Carboniferous Coal Research Articles

The petroleum generation potential and effective oil window of humic coals related to coal composition and age

Abstract A worldwide data set of more than 500 humic coals from the major coal-forming geological periods has been used to analyse the evolution in the remaining (Hydrogen Index, HI) and total (Quality Index, QI) generation potentials with increasing thermal maturity and the ‘effective oil window’ (‘oil expulsion window’). All samples describe HI and QI bands that are broad at low maturities and that gradually narrow with increasing maturity. The oil generation potential is completely exhausted at a vitrinite reflectance of 2.0–2.2%Ro or Tmax of 500–510 °C. The initial large variation in the generation potential is related to the original depositional conditions, particularly the degree of marine influence and the formation of hydrogen-enriched vitrinite, as suggested by increased sulphur and hydrogen contents. During initial thermal maturation the HI increases to a maximum value, HImax. Similarly, QI increases to a maximum value, QImax. This increase in HI and QI is related to the formation of an additional generation potential in the coal structure. The decline in QI with further maturation is indicating onset of initial oil expulsion, which precedes efficient expulsion. Liquid petroleum generation from humic coals is thus a complex, three-phase process: (i) onset of petroleum generation, (ii) petroleum build-up in the coal, and (iii) initial oil expulsion followed by efficient oil expulsion (corresponding to the effective oil window). Efficient oil expulsion is indicated by a decline in the Bitumen Index (BI) when plotted against vitrinite reflectance or Tmax. This means that in humic coals the vitrinite reflectance or Tmax values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window. The start of the effective oil window occurs within the vitrinite reflectance range 0.85–1.05%Ro or Tmax range 440–455 °C and the oil window extends to 1.5–2.0%Ro or 470–510 °C. For general use, an effective oil window is proposed to occur from 0.85 to 1.7%Ro or from 440 to 490 °C. Specific ranges for HImax and the effective oil window can be defined for Cenozoic, Jurassic, Permian, and Carboniferous coals. Cenozoic coals reach the highest HImax values (220–370 mg HC/g TOC), and for the most oil-prone Cenozoic coals the effective oil window may possibly range from 0.65 to 2.0%Ro or 430 to 510 °C. In contrast, the most oil-prone Jurassic, Permian and Carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0.85–0.9%Ro or Tmax of 440–445 °C.

Oil generation capacity of coals as a function of coal age and aliphatic structure

The relative proportions of aliphatic CH 2, CH 3, aliphatic hydrogen (H ali) together with the aliphatic chain length in a series of Carboniferous, Permian, Jurassic and Cenozoic humic coals have been analysed using FTIR and ruthenium tetroxide catalysed oxidation (RTCO) followed by GC–MS analysis of the n-monocarboxylic acids (esterified) to assess their ability to generate oil. Most of the coals contain 2–11 vol% liptinite. Only coals with almost similar Hydrogen Indices (HIs) were compared as they were considered to possess comparable hydrocarbon generation potentials. All contain isolated aromatic hydrogen (H aro) in the coal structure and a considerable proportion of aliphatic chains in the range C 16–18. HI values cannot alone explain the proportion of aliphatic CH 2, implying that for coals, H aro contributes to the measured HI. Cenozoic coals contain the highest proportion of aliphatic CH 2 and H ali, and the content of longer chain aliphatics (>C 18) increases considerably from Palaeozoic to Cenozoic coals. Aliphatic chains >C 18 are absent from,or very restricted in, the Carboniferous coals and most of the Permian coals indicate no or a negligible ability to generate oil. Jurassic coals show a slightly better potential, whereas Cenozoic coals contain aliphatic chains up to at least C 35, demonstrating the greatest capacity to generate oil in addition to significant gas potential. Multivariate data analysis suggests that the aliphatic chains >C 24 are related to the collodetrinite + liptodetrinite matrix, which is a prominent constituent of Cenozoic coals. With regard to oil potential, the coals from the major coal-forming periods may be ranked: Carboniferous ⩽ Permian < Jurassic ≪ Cenozoic. This suggests an overall floral control on oil generation potential, linked to evolution from the relatively primitive Carboniferous plants towards the complex angiosperm Cenozoic floras. These results agree with the distribution of known oil and gas accumulations sourced from coals of different age.

Flotation responses of Gondwana coal in release analysis

The characteristics of Gondwana coal are found to be different from the carboniferous coal. The lack of vitrinite content and the abundance of mineral matter (hydrophilic particles) reduce the floatability of coal. The presence of large amount of pores increases reagent consumption. Bearing all this in mind, the release analysis and collector-less flotation were performed with a high-rank coking coal of Gondwana origin. Flotation tests were carried out with different feed sizes with three different frothers – pine oil, MIBC and a polyglycol-type synthetic frother (SF). The results of release analysis and collector-less flotation changes with the feed sizes and frothers are reported. Even with the same frother, the responses of the two procedures varied with the change in feed sizes. This indicates that with the same feed size and the same coal, the responses of frothers are also dependent on the processes followed. In some cases, the release analysis procedure is better than that of collector-less flotation and vice versa.

Catagenesis of Humic Coals Inferred from the X-Ray Phase Analysis and Mathematical Modeling

Dynamics of catagenetic changes in the structure of humic coals in the Earth's interior can quantitatively be described using X-ray indices of components (phases), redistribution of which is determined by a system of differential equations in geological time. The system describes changes in the main formation parameters of coal seams in the Earth's interior (subsidence depth, temperature, pressure, and catagenesis index), on the one hand, and kinetics of catagenetic transformation of organic matter (OM), on the other. Such model makes it possible to establish regular changes in the phase composition of humic coals at different stages of coal basin formation. Using Paleozoic (Middle Carboniferous) coals of the Donets Basin as an example, it is established that main changes in the OM structure took place during the maximal subsidence of coal seams at maximal temperatures ranging from 110–15°C (for slightly metamorphosed coals of the L and G ranks) to 28°C (for anthracites) and pressures ranging from 55–74 to 146 MPa, respectively. Major processes leading to the observed X-ray phase composition of coals during the maximal subsidence of sedimentary sequences lasted approximately 40 Ma regardless of the geological age of sediments (Middle Carboniferous or Permian coal seams of the Donets or Kuznetsk coal basins, respectively).

Oil generation from coal source rocks: the influence of depositional conditions and stratigraphic age

Although it was for many years believed that coals could not act as source rocks for commercial oil accumulations, it is today generally accepted that coals can indeed generate and expel commercial quantities of oil. While hydrocarbon generation from coals is less well understood than for marine and lacustrine source rocks, liquid hydrocarbon generation from coals and coaly source rocks is now known from many parts of the world, especially in the Australasian region (MacGregor 1994; Todd et al. 1997). Most of the known large oil accumulations derived from coaly source rocks have been generated from Cenozoic coals, such as in the Gippsland Basin (Australia), the Taranaki Basin (New Zealand), and the Kutei Basin (Indonesia). Permian and Jurassic coal-sourced oils are known from, respectively, the Cooper Basin (Australia) and the Danish North Sea, but in general only minor quantities of oil appear to be related to coals of Permian and Jurassic age. In contrast, Carboniferous coals are only associated with gas, as demonstrated for example by the large gas deposits in the southern North Sea and The Netherlands. Overall, the oil generation capacity of coals seems to increase from the Carboniferous to the Cenozoic. This suggests a relationship to the evolution of more complex higher land plants through time, such that the highly diversified Cenozoic plant communities in particular have the potential to produce oil-prone coals. In addition to this overall vegetational factor, the depositional conditions of the precursor mires influenced the generation potential. The various aspects of oil generation from coals have been the focus of research at the Geological Survey of Denmark and Greenland (GEUS) for several years, and recently a worldwide database consisting of more than 500 coals has been the subject of a detailed study that aims to describe the oil window and the generation potential of coals as a function of coal composition and age.

The occurrence of potentially hazardous trace elements in five Highveld coals, South Africa

Permian coals of the southern hemisphere are generally considered to contain lower concentrations of sulfides, halogens, and trace elements when compared to northern hemisphere Carboniferous coals. Few studies have considered the trace element content in South African coals, and little or no work has been published for Highveld coals. Of the nineteen coal fields in South Africa, the Highveld coal field is one of the nine currently producing, and is second largest in terms of production. Five run of mine samples and a high ash middlings product from the Number 4 Lower seam were analyzed, totaling six sample sets. Fourteen trace elements (As, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V, and Zn) were selected for this study based on the global perception that these elements may be hazardous to human health and/or the environment when they are released during coal utilization. Several sample preparation techniques were tested using certified reference materials (SARMs 18, 19 and 20) to determine the most repeatable technique for these coals. The samples were analyzed by ICP-AES and CVAA (Hg only). Microwave digestion proved to be generally unreliable despite the utilization of several different methods. A slurry direct injection method into the ICP-AES provided good correlations with the reference material, but requires further development to enhance the confidence level in this relatively unexplored technique. Samples prepared based on three ASTM standards for the determination of trace elements in coal provided repeatable results in most instances, and were the preparation methods utilized for the Highveld coals. The trace element values determined for the Highveld coals are generally in good agreement with values available in literature for South African coals, with the exception of Hg, Mn and Cr. Hg values reported here are lower, Cr and Mn higher. Results generally agree well with analyses on the same samples conducted by the United States Geological Survey. When considering the global ranges for trace elements, the Highveld range values are within Swaine's range boundaries with the exception of Cr. Compared to the cited global average values for the fourteen trace elements determined, the values obtained for the Highveld coals generally fall below or well below these average values, with the exception of Cr and Mn. Concentrations of Cd and Cu are lower compared to global average values, and As, Mo, Pb, Se, Sb, and Zn can be considered low to very low. Arsenic is ten times lower compared to typical USA values. Concentrations of Co and Ni are similar to global averages, with V and Hg being very slightly higher. The middlings samples reported higher concentrations of most elements, related to the higher ash content of these samples. Of interest, the chalcophile elements determined are all depleted in the Highveld coals compared to global averages, and the siderophile elements are enriched or comparable to global averages. Risk-based health studies in the USA on coals with similar or higher Hg and significantly higher As contents have not reported negative health effects, and therefore it could be assumed that the mobilization of these trace elements from the five Highveld coals are unlikely to cause human health problems. Work is ongoing to determine the modes of occurrence of these HAPs and to address the partitioning behaviors and speciation states of these elements during coal utilization.

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.

Fault trap analysis of the Permian Rotliegend gas play, Lauwerszee Trough, NE Netherlands

The Lauwerszee Trough is a northwest-trending sub-basin within the Southern Permian Basin and lies in the onshore area of northeastern Netherlands. Referred to as the ‘Golden Lane’ Trend, it is the classical Lower Permian Rotliegend gas play of the Netherlands, consisting of the prolific, high net-to-gross sandstone reservoirs of the Slochteren Formation. Traps are tilted extensional fault blocks that entrap gas sourced from the Carboniferous Coal Measures. The overlying Rotliegend Ten Boer Claystone and Upper Permian Zechstein evaporitic rocks provide the top and lateral seals for the fault traps. In this study 30 fault traps were analysed in which 22 were found to have gas accumulations. Trap fill is controlled primarily by Slochteren sand-on-sand juxtaposition leakage across a fault; however, some gas accumulations as mapped appear to be filled deeper than this leakpoint and require sand-on-sand fault seal. Retained fault-seal gas columns are relatively small and mostly less than 60 m with one exception of 95 m. Seven potential Slochteren sand-on-sand fault-zone seals were identified in this study. The analysis of these fault traps revealed three possible criteria that may promote the development of such fault seals: (1) juxtaposition against a tight, shale-rich interval; (2) small isolated sand-on-sand juxtaposition area (&lt;25 000 m 2 ) typically associated with fault lengths less than 1 km; or (3) occurrence of a complex narrow fault zone. However, some sealing fault segments are associated with structural interpretation/mapping uncertainty. Minor map changes may eliminate perceived sand-on-sand fault-zone seals and explain trap fill by conventional fault juxtaposition.

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

The authors reviewed shortly the recent state of knowledge in the field of petrographic compositions and origins of the Carboniferous age coals in the Lvov-Volyn coal basin (LVB) as well as make the proper conclusions about the conditions of peat-accumulation, according to the results of former investigations performed by themselves and other researchers.

Methane generation from coal during open system pyrolysis investigated by isotope specific, Gaussian distributed reaction kinetics

A reaction kinetic model is presented to differentiate individual complexes of reactions of the thermal decomposition of sedimentary organic matter during pyrolysis experiments. This model is applied to methane generation from coal during open system pyrolysis experiments with linear heating. The reaction kinetic model is based on the concept of a certain number of reaction complexes contributing to the generation of the product methane, each reaction complex distinguished by an initial pool of precursor sites with a defined stable carbon isotope signature and a common reaction rate determining step. For each reaction the mathematical model defines Gaussian distributed activation energies, a single pre-exponential factor, an initial isotope ratio of the precursor and a single difference in activation energy between the heavy and the light isotope species. Based on this concept, stable carbon isotopes and the dynamics of thermal methane generation from a Carboniferous coal with 0.72% vitrinite reflectance are explained with a set of four independent reactions. It is suggested that these reactions represent the following pathways (listed in the order of occurrence): (I) reactions involving the cleavage of thermally unstable C–O and C–S bonds, (II) demethylation, (III) release of groups which cross link ring structures and/or secondary cracking of long chain hydrocarbons within the molecular network of the coal, and (IV) polymerisation and condensation reactions. Reactions II and III contribute the major part to total methane potential. However, the addition of the minor reactions I and IV has significant influence on the stable carbon isotope trend of methane.

Facies studies of bituminous coals in Poland

Polish bituminous coal basins are associated exclusively with Carboniferous deposits, differing in origin and geological structure. This paper presents only short review of papers of Polish authors on coal facies studies of Carboniferous coals occurring in the Lower Silesian Coal Basin (LSCB), Upper Silesian Coal Basin (USCB) and Lublin Coal Basin (LCB) of Poland. Facies investigations of Carboniferous coals of Poland have been in progress over 20 years. The results of these studies have provided new information on such subjects as: (i) recognition of main depositional conditions in paleomires, (ii) determine prevailing paleoplant communities, (iii) appraisal of peat-forming environment reconstruction-types and characteristics of paleomires. These facies analyses are connected to results of such studies as: pure coal petrology, using maceral and microlithotype composition as parameters of the environment of coal deposition, combined results of petrological, palynological and sedimentological studies.

Fluorine content and distribution pattern in Chinese coals

About 300 coal samples were collected to study the fluorine content and distribution pattern in Chinese coals in different coal basins and geologic periods. The Permo–Carboniferous and Jurassic coals in the North China Plate and Northwest China account for nearly 90% of Chinese coals and their fluorine content is 20–300 mg/kg, mostly about 50–100 mg/kg. Fluorine content of Permo–Carboniferous coals, the main steam coals in China, is 50–300 mg/kg; Jurassic coals 20–70 mg/kg. There are great differences in fluorine content of Late Permian coals in Southwest China (50–3000 mg/kg), which accounts for only 7% of Chinese coals. According to the proportions of the coals with different fluorine content in Chinese coal resources, the average fluorine content of Chinese coals is about 82 mg/kg, which is close to the world average (80 mg/kg). Most Chinese coals are low-fluorine coals (<200 mg/kg). Fluorine content in Chinese coals is closely related with structure position of coal basins, the degree of volcanic activity and magma intrusion, as well as the age, and source of the volcanic and magmatic rock. Frequent volcanic activity and magma intrusion is the main reason for fluorine-rich coals and stone coals in South Qinling Mountain (Daba Area) and Southwest China, where fluorine content is about 50–3000 mg/kg. Fluorine content in all platform areas, where magma activity is less, is comparatively low, about 20–200 mg/kg.

Distribution of potentially hazardous trace elements in coals from Shanxi province, China

Shanxi province, located in the center of China, is the biggest coal base of China. There are five coal-forming periods in Shanxi province: Late Carboniferous (Taiyuan Formation), Early Permian (Shanxi Formation), Middle Jurassic (Datong Formation), Tertiary (Taxigou Formation), and Quaternary. Hundred and ten coal samples and a peat sample from Shanxi province were collected and the contents of 20 potentially hazardous trace elements (PHTEs) (As, B, Ba, Cd, Cl, Co, Cr, Cu, F, Hg, Mn, Mo, Ni, Pb, Sb, Se, Th, U, V and Zn) in these samples were determined by instrumental neutron activation analysis, atomic absorption spectrometry, cold-vapor atomic absorption spectrometry, ion chromatography spectrometry, and wet chemical analysis. The result shows that the brown coals are enriched in As, Ba, Cd, Cr, Cu, F and Zn compared with the bituminous coals and anthracite, whereas the bituminous coals are enriched in B, Cl, Hg, and the anthracite is enriched in Cl, Hg, U and V. A comparison with world averages and crustal abundances (Clarke values) shows that the Quaternary peat is highly enriched in As and Mo, Tertiary brown coals are highly enriched in Cd, Middle Jurassic coals, Early Permian coals and Late Carboniferous coals are enriched in Hg. According to the coal ranks, the bituminous coals are highly enriched in Hg, whereas Cd, F and Th show low enrichments, and the anthracite is also highly enriched in Hg and low enrichment in Th. The concentrations of Cd, F, Hg and Th in Shanxi coals are more than world arithmetic means of concentrations for the corresponding elements. Comparing with the United States coals, Shanxi coals show higher concentrations of Cd, Hg, Pb, Se and Th. Most of Shanxi coals contain lower concentrations of PHTEs.

Mineralogy and Trace Element Contents of the Upper Carboniferous Coals from the Asma-Dilaver and Gelik Mines in Zonguldak, Turkey

This study is mainly focused on mineralogy and trace element contents of the 5 bituminous coal seams, upwards Cay, Acilik, Sulu, Hacimemis, and Kurul, from the Asma-Dilaver and Gelik underground mines in the Zonguldak Basin, Turkey. In addition, some properties of the Akalin seam from Karayigit (2001) were also used in the present study. The coal seams are located in the lower-middle part of the coal-bearing Kozlu Formation of the Westphalian A (Upper Carboniferous) age and are extensively exploited in the underground mines for mainly metallurgical cokes. A total of 43 channel coal samples that represent the whole coal thickness have been evaluated in the present study. The coal samples on an air-dried basis were characterized by variable ash yields and low total S contents. The identifiable minerals by X-ray diffraction in whole-coal samples include clay minerals (kaolinite, illite, and chlorite), quartz, calcite, dolomite, pyrite, and siderite. All calcite and dolomite, and some siderite and pyrite, were formed in cleat-fracture infillings. Calcite contents are much higher in the samples from the Asma-Dilaver mines than the Gelik mines, while their dolomite and pyrite contents are relatively lower. Accessory mineralogy in selected samples was determined with scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX). Elemental concentrations of the coal samples analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) are relatively low, and the majority have variations in their contents among coal seams. The seam means of elemental concentrations, except for trace elements Cs, Mn, Rb, and Th in some seams, fall within the ranges of values for most world coals. Some trace elements (Sc, Cr, Cu, Ga, Rb, REEs, Y, Cs, Hf, Ba, Ta, Nb, Th, W, Zr, U, Zn, Pb, Bi, Tl, Be, Mo, and Co) in all the samples correlate positively with the ash yields, indicating that they are primarily associated with mineral matter. The remaining trace elements As, Cd, Ge, Mn, Sb, and Sr have no correlation with the ash yield.

Mineralogy and Trace Element Contents of the Upper Carboniferous Coals from the Asma-Dilaver and Gelik Mines in Zonguldak, Turkey

This study is mainly focused on mineralogy and trace element contents of the 5 bituminous coal seams, upwards Cay, Acilik, Sulu, Hacimemis, and Kurul, from the Asma-Dilaver and Gelik underground mines in the Zonguldak Basin, Turkey. In addition, some properties of the Akalin seam from Karayigit (2001) were also used in the present study. The coal seams are located in the lower-middle part of the coal-bearing Kozlu Formation of the Westphalian A (Upper Carboniferous) age and are extensively exploited in the underground mines for mainly metallurgical cokes. A total of 43 channel coal samples that represent the whole coal thickness have been evaluated in the present study. The coal samples on an air-dried basis were characterized by variable ash yields and low total S contents. The identifiable minerals by X-ray diffraction in whole-coal samples include clay minerals (kaolinite, illite, and chlorite), quartz, calcite, dolomite, pyrite, and siderite. All calcite and dolomite, and some siderite and pyrite, were formed in cleat-fracture infillings. Calcite contents are much higher in the samples from the Asma-Dilaver mines than the Gelik mines, while their dolomite and pyrite contents are relatively lower. Accessory mineralogy in selected samples was determined with scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX). Elemental concentrations of the coal samples analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) are relatively low, and the majority have variations in their contents among coal seams. The seam means of elemental concentrations, except for trace elements Cs, Mn, Rb, and Th in some seams, fall within the ranges of values for most world coals. Some trace elements (Sc, Cr, Cu, Ga, Rb, REEs, Y, Cs, Hf, Ba, Ta, Nb, Th, W, Zr, U, Zn, Pb, Bi, Tl, Be, Mo, and Co) in all the samples correlate positively with the ash yields, indicating that they are primarily associated with mineral matter. The remaining trace elements As, Cd, Ge, Mn, Sb, and Sr have no correlation with the ash yield.

Deformation of upper carboniferous coal measures in the Sydney Basin: evidence for late Alleghanian tectonism in Atlantic Canada : Gibling, M. R. et al. Canadian Journal of Earth Sciences, 2002, 39 (1), 79–93

Deformation of upper carboniferous coal measures in the Sydney Basin: evidence for late Alleghanian tectonism in Atlantic Canada : Gibling, M. R. et al. Canadian Journal of Earth Sciences, 2002, 39 (1), 79–93

The Corvette Field, Block 49/24, UK Southern North Sea

abstract Corvette is a small prolific gas reservoir with reserves of 211 BSCF located on the Indefatigable Shelf in the Southern North Sea. The reservoir is the Permian Rotliegend aeolian sandstone, capped by Zechstein evaporites and sourced from the Carboniferous Coal Measures. The structure is a 'pop up' between the Gawain and Baird Fields. The field was discovered in 1996 and brought on production in 1999, with gas being evacuated via the Leman field to the Shell/Esso Bacton gas terminal.

The Barque Field, Blocks 48/13a, 48/14, UK North Sea

Abstract The Barque Field is associated with some of the earliest gas discoveries in the southern North Sea. In the Sole Pit area the reservoir, the Rotliegend Group Leman Sandstone Formation of Lower Permian age, occurs between Carboniferous Coal Measures, which source the gas, and Zechstein evaporites which form an excellent seal. Primarily aeolian, the sandstone has generally very low permeability resulting from deep burial of the Sole Pit Trough. The deepest burial and hence the maximum diagenetic damage to the reservoir was achieved in the early Late Cretaceous prior to two phases of inversion in Late Cretaceous and Mid-Tertiary. Compaction and diagenesis reduced reservoir permeability to such an extent that parts of the field would be non-productive were it not for the presence of effective natural fracture zones and well stimulation by hydraulic fracturing techniques. Though appraisal and evaluation have been relatively extensive, remaining uncertainties dictated a conservative development in conjunction with the adjacent Clipper Field. A selected initial area was developed for first gas in October 1990. Good reservoir performance from horizontal wells led to later development of the whole field.

A new Carboniferous coal/shale driven gas play in the Western Black Sea Region (Turkey)

The sedimentary sequence in the Western Black Sea region of Turkey both onshore and offshore offers many possibilities for different hydrocarbon plays. This study presents a new play, which considers Carboniferous coals and shales as source beds, Cretaceous sandstones as reservoirs and Cretaceous shales and marls as seal rocks. The evaluation of this play is performed using the petroleum system approach. Results suggest that the coals and shales have a good to very good source rock potential for gas, that the Cretaceous synrift sandstones are good reservoirs. On the other hand, the sealing efficiency of respective Cretaceous units is assumed to be sufficient based on their lithological (shales and carbonaceous marls) characteristics. Stratigraphic traps, which formed by transgression and by onlap on paleohighs, were sealed and potentially available at 97 million years (ma) before present. Structural traps related to Early Cretaceous extension were also sealed around 97 ma. On the contrary, traps formed by folding and thrusting during the Alpine orogeny only formed during the last 50 ma. The timing of gas generation and migration was determined by one and two-dimensional basin modeling in one well and along a cross-section. The modeling results indicated that during the period between 90 and 42 ma, large volumes of gas were generated from the Carboniferous source rocks. Comparison with the age of stratigraphic and structural traps showed that stratigraphic and normal fault traps were potentially available for the entire volume of generated gas and that the other structural traps associated with Alpine orogeny were available only for gas generated and/or re-migrated during the last 50 ma. The evaluation of this new play results in the conclusion, that the Western Black Sea region is worthy of further exploration for conventional accumulations of thermogenic gas.

Testing the case for a Middle Pleistocene Scandinavian glaciation in Eastern England: evidence for a Scottish ice source for tills within the Corton Formation of East Anglia, UK

The provenance of the Happisburgh Till and Corton Till of the Corton Formation is investigated using erratic clast lithologie s and allochthonou s palynomorph s to test whether the long held assumptio n that they were deposited by ice that originated in Scandinavia is valid. The results show a wide range of lithologie s including Carboniferous Limestone and Coal Measures, and Permian Magnesian Limestone that are not found in Scandinavia, and an absence of distinctive Scandinavian material such as rhomb porphyry and larvikite. Lithologies found indicate deposition by an ice sheet which flowed southwards into north‐east East Anglia from central and southern Scotland eroding and transporting materials derived from outcrops in these areas and from eastern England and the western margins of the southern North Sea Basin. It is concluded that the long held assumption that the Happisburgh Till and Corton Till of the Corton Formation were deposited by a Scandinavian ice sheet is erroneous and that they were instead deposited by Scottish ice.