion of total pore;pore size of Wufeng shales is narrower than that of Longmaxi shales.Observation and statistics of FE-SEM two-dimensional images indicate organic pores in Wufeng Formation are mainly pores with diameter less than 35 nm and have irregular shapes.While Longmaxi organic pores are mainly less than 50 nm in diameter and pore shapes mainly are nearly circular or elliptic.Based on the pore fractal dimension calculation of N2 adsorption and FE-SEM,Wufeng Formation has higher pore fractal dimension values than Longmaxi Formation,which indicates that the pore structure of Wufeng shales is more complex than that of Longmaxi shales.更多还原