Geochemical attributes, pore structures and fractal characteristics of Barakar shale deposits of Mand-Raigarh Basin, India

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 D-1 and D-2 values obtained through FHH model range from 1.17 to 2.45 and 2.54-2.70, the fractal values particularly D-2 are similar to 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 lb-River of Mand-Raigarh Basin, India.