纳米CT页岩孔隙结构表征方法——以JY-1井为例

Characterization method of shale pore structure based on nano-CT:a case study of Well JY-1

分析富有机质页岩的纳米孔隙结构是评价页岩储集性能和页岩气资源勘探开发潜力的基础。利用纳米CT及三维重构技术评价四川盆地焦石坝地区下志留统龙马溪组页岩的孔隙特征及连通性,结果表明:(1)纳米CT可以展现页岩孔隙的三维空间结构,结合其他实验方法更有利于表征页岩的孔隙特征;(2)基于纳米CT可将焦石坝页岩样品的组分分为基质矿物、有机质、孔隙和高密度矿物(如黄铁矿),其体积比分别为89.20%、6.22%、2.71%和1.87%;(3)焦石坝页岩的孔径分布范围为79~4700nm,以100~500nm为主,包括有机孔隙和无机孔隙;(4)焦石坝页岩孔隙的非均质性较强,总体具有较好的连通性,以Ⅲ级连通域为主。

An analysis on nanoporous structure of organic-rich shale is the basis for evaluating the reserving properties of shale reservoirs and the exploration and development potential of shale gas resources.In this study,the nano-CT and 3 D reconstruction technique is used to evaluate the shale pore characteristics and connectivity of the Lower Silurian Longmaxi Formation in the Jiaoshiba area of Sichuan Basin.The experimental results show that:(1)nano-CT can display the three-dimensional spatial structure of shale pores,and will be more conducive to characterize the shale pore characteristics in combination with other experimental methods;(2)based on nano-CT,four components including matrix minerals,organic matter,pores,and high-density minerals(such as pyrite)can be distinguished in shale samples with the volume ratio of 89.20%,6.22%,2.71%and 1.87%respectively;(3)the pore sizes evaluated by nano-CT range from79 nm to 4.7μm,dominated by 100~500 nm,mainly including organic pores and inorganic pores;(4)strong heterogeneity exists in shale pore,generally with better connectivity,dominated by grade III connectivity domains.