Coal Vitrinite Research Articles

Liquid-phase ozonation of vitrinites of coals of various metamorphic stages: Product composition

The fractionated products of ozonation of vitrinites of Kuznetsk coals of different metamorphic stages in chloroform have been characterized by IR spectroscopy, thermogravimetry, and gas chromatography-mass spectrometry. High-molecular-mass compounds insoluble in water prevail in the products. Water-soluble products are ketones, oxyalkanols, lower aliphatic acids, and hydroxy-and dicarboxylic aromatic acids.

Tests on Vitrinite Reflectance of Coal and Analysis of Tectonic Stress Field

AbstractIn order to deduce the tectonic stress field in North Henan by coal vitrinite reflectance, based on the principle that the tectonic stress is the main controlling factor of the vitrinite reflectance anisotropy (VRA), we made tests of coal vitrinite reflectance under microscope for directional coal specimen collected from Jiaozuo, Anyang, Hebi mining field in Henan province, and gained vitrinite reflectance ellipsoids (VRI) made up of reflectance maximum value, reflectance intermediate value and reflectance minimum value through some calculations to the testing data. The results show that the coal specimens in studied area indicate indicatrix of optical biaxial crystal, they have been suffered from intense tectonic deformation and the vitrinite reflectance anisotropy (VRA) is induced by tectonic stress. The tectonic stress field of North Henan obtained from vitrinite reflectance ellipsoids (VRI) is accordant basically with the tectonic stress field acquired from other methods, such as drilling, joints statistics and Henan province regional tectonic stress field analysis, but there is small difference that the tectonic stress field shows a left ward deflexion in Anyang and Hebi. In short, the method deducing tectonic stress field by vitrinite reflectance anisotropy (VRA) is feasible and effective.

Chemistry of thermally altered high volatile bituminous coals from southern Indiana

The optical properties and chemical characteristics of two thermally altered Pennsylvanian high volatile bituminous coals, the non-coking Danville Coal Member (Ro = 0.55%) and the coking Lower Block Coal Member (Ro = 0.56%) were investigated with the purpose of understanding differences in their coking behavior. Samples of the coals were heated to temperatures of 275 °C, 325 °C, 375 °C and 425 °C, with heating times of up to one hour. Vitrinite reflectance (Ro%) rises with temperature in both coals, with the Lower Block coal exhibiting higher reflectance at 375 °C and 425 °C compared to the Danville coal. Petrographic changes include the concomitant disappearance of liptinites and development of vesicles in vitrinites in both coals, although neither coal developed anisotropic coke texture. At 375 °C, the Lower Block coal exhibits a higher aromatic ratio, higher reflectance, higher carbon content, and lower oxygen content, all of which indicate a greater degree of aromatization at this temperature. The Lower Block coal maintains a higher CH2/CH3 ratio than the Danville coal throughout the heating experiment, indicating that the long-chain unbranched aliphatics contained in Lower Block coal liptinites are more resistant to decomposition. As the Lower Block coal contains significant amounts of liptinite (23.6%), the contribution of aliphatics from these liptinites appears to be the primary cause of its large plastic range and high fluidity.

06/01496 Sequential fatty acid analysis of a peat core covering the last two millennia (Tritrivakely lake, Madagascar): Diagenesis appraisal and consequences for palaeoenvironmental reconstruction: Disnar, J.-R. et al. Organic Geochemistry, 2005, 36, (10), 1391–1404

The genesis of the microscopic constituents of coal (macerals) and of maceral associations (microlithotypes) representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats. Peat microscopy especially promoted the understanding of humification and biological gelification, both of which are decisive for the genesis of huminites/vitrinites in brown coals and hard coals, respectively. Microbial activity during peatification has been documented by chemists, microbiologists and petrologists and, recently, by electron-microscopical observations in coals. This activity leads to the incorporation of lipid substances into the humic matter and, later, influences the chemical, physical and technological properties of vitrinites. Geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal. In this process, the hydrogel brown coal is transformed to the bitumogel bituminous coal. Coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration. The formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the “coalification jumps” of the macerals, especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite (bitumen) and micrinite (dead carbon). Bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals (bituminite, fluorinite and exsudatinite) and suggests a higher proportion of algal material in coals than was thought earlier. The genesis of various types of inertinite macerals will probably become an increasingly important subject of research, especially with regard to “rank-inertinites” that seem to attain their high inertinitic reflectance initially during coalification.Besides the origin of macerals, the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu, the peat-forming vegetation, palaeoclimate, water and nutrient supply, acidity, marine and calcareous influence and fire, with examples from Euramerican Carboniferous coals, Gondwana coals, and Tertiary brown coals. Vegetation, water and oxygen supply (Eh-conditions) are most important for the generation of coal facies.Vegetation has been reconstructed with the help of palaeobotany, including palynology, cuticular analysis and wood anatomy (in brown coals) and with the study of petrified (permineralized) peats preserved in coal balls. The microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative. However, the results of palynological and cuticular analyses should be evaluated with caution, considering the varying resistance of palynomorphs and cuticles and, in the case of palynomorphs, their possible extrapaludal origin.Microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies, especially in brown coals. The much disputed origin of brown-coal lithotypes is considered in detail. For hard coals there seems to be agreement that coal layers rich in vitrites and liptinite-poor clarite were deposited in wet-forest swamps, that microlayered liptinite-rich clarites are sub-aquatic humic muds, and that inertinite-rich durites represent oxidized peats. The origin of liptinite-rich durites is controversial (either subaquatic muds or oxidized peats, the latter perhaps from raised bogs).A recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous, oligotrophic conditions. Although raised bogs with a dense arborescent vegetation are known from Borneo, it seems not probable that most seams (which were deposited in foredeeps or steadily sinking graben zones) are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams. But, as in modern peats, striking changes of coal facies are commonly caused by hydrological events, e.g., inundations as a consequences of crevasses or of fires that burned the peat.The origin of the inertinite-rich Gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub-arctic peats is recommended.Coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite, as well as by hydrogen-rich vitrinites with a relatively low reflectance and high fluorescence, all due to a strong bacterial activity in peats of low acidity.Proposals for further research are made in the conclusions.

Variations in elemental composition of macerals with vitrinite reflectance and organic sulphur in the Greta Coal Measures, New South Wales, Australia

Abstract The elemental composition of the individual macerals in the Early Permian Greta Coal Measures of the northern Sydney Basin and adjoining Cranky Corner Basin, New South Wales, including some seams with high to very high organic sulphur contents, have been analysed in polished sections using light-element electron microprobe techniques, and the results evaluated in the light of vitrinite reflectance and other characteristics of the coals concerned. As with other Australian coals, the vitrinite macerals in each sample have the lowest proportions of carbon and highest proportions of oxygen, and the inertodetrinite and fusinite macerals the highest C and lowest O contents. Semifusinite and the liptinite macerals have intermediate C and O percentages. Organic sulphur and organic nitrogen are also highest in the vitrinite macerals of the individual samples, and lowest in the fusinite and inertodetrinite components. The vitrinite macerals in the Puxtrees seam of the Greta Coal Measures on the Muswellbrook Anticline, in the upper Hunter Valley, have similar elemental compositions (78% C) and similar reflectance values (Rv max around 0.7%) to vitrinites in the Late Permian bituminous coals in other parts of the Sydney-Bowen Basin. The vitrinites in the seams of the Cranky Corner Basin also have similar carbon contents to the Puxtrees seam material, suggesting a similar rank level, but have much lower vitrinite reflectance values (Rv max = 0.4–0.5%), probably due to marine influence associated with the depositional system. The vitrinites in the Greta seam on the Lochinvar Anticline, in the Lower Hunter region, have higher carbon contents (83%) than the Puxtrees material, suggesting a higher rank level, but similar to lower vitrinite reflectance values (Rv max = 0.6–0.7%). Vitrinite carbon is also constant through the seam profile, despite upwardly decreasing reflectance values in the seam due to progressive increases in marine influence. The vitrinites in the upper Greta seam and the Cranky Corner Basin coals have high to very high organic sulphur contents, again probably due to marine influence on the depositional process. The vitrinites in the Cranky Corner Basin coals, which have particularly high organic sulphur contents, also have somewhat lower oxygen contents in relation to their carbon percentages than those of other Australian seams, suggesting that the additional organic sulphur has replaced oxygen in the macerals' molecular structure. The macerals, especially the vitrinites, in the coals with high organic sulphur and anomalously low vitrinite reflectance also have up to 0.5% Al and 1% Ca intimately associated with the organic matter. Similar organically associated inorganic elements are commonly found in lower-rank (e.g. sub-bituminous) coals, but are usually lost from the organic matter at higher rank levels. The coals of the Greta Coal Measures therefore have vitrinite carbon contents consistent with a high volatile bituminous rank, but those seams or parts of seams with high organic sulphur due to substantial marine influence appear to have preserved the vitrinite reflectance values and organically associated inorganic elements more typical of lower-rank, sub-bituminous materials.

Variations in coal maceral chemistry with rank advance in the German Creek and Moranbah Coal Measures of the Bowen Basin, Australia, using electron microprobe techniques

Variations in the elemental composition of individual macerals in seams from the Permian German Creek and Moranbah Coal Measures in the Bowen Basin of Queensland have been studied over a wide range of coal ranks, using light-element electron microprobe techniques, to establish the coalification tracks of key macerals in a single coal-bearing interval from subbituminous through bituminous coal to anthracite. Vitrinite reflectance (Rv max) in the seams studied increases from 0.39% in the western part of the basin to over 3.5% in the east, apparently due to increases in burial depth. The study extends significantly the rank range covered by previous work on elemental analysis of individual macerals in the Gunnedah Basin, and provides a more useful basis than whole-coal analysis to evaluate the performance of coals in different utilisation processes. The microprobe results show that the carbon content of the telocollinite increases dramatically from 66% to 90% as the vitrinite reflectance of the coals (Rv max) increases from 0.39% to around 1.75%, but increases only slightly, from 90% to 91%, as Rv max increases from 1.75% to 3.52%. Oxygen decreases from around 26% to approximately 5% as Rv max increases from 0.39% to around 1.75%, and then decreases only very slightly into the anthracite range. The nitrogen content of the telocollinite in these coals also appears to decrease slightly with rank advance, and appears moreover to display a relatively abrupt drop at around 2% Rv max. This may be associated with the development of ammonium illite in the mineral matter. Organic sulphur in the telocollinite, on the other hand, seems to remain essentially constant with rank advance, at least in this particular succession. In contrast to vitrinite, fusinite and inertodetrinite have significantly higher but somewhat more constant carbon contents, varying only from around 81% to 93% C over the rank range studied. Oxygen in these macerals decreases from around 12% to a little over 2% with the same degree of rank advance. Sulphur and possibly nitrogen also appear to be significantly lower in fusinite and inertodetrinite than in the vitrinite of the same coal samples. Semifusinite is somewhat more variable in composition, with characteristics intermediate between those of the fusinite/inertodetrinite and those of the vitrinite in the same coal over the rank range studied.

05/00548 Studies of the coal facies in Western Ukraine (the Lvov-Volyn basin)

The genesis of the microscopic constituents of coal (macerals) and of maceral associations (microlithotypes) representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats. Peat microscopy especially promoted the understanding of humification and biological gelification, both of which are decisive for the genesis of huminites/vitrinites in brown coals and hard coals, respectively. Microbial activity during peatification has been documented by chemists, microbiologists and petrologists and, recently, by electron-microscopical observations in coals. This activity leads to the incorporation of lipid substances into the humic matter and, later, influences the chemical, physical and technological properties of vitrinites. Geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal. In this process, the hydrogel brown coal is transformed to the bitumogel bituminous coal. Coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration. The formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the “coalification jumps” of the macerals, especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite (bitumen) and micrinite (dead carbon). Bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals (bituminite, fluorinite and exsudatinite) and suggests a higher proportion of algal material in coals than was thought earlier. The genesis of various types of inertinite macerals will probably become an increasingly important subject of research, especially with regard to “rank-inertinites” that seem to attain their high inertinitic reflectance initially during coalification.Besides the origin of macerals, the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu, the peat-forming vegetation, palaeoclimate, water and nutrient supply, acidity, marine and calcareous influence and fire, with examples from Euramerican Carboniferous coals, Gondwana coals, and Tertiary brown coals. Vegetation, water and oxygen supply (Eh-conditions) are most important for the generation of coal facies.Vegetation has been reconstructed with the help of palaeobotany, including palynology, cuticular analysis and wood anatomy (in brown coals) and with the study of petrified (permineralized) peats preserved in coal balls. The microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative. However, the results of palynological and cuticular analyses should be evaluated with caution, considering the varying resistance of palynomorphs and cuticles and, in the case of palynomorphs, their possible extrapaludal origin.Microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies, especially in brown coals. The much disputed origin of brown-coal lithotypes is considered in detail. For hard coals there seems to be agreement that coal layers rich in vitrites and liptinite-poor clarite were deposited in wet-forest swamps, that microlayered liptinite-rich clarites are sub-aquatic humic muds, and that inertinite-rich durites represent oxidized peats. The origin of liptinite-rich durites is controversial (either subaquatic muds or oxidized peats, the latter perhaps from raised bogs).A recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous, oligotrophic conditions. Although raised bogs with a dense arborescent vegetation are known from Borneo, it seems not probable that most seams (which were deposited in foredeeps or steadily sinking graben zones) are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams. But, as in modern peats, striking changes of coal facies are commonly caused by hydrological events, e.g., inundations as a consequences of crevasses or of fires that burned the peat.The origin of the inertinite-rich Gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub-arctic peats is recommended.Coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite, as well as by hydrogen-rich vitrinites with a relatively low reflectance and high fluorescence, all due to a strong bacterial activity in peats of low acidity.Proposals for further research are made in the conclusions.

The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania: 2. Songwe-Kiwira Coalfield

This study provides coal quality, petrological, palynological and geochemical (Rock Eval) data on Permian coal seams and associated shales and mudstones of the Karoo Supergroup of the Songwe-Kiwira Coalfield, Tanzania. The coal seams, which have a cumulative thickness of 6.80 m, occur in the shale–coal–sandstone facies of the Mchuchuma Formation of Artinskian to Kungurian(?) age. Coal quality data (calorific values, volatile matter contents) and vitrinite reflectances indicate high volatile C bituminous to high volatile A bituminous coals, having relatively high ash yields (22–49 wt.%) and highly variable sulphur contents (0.17–9.2 wt.%). They could be used to fuel small-scale power generation units thereby providing electricity to nearby towns and villages. Also, the coals could be used as a substitute for wood, which is becoming increasingly scarce. In rural Tanzania, charcoal is still the main energy source for cooking, and wood is used extensively in brick kilns and for making roofing tiles. Petrological analysis indicated that the coals are dominated by dull to banded dull lithotypes, with seams at the base of the Mchuchuma Formation enriched in inertinite macerals (up to 83 vol.%), whereas up-section vitrinite contents increase. Palynological analyses indicated that the assemblage in the lower Mchuchuma Formation ( Scheuringipollenites assemblage) is dominated by trilete spores, whereas in the remainder of the section, non-taeniate disaccates dominate ( Scheuringipollenites–Protohaploxypinus assemblage). Facies critical macerals suggest for most seams a marsh/wet forest swamp depositional setting, which is consistent with the palynological data. Rock Eval analyses indicate type II/III kerogen, with Tmax (°C) values ranging from 426 to 440, corresponding to the early stage of hydrocarbon generation. Thermal Alteration Indices (2 to 2+) and vitrinite reflectance levels (0.60–0.83 Ro (%) support the Rock Eval maturity assessment, and despite the predominance of terrestrial-derived organic matter, there is evidence of oil generation and expulsion in the form of cavity and fracture filling exsudatinite.

Fluorescing macerals in South African coals

Maceral, microlithotype and fluorescing maceral content were analysed along with the vitrinite relative fluorescence measurements. Thirty samples from the South Africa Soutpansberg, Waterberg and Main Karoo Basins were investigated. These results were also compared with previously measured vitrinite reflectance values. The application of fluorescence techniques has allowed the identification of much higher liptinite content (about 5%) as compared with the results of routine maceral analysis in white light. Results presented provide an explanation of this difference, which is caused by difficulties in identifying fine liptodetrinite particles under illumination by the halogen lamp. Therefore, detritic particles of uncertain affinity should be verified under fluorescing light during routine maceral analysis. The presence and intensity of the fluorescing vitrinite in South African coals were also studied. The occurrence of this component is connected with the rank of coal but could be also affected by the facies (sample no. B 35) and in situ coal oxidation (sample no. B 3). The relative fluorescence intensity of vitrinite depends on the rank of the coal but also on its degree of oxidation. It seems also to be connected with the expulsion of oil which enhances its intensity. The influence of the fluorescing macerals content on some coal properties was proved by the positive correlation between fluorescing vitrinite as well as sum of fluorescing macerals and calorific value (0.66 and 0.74 corr. coeff., respectively). This proves the necessity of fluorescence application in routine maceral analysis carried out for coal quality evaluation.

Control of the chemical structure of perhydrous coals; FTIR and Py-GC/MS investigation

This work analyses a set of perhydrous coals (mainly composed of huminite/vitrinite maceral group) in order to determine the inter-relations between the hydrogen content and the modifications in the coal structure at a molecular level. The study involves the direct solid state characterisation of the coal combined with the analysis of representative fragments of the coal network obtained through flash-pyrolysis. The perhydrous character of the coals is not reflected either in the aliphatic hydrogen concentration (from FTIR data) or by the presence of straight-chain aliphatic moieties in the pyrolysates. This structural study shows that perhydrous coals contain mainly aromatic structures with 1–2 rings and a very small concentration of aromatic rings of large size. In agreement with this, phenol and alkyl phenols are the most prominent degradation products whereas other aromatic compounds (mainly benzene and naphthalene derivatives) are minor and probably evaporative compounds. The major structural elements in the samples studied are simple phenols with a preponderance of substituted para alkyl. The results obtained show that the processes of hydrogen enrichment affect the reactions of aromatisation and condensation. During the natural evolution of the perhydrous coals the transformations of the oxygenated functionalities in the lignin precursor seem to have taken place without the parallel structural reorganisation of the lignin framework responsible for the formation of polycyclic aromatic systems. As a result, the chemical structure of perhydrous vitrinites in coals is substantially modified with respect to that described in ‘normal’ coals. The results obtained also indicate that the source of hydrogen content and the effect that it has during the subsequent evolution process of the coals, affects the chemical structure of the perhydrous vitrinite and hence its properties and behaviour.

Elemental composition of coal macerals in relation to vitrinite reflectance, Gunnedah Basin, Australia, as determined by electron microprobe analysis

The elemental composition of macerals in high-volatile bituminous coals from the Gunnedah Basin, New South Wales, Australia, has been analysed by light-element electron microprobe techniques. The results have been evaluated in relation to maximum vitrinite reflectance trends in vertical section, including the effects of marine influence and igneous intrusions on the coal-bearing sequence. Mean maximum vitrinite (telocollinite and desmocollinite) reflectance for the analysed samples ranges from 0.63% to 0.99%, and to 2.2% for coal affected by igneous intrusions. The carbon content of the vitrinite, as determined by electron microprobe, ranges from 79.74% to 86.07%, and up to 89.06% for the heat-affected coal studied. A simple relationship cannot be established between the reflectance of the vitrinite and its carbon content over this range of coal samples. Vitrinite in marine influenced coals (with suppressed reflectance) appears to have a slightly higher carbon content than vitrinite in isorank coals without marine influence. The increase in carbon may be due to incorporation of carbon and sulphur–rich lipoid material into the vitrinite component. Notwithstanding these differences, the carbon content of vitrinite (telocollinite) seems to be affected only slightly by the depositional changes that cause suppression of vitrinite reflectance in marine-influenced coals. Telocollinite carbon content may therefore be a useful alternative to vitrinite reflectance as a rank indicator in maturation studies. The carbon content of whole-coal samples, determined by ultimate analysis, shows in vertical section a trend intermediate between the carbon of the vitrinite determined by electron microprobe and that of the associated inertinite macerals. Whole-coal analysis data in this range depend on the relative proportions of the different macerals present, as well as the rank of the coal concerned. Coals affected by igneous intrusion show a different relationship between carbon and oxygen of vitrinite (telocollinite), relative to coals where the rank is determined by depth of burial alone. The difference in C–O relationships suggests that the short-term heating associated with intrusions produces chemical changes in macerals that are not paralleled in more normal rank advance.

Thermally excited multiplet states in macerals separated from bituminous coal

Electron paramagnetic resonance searches of thermally excited multiplet states in macerals, exinite, vitrinite, and inertinite of Polish medium-rank coal (85.6 wt% C), were performed. Numerical analysis of lineshape indicates a multicomponent structure of the EPR spectra of macerals heated at 300 degrees and 650 degrees C. EPR spectra of exinite and vitrinite are a superposition of broad Gauss, broad Lorentz (Lorentz 1), and narrow Lorentz (Lorentz 3) lines. Two narrow Lorentz (Lorentz 2 and Lorentz 3) lines were observed in the resonance absorption curves of inertinite. The influence of the measuring temperature (100-300 K) on the EPR lines of the macerals was also studied. The experimentally obtained temperature dependence of the EPR line intensities were fitted by the theoretical functions characteristic for paramagnetic centers with ground doublet state (S = 12) and paramagnetic centers with thermally excited triplet (S = 1) and quadruplet (S = 32) states. Thermally excited multiplet states were found in exinite and vitrinite. Both paramagnetic centers with doublet ground state (S = 12) and paramagnetic centers with thermally excited states, probably quadruplet states (S = 32), exist in the group of paramagnetic centers of exinite and vitrinite with the broad Lorentz 1 lines. Intensities (I) of the broad Gauss and the narrow Lorentz 3 lines of exinite and vitrinite changes with temperature according to the Curie law (I = C/T). The existence of thermally excited multiplet states was not stated for inertinite. The two groups of paramagnetic centers of inertinite with Lorentz 2 and Lorentz 3 lines obey the Curie law. Copyright 2000 Academic Press.

00/01713 Structure analysis of oil shale and the development of fuel production technology

Reflectance FTIR microspectroscopy has been used to investigate the chemical structure of the liptinite macerals, alginite, bituminite, sporinite, cutinite and resinite in bituminous coals of Carboniferous to Tertiary age. In comparison with the spectra of vitrinite in the same coals, the micro-FTIR spectra of liptinite macerals are characterized by stronger aliphatic CHx absorptions at 3000–2800 and 1460–1450 cm−1, less intense aromatic CC ring stretching vibration and aromatic CH out of plane deformation at 1610–1560 and 900–700 cm−1 respectively and various intense acid CO group absorptions at 1740–1700 cm−1. The peaks at 1000–900 cm−1 due to aliphatic CH2 wagging vibrations in olefins and at 730–720 cm−1 due to CH2 rocking vibration in long chain aliphatic substances ([CH2]n, n≥4), are characteristic of liptinite macerals. Collectively the micro-FTIR spectral characteristics indicate that liptinite is composed of greater numbers of long chain aliphatics, fewer aromatics and a broader range of oxygen-containing groups than other macerals. Marked differences exist in micro-FTIR spectra within the liptinite maceral group. Alginite has the strongest aliphatic and least aromatic absorptions followed by bituminite, resinite, cutinite and sporinite. The aliphatic components in alginite are the longest chained and least branched whereas those in sporinite are the shortest chained and most branched. Bituminite, resinite and cutinite are intermediate. Notable differences in micro-FTIR spectra of individual liptinite macerals, such as intensities and peak locations of aromatic CC in alginite, CO groups in bituminite and resinite and substituted aromatic CH and C–O–C groups in cutinite and sporinite, also exist, which are attributed to differences in depositional environments or biotaxonomy.

Time–temperature relations for the remagnetization of pyrrhotite (Fe 7S 8) and their use in estimating paleotemperatures

Paleotemperature controls the maturation of coal and hydrocarbons in sedimentary basins and is also important in determining paleogeothermal gradient and hence tectonic style in exhumed metamorphic terrains. One method of estimating paleotemperature analyses the partial remagnetization of a rock due to heating in thick volcanic or sedimentary sequences, over subcrustal heat sources such as plumes, or at convergent plate margins. The overprinted natural remanent magnetization (NRM) of a rock records both the age and the paleotemperature of remagnetization, but a temperature correction from laboratory to geological time scales is required, using theoretical time–temperature relations. Time–temperature relations are well known for magnetite (Fe 3O 4) but are reported here for the first time for pyrrhotite (Fe 7S 8), another common NRM carrier. Data for each mineral separately yield independent estimates of paleotemperature if geologically reasonable estimates of heating time can be made. Paleotemperature can be estimated without geological input if data for both minerals are combined. Together with the age of remagnetization, determined from the paleomagnetic pole of the NRM overprint, these paleotemperature estimates can be used to infer the history of heating and uplift following burial. As a test case, we examine thermally acquired NRM overprints carried by pyrrhotite (Fe 7S 8) and magnetite (Fe 3O 4) in the Milton Monzonite of southeastern Australia. These overprints record a heating event about 100 Ma ago, probably thermal doming prior to rifting of the Tasman Sea, that upgraded coal rank in the Sydney Basin. Extrapolating from laboratory to geological times, using the new time–temperature contours for pyrrhotite, we estimate that the presently exposed Sydney Basin in the vicinity of the Milton Monzonite was remagnetized by heating to 165±30°C for ≈100 ka. Assuming a paleogeothermal gradient of 70°C/km appropriate for young or incipient rifts, the depth of burial at the time of remagnetization is estimated to have been 2.3±0.4 km. This figure is in excellent agreement with independent estimates based on reflectance data for the coal accessory mineral vitrinite.

In-situ analysis of solid bitumen in coal: examples from the Bowen Basin and the Illinois Basin

Solid bitumen and associated vitrinite from selected coals from the Bowen Basin and the Illinois Basin were studied using electron microprobe and micro-FTIR techniques. The coal studied covers a range of vitrinite reflectance from 0.59% to 1.33%. Carbon content in the bitumen is generally lower than in vitrinite in coals with vitrinite reflectance below 0.67%. In coals with reflectance above 0.67%, carbon content of bitumen is higher than in vitrinite, reflecting higher aromaticity due to hydrocarbon generation. Sulfur and iron content are comparable between vitrinite and bitumen. Functional group distribution suggests the presence of two types of bitumen in the Illinois Basin coals. The more aliphatic variety occurring in veins and cleats is interpreted as pre-gas generation bitumen, and the more aromatic variety filling cells and voids in inertinite as post-gas generation bitumen.

99/03571 Expulsion of oil from petroleum source rocks: inferences from pyrolysis of samples of unconventional grain size: Inan, S. et al. Org. Geochem., 1998, 29, (1–3), 45–61

Reflectance FTIR microspectroscopy has been used to investigate the chemical structure of the liptinite macerals, alginite, bituminite, sporinite, cutinite and resinite in bituminous coals of Carboniferous to Tertiary age. In comparison with the spectra of vitrinite in the same coals, the micro-FTIR spectra of liptinite macerals are characterized by stronger aliphatic CHx absorptions at 3000–2800 and 1460–1450 cm−1, less intense aromatic CC ring stretching vibration and aromatic CH out of plane deformation at 1610–1560 and 900–700 cm−1 respectively and various intense acid CO group absorptions at 1740–1700 cm−1. The peaks at 1000–900 cm−1 due to aliphatic CH2 wagging vibrations in olefins and at 730–720 cm−1 due to CH2 rocking vibration in long chain aliphatic substances ([CH2]n, n≥4), are characteristic of liptinite macerals. Collectively the micro-FTIR spectral characteristics indicate that liptinite is composed of greater numbers of long chain aliphatics, fewer aromatics and a broader range of oxygen-containing groups than other macerals. Marked differences exist in micro-FTIR spectra within the liptinite maceral group. Alginite has the strongest aliphatic and least aromatic absorptions followed by bituminite, resinite, cutinite and sporinite. The aliphatic components in alginite are the longest chained and least branched whereas those in sporinite are the shortest chained and most branched. Bituminite, resinite and cutinite are intermediate. Notable differences in micro-FTIR spectra of individual liptinite macerals, such as intensities and peak locations of aromatic CC in alginite, CO groups in bituminite and resinite and substituted aromatic CH and C–O–C groups in cutinite and sporinite, also exist, which are attributed to differences in depositional environments or biotaxonomy.

99/00019 Coprocessing Yanzhou coal with petroleum residue

The genesis of the microscopic constituents of coal (macerals) and of maceral associations (microlithotypes) representing various coal components is discussed in light of recent advances that have been made in the study of coals and modern peats. Peat microscopy especially promoted the understanding of humification and biological gelification, both of which are decisive for the genesis of huminities/vitrinites in brown coals and hard coals, respectively. Microbial activity during peatification has been testified by chemists, microbiologists, and petrologists, and also recently by electron-microscopical observations matter and later, influences the chemical, physical and technological properties of vitrinites. Geochemical gelification transform the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal. In this process, the hydrogel brown coal is transformed to the bitumogel bituminous coal. “Coal as a source rock for oil” has become an important research subject for coal petrologists (and oil exploration!). The formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to “coalification jumps” of the macerals, especially liptinite and vitrinites and to the generation of secondary macerals like exsudatinite (bitumen) and micrinite (dead carbon). Bituminization in coal has been revealed by the use of fluorescence microscopy that also showed the presence of new liptinite macerals (bituminite, fluorinite and exsudatinite) and suggests a higher proportion of algal material in coals than was thought earlier. The genesis of various inertinites will probably become an increasingly important subject of research, especially with regard to “rankinertinites” which seem to attain their high inertinitic reflectance during early coalification.Besides the origin of macerals, the origin of various coal facies in terms of maceral associations is considered in relation to the paleogeographic depositional milieu, the peat-forming vegetation, paleoclimate, water and nutrient supply, acidity, marine and calcareous influence, and fire, with examples from Euramerican Carboniferous coals, Gondwana coals and Tertiary brown coals. Vegetation and water and oxygen supply (Eh-conditions) are most important for the formation of coal facies. Vegetation has been reconstructed with the help of paleobotany, including palynology, cuticular analysis and wood anatomy (in brown coals) and with the study of petrified peats preserved in coal balls. The microscopical investigation of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative. However, the results of palynological and cuticular analyses should be evaluated with caution considering their varying resistance and, in the case of palynomorphs, their possible extrapaludal origin. Microscopical studies of modern peats derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies, especially in brown coals. The much disputed origin of brown coal lithotypes is considered in detail. For hard coals there seems to be agreement that coal layers rich in vitrite and liptinite-poor clarite were deposited in wet forest swamps, that microlayered liptinite-rich clarites were subaquatic humic muds, and that inertinite-rich durites were oxidized peats. The origin of liptiniterich durites is controversial; they are either subaquatic muds or oxidized peats the latter perhaps from raised bogs. A recent trend is the assumption that may of not all mineable coal seams have been deposited in raised bogs under ombrogeneous, oligotrophic conditions. Although raised bogs with a dense arborescent vegetation are known from Borneo, it seems not probable that most seams (which were deposited in foredeeps or steadily sinking graben zones) are of ombrogeneous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for some seams. But, as in modern peats, striking changes of seam facies are commonly caused by hydrological events, for example, inundations as a consequence of crevasses or of fires that burnt the peat. The origin of the inertinite-rich Gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub-arctic peats is recommended. Coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite, as well as hydrogen-rich vitrinites with a relatively low reflectance and high fluorescence, all due to a strong bacterial activity in peats of low acidity.Proposals for further work will be made in the conclusions [see Discussion].

Abstract: Coal Geology And Underground-Mine Degasification Applied To Horizontal Drilling For Coal-Bed Methane

In eastern Oklahoma’s Arkoma Basin in I998 at least three energy companies drilled coalbed methane wells 700-2,000 feet deep that eventually penetrated 700-800 feet horizontally into the 4-6-foot-thick Hartshorne coal, but also drilled through shale, mudstone, and interlaminated shale and sandstone. Those well segments in shale and mudstone may collapse, leading to well abandonment. Obviously coal will not be penetrated if the bit drifts into strata overlying or underlying the coalbed. Coal may be missing if the bit intersects a normal fault, a thick noncoal parting, or a channel-fill sandstone. and to hold down costs. Also data should be tabulated and maps constructed showing net coalbed thickness, cleat frequency and orientation, coalbed structural contours, faults and secondary coal fractures, cleat-filling minerals, coal-rank isocarbs, inherent moisture, vitrinite reflectance, and lithology of strata overlying or underlying the coalbed. Most of these items, in addition to the laws of gas movement, affect or control the permeability and porosity of the coalbed methane reservoir and the flow of gas to the well. company into the 4-ft-thick Hartshorne coal in an underground inine in Oklahoina in the middle 1970’s, removing great quantities of 97% methane gas without hydraulic fracturing. to drain gas from coal beds in underground mines, should be applied to maximize success in coalbed methane drilling, production, and profit. Coal geology studies, including coal characterization before drilling begins, should help in lease selection Twenty-three horizontal, openhole, experimental boreholes, 300-2,200 feet long, were drilled by a coal Therefore, detailed geological evaluation, combined with information from the history of horizontal drilling

Abrupt changes (jumps) in reflectance values and chemical compositions of artificial charcoals and inertinite in coals

Abrupt changes (jumps) in reflectance values and chemical compositions of charcoals during heating experiments in muffle and thermal gravimetric analyzer ovens occur at mean maximum reflectance values of about 0.50–0.60%, 1.10–1.20%, 1.40–1.50%, 2.20–2.30%, 2.80–2.90% and 3.70–3.90% ( R max). These abrupt changes are similar to the so called `coalification jumps' in vitrinite or liptinite in coals. Jumps are much more notable in low temperature charcoals (formed at less than 400°C) than in high temperature charcoals (formed at greater than 400°C). Abrupt changes in chemical composition are coincident with jumps in reflectance as evident from sudden decreases or increases in functional groups as determined by FTIR-spectra. The jumps in composition of charcoals (intertinites) during charring experiments explains the multi-modal reflectance distributions commonly documented in coals. The distribution of reflectance values and FTIR spectral characteristics of inertinite in some Western Canadian coals is consistent with a model of charring that incorporates discrete compositional jumps. The `jumps' in reflectance values and chemical compositions probably reflect progressive breaking of chemical bonds in response to attainment of specific threshold activation energies.

Micro-FTIR spectroscopy of liptinite macerals in coal

Reflectance FTIR microspectroscopy has been used to investigate the chemical structure of the liptinite macerals, alginite, bituminite, sporinite, cutinite and resinite in bituminous coals of Carboniferous to Tertiary age. In comparison with the spectra of vitrinite in the same coals, the micro-FTIR spectra of liptinite macerals are characterized by stronger aliphatic CH x absorptions at 3000–2800 and 1460–1450 cm −1, less intense aromatic CC ring stretching vibration and aromatic CH out of plane deformation at 1610–1560 and 900–700 cm −1 respectively and various intense acid CO group absorptions at 1740–1700 cm −1. The peaks at 1000–900 cm −1 due to aliphatic CH 2 wagging vibrations in olefins and at 730–720 cm −1 due to CH 2 rocking vibration in long chain aliphatic substances ([CH 2] n , n≥4), are characteristic of liptinite macerals. Collectively the micro-FTIR spectral characteristics indicate that liptinite is composed of greater numbers of long chain aliphatics, fewer aromatics and a broader range of oxygen-containing groups than other macerals. Marked differences exist in micro-FTIR spectra within the liptinite maceral group. Alginite has the strongest aliphatic and least aromatic absorptions followed by bituminite, resinite, cutinite and sporinite. The aliphatic components in alginite are the longest chained and least branched whereas those in sporinite are the shortest chained and most branched. Bituminite, resinite and cutinite are intermediate. Notable differences in micro-FTIR spectra of individual liptinite macerals, such as intensities and peak locations of aromatic CC in alginite, CO groups in bituminite and resinite and substituted aromatic CH and C–O–C groups in cutinite and sporinite, also exist, which are attributed to differences in depositional environments or biotaxonomy.