Geochemical attributes, pore structures and fractal characteristics of Barakar shale deposits of Mand-Raigarh Basin, India. (May 2019)

• Record Type: Journal Article
• Authors: Kumar, Susheel; Mendhe, Vinod Atmaram; Kamble, Alka Damodhar; Varma, Atul Kumar; Mishra, Divya Kumari; Bannerjee, Mollika; Buragohain, John; Prasad, Amal Kishore
• Is Part Of: Marine and petroleum geology. Volume 103(2019)
• Page Start: 377
• Page End: 396
• Publication Date: 2019-05
• Subjects: Geochemical attributes -- Pore structures -- Fractal dimensions -- Shale matrix -- Heterogeneity; 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.2019.02.026
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: Pore structures in the shale matrix are an essential factor affecting the storage capacity of gas of shale beds as well as production performance. Twenty organic-rich shale samples at different depths were collected from Barakar Formation of Mand-Raigarh basin, to examine the pore structure and their fractal characteristic. Fractal dimension was calculated by following FHH theory to investigate the complexity of pore surfaces, storage mechanism and the pore network system. The complex pore system influenced by thermal cracking of organic matter, pore dissolution during geochemical weathering and tectonics of the basins having surface area 5.56–23.94 m 2 /g (avg. 14.21 m 2 /g). Whereas, the pore volume determined using the BJH model varying from 0.035 to 0.076 cc/g (avg. 0.053 cc/g). FTIR spectrum demonstrated that significant presence of aliphatic side chains and aromatic carbon structures existing in studied shale influencing the pore volume. It is summarized that pores and matrix of shale are built by complex mixtures of organic and inorganic content. Further, the pores are categorized into organic pores evolved during thermal cracking, inter-granular, intra-granular and inter-crystalline due to the large content of altered clays and minerals showing fissile nature. The SEM-EDX derived facies indicating the involvement of different chemical constituents following the trend of alteration as well as carbon enrichment. The D1 and D2 values obtained through FHH model range from 1.17 to 2.45 and 2.54–2.70, the fractal values particularly D2 are ∼3 demonstrating the pore surfaces and structure of studied shales beds are complex and heterogeneous. This study helps to enhance the exploration and advancement in the shale gas resources from Ib-River of Mand-Raigarh Basin, India. Highlights: Shale beds of Mand-Raigarh Basin, India investigated for geochemical, pore and fractal attributes. Pore hysteresis mainly comprises H1-type-II and H4-type-IV curves indicating dominance of cylindrical and bottle-neck pores. Fractal dimensions D2 controls the adsorption mechanism in matrix associated micro and meso-macro pores. Heterogeneity in organo-inorganic contents governing formation of fractal surfaces and pore openings. The existing complex pore geometry elucidated by SEM images may be critical issue for gas flow network.