Browsing by Author "P.K. Rajak"

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A study on assessment of hydrocarbon potential of the lignite deposits of Saurashtra basin, Gujarat (Western India)
(Springer International Publishing, 2017) Prakash K. Singh; V.K. Singh; P.K. Rajak; Neeraj Mathur
In the present investigation, Bhavnagar lignites of the Saurashtra basin (Gujarat) have been studied to assess their hydrocarbon generating potential. The samples of upper as well as lower lignite seams have been studied through microscopy and subjected to various chemical analyses viz. proximate analysis, ultimate analysis and Rock-Eval Pyrolysis. These lignites have high moisture and low to moderate ash yield but are characterized by high volatile matter. Petrographically they comprise predominantly of huminite group maceral while liptinite and inertinite groups occur in subordinated amount. Huminite is chiefly composed of detrohuminite and telohuminite. The Tmax (av. 416.23 °C) and huminite reflectivity (0.28%–0.30%) indicate a low degree of maturity for these lignites which is also substantiated by the Tmax versus hydrogen index plot. The organic matter is subjugated by kerogen Type-III with a potential to expel hydrocarbon on liquefaction. Study further reveals that the fixed hydrocarbon is several folds higher than the free hydrocarbons. Being high in reactive maceral content, a high ‘conversion’ and good ‘oil yield’ values for these lignites were observed. Thus, the empirically derived values match well with those obtained through the experimental values of Rock-Eval Pyrolysis and validate their hydrocarbon generating potential. © 2017, The Author(s).
Environmental geochemistry of selected elements in lignite from Barsingsar and Gurha mines of Rajasthan, Western India
(Geological Society of India, 2015) Prakash K. Singh; P.K. Rajak; M.P. Singh; A.S. Naik; Vijay Kumar Singh; S.V. Raju; Sanjay Ojha
The present paper contains the result of investigation carried out on selected trace elements in the less studied lignite deposits of Rajasthan, Western India. The study has been made on two new lignite deposits–Barsingsar and Gurha. The former has elevated ash content (mean 20.8%) than the latter one (mean 5.1%) and both of them have high volatile matter (mean 43.7% and 49.9% respectively). The lignite samples have been studied for selected elements like Fe, Ca, Mg, Mn, K, Na, Cu, Co, Ni, Cr, Zn, Pb, Cd and As. The elements like Cd, Co, Ni, Pb and Cu occur in high concentration when compared to the Clarke values for brown coal. Ca and Mg relate positively with organic matter in Barsingsar lignite indicating their organic source while K, Cu, Co, Pb and Cd indicate their inorganic origin. Ca might have come in contact with the organic matter during humification and would have become a part of humate. The elements like Cu, Co, Ni, Cr, Cd and Pb showing strong affinity with inertinite could have got associated with the mineral matter present in the fusinite and funginite macerals. In Gurha lignites Pb and Co have shown their affinity with inorganic matter which could have been drawn from sulphides and clay minerals. © 2015, Geological Society of India.
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
Paleomires of Eocene lignites of Bhavnagar, Saurashtra basin (Gujarat), western India: Petrographic implications
(Geological Society of India, 2017) Prakash K. Singh; Vijay K. Singh; M.P. Singh; P.K. Rajak
The Tertiary basins of Gujarat have always been a potential target for their hydrocarbon resources. The lignite resources of the region have also been an important field of research. The present paper presents the results of the petrological study carried out on the lignites of the Saurashtra basin. For this purpose samples were collected from lower and upper lignite seams from the Surkha lignite mine of Bhavnagar, Saurashtra. These samples were subjected to detailed petrographic analysis (both maceral and microlithotype). The study reveals that these lignites are dominantly composed of huminite group macerals while liptinite and inertinite group macerals occur in subordinate amounts. These lignites have attained a thermal maturity up to 0.28-0.30 percent vitrinite reflectance (VRr) which classifies them as ‘low rank C’ coals. Moreover, Bhavnagar lower lignite seam shows relatively less gelification as compared to the upper seam which suffered relatively more biochemical degradation. These lignites are characterized by high gelification index (GI) and low tissue preservation index (TPI). With the help of petrography based facies models an attempt has been made to reconstruct the environment of the paleomire of these lignites. © 2017, Geological Society of India.
Peat swamps at Giral lignite field of Barmer basin, Rajasthan, Western India: understanding the evolution through petrological modelling
(Springer Verlag, 2016) Prakash K. Singh; P.K. Rajak; M.P. Singh; V.K. Singh; A.S. Naik; Alok K. Singh
The lignite samples collected from Giral lignite field of Barmer basin have been subjected to petrological investigation. The data generated has been discussed to understand the evolution of the paleomires of these lignites. The present study reveals that these low rank C coals are chiefly composed of huminite group macerals, mainly telohuminite and detrohuminite, while liptinite and inertinite group macerals occur in subordinate amounts. Not much variation in the maceral composition from Seam-I to Seam-VIII has been observed. Barmer lignites are characterized by a very high GI (>10) and moderate TPI indicating topogenous mire in the basin which was permanently flooded. The GI and TPI values and the petrography-based facies critical models indicate that these lignites originated mostly under wet forest swamp to clastic marsh having telmatic to limno-telmatic conditions with a moderate rate of subsidence and a very slow fall in ground water table. Further, the GWI and VI values are suggestive of mesotrophic to rheotrophic hydrological conditions having the dominance of herbaceous to marginal aquatic vegetation. There were spells of periodic drowning of peat especially during the formation of Seam-VII. Moderately high concentration of calcium in these lignites along with the presence of framboidal pyrite indicate enhanced sulphate-reducing bacterial activity present in carbonate and sulphate-rich waters in the basin during peat formation. © 2016, The Author(s).
Petrographic characteristics and paleoenvironmental history of Eocene lignites of Cambay basin, Western India
(Springer International Publishing, 2017) Prakash K. Singh; Vijay K. Singh; M.P. Singh; P.K. Rajak
Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin (Gujarat) were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group (71.6%–86.3%) followed by liptinite (10.1%–19.3%) and inertinite (3.6%–11.0%) maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index (GI) and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxygenated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin. © 2017, The Author(s).
Petrological and geochemical investigations of Rajpardi lignite deposit, Gujarat, India
(2012) Prakash K. Singh; M.P. Singh; Alok K. Singh; A.S. Naik; Vikas K. Singh; Vijay K. Singh; P.K. Rajak
The present paper entails the petrographic and chemical characteristics of the lignite samples drawn from the Rajpardi lignite deposit of Bharuch district, Gujarat. This lignite contains a high concentration of huminite which is dominated by telohuminite, followed by detrohuminite. Liptinite and inertinite macerals are very low in concentration. The dominant microlithotype is humite. Its elevated volatile matter and high hydrogen content depicts its perhydrous nature. The study reveals that this lignite originated in a limno-telmatic to telmatic condition. The paleomire is further characterized as a wet moor having moderate to high flooding with good tissue preservation and increasing bacterial activity.
Study of Hydrocarbon Source Potential of Kapurdi Lignites of Barmer Basin, Rajasthan, Western India
(Springer, 2021) P.K. Rajak; V.K. Singh; Aniruddha Kumar; Vishvajeet Singh; Ankita Rai; Shweta Rai; K.N. Singh; Mamta Sharma; A.S. Naik; Neeraj Mathur; Prakash K. Singh
The present investigation is an attempt to study hydrocarbon source potential of early Paleogene lignites of Kapurdi, Barmer Basin. The samples collected from the working mines have been subjected to petrographic and geochemical analyses. The petrographic study includes both maceral as well as microlithotype analyses whereas geochemical study includes proximate and ultimate analyses. Besides, rock eval pyrolysis, FTIR and NMR studies have also been carried out. The analytically generated data were also correlated and checked with empirical equations. The study shows that these lignites of Barmer Basin are rich in kerogen type-III organic matter and contain high concentration of reactive macerals (huminite + liptinite) to the tune of ∼98% (mineral matter free basis) and they have attained low maturity (Rmax is 0.43%). These lignites have a fairly high conversion factor (95–97%) and oil yield (65–67%) which is also supported by the rock-eval data. Further, 1H and C13 shifts of NMR also suggest a high potential of hydrocarbon of Kapurdi lignites. © 2021, GEOL. SOC. INDIA.
Understanding the paleomires of Eocene lignites of Kachchh Basin, Gujarat (Western India): petrological implications
(Springer International Publishing, 2017) Prakash K. Singh; Vijay K. Singh; M.P. Singh; P.K. Rajak
The present paper entails the results of the investigations carried out on the lignite deposits of Kachchh Basin. The lignite samples were drawn from five lignite seams from Panandhro lignite field (Seam-I to -V) and eight lignite seams (Seam-I to -VIII) from the Matanomadh lignite field which are currently operational. The petrographic analysis of the lignites indicates a dominance of huminite group of macerals which is mainly contributed by ulminite-A, ulminite-B, attrinite, densinite, and phlobaphinite. Liptinite (chiefly sporinite, cutinite, resinite, and liptodetrinite) and inertinite (chiefly fusinite, funginite, and inertodetrinite) groups occur in subordinated amount. The mineral matter occurs in moderate concentration. Though sulfur content is high in these lignites, there is no fixed trend of variation of sulfur from bottom seam to top seam. The investigation reveals a flooded forest swamp having high rate of degradation. However, there were a few drier periods indicated by relatively more inertinite macerals. The petrography-based models indicate that the Kachchh lignites of Gujarat evolved in coastal marshy setting under transgressive phase. However, there were few intermittent fluvial activities giving rise to supratidal flood plain. This led to the formation of the associated carbonaceous shales in the basin. © 2017, The Author(s).