The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough...The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough is a failed arm of the triple junction of an inland sedimentary basin that extends in a NE-SW direction from the Gulf of Guinea in the south,to the Chad Basin in the north.A total of twenty-nine(29)coal samples were obtained from nineteen coal localities in the Upper(UBT),Middle(MBT),and Lower Benue Trough(LBT).The high average volatile matter yield,low average ash yield,high calorifc value(24.82 MJ/kg,on average),and low sulphur values indicate good quality coal deposits.The organic matter is dominated by vitrinite,reported at an average of 59.3%by volume(mineral-matter free).Variation was noted in the inertinite content across three sub-regions.Liptinite macerals were not commonly observed in the studied samples and were absent in the MBT samples.Coal facies studies decipher the paleoenvironmental conditions under which the vegetation accumulated.Indices commonly used are the gelifcation index(GI),tissue preservation index(TPI),ground water index(GWI and variations),vegetation index(VI),and wood index(WI).Comparing the array of coal facies models applied,the MBT samples difer from the UBT and LBT samples,concurring with the coal quality data.The UBT and LBT coals formed in an upper deltaic to drier piedmont plane depositional environment,while the MBT coal formed in a lower deltaic marsh to wet forest swamp depositional environment.All samples indicate an ombrotrophic paleomire.In view of the modifed equations and the plots used,interpreting depositional environments from just a single model is not reliable.展开更多
Structural changes due to coalification and oxidation influence the coal quality, geochemically and petrologically. Understanding of the coal structures helps to predict the behaviour of coal at various processes. The...Structural changes due to coalification and oxidation influence the coal quality, geochemically and petrologically. Understanding of the coal structures helps to predict the behaviour of coal at various processes. The objective of this paper is to study the changes in organic structure and mineral phase transformation during combustion. Different density fractions were generated and then heated at different temperatures from 200 to 1000 ℃. Petrography, Fourier transform infrared spectroscopy （FTIR） and X-ray diffraction （XRD） were carried out on all the density fractions aimed to accomplish this objective. Here, through petrography, it was observed that the vitrinite and liptinite macerals disappear at higher temperature while porous inertinite is seen. The inertinite structure is exposed which is assumed by the presence of -OH and C-O-C stretches with the aromatic nucleus （CH） and three to four adjacent H from FTIR spectra. Moreover, it can be concluded that aliphatic groups get collapsed at high temperature. In case of inorganic matter, through XRD and FTIR, it is also revealed that with increasing temperature, clay minerals converted into elemental oxides. Hence, this study is suggesting that the structures of coal are altered by the degree of contact metamorphism.展开更多
Jurassic and Triassic coals and organic matter-rich shales of the Tabas Basin, Iran, were investigated with respect to their thermal maturation and petrographic composition. The Triassic coals of the Parvadeh coal fie...Jurassic and Triassic coals and organic matter-rich shales of the Tabas Basin, Iran, were investigated with respect to their thermal maturation and petrographic composition. The Triassic coals of the Parvadeh coal field range in vitrinite reflectance between 1.17% and 1.37% and the Jurassic coals of the Mazino coal field between 2.08% and 2.29% VRr. Maceral analysis revealed a predominance of vitrinite in all samples, with slightly higher percentages of inertinite in the Jurassic samples. Rock-Eval analyses confirm the presence of type III kerogen in the Triassic coals, while the Jurassic coals contain strongly carbonized residual kerogen. The range of sulfur contents for coals from the Parvadeh coal field (0.37% to 4.64%) and Mazino coal field (0.45% to 2.92%) is related to the effect of marine water in peat. The studied samples are characterized by the predominance of short- over long-chained n-alkanes. The relatively high Pr/Ph ratios indicate predominance of terrestrial organic matter whereas Pr/n-C17 and Ph/n-C18 ratios prove oxic conditions during deposition. In addition, the DBT/Phen ratio shows that these coals formed in fluvial/deltaic environments. Molecular geochemical parameters such as carbon preference index (CPI, 0.99-1.04), methyl phenanthrene index (MPI, 1.20-1.60), methyl naphthalene ratio (MNR, 1.61-3.45), and ethyl naphthalene ratio (ENR, 4-6.78) confirm the high maturity of the samples. Burial and thermal history reconstruction indicates necessity of an erosional thickness of about 4000 m in the Parvadeh area. Towards the Mazino area, a higher basal heat flow up to 80 mW m^-2 is assumed for the Paleogene leading to higher maturities.展开更多
With this study,the hydrocarbon generation potential of Miocene aged coals around Arguvan-Parçikan in the northern district of Malatya province was evaluated with the aid of petrological and organic geochemical d...With this study,the hydrocarbon generation potential of Miocene aged coals around Arguvan-Parçikan in the northern district of Malatya province was evaluated with the aid of petrological and organic geochemical data.According to organic petrography,coal quality data,and low thermal maturity,the Arguvan-Parçikan coals are of high-ash,high-sulfur subbituminous B/C rank.The organic fraction of the coals is mostly comprised of humic group macerals,with small percentages derived from the inertinite and liptinite groups.The mineral matter of the coals is comprised mainly of calcite and clay minerals.The total organic carbon(TOC,wt%)values of the shale and coal samples are between 2.61 wt%and 43.02 wt%,and the hydrogen index values are between 73 and 229 mg HC/g TOC.Pyrolysis(T_(max),PI),huminite/vitrinite reflectance(R_(o),%),and biomarker ratios CPI,Pr/Ph ratio,Ts/(Ts+Tm)ratio,C_(32) homohopane ratio(22S/22S+22R)and C_(29)ββ/(ββ+ααsterane ratio)indicate that the organic matter of the studied coals is thermally immature.When all these data are taken together,Miocene aged coals around Arguvan are suitable for hydrocarbon generation,especially gas,in terms of organic matter type(Type III and Type II/III mixed),organic matter amount(>10 wt%TOC),however,low liptinitic macerals(<15%–20%),low hydrogen index(<200 mg HC/g TOC)and low thermal maturity values inhibit the hyrocarbon generation.展开更多
基金The support of the Department of Science and Innovation through its funding agency,the National Research Foundationthe Centre of Excellence for Integrated Mineral and Energy Resource Analysis(DSI-NRF CIMERA)towards this research is hereby acknowledged.
文摘The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough is a failed arm of the triple junction of an inland sedimentary basin that extends in a NE-SW direction from the Gulf of Guinea in the south,to the Chad Basin in the north.A total of twenty-nine(29)coal samples were obtained from nineteen coal localities in the Upper(UBT),Middle(MBT),and Lower Benue Trough(LBT).The high average volatile matter yield,low average ash yield,high calorifc value(24.82 MJ/kg,on average),and low sulphur values indicate good quality coal deposits.The organic matter is dominated by vitrinite,reported at an average of 59.3%by volume(mineral-matter free).Variation was noted in the inertinite content across three sub-regions.Liptinite macerals were not commonly observed in the studied samples and were absent in the MBT samples.Coal facies studies decipher the paleoenvironmental conditions under which the vegetation accumulated.Indices commonly used are the gelifcation index(GI),tissue preservation index(TPI),ground water index(GWI and variations),vegetation index(VI),and wood index(WI).Comparing the array of coal facies models applied,the MBT samples difer from the UBT and LBT samples,concurring with the coal quality data.The UBT and LBT coals formed in an upper deltaic to drier piedmont plane depositional environment,while the MBT coal formed in a lower deltaic marsh to wet forest swamp depositional environment.All samples indicate an ombrotrophic paleomire.In view of the modifed equations and the plots used,interpreting depositional environments from just a single model is not reliable.
文摘Structural changes due to coalification and oxidation influence the coal quality, geochemically and petrologically. Understanding of the coal structures helps to predict the behaviour of coal at various processes. The objective of this paper is to study the changes in organic structure and mineral phase transformation during combustion. Different density fractions were generated and then heated at different temperatures from 200 to 1000 ℃. Petrography, Fourier transform infrared spectroscopy （FTIR） and X-ray diffraction （XRD） were carried out on all the density fractions aimed to accomplish this objective. Here, through petrography, it was observed that the vitrinite and liptinite macerals disappear at higher temperature while porous inertinite is seen. The inertinite structure is exposed which is assumed by the presence of -OH and C-O-C stretches with the aromatic nucleus （CH） and three to four adjacent H from FTIR spectra. Moreover, it can be concluded that aliphatic groups get collapsed at high temperature. In case of inorganic matter, through XRD and FTIR, it is also revealed that with increasing temperature, clay minerals converted into elemental oxides. Hence, this study is suggesting that the structures of coal are altered by the degree of contact metamorphism.
文摘Jurassic and Triassic coals and organic matter-rich shales of the Tabas Basin, Iran, were investigated with respect to their thermal maturation and petrographic composition. The Triassic coals of the Parvadeh coal field range in vitrinite reflectance between 1.17% and 1.37% and the Jurassic coals of the Mazino coal field between 2.08% and 2.29% VRr. Maceral analysis revealed a predominance of vitrinite in all samples, with slightly higher percentages of inertinite in the Jurassic samples. Rock-Eval analyses confirm the presence of type III kerogen in the Triassic coals, while the Jurassic coals contain strongly carbonized residual kerogen. The range of sulfur contents for coals from the Parvadeh coal field (0.37% to 4.64%) and Mazino coal field (0.45% to 2.92%) is related to the effect of marine water in peat. The studied samples are characterized by the predominance of short- over long-chained n-alkanes. The relatively high Pr/Ph ratios indicate predominance of terrestrial organic matter whereas Pr/n-C17 and Ph/n-C18 ratios prove oxic conditions during deposition. In addition, the DBT/Phen ratio shows that these coals formed in fluvial/deltaic environments. Molecular geochemical parameters such as carbon preference index (CPI, 0.99-1.04), methyl phenanthrene index (MPI, 1.20-1.60), methyl naphthalene ratio (MNR, 1.61-3.45), and ethyl naphthalene ratio (ENR, 4-6.78) confirm the high maturity of the samples. Burial and thermal history reconstruction indicates necessity of an erosional thickness of about 4000 m in the Parvadeh area. Towards the Mazino area, a higher basal heat flow up to 80 mW m^-2 is assumed for the Paleogene leading to higher maturities.
基金CUBAP(Sivas Cumhuriyet University Scientific Research Projects)M-610 Project.
文摘With this study,the hydrocarbon generation potential of Miocene aged coals around Arguvan-Parçikan in the northern district of Malatya province was evaluated with the aid of petrological and organic geochemical data.According to organic petrography,coal quality data,and low thermal maturity,the Arguvan-Parçikan coals are of high-ash,high-sulfur subbituminous B/C rank.The organic fraction of the coals is mostly comprised of humic group macerals,with small percentages derived from the inertinite and liptinite groups.The mineral matter of the coals is comprised mainly of calcite and clay minerals.The total organic carbon(TOC,wt%)values of the shale and coal samples are between 2.61 wt%and 43.02 wt%,and the hydrogen index values are between 73 and 229 mg HC/g TOC.Pyrolysis(T_(max),PI),huminite/vitrinite reflectance(R_(o),%),and biomarker ratios CPI,Pr/Ph ratio,Ts/(Ts+Tm)ratio,C_(32) homohopane ratio(22S/22S+22R)and C_(29)ββ/(ββ+ααsterane ratio)indicate that the organic matter of the studied coals is thermally immature.When all these data are taken together,Miocene aged coals around Arguvan are suitable for hydrocarbon generation,especially gas,in terms of organic matter type(Type III and Type II/III mixed),organic matter amount(>10 wt%TOC),however,low liptinitic macerals(<15%–20%),low hydrogen index(<200 mg HC/g TOC)and low thermal maturity values inhibit the hyrocarbon generation.
