Geochemical and petrographical fingerprints of coal bed methane potential in the Son-valley Basin, India

• Published in: Arabian journal of geosciences Vol. 15; no. 23
• Main Authors: Kumar, Susheel, Varma, Atul Kumar, Mendhe, Vinod Atmaram, Kumar, Shikhar, Bhan, Uday
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-12-2022; Springer Nature B.V
• Subjects: Bituminous coal; Carbon; Carbon dioxide; Coal; Coalbed methane; Earth and Environmental Science; Earth science; Earth Sciences; Geochemistry; Hydrocarbons; Hydrogen; Kerogen; Methane; Minerals; Organic carbon; Organic matter; Original Paper; Oxygen; Permian; Reflectance; Rock; Rocks; Total organic carbon; Valleys; India; Micro-petrography; Son-valley Basin; Rock–Eval pyrolysis; Coal bed methane; Gas adsorption
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-022-11007-3

The present investigation aims to evaluate the coal bed methane (CBM) potential of the Permian coal deposits in the Son-valley Basin, India, using a series of geochemical, organic petrological, and gas adsorption experiments. The results of the proximate analysis and the relation between atomic hydrogen to carbon (H/C) and oxygen to carbon (O/C) ratios mark the sub-bituminous to bituminous rank of these coals, which are suitable for generating CBM. The thermally cracked hydrocarbons released under the Rock–Eval S2 curve (77.29–168.54 mg HC/g rock) along with the TOC (total organic carbon) content (TOC: 42.53–71.42 wt%) reflect excellent source rock potential for hydrocarbon generation. The hydrogen index (HI) and oxygen index (OI) ranging from 110 to 332 mg HC/g TOC and from 3 to 9 mg CO
2
/g TOC, respectively, indicate the presence of type III kerogen with the mixture of type II and III kerogen. The Rock–Eval
T
max
and estimated vitrinite reflectance values mostly suggest an early mature to peak mature phase of oil/wet gas generation. Besides, the studied coals are dominated by ligno-cellulosic vitrinite (39.71–56.83 vol.%), with a substantial volume of inertinite (30.54–45.49 vol.%), and labile liptinite (9.71–22.15 vol.%) macerals (on mineral matter-free basis), which may advocate gas-prone nature of these coals. The relations of the Langmuir volume (
V
L
: 17.4–21.6 cc/g on a dry ash-free basis) with organic and inorganic constituents of the coals reveal the integrated influence of organic matter, minerals, and thermal maturity of kerogen on gas sorption capacity.