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Relationship between pore characteristics and occurrence state of shale gas; a case study of Lower Silurian Longmaxi Shale in the upper Yangtze Platform, south China

Chen Lei, Jiang Zhenxue, Liu Keyu, Wang Pengfei, Liu Yu, Bi He, Gao Fenglin, Zhang Chen and Ji Wenming
Relationship between pore characteristics and occurrence state of shale gas; a case study of Lower Silurian Longmaxi Shale in the upper Yangtze Platform, south China
Interpretation (Tulsa) (May 2017) 5 (3): SL43-SL55

Abstract

We have used focused ion beam-helium ion microscopy and low-pressure N (sub 2) adsorption to investigate the pore characteristics of Lower Silurian Longmaxi shale. These results, combined with the molecular potential energy theory, reveal the relationship between pore size and the occurrence state of shale gas. Our results reveal that (1) the pore volume and the specific surface area of Lower Silurian Longmaxi shale are mainly contributed by the pores with diameters of less than 10 nm. Nanoscale organic-matter pores are predominant, and the pore surface is not generally smooth and has fractal characteristics. (2) When the distance between the methane molecule and the pore wall in organic-matter pores is limited to 2 nm, there is a strong interaction force between them, and the methane molecule is affected by the interaction force and is in the adsorbed state accordingly. When the distance between them is greater than 2 nm, the interaction force can be ignored, and the methane molecule is not affected by the interaction force and is in the free state accordingly. (3) In the pores having a radius greater than 2 nm, the adsorption capacity is positively correlated with the specific surface area; whereas in the pores having a radius smaller than 2 nm, the average gas concentration is related to the pore radius. (4) First, the adsorption-zone volume increases, and then it decreases with increasing pore diameter. When the pore diameter ranges from 1 to 6 nm, the adsorption-zone volume is significantly larger than the free-zone volume. Within this range, the adsorption volume nearly equals the pore volume. When the pore diameter ranges from 6 to 60 nm, the adsorption volume gradually decreases, whereas the free volume increases, which equals the adsorption volume when the diameter reaches 15 nm.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 5
Serial Issue: 3
Title: Relationship between pore characteristics and occurrence state of shale gas; a case study of Lower Silurian Longmaxi Shale in the upper Yangtze Platform, south China
Affiliation: China University of Petroleum, State Key Laboratory of Petroleum Resources and Prospecting, Beijing, China
Pages: SL43-SL55
Published: 201705
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 64
Accession Number: 2017-085795
Categories: Economic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N28°00'00" - N30°00'00", E107°00'00" - E110°00'00"
Secondary Affiliation: CSIRO Earth Science and Resource Engineering, CHN, ChinaChina University of Mining and Technology, CHN, ChinaPetroChina, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201745
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