Investigation into the apparent permeability and gas-bearing property in typical organic pores in shale rocks. (December 2019)

• Record Type: Journal Article
• Authors: Ji, Lili; Lin, Mian; Jiang, Wenbin; Cao, Gaohui; Zhou, Ji; Luo, Chao
• Is Part Of: Marine and petroleum geology. Volume 110(2020)
• Page Start: 871
• Page End: 885
• Publication Date: 2019-12
• Subjects: Typical organic pores -- Apparent permeability in OM -- Gas-bearing property of OM -- High pressure and temperature -- Rock compressibility; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2019.08.030
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: Although substantial advances have been made in investigating the storage and transport properties of shale gas in past decades, understanding of the flow characteristics and gas-bearing property in organic pores remains limited. In this paper, organic pores in the organic matter (OM) of the marine Longmaxi Formation are classified into six types based on the morphology and sizes of nanoscale pores. The structures of the six types of typical organic pores under high temperature and pressure are investigated based on the digital core compressibility method introduced in this paper. The results show that the pore-size distribution and connectivity of organic pores under high temperature and pressure are considerably different from those under conventional conditions. The apparent permeability of OM with different proportions of macropores, mesopores, and micropores are analyzed. The results demonstrate that the permeability of OM with Type 1 organic pores has the largest changes after compaction, whereas OM with Type 5 organic pores has a relatively smaller change. The regularities of the absolute adsorption amount and the free gas amount of OM with typical organic pores are also investigated. The absolute adsorption amount of OM decreases with the proportion of macropores, whereas the amount of free gas of OM increases. Finally, a chart of the absolute adsorption amount and the free gas amount of OM at different depths is given, which is helpful for estimating the gas-bearing capacity of OM and preliminary understanding the quality of a shale reservoir. Highlights: Organic pores in OM are classified into six types based on the morphology of organic pores. A digital core compressibility method is introduced to study shales under reservoir condition. The apparent permeability of typical organic pores under reservoir condition are investigated. The charts of the gas-bearing capacity for organic pores at different depth are presented.