渝东北下寒武统牛蹄塘组页岩微纳米孔隙结构特征

中国南方下寒武统牛蹄塘组页岩是目前页岩气勘探的主要目的层位之一，然而在渝东北地区其勘探效果不尽如人意，原因在于其孔隙结构特征并未清楚.采用聚焦离子束扫描电子显微镜、纳米C和气体吸附实验等方法对渝东北地区下寒武统牛蹄塘组页岩微纳米孔隙结构进行了定量表征.结果表明，牛蹄塘组页岩的微纳米孔隙类型主要为无机质孔隙，包括粒间孔和粒内孔，而N₂吸附滞后环类型属于4型，对应孔隙类型为单边狭缝型孔隙；牛蹄塘组页岩的平均总孔体积为0.0317mL/g，平均总比表面积为34.7m2/g.牛蹄塘组页岩过高的演化程度导致有机质孔隙不发育，进而导致其微纳米孔隙具有较差的连通性；中孔贡献了绝大部分的孔体积，而微孔则贡献了相对较多的比表面积. 

Micro-Nano Pore Structure Characteristics in the Lower Cambrian Niutitang Shale,Northeast Chongqing

Lower Cambrian Niututang Formation shale in south China is one of the main target zones for shale gas exploration. However, the exploration of shale in northeastern Chongqing is not satisfactory as the pore structure of the shale is unclear. This study examined pores in shale samples from the Niutitang Formation using focused ion-beam scanning electron microscopy, nano-CT, and gas adsorption analysis. Results show that pores in Niutitang shale are rare and have small diameters and poor connectivity. Most Niutitang-shale pores are inorganic pores, including intraparticle and intergranular pores. N₂ adsorption hysteresis loop of Niutitang shale belongs to type H4 corresponding to narrow slit pore. The average total pore volume of the Niutitang shale is 0.0317mL/g, and the average total surface area is 34.57m2/g. Over-high thermal evolution degree resulting small number of organic pores and poor connectivity of micro-nano pores in Niutitang shale. Mesopores contributed most of the pore volume and micropores contributed more pore surface area than that of mesopores.