Organic geochemical and petrographical characteristics of the Nagaur lignites, Western Rajasthan, India and their releva
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ORIGINAL PAPER
Organic geochemical and petrographical characteristics of the Nagaur lignites, Western Rajasthan, India and their relevance to liquid hydrocarbon generation Alok Kumar Singh 1 & Alok Kumar 1 & Mohammed Hail Hakimi 2 Received: 5 February 2018 / Accepted: 19 July 2018 # Saudi Society for Geosciences 2018
Abstract The article presents the geochemical and petrographical characteristics of Paleocene lignite deposits of the Nagaur Basin to appraise the regional rank variation, organic matter maturity, and liquid hydrocarbon generative potential. The petrographical investigation indicated that the analyzed lignites contain abundant huminite group macerals with a significant amount of the liptinite group macerals while the concentration of inertinite group is less in comparison to huminite and liptinite group. The huminite reflectance (%R0) indicates that lignite samples of Nagaur Basin are thermally immature in nature and lignite to subbituminous B in rank. Immaturity of samples has a significant influence on the proximate results of the samples, especially on moisture and volatile matter concentration and low fixed carbon percentage. The analyzed lignites have TOC and S2 values that range from 30.4 to 43.0 and 58.0 to 130.7 mg HC/g rock, respectively, which shows that these lignites have excellent hydrocarbon generation potential and make them industrially important, considering the huge lignite reserve in the study area region. The Rock-Eval pyrolysis and ultimate analysis also reveal that these lignite samples mainly contained mixed type II–III kerogens with significant potential for both liquid hydrocarbon and gas generation. These kerogens are dependable on the maceral composition that was derived from the microscopic study. The presence of the high huminite with significant amount of liptinite (more than 15%) macerals also suggests that these lignites can act as a good source rock for hydrocarbon generation. Keywords Paleocene coals . Liptinite maceral . Liquid hydrocarbon generation . Western Rajasthan . India
Introduction Hydrocarbon generation potential from coal and lignite deposits of various coal-bearing sedimentary basins, especially in the Mesozoic and Cenozoic Era, has been the interesting research problem, and a number of researchers have tried to establish that the terrestrial organic matter may act as source and it can also participate in the generation of hydrocarbon (Hunt 1991; Diessel 1992; Fleet and Scott 1994; Isaksen et al.
* Alok Kumar Singh [email protected]; [email protected] 1
Rajiv Gandhi Institute of Petroleum Technology, Amethi, Jais 229304, India
2
Geology Department, Faculty of Applied Science, Taiz University, 6803 Taiz, Yemen
1998; Singh and Singh 2001; Sykes 2001; Sykes and Snowdon 2002; Wilkins and George 2002; Singh and Singh 2003; Singh and Singh 2005; Hakimi and Abdullah 2013; Singh and Kumar 2017b). Many of these investigations have demonstrated that the main criteria for liquid hydrocarbon generation are maceral content and the paleodepositional condit
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