Characteristics and controlling factors of microscopic pore structure of Longmaxi Formation in Sichuan Basin and its periphery

Abstract

Abstract: Microscopic pore structure of the Lower Silurian Longmaxi Formation organic matter-rich shale in the Sichuan Basin and its periphery was systematically studied by using argon-ion polishing-scanning electron microscope (SEM), low-temperature liquid nitrogen adsorption/desorption and other techniques and methods. Moreover, the main factors controlling the nano-scale microscopic pore structure were discussed. The results indicate that pores in the Longmaxi Formation organic matter-rich shale in the Sichuan Basin and its periphery are in nano-scale with diverse types, such as organic matter pore, intergranular pore, intragranular pore, intercrystal pore, dissolved pore, and micro-fractures. The organic matter pore and intergranular pore are better developed. The complex microscopic pore structure of the shale is mostly composed of open pores, including cylinder pores and parallel slate pores with open ends. The radius of microscopic pores are typically 2-80 nm, suggesting as medium pores. Analysis reveals that organic carbon content is the major factor controlling the development of nano-scale pores and the important material basis for the occurrence of shale gas.

Key words: Longmaxi Formation, the Sichuan Basin and its periphery, nano-scale pore structure, nitrogen adsorption/desorption, argon-ion polishing-scanning electron microscope (SEM)

Wei Pengfei, Zhang Jinchuan, Long Shuai, Peng Jianlong, Deng Ende, L?Yannan, Ma Yulong. Characteristics and controlling factors of microscopic pore structure of Longmaxi Formation in Sichuan Basin and its periphery[J]. China Petroleum Exploration, 2016, 21(5): 42-51.

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