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《Geochimica》 2017-06
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Pore structure characteristics and gas storage significance of Wufeng Formation shale from eastern Chongqing, China, based on the NLDFT model

WANG Peng;GENG An-song;WU Liang-liang;FANG Xin-yan;State Key Laboratory of Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences;University of Chinese Academy of Sciences;  
The study on the microscopic pore structure of shale is of great significance to performing resource assessments and understanding the accumulation mechanism of shale gas. Various test methods and models have been used to represent pore structures within different pore ranges of shale. However, it is not sufficiently accurate to represent the pore size distribution in the whole pore diameter range by simply splicing the results of different test methods and models. Therefore, ten samples of Wufeng Formation shale from the Shizhu area of the East Sichuan Basin, China, were selected to perform a series of measurements, including the determination of total organic carbon(TOC) and mineral composition. The specific surface area and pore volume obtained from the non-local density functional theory(NLDFT) with CO2-N2 adsorption data were compared with those from the density functional theory(DFT). Finally, the pore structures and significance of the pore structures on the storage of shale gas were discussed. The results showed that Wufeng Formation shale has a very high brittle mineral content. The brittleness index is in the range of 0.52~0.88(average: 0.71), indicating that the shale is very easy fractured. Micropores are the most important spaces for adsorbed shale gas, because they provide the majority of the specific surface area for adsorbing shale gas, with an average specific surface area of 18.27 m2/g, accounting for 81.61% of the total specific surface area. Mesopores and macropores are the most important storage space for free shale gas, because they provide the majority of the pore volume used for storing free shale gas, with an average pore volume of 22.51 × 10–3 cm3/g, accounting for 81.48% of the total pore volume. In the Shizhu area of eastern Chongqing, the contents of the adsorbed shale gas identified using the NLDFT model are significantly higher than those from previous assessments based on other models. The contents of free shale gas identified by the NLDFT model are also higher than those from previous assessments based on other models.
【Fund】: 中国科学院战略性先导科技专项(B)(XDB10010502)
【CateGory Index】: P618.13
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