Rank Bituminous Coal Research Articles

Reservoir rock typing assessment in a coal-tight sand based heterogeneous geological formation through advanced AI methods

Geoscientists now identify coal layers using conventional well logs. Coal layer identification is the main technical difficulty in coalbed methane exploration and development. This research uses advanced quantile–quantile plot, self-organizing maps (SOM), k-means clustering, t-distributed stochastic neighbor embedding (t-SNE) and qualitative log curve assessment through three wells (X4, X5, X6) in complex geological formation to distinguish coal from tight sand and shale. Also, we identify the reservoir rock typing (RRT), gas-bearing and non-gas bearing potential zones. Results showed gamma-ray and resistivity logs are not reliable tools for coal identification. Further, coal layers highlighted high acoustic (AC) and neutron porosity (CNL), low density (DEN), low photoelectric, and low porosity values as compared to tight sand and shale. While, tight sand highlighted 5–10% porosity values. The SOM and clustering assessment provided the evidence of good-quality RRT for tight sand facies, whereas other clusters related to shale and coal showed poor-quality RRT. A t-SNE algorithm accurately distinguished coal and was used to make CNL and DEN plot that showed the presence of low-rank bituminous coal rank in study area. The presented strategy through conventional logs shall provide help to comprehend coal-tight sand lithofacies units for future mining.

Geochemistry of the Leatherwood coal in eastern Kentucky with an emphasis on enrichment and modes of occurrence of rare earth elements

The Middle Pennsylvanian (Bolsovian) Leatherwood coal in the central part of eastern Kentucky is a moderately thick, moderate-S seam that has been one of the major energy resources in the region. Much of the seam profile consists of clarain, dull clarain, and durain with some brighter lithologies at the base of the seam and in the upper portion of the coal at one site. A previous study emphasized petrographic trends. In this investigation, the geochemistry of the coal is examined. Some elements, such as Ge and Ga, are enriched at 2× and 5× the World hard coal averages in the coal lithotypes adjacent to rock (roof, floor, partings). Arsenic and other chalcophile elements (Zn, Co, Ni) tend to be concentrated at the top and bottom of the seam profiles and below partings, generally in the coals with the highest pyritic sulfur content. Manganese enrichments occur in bright clarain lithologies at one site. No coal lithology reaches a 5× the World hard coal average, but samples between the 2× and 5× World hard coal averages tend to be at the top and bottom of the coal seam. Most coal samples tend to have a light rare earth element (LREE) enrichment. The basal lithotype at all sites, though, has a heavy REE enrichment and, via inference from the Zr and TiO2 concentrations, a smaller influx of detrital minerals than the basal lithotypes in many Appalachian coals. While the nature of REE associations is complicated by the high volatile A bituminous coal rank, the relatively high concentrations of the heavy REE suggest an original, albeit possibly not exclusive, organic association for those elements.

Physically mixed black liquor as a catalytic additive for pressurised steam gasification of different rank bituminous coals

Increasing prices and limited availability of oil and natural gas resulted in the popularity of gasification-based coal chemical production. However, the problems with low fuel conversion and high CO2 emission are hindering its competitiveness with other fossil fuels. Blending black liquor from the pulp and paper industry with coal could potentially mitigate the problem due to its carbon neutrality and high catalyst content, but their performance needs extensive analysis. Therefore, three bituminous coals with variable petrographic composition and ash content were physically mixed with various loadings of black liquor (5–20%wt) and gasified under pressurised steam at 800–1000 °C. The parameters such as syngas production and carbon conversion were measured and kinetic parameters were calculated with Random Pore Model, Grain Model and Isoconversional Model. The results have shown that the presence of black liquor has equally increased the gasification performance of each coal despite their different reactivity. For most reactive samples with an addition of 10%wt. Black liquor, the syngas yield had grown by up to 61%, carbon conversion increased by up to 23% and energies of activation reached as low as 39 kJ⋅mol-1, which makes the approach highly competitive against other catalytic impregnation methods.

Petrographic and geochemical characterization of coal from Santa Susana Basin, Portugal

The current and future importance of coal as a geological resource is related with the production of coke, carbon materials, carbon derivatives and other chemical products as well as a promising alternative source of critical trace elements. This study aims the comprehensive characterization of coals from the Santa Susana Basin (SSB), SW of Portugal. The SSB is a Pennsylvanian continental basin located along the Santa Susana Shear Zone that separates two tectonostratigraphic zones of Iberian Massif. Samples of coal and coaly silt-claystone from the main outcrops, Jongeis and Vale de Figueira, were collected for this study. The methodologies used for the petrographic and geochemical characterization included: optical microscopy, scanning electron microscopy with energy dispersive X-ray spectrometry, proximate and elemental analysis and inductively coupled plasma mass spectrometry (ICP-MS). The results demonstrate that the organic matter of coal from SSB is essentially composed of vitrinite and small amounts of inertinite. The mineral matter includes detrital minerals (mainly quartz and clay minerals), iron oxides and oxidized and non-oxidized framboidal pyrite. Epigenetic carbonates (dolomite and ankerite) were only observed in samples from Jongeis outcrop. Vitrinite random reflectance of the samples ranges between 0.90% and 1.25%, indicating a bituminous coal rank. The slightly higher vitrinite reflectance and the occurrence of epigenetic carbonates in samples from Jongeis can be related with differentiated burial history of the basin and post-depositional processes including fluids circulation that may have promoted the enhancement of the thermal maturity. When compared with the geochemical composition of worldwide hard coals, samples from Vale de Figueira are significantly enriched in Cs and In, while samples from Jongeis are significantly enriched in In and Mn. Considering the elements' mode of occurrence, the majority of elements are preferentially associated with mineral matter. The elements S, Cd, Mo, Pb and Se have organic affinity. The strong positive correlation between Ca and Mg, Mn and Te indicates their association with carbonate phases, which is in accordance with the carbonate composition.

Neutron scattering study of vitrinite: Insights into sub-micrometer inclusions in North American Carboniferous coals of bituminous rank

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 ~7–12nm in diameter, and have concentrations of the order of 1017cm−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 ~50nm, concentrations of ~1014cm−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 ~100m2/cm3 and for the large inclusions ~2m2/cm3.

Superimposed thermal histories in the southern limit of the Ossa Morena Zone – Portugal

AbstractThe Mississippian volcano-sedimentary complex in the Toca da Moura – Cabrela areas represents remnants of intra-volcanic marine sedimentary basins, formed during the collision between the Ossa Morena Zone with the South Portuguese Zone. These rock units are unconformably overlain by the Pennsylvanian intramontane coal-bearing Santa Susana Basin. Vitrinite reflectance determinations from rocks of these two basins indicate two episodes of thermal maturation. During the first episode, the Toca da Moura – Cabrela volcano-sedimentary complexes attained high maturation levels, equivalent to anthracite coal rank (3.0–3.5% Roran), which pre-dates the middle Moscovian Santa Susana Basin. The Santa Susana Basin attained moderate maturation levels equivalent to bituminous coal rank (1.35–1.5% Roran) recording a second episode of thermal maturation. Here, peak thermal conditions did not overprint the first maturation episode. The observed effects of magmatic intrusion on the thermal maturity and the lack of any increase in vitrinite reflectance with depth through c. 400 m of section in borehole SDJ-1 indicate high geothermal gradients during the first maturation episode. A contemporaneous magmatic event associated with the c. 335–320 Ma Cuba-Alvito Gabbros/Diorites of the Beja Massif was the possible cause for the high geothermal gradients postulated for the first maturation episode. Burial under a post-upper Moscovian sedimentary cover was the most likely process to account for the maturation levels determined for the Santa Susana Basin and for the second episode of thermal maturation.

Protosalvinia revisited, new evidence for a land plant affinity

The Upper Devonian Protosalvinia phytoclasts from Ohio Shale and its host rock were analyzed using GC/MS, GC-ir/MS, in situ FTIR and pyrolysis–GC/MS, in order to determine its chemical composition and to discuss the taxonomic position of this enigmatic fossil. Based on molecular ratios, the maturity of the organic matter present in the phytoclasts and rocks is comparable to a bituminous rank coal. Diagenetic products of Chlorobiaceae carotenoids were observed in the hosting rocks of Protosalvinia, indicating that anoxia prevailed during the sedimentary deposition. The soluble organic matter of phytoclasts shows land-derived biomarkers including long chain n-alkanes with a slight odd/even predominance and bicyclic sesquiterpenes with eudesmane skeletons. The carbon isotopic composition of n-alkanes is consistent with a land plant origin. The macromolecular fraction of Protosalvinia consists of a condensed aromatic network. The pyrolysis products of the phytoclasts show polycyclic aromatic hydrocarbons commonly observed in coals, including naphthalenes, phenanthrenes and dibenzofurans. Based on what is known about the thermal evolution of organic matter, these components could derive from demethylation and condensation of phenylpropanoids or polysaccharides present in the original structure of Protosalvinia. The former components are exclusively metabolized by land plants.

Characterization of water-soluble organic compounds released from black shales and coals

Knowledge of the composition of dissolved organic compounds as well as the main controls on their mobilization from natural organic matter is prerequisite for a comprehensive understanding of the fluid–rock interactions taking place in shale environments and coal seams over both geological and human timescales. In this study, black shales and coals from five different geological settings and covering the maturity range Ro=0.3–2.6% were extracted with deionized water. The dissolved organic carbon (DOC) yields were found to decrease rapidly with increasing diagenesis and remain low throughout catagenesis. Four different fractions of DOC have been qualitatively and quantitatively characterized in the study using size exclusion chromatography (SEC). Acetate is the dominant low molecular weight organic acid (LMWOA) in all extracts of shales and coals of bituminous rank. The concentrations of individual LMWOA also decrease with increasing maturity of the samples except for acetate extracted from the overmature Posidonia shale from the Haddessen well, which was influenced by hydrothermal brines. The positive correlation between the Oxygen Index (OI) and respective LMWOA yield indicates that OI is a significant factor influencing the extraction of organic acids from shales. The yields of both DOC and individual organic acids normalized to TOC are in the same order of magnitude for coals and shales with the same maturity. However, the extracts of coals tend to contain more aromatic compounds and the molecular masses of most constituents included in macromolecular fractions are higher than for shale extracts. These results suggested that different kerogen types show comparable amounts of DOC being extracted, but different DOC composition. Thus, both the origin of organic matter and thermal maturation progress during deposition has significant influence on water extract composition.

Co-combustion characteristics of sewage sludge with different rank bituminous coals under the O2/CO2 atmosphere

The effects of sewage sludge (SS) blended ratio, O2/CO2 ratio, and type of bituminous coal on the co-combustion characteristics of SS with bituminous coals were investigated. Thermogravimetric analysis was used to analyze the co-combustion profiles. Results show that TG curve shifts to a lower temperature with increasing SS blended ratio and O2/CO2 ratio. A distinct transition section exists at fixed carbon combustion of the blended fuels stage, and the temperature range of this transition section decreases significantly with increasing O2/CO2 ratio. The combustion property indexes of blended fuel increase with increasing SS blended ratio and O2/CO2 ratio. However, effect of O2/CO2 ratio on increasing the overall co-combustion characteristics becomes smaller when the oxygen concentration exceeds 30 %. Comparing SS blended with Huaibei (HB) bituminous coal, the SS blended with Shenhua (SH) bituminous coal (high-rank bituminous coal) combustion has the good combustion performance.

The structural evolution of organic matter during maturation of coals and its impact on petroleum potential and feedstock for the deep biosphere

The structural evolution of coals during coalification from peat to the end of the high volatile bituminous coal rank (VRr=0.22–0.81%) has been studied using a natural maturity series from New Zealand. Samples were studied using a range of standard coal analyses, Rock–Eval analysis, infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and pyrolysis gas chromatography (Py-GC). The structural evolution of coal during diagenesis and moderate catagenesis is dominated by defunctionalisation reactions leading to the release of significant amounts of oxygen and thereby to an enrichment of aromatic as well as aliphatic structures within the residual organic matter. Based on the evolution of pyrolysis yields and elemental compositions with maturity it can be demonstrated that oxygen loss is the major cause for increasing Hydrogen Index values or hydrocarbon generating potentials of coals at such maturity levels. For the first time, the loss of oxygen in form of CO2 has been quantified. During maturation from peat to high volatile bituminous coal ranks ∼10–105mg CO2/g TOC has been released. This is equivalent to 2.50E−4 to 1.25E−3mg CO2 generated from every litre of sediment per year falling into the range of deep biosphere utilisation rates. Immature coals, here New Zealand coals, therefore manifest the potential to feed deep terrestrial microbial life, in contrast to more mature coals (VRr>∼0.81%) for which defunctionalisation processes become less important.

Notes on the origin of altered macerals in the Ragged Edge of the Pennsylvanian (Asturian) Herrin coalbed, Western Kentucky

The Ragged Edge of the Herrin (Western Kentucky No. 11) coal bed has a variety of maceral textures and assemblages that do not fit in the conventional vitrinite and inertinite definitions as established by the International Committee for Coal & Organic Petrology. Within a narrow zone at the marine margin of the coalbed, the coal is brecciated and cemented by carbonate with some of the brecciated clasts metamorphosed to anthracite-level vitrinite reflectances. This is in contrast to the ambient high volatile C bituminous coal rank in the region. Low-rank peat-like textures are preserved in the clasts, suggesting that the metamorphism took place soon after deposition of the peat. Geochemical and mineralogical evidences suggest that the increase in reflectance was the consequence of the channeling of hydrothermal fluids through the breccia. The narrow zone of metamorphism and, further, the juxtaposition of breccia clasts of varying degrees of metamorphism suggest that the hydrothermal influx occurred at shallow depths of burial, perhaps shortly following deposition of the peat.

Systematics of pyrolytic N2 and CH4 release from peat and coals of different thermal maturity

Open system non-isothermal (programmed) pyrolysis with a constant heating rate of 0.5 °C/min up to a final temperature of 1200 °C was used to study the liberation of molecular nitrogen (N2) and methane (CH4) from organic-rich sedimentary matter of different thermal maturity. The sample set analysed comprised peats, lignites, bituminous coals and anthracites. Temperature ranges, shapes and intensities of pyrolytic peaks in the CH4 and N2 pyrograms are sensitive indicators of the chemical composition of the sedimentary organic matter and may serve as characteristic fingerprints of organofacies and depositional environment. Within the coalification sequence, an increase in total organic carbon (TOC)-normalized methane yields was observed from peat to medium volatile bituminous coal, followed by a distinct decrease for the anthracites. The onset of methane and nitrogen liberation temperatures shifted towards higher temperatures with increasing rank, reflecting the increase in thermal stability of the residual organic matter. A systematic temperature shift was also observed for the methane generation maximum (peak). The N2 pyrograms exhibit bimodal generation curves (two maxima) up to the bituminous coal rank, while essentially only one single high-temperature N2 generation maximum persists at the anthracite level. This is attributed to a predominance of nitrogen-containing moieties (e.g. pyridinic and pyrrolic) of high thermal stability. The N2 pyrograms of the lignites show a higher degree of complexity, indicating a substantial variability in nitrogen-containing compound groups. Characteristic N2 spikes were found in the Miocene lignites of the Lower Rhine Basin, similar to those observed previously in Greek lignites. The origin of these “anomalies” and their relation to depositional environment and diagenesis still remains unknown.

Hartshorne coal rank applied to Arkoma Basin coalbed methane activity, Oklahoma, USA

Coal rank, generalized for all coal beds at or near the surface, in the eastern Oklahoma coalfield has been known since 1915. Near the surface (depths <305m, <1000ft), coal rank increases from high volatile bituminous to low volatile bituminous from west to east in the Arkoma Basin in Oklahoma. The rank of subsurface (depths >305m, >1000ft) coals in Arkoma Basin coalbed methane (CBM) prospects was previously unknown. A new Hartshorne coal (Middle Pennsylvanian) rank map is based on mean maximum vitrinite reflectance values of 0.76% to 2.41% Rmax from 70 coal samples from vertical depths of 0 (surface) to 1327m (4355ft). Hartshorne coal rank in the subsurface increases from high-volatile bituminous to semianthracite from west to east in the Arkoma Basin in Oklahoma. Bituminous rank boundaries changed considerably from earlier surface rank maps (primarily by increasing the area of medium volatile bituminous rank coal in the subsurface) and revealed a previously unknown semianthracite rank area. This discrepancy is significant because the rank of deep (>305m, >1000ft) coal resource assessments and CBM exploration projects have been based on shallow coal rank assignments.A total of 2635 Hartshorne (Hartshorne, Lower Hartshorne, and Upper Hartshorne) CBM wells have been completed in Oklahoma since 1988. Most (1610) wells are horizontal with lateral lengths ranging from 4 to 1498m (14 to 4914ft; an average of 669m [2195ft]). Coal in most Hartshorne CBM wells is medium volatile bituminous rank. Hartshorne coal is semianthracite rank in about 160 CBM wells in Le Flore County. The four Hartshorne CBM wells with the highest initial potential (IP) gas rates (48 to 65 thousand cubic meters per day, Mcmd; 1.7 to 2.3 million cubic feet per day, MMcfd) are medium volatile bituminous rank from horizontal wells in Haskell and Pittsburg counties. IP gas rates<28.3 Mcmd (<1 MMcfd) in low volatile bituminous and semianthracite rank Hartshorne horizontal CBM wells may be low due to complications in drilling into high rank coals with cleat spacing <1cm, to stimulation differences, or to gas migration into adjacent sandstone channels.

X-Ray Absorption Near Edge Structure Spectrometry Study of Nickel and Lead Speciation in Coals and Coal Combustion Products

The fate and environmental impacts of trace elements from coal fired power stations are a significant concern because of the large quantities of coal used as an energy source. The ultimate environmental fate and health impact of some of these trace elements is dependent on their various forms and oxidation states. Nickel and lead are two of the trace elements classified as “priority pollutants” by the National Pollutant Inventory (NPI) in Australia. This study attempts to understand speciation of nickel and lead in coal and coal combustion products from five coal fired power stations in Australia where bituminous rank coals are utilized. Non-destructive X-ray Absorption Near Edge Structure Spectrometry (XANES) was used to determine speciation of these metals. Semiquantitative speciation of nickel and lead was calculated using a linear combination fit of XANES spectra obtained for selected pure reference compounds. In all fly ash samples, 28−80% of nickel was present as nickel in NiSO4 form, which is a more toxic and more bioavailable form of nickel. Less toxic NiO was detected in fly ash samples in the range of 0−15%. Speciation of lead revealed that 65−70% is present as PbS in the feed coals. In all fly ash samples analyzed, lead comprised different proportions of PbCl2, PbO, and PbSO4. PbCl2 and PbSO4 contents varied between 30−70% and 30−60%, respectively. Chemical reactions resulting in nickel and lead transformation that are likely to have occurred in the post-combustion environment are discussed.

The use of numerical simulation in predicting coalbed methane producibility from the Gates coals, Alberta Inner Foothills, Canada: Comparison with Mannville coal CBM production in the Alberta Syncline

Abstract Two medium to low volatile bituminous rank coals in the Lower Cretaceous Gates Formation (Mannville equivalent), Inner Foothills of Alberta, were cored as part of a coalbed methane exploration program. The target seams (Seam 4 and Seam 10) were intersected at 652 m and 605 m, respectively. The coals were bright banded, relatively competent and reasonably cleated, with cleat spacing between 5–20 mm. The FMI (Formation Micro-Imaging) log identified two primary fracture directions, corresponding to both face and butt cleats, which were developed almost equally in some coal intervals. The amount of shearing was limited, in spite of the presence of numerous thrust faults and fold structures in the corehole vicinity. Total gas content was high, with an average of 17.7 cm 3 /g (arb; 568.1 scf/t). An adsorption isotherm of the thick Seam 4 showed gas saturation levels of 90% at in-situ reservoir conditions. Methane content was 92–96% and carbon dioxide levels were less than 2%. Isotopic studies on the methane confirmed the thermogenic origin of the gas, as anticipated based on the coal rank. The coal seams were fracture stimulated using 50/50 nitrogen and fresh water along with 9 to 12 tons of 12/20 mesh sand used as a proppant. It is believed that the coals were not stimulated properly because of the small proppant volume and the complex — and often unpredictable — fracture pattern in coals, particularly in the Inner Foothills region that has high stress anisotropy. An injectivity test showed coal absolute permeability to be less than 1 mD, the skin to be − 2 (indicating a slightly damaged coal) and water saturation in the cleats to be 90%. A four-month production test was conducted; gas rates declined from 930 to 310 m 3 /d (33 to 11 MCFD) and water rates were low ( constructive interference in depressurizing the coal reservoirs and accelerating gas production over short periods of time was demonstrated. Coal quality data from a nearby underground mine shows that drilling horizontal wellbores in the Gates coals would be challenging because of unfavourable geomechanical properties, such as low cohesion and unconfined compressive strength values, and structural complexity.

1D-NMR and 2D-NMR analysis of the thermal degradation products from vitrinites in relation to their natural hydrogen enrichment

A study of coal products obtained from Gray-King pyrolysis at 550 °C was carried out in order to obtain information about the chemical modifications of the huminite/vitrinite structure resulting from different processes of natural hydrogen-enrichment. The high oil yield obtained, the similarity between the infrared spectra of the generated oils and those of the parent vitrinite as well as the parallelism between the compositional data deduced for these oils and those obtained by means of Curie point pyrolysis-gas chromatography/mass spectrometry justify the use of this thermal approach. Gray-King pyrolysis is preferable to other techniques because it is possible to make an accurate mass balance, a thorough study of the solid residues and a full characterization of both the volatile and non-volatile fractions of the degradation products. From a study of selected perhydrous coals, mainly composed of the vitrinite maceral group, only in the low reflectance Jurassic coal from the Whitby (England) basin (WJVl) was the incorporation of lipoidal material evident, due to the significant contribution of long-chain alkyl aromatics in its oil. The structure of the vitrinite in the other Jurassic coals, the high reflectance sample from the Whitby basin (WJVh) and the coals from the Asturias (Spain) and Portugal basins (AJV and PGJV, respectively), is probably similar to that described for non-perhydrous vitrinites in the subbituminous coal rank. However, the presence of assimilated hydrogenated substances of a secondary nature, in particular for AJV and PGJV, hinders the cross-linking and condensation processes typical of the transit to the bituminous coal rank. In Cretaceous coals, from Teruel (Spain) and Utah (EEUU), (TCV and UCV, respectively), whose perhydrous character is mainly due to the specific hydrogenated nature of their botanical precursors, the incorporation of aliphatic structures via covalent oxygen linkages is proposed. The results obtained may be useful for establishing accurate structural models for perhydrous vitrinites. At the same time, the data obtained will contribute to explain the involvement of the high hydrogen content in the suppression of vitrinite reflectance.

Effect of hydrothermal treatment on the extraction of coal in the CS 2/NMP mixed solvent

The extraction of four Chinese different rank bituminous coals with the carbon disulfide/ N-2-pyrrolidinone (CS 2/NMP) mixed solvent (1:1 by volume) was carried out in room temperature. It was found that one of middle bituminous raw coal of the four coals gave more than 74% (daf) extraction yield, suggesting an associative structural model for the coal. The four coals were hydrothermal treated under different conditions, and it was found that the extraction yields of the treated coals obviously increased. This will have great significance for coal liquefaction. FTIR measurements show the removal of minerals after the hydrothermal treatment of coals suggesting the dissociation of the coal aggregation structure due to ionic interactions and/or hydrogen bonds broken because of the removal of oxygen and hydroxyl oxygen proceeded through ionic pathways, resulting in the extraction yields of the treated coals increase. However, breaking of π-cation interactions by hydrothermal treatment may be one of possible mechanisms for the enhancement of extraction yield of higher rank of treated coal. The mechanism of hydrothermal treatment of coal was discussed in the paper.

A review of the timing of coalification in the light of coal seam erosion, clastic dykes and coal clasts

Abstract Coal seam erosion, clastic dykes penetrating coal seams, and studies of coal clasts occurring in Late Paleozoic basins are used to demonstrate that coalification to the rank of subbituminous and bituminous coal occurred rapidly at shallow depth in some parts of the Variscan orogen, implying a precondition of high paleotemperatures for the coal basins. The origin of clastic dykes, particularly in the (?) Bolsovian (=Westphalian C) deposits of the Plzeň and Kladno-Rakovnik continental basins (Czech Republic) is shown to be a relevant factor in determining the timing of coalification. [Pesek J. (1978). Erosion and clastic dikes in coal seams of the central Bohemian basins and their significance for determination of plant substance coalification. Folia Musei Rerum Naturalium Bohemiae Occidentalis, Geologica 12, 1–34.] is of the opinion that the 50–100 cm deep fractures filled with superposed clastics originated in “fully ranked” high volatile bituminous coal, exposed during a hiatus between the (?) Early Westphalian C (Early Bolsovian) and Late Westphalian D (Late Asturian). These dykes have either irregular shape or form conic bodies with sharp boundaries. Their filling does not show any signs of postsedimentary deformation. Coal clasts occurring in clastic sediments either close to or far above the roof of coal seams are a few millimetres up to several centimetres in size, being subangular or angular. However, there also exist clasts of which one side is angular to subangular, whereas the opposite side is markedly sharp. In some basins coal clasts are embedded in units of the same age. They are mostly of somewhat lower rank (by 0.01–0.03%) than the nearest coal seam. Whereas [Gayer, R. A., Pesek, J., Sýkorova, I., Valterova, P., 1996. Coal clasts in the upper Westphalian sequence of the South Wales coal basin: implication for the timing of maturation and fracture permeability. In: Gayer, R., Harris, J. (Eds.), Coalbed methane and coal geology, Geological Society Special Publication 109, pp. 103–130.] presumed in the South Wales foreland Basin a burial level of about 1 km with an elevated geothermal gradient (60 °C/km), enhanced by hot fluids along thrusts, resulting in rapid coalification to the bituminous coal rank, no deep burial of organic matter could have occurred in the intramontane basins of the Bohemian Massif. Coalification of the Late Paleozoic seams must have proceeded at a very high rate. The only logical reason leading to such rapid coalification of biomass could have been high value of geothermal gradient at least in the basins of the Bohemian Massif.

Influence of a basic intrusion on the vitrinite reflectance and chemistry of the Springfield (No. 5) coal, Harrisburg, Illinois

The Springfield (No.5) coal, a Pennsylvanian-age high volatile B bituminous rank coal in the Carbondale Formation, is mined in the southeastern section of the Illinois Basin. Intruded into this coal is a 10.1-m-wide basic dike that is near vertical through the extent of the mined coal bed, and strikes N 22° W. The intrusion and the effects it had on the coal were studied petrographically and geochemically. Using a published heat flow model by Carslaw and Jaeger (1959) [Carslaw, H.S., Jaeger, J.C., 1959. Conduction of Heats in Solids. Oxford University Press] in conjunction with thin-section microscope analysis, a contact temperature of ∼600 °C was determined. Vitrinite reflectance was measured for a suite of coal samples collected distal to the intrusion. Vitrinite reflectance values rose uniformly from the ambient reflectance values of ∼0.69%, at just greater than one-dike thickness away, to ∼5% at the dike/coal contact. The increase in reflectance values for samples within ∼1.2 times dike thickness is concordant with data published by Bostick and Pawlewicz (1984) [Bostick, N.H., Pawlewicz, M.J., 1984. Paleotemperatures based on vitrinite reflectance of shales and limestones in igneous dike aureoles in the Upper Cretaceous Pierre shale, Walsenburg, Colorado. In: Woodward, J.G., Meissner, F.F., Clayton, J.L. (Eds.). Hydrocarbon Source Rocks of the Greater Rocky Mountain Region. Rocky Mountain Association of Geologists, pp. 387–392] on the effects of mafic intrusions into Cretaceous-age shales in Walsenburg, Colorado. Comparison of Colorado data with data from these sites indicates that, despite differences in intrusion temperature, timing, or coal rank at time of the intrusion, ambient mean vitrinite reflectance values remain unchanged at just greater than one-dike width from an intrusion.

Characterization and non-isothermal decomposition kinetics of some Turkish bituminous coals by thermal analysis

The thermal behavior of five bituminous coal samples was investigated in non-isothermal condition by thermal analysis. The integral method was used in the analysis of TGA data in order to determine the decomposition kinetics. The main region of the sample's weight loss, arising from the conversion of organic matter to gas, occurred within the temperature range 400–600 °C. The thermal parameters derived from TG and DTG curves were correlated with petrographic, proximate and ultimate analyses data. The results indicated that H/C ratio, fuel ratio, mean vitrinite reflectance and petrofactor could be qualitatively used in the prediction of the TG and burning behavior of various rank bituminous coals.