Petrographic characteristics and paleomires of Mand-Raigarh coals, Mahanadi Gondwana Basin, Chhattisgarh, India

Abstract

Mand-Raigarh coalfield is one of the largest coalfields in the Mahanadi basin. The Geological Survey of India carried out initial study primarily on exploration. However, detailed petrographic and geochemical characters of the coals have not been done so far. This investigation is an attempt for petrographic and geochemical appraisal of the coals. Moreover, effort is also made for possible interpretation on development of coal facies. The results drawn from 30 composite coal samples suggest coals are rich in vitrinite, with collotelinite as the dominant maceral while liptinite macerals register low concentration. Dominant mineral assemblages found were clay minerals, pyrite was recorded as disseminated, framboidal and euhedral forms, carbonates recorded were mainly siderites. The vitrinite reflectance random (VRo) mean values range from 0.44 % to 0.56 %, and the rank of coal is suggested as high volatile 'B' to 'A' subbituminous in rank. The rock-eval pyrolysis reveal TOC content varying from 37 % to 68.83 %, while low hydrocarbon generating potential is evident from low S2 and T max values. The Hydrogen Index (HI) versus Oxygen Index (OI) plot reveal that the samples belong to Kerogen type-II-III with input dominantly from terrestrial source, some samples also fall in Kerogen type-II domain indicating lacustrine input. Vitrinite reflectance result indicate that the samples are immature and approaching oil window, which is in agreement with data of the Rock-Eval parameters. The gelification index (GI) and tissue preservation index (TPI) indicate that the coal developed in a telematic set up with high tree density. The ground water index (GWI) and vegetation index (VI) demonstrate that the peat developed as an ombrogenous bog.

Microstructural relation of macerals with mineral matter in coals from Ib valley and Umaria, Son-Mahanadi basin, India

“…The present paper entails an initial examination of the surface morphology of maceral and their relationship with the mineral matter in some coal samples collected from Ib river valley, Mahanadi basin, Odisha and Umaria coalfield, Madhya Pradesh. Some recent contributions on coal deposits of the Mahanadi valley have been made by Singh et al 2013, Naik et al 2016and Mishra et al 2016a. Nevertheless, the present study carried out under SEM and XRD would help in identifying their potential utilisation.…”

Petrographic studies to delineate suitable coal seams for coal liquefaction and their palaeo-environmental analysis: A case study from the Ib river and Mand-Raigarh coalfields of the Mahanadi valley coalfields, India

“…A facies model has been used including mineral matter concentration along with other maceral composition (modified after Singh and Singh 1996) to understand the various conditions of peat formation in the Ib and Mand-Raigarh coalfields. In the Ib river coalfield, most of the coal seams evolved under an alternate oxic to anoxic moor to wet condition due to intermittent to high flooding in the palaeomire, while the coal seams of the Mand-Raigarh coalfield have been evolved under a fluctuating alternate oxic and anoxic condition to oxic conditions with a sudden high flooding of the mire (Naik et al 2016) (figure 7).…”

Characteristics of coal-measure source rock and gas accumulation belts in marine-continental transitional facies fault basins: A case study of the Oligocene deposits in the Qiongdongnan Basin located in the northern region of the South China Sea

“…The coal dominated by the mirror group is known to be conducive to generate gas, and the coal dominated by the shell group (including the sapropelinite) has been confirmed to be conducive to oil production. Meanwhile, the coal dominated by the inertinite will not be conducive to hydrocarbon production, and the difference between the total hydrocarbon yields of the hydrogen-poor coal and the hydrogen-rich coal could potentially be up to five times more (Liu et al., 2000; Nail et al., 2016).…”