Browsing by Author "D. Mohanty"

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Eocene lignites from Cambay basin, Western India: An excellent source of hydrocarbon
(Elsevier B.V., 2016) P.K. Singh; V.K. Singh; P.K. Rajak; M.P. Singh; A.S. Naik; S.V. Raju; D. Mohanty
In the present paper lignites from the Cambay basin have been studied for their hydrocarbon potential. The samples were collected from three lignite fields–Vastan, Rajpardi and Tadkeshwar, and were investigated by petrography, chemical analyses and Rock-Eval pyrolysis. The results are well comparable with the empirically derived values. The study reveals that these ‘low rank C’ lignites are exceedingly rich in reactive macerals (huminite + liptinite) while inertinite occurs in low concentration. These high volatile lignites generally have low ash yield except in few sections. The Rock-Eval data indicates the dominance of kerogen type-III with a little bit of type-II. The study reveals that the lignites of Vastan (lower and upper seams) and Tadkeshwar upper seam are more gas-prone while Rajpardi and Tadkeshwar lower seams are oil-prone. Further, the fixed hydrocarbons are several times higher than the free hydrocarbons. The relation between TOC and fixed hydrocarbon indicates that these lignites are excellent source rock for hydrocarbon which could be obtained mainly through thermal cracking. The empirically derived values reveal a high conversion (94–96%) and high oil yield (64–66%) for these lignites. © 2015 China University of Geosciences (Beijing) and Peking University
Maturity Parameter of Carbonaceous and Coaly Matter Revealed through Raman Spectroscopy
(Geological Society of India, 2024) A.S. Naik; Govind Kumar; Vishvajeet Singh; Prakash K. Singh; Manju Kumari; D. Mohanty; R.K. Majhi; N. Upadhyay
This article presents the results of ten coal samples of sub-bituminous rank collected from working mines in Chhattisgarh, India, and subjected to proximate and ultimate analysis, organic petrology and Raman spectroscopic study to reveal their maturity parameters and structural characteristics of carbonaceous materials. Vitrinite reflectance measurement was also performed to understand the maturity parameter, with values ranging from 0.35% to 0.57%. The research is unique as it combines petrological, geochemical and spectroscopic technique on coals of Hasdeo basin. Conventional parameter, volatile matter ranges from 21.83 and 33.68% suggesting low maturity. The ash yield values range from 12.04 and 26.61%. Petrographically, the coals are vitrinite rich ranging from 53.95 to 63.47% while the inertinite group range from 17.9 to 29.2%. The liptinite concentration the samples remain below 10%. The maceral constitution of the coals indicates carbonaceous materials undergoing early diagenetic phase. The Raman results showed the presence of the D and G bands, two prominent spectral signatures, which are typical of natural materials rich in carbon. The Raman shift recorded for the D band ranges from 1348 to 1385 cm-1 and for the G band, the Raman shift was recorded between 1607 to 1616 cm-1. The ratio of the various parameters derived from the two bands aid to understand the material response to the changing physical and chemical variables in the geological setup. The intensity ratio of the ID /IG band ranged from 0.15 to 0.79 (average 0.50), while the (G-D1) parameter ranges from 225 to 260 indicating heterogeneity in the samples. However, the ratio of AD1 /AG did not show any regularity, with values ranging from 0.07 to 1.85. The investigation elucidates that by integrating Raman spectroscopy analysis with vitrinite reflectance (VRo), we can discern distinctive structural attributes characteristic of immature kerogen. Furthermore, the petrological, proximate, and ultimate data collectively corroborate the carbonaceous, coaly material in its early stages of coalification. © 2024 Geological Society of India, Bengaluru, India.
Mineralogical Studies of Mahanadi Basin coals based on FTIR, XRD and Microscopy: A Geological Perspective
(Springer, 2021) A.S. Naik; B. Behera; U.K. Shukla; H.B. Sahu; P.K. Singh; D. Mohanty; K. Sahoo; D. Chatterjee
This paper is an attempt to investigate the mineral matter constituents in Permian coals of Mahanadi basin, India. Twenty two bulk samples from the working mines have been selected for the study. Analytical techniques such as X-Ray diffraction, Fourier transform infrared spectroscopy coupled with coal microscopy have been used in this study for rapid characterization. The chief mineral phases are quartz, kaolinite, orthoclase, muscovite, and chlorite in order of increasing abundance in all the samples. Petrographic analysis reveal the dominance of Vitrinite (36.17%) followed by the Inertinite (32.33%), Liptinite (14.30%) group of macerals and mineral matter (17.18%). Mineral matter in the voids and cell lumens is common mode of occurrence in the coals which can be attributed to syngenetic and epigenetic types. The proximate analysis suggest the coals have high ash yield (8.37% to 38.46% on air dried basis) with high volatile matter (10.8% to 35.51% on air dried basis) making it suitable for thermal power plants. © 2021, GEOL. SOC. INDIA.
Organic Petrological Facets and the Evolution of Paleomire, Matasukh Lignite Deposits, Rajasthan, India
(Springer, 2023) A.S. Naik; Vishvajeet Singh; D. Mohanty; R.K. Majhi; Govind Kumar; N. Upadhyay; Manju Kumari; Shweta Rai
The present research work attempts to understand the organo-petrological facets of the lignite hosted in the Tertiary successions in Rajasthan. The maceral diversity was analyzed qualitatively and quantitatively which recorded huminite as the dominant microscopic constituent followed by inertinite and liptinite. The rank parameter of coal evaluated through vitrinite reflectance measurement random (VRo) shows the values vary between 0.19 to 0.27% suggesting lignite in rank. The petrographic investigation point towards the primary phase of degradation of organic matter corroborated through the dominance of huminite suggesting frequent flooding and the presence of funginite, demonstrating intense fungal activity in the mire. The paleodepositional model records elevated values of gelification Index (GI) ranging from 1.63 to 3.88 with well-preserved cell structures pointing towards an early phase of coalification. The model and plot of GI and TPI show that the paleomire developed in a limnic setting. © 2023, Geological Society of India.
Petrographic characteristics and paleomires of Mand-Raigarh coals, Mahanadi Gondwana Basin, Chhattisgarh, India
(Springer Verlag, 2016) A.S. Naik; M.P. Singh; N. Volkmann; P.K. Singh; D. Mohanty; D. Kumar
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’ sub-bituminous 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 Tmax 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. © 2016, The Author(s).