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Maria Mastalerz - One of the best experts on this subject based on the ideXlab platform.
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changes in chemistry of Vitrinite in coal through time insights from organic functional group characteristics
International Journal of Coal Geology, 2021Co-Authors: Maria Mastalerz, Agnieszka Drobniak, James C. HowerAbstract:Abstract Is the signature of the original plant communities preserved in coal, or is that signature overprinted by depositional and diagenetic processes? To address this question, Pennsylvanian coals from the Illinois and Appalachian basins were compared to Cretaceous, Paleocene, and Eocene coals of comparable coalification levels as shown by Vitrinite reflectance. Three reflectance intervals—0.52–0.55, 0.58–0.62, and 0.68–0.71%—were considered, and in total 51 samples were analyzed. Although data on proximate and ultimate analyses and petrographic composition were compared on whole coal samples, the maceral Vitrinite was the main target of this comparison because’ aside from being the dominant component of all the samples, it offers the best chance to preserve the signature of the original woody material. An in-situ micro-FTIR technique was used to collect data on the functional group distribution of Vitrinite, and FTIR-derived parameters were compared between different age groups with a special emphasis on the differences between Pennsylvanian and the Cretaceous Vitrinite. The main difference between Cretaceous and Pennsylvanian coals is reflected in their oxygen content, which is higher for the Cretaceous coals. On the functional group level, the only significant difference was detected in the CH2/CH3 ratio, which had higher values for Vitrinite in the Cretaceous samples. Other parameters both within the coal and the Vitrinite showed comparable scatter within age groups as those between the age groups. It is suggested that oxygen content in coal and CH2/CH3 ratio in Vitrinite reflect differences in the original biomass, and the variations in other parameters such as C, H, N, volatile matter, calorific value, or the majority of FTIR-derived parameters are a function of both depositional and post-depositional factors.
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Assessing the thermal maturity of black shales using Vitrinite reflectance: Insights from Devonian black shales in the eastern United States
International Journal of Coal Geology, 2020Co-Authors: Bei Liu, Maria Mastalerz, Juan Teng, Juergen SchieberAbstract:Abstract Thermal maturity of source rocks indicated by Vitrinite reflectance (Ro) is an important and reliable parameter to determine the petroleum potential of sedimentary basins. Originally, Ro was used to characterize the degree of coalification of coals and thus works well for coal seams, but it has limitations when used to determine the thermal maturity of black shale successions. A suite of six coal-shale pairs from the Upper Devonian black shale formations in the eastern United States (New Albany Shale, Ohio Shale, Dunkirk Shale, and Rhinestreet Shale) was selected to study the applicability of Ro in assessing the thermal maturity of black shale successions. The results show that Vitrinite in the studied coal samples is dominated by collotelinite, whereas Vitrinite in black shales occurs as small dispersed particles (~5 μm) in the mineral matrix. When comparing the size and morphology of dispersed Vitrinite particles in shales and collotelinite fragments in coals, Vitrinite in shales and adjacent coals should have the same origin. The measured mean random Ro of Vitrinite in coals ranges from 0.51–0.68%, and is 0.04–0.11% (average 0.07%) lower than that of dispersed Vitrinite particles in enclosing shales. This observation contrasts with previously reported Ro suppression in liptinite-rich black shales. A high standard deviation of Ro measurements indicates a highly heterogeneous nature of Vitrinite in black shales. Three mechanisms can be envisioned to contribute to the higher Ro of dispersed Vitrinite particles in black shales relative to enclosed coals. First, small Vitrinite particles may become more oxidized because small particles are more frequently suspended during transport to the site of deposition and reworking of bottom sediments after deposition than large pieces of driftwood that will turn into enclosed coal lenses during burial diagenesis. Second, misidentification of zooclast (e.g., chitinozoan) fragments as Vitrinite due to loss of diagnostic morphology. Third, various macerals in the Vitrinite group (e.g., corpogelinite and collotelinite) may have had different original reflectance values. Based on the petrographic characteristics of Vitrinite and Vitrinite-like particles, caution should be applied when using the Ro values of dispersed Vitrinite and Vitrinite-like particles in black shales as indicators of thermal maturity.
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neutron scattering study of Vitrinite insights into sub micrometer inclusions in north american carboniferous coals of bituminous rank
International Journal of Coal Geology, 2018Co-Authors: Andrzej P Radlinski, Maria MastalerzAbstract:Abstract Results of SANS and USANS measurements performed on a series of six Vitrinite samples having Vitrinite reflectance (Ro) values ranging from 0.55% (high volatile bituminous rank) to 1.28% (medium volatile bituminous rank) were analyzed. Experimental data were acquired for two sample forms: platelets cut parallel to the bedding and pellets made up of randomly oriented, nearly-monodisperse particles. Numerical analysis indicates the presence of sub-micron sized inclusions embedded in the organic matrix. For the lowest-rank Vitrinites, the dominating inclusions are monodisperse are ~ 7–12 nm in diameter, and have concentrations of the order of 1017 cm− 3. Their shape is anisotropic, with the surface-to-volume ratio about three times larger than for a solid sphere. The higher-rank Vitrinites contain much larger monodisperse inclusions having diameters of ~ 50 nm, concentrations of ~ 1014 cm− 3, large surface-to-volume ratios, and fuzzy interfaces with the organic matrix. Inclusions of a similar size and concentration are also present in the lowest-rank sample, but are much less frequent than the small inclusions. We provisionally interpret those objects as inclusions of mineral matter, most likely associated with original plant material. The internal specific surface area (SSA) calculated for the small mineral matter inclusions is ~ 100 m2/cm3 and for the large inclusions ~ 2 m2/cm3.
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comparative optical properties of macerals and statistical evaluation of mis identification of Vitrinite and solid bitumen from early mature middle devonian lower mississippian new albany shale implications for thermal maturity assessment
International Journal of Coal Geology, 2016Co-Authors: Yinzhi Wang, Lin Wei, Maria MastalerzAbstract:Abstract Vitrinite reflectance (VRo in %) is used routinely to quantify thermal maturity in sedimentary basins. Reflectance and fluorescence of other macerals such as solid bitumen and amorphous organic matter (AOM) can provide an independent means to assess thermal maturity and hydrocarbon generation potential. However, similarity in petrographic characteristics of these macerals, solid bitumen and Vitrinite in particular, often causes difficulties with their identification and, consequently, reflectance can be measured on misidentified particles, making reported VRo values unreliable. The purpose of this study is to compare reflectance values of various macerals in early mature shales and to evaluate the implications of misidentifying solid bitumen and Vitrinite for assessing thermal maturity. To address this issue, 15 organic-matter-rich samples from the Middle Devonian/Lower Mississippian New Albany Shale from a corehole in Daviess County, Indiana, were selected. These samples were chosen because they had distinct and easily identified AOM, solid bitumen, Vitrinite, and inertinite particles, allowing for statistically relevant comparisons. VRo values (0.57 to 0.65%) of the studied sample suite cover the early mature stage, and expressed no trend with depth. In comparison, reflectance values of solid bitumen (BRo) and AOM (AOMRo) from the same samples are lower, and range from 0.44 to 0.52% and 0.27 to 0.31%, respectively. These differences are accompanied by corresponding differences in chemistry of macerals as demonstrated by the micro-FTIR technique. Specifically, compared to Vitrinite and inertinite, solid bitumen shows lower aromaticity, and compared to AOM and alginite, it exhibits shorter aliphatic chains. Reflectance was observed to vary systematically; samples having higher VRo also feature elevated solid bitumen and AOM reflectance values. The relationship between Vitrinite and solid bitumen can be expressed by the following equation: Vitrinite reflectance equivalent (VRoE in %) = (0.83 × BRo) + 0.22, whereas for Vitrinite and AOM, VRoE = (0.84 × AOMRo) + 0.38. Statistical evaluation of the differences in reflectance values caused by maceral misidentification indicates that in extreme cases, when a petrographer cannot distinguish between Vitrinite and solid bitumen, the reflectance can be shifted by 0.06–0.09%. For this set of samples, such a difference could shift maturity assessment from early mature to immature. In more common cases, when the analyst can distinguish between the macerals but has difficulties with their overlapping reflectance interval, the reflectance difference that results from misidentification is only within a 0.0–0.02% range. Therefore, if the level of uncertainty in maceral identification can be determined, the calculation of VRoE values from measured BRo, can reduce inaccuracy in VRo values for interpreting the thermal histories of sedimentary basins, which, in turn, is essential for the assessment of oil and gas resources and for building a successful exploration model.
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mapping the chemistry of resinite funginite and associated Vitrinite in coal with micro ftir
Journal of Microscopy, 2013Co-Authors: Yanyan Chen, Maria Mastalerz, Luis Dethere Caro, Arndt Schimmelmann, Astrid BlandonAbstract:Micro-FTIR mapping is a powerful tool for nondestructive, in situ chemical characterization of coal macerals at high resolution. In this study, the chemistry of resinite, funginite and associated Vitrinite is characterized via reflectance micro-FTIR for Cenozoic high volatile C bituminous coals from Colombia. In comparison with the micro-FTIR spectra of Vitrinite and inertinite, the corresponding spectra of liptinite macerals in the same coals are characterized by stronger aliphatic CH(x) absorbance at 3000-2800 and 1460-1450 cm⁻¹, but less intense aromatic C=C ring stretching vibration and aromatic CH(x) out-of-plane deformation at 700-900 cm⁻¹. The aliphatic components in resinite have the longest carbon chains and are least branched, bestowing the highest hydrocarbon generation potential on resinite among the three macerals studied. In contrast, funginite exhibits the strongest aromatic character, the highest aromaticity, the lowest 'A' factor values and the lowest C=O/C=C ratios among the three maceral groups. Vitrinite generally displays intermediate chemical characteristics. Reflectance micro-FTIR mapping of coal samples further confirms the aliphatic character of resinite and the aromatic nature of funginite. In addition, chemical mapping of resinite and adjacent Vitrinite shows that Vitrinite immediately adjacent to resinite displays higher aliphatic CH(x) stretching intensity than more distant Vitrinite, suggesting that chemical components from resinite can diffuse over short distances into adjacent Vitrinite, specifically causing hydrogen enrichment. It needs to be pointed out, however, that the region of influence is localized and limited to a narrow zone, whose extent likely depends on resinite's properties, such as its size and aliphatic material content. This way, the chemical map of resinite and associated Vitrinite provides direct evidence of the intermaceral effects occurring during the peat forming stage or during later coalification. No influence of funginite (primarily fungal spores and sclerotia) on the chemistry of adjacent Vitrinite has been demonstrated, which is likely due to the highly aromatic structure of this type of funginite.
Lila W. Gurba - One of the best experts on this subject based on the ideXlab platform.
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interpretation of Vitrinite reflectance depth profiles in the northern denison trough bowen basin australia
International Journal of Coal Geology, 2020Co-Authors: A A Kalinowski, Lila W. GurbaAbstract:Abstract The Denison Trough, Bowen Basin, Australia, is a mature hydrocarbon province that contains Permian to Triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions. The sandstone reservoirs of the Permian Aldebaran Sandstone, Freitag Formation and Catherine Sandstone of the Northern Denison Trough (NDT) were evaluated for their CO2 storage potential as part of the Queensland Government’s ZeroGen CO2 Capture and Storage Project, which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity, making them unsuitable for large scale injection and storage in this area. To better understand the factors acting to degrade these reservoirs, the purpose of the current study was to establish a thermal maturity framework for the Permian sandstone reservoirs of the Northern Denison Trough based on Vitrinite reflectance measurements of coals and Rock-Eval analysis of coals and shales from the Aldebaran Sandstone through to the Catherine Sandstone. Mean maximum Vitrinite reflectance of coals (Rmax) ranges from 0.55% to 0.93%, and estimated maximum burial temperatures calculated from Vitrinite reflectance fall between 83 oC – 125 oC. Calculation of palaeotemperatures from Vitrinite reflectance data has been hampered by inversions of depth-reflectance profiles at the top of the Aldebaran Sandstone and scatter in Vitrinite reflectance data. This has been attributed to depositional effects (including the major marine flooding surfaces at the top of the Aldebaran Sandstone) that have affected Vitrinite reflectance evolution in the NDT, producing low reflecting, fluorescing, perhydrous Vitrinite near marine flooding surfaces, and subhydrous Vitrinite when oxidising conditions prevailed. A Vitrinite reflectance difference of up to 0.2% Rmax is detected in an isometamorphic coal, an equivalent palaeotemperature difference of approximately 19 oC. The abundance of perhydrous Vitrinite has resulted in largely suppressed Vitrinite reflectance throughout the examined Permian interval in the Northern Denison Trough, and the presence of both perhydrous and subhydrous Vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals. Rock-Eval analysis provides supporting and calibrating maturity data. Tmax over the studied interval ranges from 421 oC to 447 oC, generating a positive, broadly linear correlation between Rmax and Tmax that is applicable specifically to the NDT. Tmax suppression was also detected in perhydrous coals. Hydrogen index serves to evaluate the level of Vitrinite reflectance suppression through an inverse relationship between the two parameters. The Rock-Eval data confirms the oil generation potential of coals in the NDT while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential. This study brings new insights into the thermal maturity framework in the NDT and highlights the importance of reliable Vitrinite reflectance data for calculation of maximum burial temperatures, particularly in underexplored or frontier areas.
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maceral characteristics and Vitrinite reflectance variation of the high rank coals south walker creek bowen basin australia
Indonesian Journal on Geoscience, 2013Co-Authors: Asep Kurnia Permana, Colin R. Ward, Lila W. GurbaAbstract:DOI: 10.17014/ijog.v8i2.156 The Permian coals of the South Walker Creek area, with a Vitrinite reflectance (Rvmax) of 1.7 to 1.95% (low-volatile bituminous to semi-anthracite), are one of the highest rank coals currently mined in the Bowen Basin for the pulverized coal injection (PCI) market. Studies of petrology of this coal seam have identified that the maceral composition of the coals are dominated by inertinite with lesser Vitrinite, and only minor amounts of liptinite. Clay minerals, quartz, and carbonates can be seen under the optical microscope. The mineral matter occurs in association with Vitrinite and inertinite macerals as syngenetic and epigenetic mineral phases. The irregular pattern of the Vitrinite reflectance profile from the top to the bottom of the seam may represent a response in the organic matter to an uneven heat distribution from such hydrothermal influence. Examination of the maceral and Vitrinite reflectance characteristics suggest that the mineralogical variation within the coal seam at South Walker Creek may have been controlled by various geological processes, including sediment input into the peat swamp during deposition, mineralogical changes associated with the rank advance process or metamorphism, and/or hydrothermal effects due to post depositional fluid migration through the coal seam.
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variations in elemental composition of macerals with Vitrinite reflectance and organic sulphur in the greta coal measures new south wales australia
International Journal of Coal Geology, 2007Co-Authors: Colin R. Ward, Zhongsheng Li, Lila W. GurbaAbstract: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.
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Vitrinite reflectance anomalies in the high volatile bituminous coals of the gunnedah basin new south wales australia
International Journal of Coal Geology, 1998Co-Authors: Lila W. Gurba, Colin R. WardAbstract:Abstract The rank of the Permian coals in the Gunnedah Basin has been analyzed using both petrographic and chemical methods. Apart from the effects of local igneous intrusions, a number of seams in the sequence have Vitrinite reflectance values (Rv max) that deviate significantly from the trend expected with a steady downward increase in coalification. Correlation of these anomalies with interpreted depositional environments suggests that abnormally low Vitrinite reflectance values in the sequence occur in seams either overlain by or intimately associated with marine strata. The three-dimensional distribution of such low reflectance values, in part of the section at least, can be related either to the lithofacies pattern or post-depositional groundwater flow associated with a major fan-delta system. Coals with anomalously high Vitrinite reflectance values appear to contain material described elsewhere as pseudoVitrinite, a component not previously reported in Australian Permian bituminous coals. Both low-value and high-value anomalies need to be taken into account when interpreting maturation patterns from Vitrinite reflectance data. In some cases other rank indicators such as air-dried moisture may be useful to complement Vitrinite reflectance in rank studies of high volatile bituminous coals. Abnormally low Vitrinite reflectance values due to environmental factors such as marine influence, on the other hand, may be used to identify flooding-surface sequence boundaries in the basin for stratigraphic and sedimentological investigations.
Colin R. Ward - One of the best experts on this subject based on the ideXlab platform.
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coal derived unburned carbons in fly ash a review
International Journal of Coal Geology, 2017Co-Authors: John G Groppo, Colin R. Ward, Uschi M Graham, Irena Kostova, Mercedes M MarotovalerAbstract:Abstract Unburned carbon (UC) in fly ash indicates inefficiency in combustion and may be an impediment to the beneficial use of fly ash or ash products in a variety of applications. The characteristics of the coal-derived UC are a function of the rank and type of the coal, as well as the size of the feed coal and the combustion conditions. At any coal rank, inertinite macerals are inherently more difficult to combust than the associated Vitrinite, and some will have a tendency to appear in the fly ash more or less unchanged from their appearance in the feed coal. The nature of UCs resulting from Vitrinite is dependent upon the coal rank. Low-rank huminite/Vitrinite will tend to form an isotropic char; bituminous Vitrinite will appear as isotropic and anisotropic cokes; and anthracite Vitrinite, naturally anisotropic, is observed as partially combusted Vitrinite fragments in the ash. The absorption of air entraining agents by UCs limits the use of high-UC fly ashes as a Portland cement substitute, with both standards organizations and regulatory bodies imposing limits on the acceptable UC concentrations. UC in fly ash can be used to adsorb organic compounds (such as phenols, dyes, herbicides, polychlorinated biphenyls, and petroleum constituents) and to capture trace elements (particularly Hg) from flue gas. UCs can also be used as sources of activated carbons, manufacture of graphite, and cokes in the metallurgical industry, as well as a source of carbon to feed back into the boiler. Beneficiation of fly ash to segregate relatively UC-free or UC-rich splits for beneficial re-use can be done by size classification, electrostatic separation, and froth flotation, as well as density separation, acid digestion, and incipient fluidization. Thermal processing may also be used to burn off the UC, leaving a relatively UC-free fly ash as the product.
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maceral characteristics and Vitrinite reflectance variation of the high rank coals south walker creek bowen basin australia
Indonesian Journal on Geoscience, 2013Co-Authors: Asep Kurnia Permana, Colin R. Ward, Lila W. GurbaAbstract:DOI: 10.17014/ijog.v8i2.156 The Permian coals of the South Walker Creek area, with a Vitrinite reflectance (Rvmax) of 1.7 to 1.95% (low-volatile bituminous to semi-anthracite), are one of the highest rank coals currently mined in the Bowen Basin for the pulverized coal injection (PCI) market. Studies of petrology of this coal seam have identified that the maceral composition of the coals are dominated by inertinite with lesser Vitrinite, and only minor amounts of liptinite. Clay minerals, quartz, and carbonates can be seen under the optical microscope. The mineral matter occurs in association with Vitrinite and inertinite macerals as syngenetic and epigenetic mineral phases. The irregular pattern of the Vitrinite reflectance profile from the top to the bottom of the seam may represent a response in the organic matter to an uneven heat distribution from such hydrothermal influence. Examination of the maceral and Vitrinite reflectance characteristics suggest that the mineralogical variation within the coal seam at South Walker Creek may have been controlled by various geological processes, including sediment input into the peat swamp during deposition, mineralogical changes associated with the rank advance process or metamorphism, and/or hydrothermal effects due to post depositional fluid migration through the coal seam.
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variations in elemental composition of macerals with Vitrinite reflectance and organic sulphur in the greta coal measures new south wales australia
International Journal of Coal Geology, 2007Co-Authors: Colin R. Ward, Zhongsheng Li, Lila W. GurbaAbstract: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.
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Vitrinite reflectance anomalies in the high volatile bituminous coals of the gunnedah basin new south wales australia
International Journal of Coal Geology, 1998Co-Authors: Lila W. Gurba, Colin R. WardAbstract:Abstract The rank of the Permian coals in the Gunnedah Basin has been analyzed using both petrographic and chemical methods. Apart from the effects of local igneous intrusions, a number of seams in the sequence have Vitrinite reflectance values (Rv max) that deviate significantly from the trend expected with a steady downward increase in coalification. Correlation of these anomalies with interpreted depositional environments suggests that abnormally low Vitrinite reflectance values in the sequence occur in seams either overlain by or intimately associated with marine strata. The three-dimensional distribution of such low reflectance values, in part of the section at least, can be related either to the lithofacies pattern or post-depositional groundwater flow associated with a major fan-delta system. Coals with anomalously high Vitrinite reflectance values appear to contain material described elsewhere as pseudoVitrinite, a component not previously reported in Australian Permian bituminous coals. Both low-value and high-value anomalies need to be taken into account when interpreting maturation patterns from Vitrinite reflectance data. In some cases other rank indicators such as air-dried moisture may be useful to complement Vitrinite reflectance in rank studies of high volatile bituminous coals. Abnormally low Vitrinite reflectance values due to environmental factors such as marine influence, on the other hand, may be used to identify flooding-surface sequence boundaries in the basin for stratigraphic and sedimentological investigations.
Paul C. Hackley - One of the best experts on this subject based on the ideXlab platform.
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understanding and distinguishing reflectance measurements of solid bitumen and Vitrinite using hydrous pyrolysis implications to petroleum assessment
AAPG Bulletin, 2018Co-Authors: Paul C. Hackley, Michael D LewanAbstract:Solid bitumen is a common organic component of thermally mature shales and typically is identified by embayment against euhedral mineral terminations and by groundmass textures. However, because these textures are not always present, solid bitumen can be easily misidentified as Vitrinite. Hydrous pyrolysis experiments (72 hours, 300-360°C) on shale and coal samples show solid bitumen reflectance (BRo) in shales is less responsive to thermal stress than Vitrinite reflectance (VRo) in coal. This effect is most pronounced at lower experimental temperatures (300-320°C) whereas reflectance changes are more similar at higher temperatures (340-360°C). Neither a ‘Vitrinite-like’ maceral or ‘suppressed Vitrinite’ was identified or measured in our sample set; rather, the experiments show that solid bitumen matures slower than Vitrinite. The data may explain some reports of ‘Vitrinite reflectance suppression’, particularly at lower thermal maturity (VRo≤1.0%), as a simple case of solid bitumen being mistaken for Vitrinite. Further, the experimental results confirm previous empirical observations that VRo and BRo are more similar at higher maturities (VRo>1.0%). It is suggested that ‘Vitrinite reflectance suppression’, commonly reported from upper Paleozoic marine shales of early to mid-oil window maturity, is a misnomer. This observation has important implications to petroleum exploration models and resource assessment because it may change interpretations for the timing and spatial locations of kerogen maturation and petroleum generation.
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Suppression of Vitrinite reflectance by bitumen generated from liptinite during hydrous pyrolysis of artificial source rock
Organic Geochemistry, 2018Co-Authors: K.e. Peters, Paul C. Hackley, J.j. Thomas, Andrew E. PomerantzAbstract:Abstract Mean random Vitrinite reflectance (Ro) is the most widely accepted method to determine thermal maturity of coal and other sedimentary rocks. However, oil-immersion Ro of polished rock or kerogen samples is commonly lower than Ro values measured in samples from adjacent Vitrinite-rich coals that have undergone the same level of thermal stress. So-called suppressed Ro values have also been observed in hydrous pyrolysis experiments designed to simulate petroleum formation. Various hypotheses to explain Ro suppression, such as sorption of products generated from liptinite during maturation, diagenetic formation of perhydrous Vitrinite or overpressure, remain controversial. To experimentally test for suppression of Vitrinite reflectance, artificial rock was prepared using silica and a calcined blend of limestone and clay with various proportions of thermally immature Vitrinite-rich Wyodak-Anderson coal and liptinite-rich kerogen isolated from the oil-prone Parachute Creek Member of the Green River Formation. The samples were subjected to hydrous pyrolysis for 72 h. at isothermal temperatures of 300 °C, 330 °C, and 350 °C to simulate burial maturation. Compared to artificial rock that contains only coal, samples with different proportions of oil-prone kerogen show distinct suppression of calibrated Ro at 300 °C and 330 °C. The reflectance of solid bitumen generated during heating of the samples is lower than that of the associated Vitrinite and does not interfere with the Ro measurements. These results provide the first experimental evidence that Ro suppression occurs in Vitrinite mixed with liptinite-rich kerogen in a rock matrix. Although the precise chemical mechanism for Ro suppression by liptinite remains unclear, free radicals generated from solid bitumen and associated volatile products during maturation of liptinite may contribute to termination reactions that slow the aromatization and rearrangement of polyaromatic sheets in Vitrinite, thus suppressing Ro. This mechanism does not preclude Ro suppression that might result from overpressure or differences in redox conditions during diagenesis.
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thermal maturity of northern appalachian basin devonian shales insights from sterane and terpane biomarkers
Fuel, 2013Co-Authors: Paul C. Hackley, Robert T Ryder, Michael H Trippi, Hossein AlimiAbstract:Abstract To better estimate thermal maturity of Devonian shales in the northern Appalachian Basin, eleven samples of Marcellus and Huron Shale were characterized via multiple analytical techniques. Vitrinite reflectance, Rock–Eval pyrolysis, gas chromatography (GC) of whole rock extracts, and GC–mass spectrometry (GCMS) of extract saturate fractions were evaluated on three transects that lie across previously documented regional thermal maturity isolines. Results from Vitrinite reflectance suggest that most samples are immature with respect to hydrocarbon generation. However, bulk geochemical data and sterane and terpane biomarker ratios from GCMS suggest that almost all samples are in the oil window. This observation is consistent with the presence of thermogenic gas in the study area and higher Vitrinite reflectance values recorded from overlying Pennsylvanian coals. These results suggest that Vitrinite reflectance is a poor predictor of thermal maturity in early mature areas of Devonian shale, perhaps because reported measurements often include determinations of solid bitumen reflectance. Vitrinite reflectance interpretations in areas of early mature Devonian shale should be supplanted by evaluation of thermal maturity information from biomarker ratios and bulk geochemical data.
Iwona Jelonek - One of the best experts on this subject based on the ideXlab platform.
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reservoir parameters and maceral composition of coal in different carboniferous lithostratigraphical series of the upper silesian coal basin poland
International Journal of Coal Geology, 2013Co-Authors: Slawomir Kedzior, Iwona JelonekAbstract:Abstract Laboratory tests were carried out on coal samples taken from mine openings of selected coal mines in the Upper Silesian Coal Basin. The analyses involved maceral composition (Vitrinite, inertinite and liptinite group) and Vitrinite reflectance on the one hand, and reservoir parameters (coal permeability and effective porosity) on the other. The results are compared. Samples with high values of coal permeability are characterized by Vitrinite contents of ca 60%, and samples with the lowest permeability by Vitrinite contents of 40%. The Vitrinite-rich bright coals are brittle and prone to crushing caused by tectonic pressures. Moreover, coal permeability is more strongly anisotropic in the bright coals of the Cracow Sandstone and the Mudstone Series than in the dull coals of the Upper Silesian Sandstone Series. In bright coals, permeability is much along the direction parallel to vitrain layers. Good reservoir parameters such as permeability and effective porosity are crucial for fluid flow through the coal seams and, thus, successful coalbed methane exploitation. In the Upper Silesian Coal Basin, Cracow Sandstone- and Mudstone Series with Vitrinite-rich coals should be a good target, though serious geological problems must first be overcome.
