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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CT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H4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0.031 7mL/g,平均总比表面积为34.57m~2/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.
The Lower Cambrian Niutitang Group shale in southern China is one of the main stratigraphic targets for shale gas exploration in the south of China, however, its exploration results in the northeastern Chongqing area are not satisfactory due to the fact that the pore structure characteristics are not clear. FTIR, X-ray photoelectron spectroscopy, focused ion beam scanning electron microscopy, nano-CT and gas adsorption experiments were used to quantitatively characterize the micro-nano pore structure of the Lower Cambrian Niutitang shale in the northeastern Chongqing.The results show that micro- The pore types are mainly inorganic pores, including intergranular pores and intragranular pores, whereas the N2 adsorption lag ring belongs to type H4 and the corresponding pore type is single-sided slit-type pores. The average total pore volume of Niutitang shale is 0.031 7mL / g, and the average total surface area was 34.57m ~ 2 / g. The high degree of evolution of the shale in the Niutitang Formation led to the undeveloped porosity of the organic matter, leading to poor connectivity of the micro / The vast majority of pore volume, while the micropores contribute to the relatively large specific surface area.