湘鄂西地区志留系龙马溪组页岩微观孔隙结构特征及定量表征

湘鄂西地区为南方海相页岩气勘探开发潜力区之一,志留系龙马溪组是其有利的页岩气层段。利用氩离子抛光—扫描电镜、低温低压氮气和二氧化碳吸附等实验对该区4口取心井的页岩样品孔隙结构进行了定性和定量的联合表征。实验结果表明:该区页岩发育有粒间孔、粒内孔、有机孔、有机质—黏土矿物复合孔以及解理缝,其中最为发育的是黏土矿物与自生矿物相间的粒间孔、有机质—黏土矿物复合孔以及有机孔。页岩样品比表面积为8.038~24.552 m²/g,平均为13.769 m²/g,BJH孔径中孔直径为8.21~13.79 nm,平均为10.43 nm,其中LY1井孔径最大为11 nm,是该井有构造缝发育所致。

Micro-pore structure characteristics and quantitative characterization of Silurian Longmaxi shale in western Hubei and Hunan areas

The western Hubei and Hunan areas are one of the potential areas for marine shale gas exploration and development in the south,while the Lower Silurian Longmaxi Formation is one of the favorable shale gas intervals.In this study,the pore structures of shale samples from four coring wells in this area were characterized qualitatively and quantitatively by FE-SEM,low-temperature and low-pressure N2 and CO2 isothermal adsorption experiments.The experimental results show that there are abundant of interparticle pores,intraparticle pores,organic pores,compound pores of organic-clay minerals,as well as cleavage cracks in the shale,among which the most developed are interparticle pores of clay minerals and autogenous minerals,compound pores of organic-clay minerals and organic pores.The specific surface area of the shale is from 8.038 m²/g to 24.552 m²/g,with an average of 13.769 m²/g.The median diameter of the BJH pore diameter is from 8.21 nm to 13.79 nm,with an average of 10.43 nm.The largest pore diameter of Well LY1 is 11 nm,which is caused by the development of structural fractures in the well.