International Journal of Coal Geology最新文献

{"title":"Burial and thermal history modeling of basins in convergent oblique-slip mobile zones: A case study of the Ardmore Basin, southern Oklahoma","authors":"Ian A. Cox,&nbsp;Jack C. Pashin","doi":"10.1016/j.coal.2024.104486","DOIUrl":"10.1016/j.coal.2024.104486","url":null,"abstract":"<div><p>The burial and thermal history of sedimentary basins within oblique-slip mobile zones are unique and multifaceted, with irregular periods of subsidence that are closely related to compressional and shear stress. Modern basin modeling techniques can constrain the timing of tectonic events and thermal history as well as determine rates and magnitudes of basin subsidence, which in turn, helps guide exploration for hydrocarbons. The work presented here is the first modern basin modeling effort in the Ardmore Basin in southern Oklahoma. The study uses 12 one-dimensional burial history models to evaluate the thermal maturity of the Late Devonian (Famennian)–Early Mississippian (Tournaisian) Woodford Shale and the Early–Late Mississippian (Tournaisian–Serpukhovian) Caney Shale hydrocarbon source rocks. All models display a similar tectonic evolution with subsidence during and following Cambrian Iapetan rifting, tectonic stability during a Silurian–Late Mississippian passive margin phase, Pennsylvanian synorogenic subsidence, Permian post-orogenic subsidence, Late Permian–Early Cretaceous regional uplift and unroofing, and Early Cretaceous–Paleogene subsidence of the Gulf of Mexico Basin. Episodic Pennsylvanian subsidence appears to have been synchronous with sequential uplift of the Wichita Uplift and the Arbuckle Uplift in response to major left-lateral transpression. Rapid and high magnitude Late Mississippian–Permian subsidence (&gt;250 m/m.y.; 820 ft/m.y. in basin synclines) suggests the Ardmore Basin functioned episodically as an elevator basin, which is typical of sedimentary basins in oblique-slip mobile zones. The Devonian–Mississippian shale section has a broad range of thermal maturity (vitrinite reflectance, 0.40–2.00% R_o), which is strongly dependent on structural position. Isoreflectance lines are subhorizontal and cross-cut structure, indicating post-kinematic thermal maturation in which strata are thermally immature in uplifts and thermally overmature in the deepest synclines. The post-kinematic pattern is a product of a rapid, early phase of synkinematic thermal maturation that has been obscured by a prolonged period of post-kinematic thermal maturation. Variations in basal heat flow, structural history, and general variability of hydrocarbon source rock organic composition, particularly at low thermal maturity levels, have resulted in a modest degree of scatter in the vitrinite reflectance-depth data.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140142208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleovegetation and environment during deposition of the Late Oligocene sub-bituminous coal in the Bobov Dol Basin (SW Bulgaria) as deduced from petrographic and geochemical characteristics","authors":"Alexander Zdravkov ,&nbsp;Achim Bechtel ,&nbsp;Doris Groβ ,&nbsp;Ivan Kojić ,&nbsp;Ksenija Stojanović ,&nbsp;Dragana Životić","doi":"10.1016/j.coal.2024.104489","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104489","url":null,"abstract":"<div><p>Coal and carbonaceous shale samples were taken from the Late Oligocene Bobov Dol Basin, SW Bulgaria. Seams I^a, I, II^a+b, III, IV and V from the coal-bearing Bobov Dol Fm. were sampled to provide insights into the peat forming vegetation and depositional environment based on detailed organic petrological and geochemical study.</p><p>The petrographic composition indicates that both coals and carbonaceous shales contain predominantly terrestrial organic matter with abundant huminite macerals and locally enriched liptinite macerals. Inertinite is rare or absent. Good tissue preservation in seams I, IV and V indicates deposition under wet sedimentary environment, whereas predominance of detrohuminite and lower Tissue Preservation Index (TPI) in seams I^a, II^a+b and III are linked to enhanced humification of the plant remains due to changes in the hydrological regime. The low percent of inertinite and the overall high Gelification Index (GI), however, argue for peat formation under wetter climatic settings, whereas low to moderate ash yields of coal samples indicate organic matter deposition in oligo- to mesotrophic topogenous mires. Reconstructed evolution of the environmental settings during peat formation denotes differences which might be caused by changes in the hydrological regime and tectonic activity.</p><p>The biomarker composition shows prevalence of gymnosperm-derived sesqui- and diterpenoids, followed by lower concentration of <em>n</em>-alkanes (apart from the carbonaceous shale samples from seam I^a), whereas angiosperm-derived non-hopanoid triterpenoids, acyclic isoprenoids, steroids and hopanoids, are generally present in minor amounts. Diterpenoid composition indicates dominant contribution from <em>Cupressaceae and Pinaceae</em> conifers. Minor amounts of predominantly lupane-type non-hopanoid triterpenoids denote limited development of angiosperm vegetation, presumably mostly related to <em>Betulaceae</em> family. Relative abundance of mid-chain (<em>n</em>-C₂₁_–₂₅) <em>n</em>-alkanes, associated with elevated proxy ratio (Paq) furthermore, suggest possible contribution from aquatic macrophytes to peat formation. Very low hopane concentrations and low/moderate ββ/(ββ + αβ) hopane ratios imply minor aerobic bacterial activity under mild acidic conditions. The presence of inorganic carbon suggests that environmental acidity might be controlled by the occasional input of neutral to slightly alkaline ground waters. Moderate sulfur contents and the occurrence of hopenes denote anaerobic bacterial activity after organic matter burial.</p><p>Low maturity of the organic matter and limited hydrocarbon generation potential is indicated by the low huminite reflectance, hopane (C₃₁ 22S/(22S + 22R)) and sterane (αααC₂₉ 20S/(20S + 20R)) isomerization ratios, as well as Rock-Eval parameters, T_max and Production Index (PI).</","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000466/pdfft?md5=58097d7fb199eb77d4664ea947499359&pid=1-s2.0-S0166516224000466-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140113386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Depositional environmental controls on mechanical stratigraphy of Barakar Shales in Rajmahal Basin, India","authors":"Chinmay Sethi ,&nbsp;Bodhisatwa Hazra ,&nbsp;Mehdi Ostadhassan ,&nbsp;Hem Bahadur Motra ,&nbsp;Arpan Dutta ,&nbsp;J.K. Pandey ,&nbsp;Santosh Kumar","doi":"10.1016/j.coal.2024.104477","DOIUrl":"10.1016/j.coal.2024.104477","url":null,"abstract":"<div><p>Understanding mechanical behaviour of shale is essential for efficient shale gas extraction, which can vary in different depositional settings. The impact of sedimentary environment on shale characteristics, such as mineralogical composition, total organic carbon content (TOC), and petrophysical properties, has been extensively researched. However, its influence on shale mechanical properties, especially in defining mechanical stratigraphy for targeting specific fracturing intervals, remains less explored. In this study, the influence of depositional environment on the mechanical properties of shale samples from the Rajmahal Basin is evaluated. Tensile strength of the samples was measured by the Brazilian splitting tensile strength and the brittleness index was calculated as a measure of mechanical properties. In addition, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray fluorescence spectroscopy (XRF), Rock-Eval 6, and X-ray diffraction (XRD) analysis were carried out to assess geochemical characteristics of the samples from different perspectives. The results revealed that such geochemical variations that are generally controlled by the depositional environment, would impact the mechanical properties of the samples. Based on major and trace elements proxies, the depositional environment was determined to be passive continental margin, with hot and humid paleoclimatic conditions and freshwater anoxic settings. Tensile strength and brittleness index of the shale samples was observed to vary between 0.93 and 4.12 MPa and 0.71 to 3.40, respectively, while samples with the TOC exceeding 15 wt% had a strong negative correlation with tensile strength, as reasonably expected, due to weakening impact of the sedimentary organic matter on the shale matrix. Tensile strength and brittleness index correlated positively with clay mineral content, particularly their type, but negatively with the quartz content. Furthermore, samples abundant in biogenic silica exhibited reduced brittleness compared to those with lithogenic silica. Nevertheless, the variation in mechanical properties with burial depth was not substantial, and the examination of stress-strain curves indicated an overall brittle nature of the layer where the samples were retrieved from. Overall, achieving more robust conclusions regarding mechanical stratigraphy within the studied section of the Rajmahal Basin, would necessitate additional vertical sampling.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016651622400034X/pdfft?md5=bd21868cdd4fd641dff8cbd837f24e75&pid=1-s2.0-S016651622400034X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140069814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quality and composition of Lower Cretaceous carbonate source rocks and seepage oils in the Belize Basin, southern Belize, Central America","authors":"B. Holland ,&nbsp;P. Alsen ,&nbsp;H.P. Nytoft ,&nbsp;A. Rudra ,&nbsp;H. Sanei ,&nbsp;H.I. Petersen","doi":"10.1016/j.coal.2024.104478","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104478","url":null,"abstract":"<div><p>The Belize Basin in southern Belize, Central America, contains numerous seepage oils derived from marly and carbonate source rocks, but since no definitive source rocks have been identified the source remains uncertain. This study examines by pyrolysis and organic petrography the source rock quality and maturity of 66 samples collected from three newly exposed carbonate sections in the southeastern Belize Basin together with organic geochemical analysis of five new occurrences of seepage oils from the southern Belize Basin. Combined ammonite and aptychi biostratigraphy suggest a Berriasian to Hauterivian age of the source rock samples. Low T_max values show the samples are thermally immature. Numerous samples are oil-prone and have Hydrogen Index values &gt;300–400 mg HC/g TOC, reaching a maximum of 768 mg HC/g TOC. The samples with source rock potential contain from 32 to 64% pyrolysable organic carbon and contains liptinite-rich Type II kerogen consisting of alginite, bituminite, and liptodetrinite. The calculated Ultimate Expulsion Potential (UEP) of a 22.5 m thick section amounts to ∼2.5 mmboe/km². This generation capacity is volumetrically relatively small, but it could be compensated for by a thicker source rock section. However, the identified source rocks could account for the seepage oils in the Belize Basin, and they are thus the first documentation of Lower Cretaceous source rocks in Belize. A plausible explanation for the widespread occurrence of seepage oils in the Belize Basin could be generation from organic-rich layers with bituminite and alginite. In line with this and previously examined seepage oils, the new variably degraded oils were sourced from carbonate source rock facies.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140062099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics of the low-pressure spatial and temporal distributions of oil- and gas-bearing layers in the Ordos Basin, China","authors":"Yang Qin ,&nbsp;Chiyang Liu ,&nbsp;Lei Huang ,&nbsp;Jianqiang Wang ,&nbsp;Junfeng Zhao ,&nbsp;Deyong Shao ,&nbsp;Lihua Yang ,&nbsp;Xiaochen Zhao ,&nbsp;Ehsan Khalaf ,&nbsp;Shaohua Zhang ,&nbsp;Nan Du","doi":"10.1016/j.coal.2024.104476","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104476","url":null,"abstract":"<div><p>Abnormal pressure conditions and spatial variations have direct and powerful influences on the aggregation, dissipation, accumulation and development of hydrocarbons under subsurface conditions, and they are extremely important aspects that must be focused on for safe coal mining and oil and natural gas development. The Ordos Basin, located in the western part of the North China Craton (NCC), contains significant reserves of oil, gas, coal and other mineral resources and is a typical low-pressure basin. This paper conducts an overall analysis and comprehensive comparison of the spatial and temporal variations in the pressure coefficients of oil and gas areas in the Ordos Basin. The analysis is based on a dataset comprising 589 sets of pressure coefficient–depth data from hydrocarbon layers that are uniformly classified in the basin's main oil and gas fields. Notably, high-pressure features develop in the basin only in the gas fields located in the centres of areas with high gas generation intensity, in individual sections of lithological seals and in the gas layers beneath the gypsum salts of the Ordovician Majiagou Formation. The Mesozoic oil layers and Paleozoic gas layers throughout the basin, which are buried at depths up to 4500 m and within a stratigraphic era spanning 3 × 10⁸ years, generally dominate low pressures, and these abnormal pressure features are not noticeably affected by spatial or temporal variations. Additionally, the ranges of the pressure coefficients and the distributions of the peak values of the oil and gas layers in the upper-oil and lower-gas areas (UOLGAs) generally resemble each other. The pressure coefficients for gas reservoirs only slightly exceed those for oil reservoirs. These unique features are rare in many large- and medium-sized petroleum bearing-basins worldwide. Excluding the high abnormal pressure data of the subsalt gas layer in the basin, based on the magnitudes, proportions, and distributions of the pressure coefficients of the gas layers, as well as the geological background, it is possible to classify the 10 gas fields in the basin into five distinct categories: (1) weak low-pressure dominated; (2) weak low-pressure dominated, mixed with high-pressure; (3) weak low-pressure dominated, supplemented with normal pressure; (4) normal and weak low pressures coexisting; and (5) abnormally high pressure dominated. Regarding the spatial distribution, the pressure coefficients of the gas layers exhibit a macroscopic pattern of gradual increase from the northern to the southern regions. Furthermore, the unique characteristics of the generally low pressures in the basin, in the coalfield (mine) gas pressure coefficient, in the gas content, and in the gas explosion frequency correspond to the performance and can be corroborated by each other. This study provides a scientific basis and theoretical foundation for a profound understanding of the accumulation (mining) effects of evolution-modifica","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140016118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Artificial maturation of a Silurian hydrocarbon source rock: Effect of sample grain size and pyrolysis heating rate on oil generation and expulsion efficiency","authors":"Abid Bhullar ,&nbsp;Sedat İnan ,&nbsp;Salman Qathami ,&nbsp;Tülay Y. İnan","doi":"10.1016/j.coal.2024.104475","DOIUrl":"10.1016/j.coal.2024.104475","url":null,"abstract":"<div><p>Although artificial maturation of hydrocarbon source rocks by laboratory pyrolysis is far from representing natural maturation, it is a useful tool to investigate the process. In this study, we used routine open system pyrolysis for powder samples and Restricted System anhydrous Pyrolysis (RSP) for cm-sized Silurian shale source rock fragments to artificially mature the samples to different end-temperatures in the presence of a flowing carrier gas. Maturation experiments on rock fragments enable the simulation of physical barriers for the generated hydrocarbons that need to be overcome before expulsion from the source rock can occur. Based on the artificial maturation results in this study, oil expulsion efficiency from the Silurian shale source rock was 46% at the early oil generation stage and increased to 74% at approximately the peak oil generation stage.</p><p>Furthermore, we have compared artificial maturation results from powder-form and fragment-form samples with natural-maturation series and found that artificial maturation of fragment-form samples sufficiently resembles natural maturation of the Silurian shales. It is therefore possible to simulate the early, middle and peak oil generation stages of natural maturation and expulsion efficiencies. This implies that, lab-based oil expulsion efficiencies from increasing maturity and hydrocarbon generation can be incorporated into the basin modeling.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139977970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oil migration from internal and external source rocks in an unconventional hybrid petroleum system, Montney Formation, western Canada","authors":"Arka Rudra ,&nbsp;James M. Wood ,&nbsp;Victoria Biersteker ,&nbsp;Hamed Sanei","doi":"10.1016/j.coal.2024.104473","DOIUrl":"10.1016/j.coal.2024.104473","url":null,"abstract":"<div><p>Unconventional hybrid petroleum systems are partially to entirely self-sourced. Their hydrocarbons are generated within internal (intraformational) organic-rich mudstone source rocks and subsequently migrate into adjacent organic-lean reservoir beds composed of sandstone, siltstone or carbonate. Hybrid systems with volumetrically dominant reservoir-quality rocks can additionally receive hydrocarbon charge by longer-range migration from external source rocks. However, few previous studies of hybrid systems have focused on the migration and mixing of hydrocarbons from both internal and external sources. To address this shortfall, this study presents an integrated organic geochemistry and stable carbon isotope investigation of drill-core and produced hydrocarbon liquid samples from two wells in a major unconventional hybrid petroleum system in the Montney Formation of western Canada. The results reveal distinct geochemical trends with increasing depth through the upper part of the Montney Formation including decreased C₃₀₊ biomarker compounds, increased depletion of saturate compared to aromatic δ¹³C values, and increased proportions of saturates and mobile oil. These trends indicate that oil from external source rocks of the overlying Doig Formation migrated into the upper part of the Montney Formation. Downward migration of externally sourced Doig oil resulted in a broad transition zone where Doig-sourced oil mixed with locally migrated lighter oil generated within internal Montney source rocks of slightly higher thermal maturity. This study sheds new light on the migration and mixing of disparate oil charges in the Montney Formation, and likely has widespread applicability to other similar unconventional hybrid petroleum systems that had hydrocarbon contributions from both internal and external source rocks.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000302/pdfft?md5=30d314e612ac17b7d69d7912fc940d1a&pid=1-s2.0-S0166516224000302-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139938900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantitative characterization of the evolution of in-situ adsorption/free gas in deep coal seams: Insights from NMR fluid detection and geological time simulations","authors":"Yanbin Yao ,&nbsp;Feng Wang ,&nbsp;Dameng Liu ,&nbsp;Xiaoxiao Sun ,&nbsp;Hui Wang","doi":"10.1016/j.coal.2024.104474","DOIUrl":"10.1016/j.coal.2024.104474","url":null,"abstract":"<div><p>Accurate quantification of the coexistence of adsorbed and free gas content holds the utmost significance for estimating gas-in-place resources and predicting gas production dynamics. In this study, we conducted real-time isothermal adsorption experiments and NMR fluid monitoring on stress-confining core samples, from the Zhengzhuang Block's No.3 coal seam in the southern Qinshui Basin. Our focus was on assessing multi-phase methane gas contents within coal under various pressure and temperature (P/T) conditions. By integrating experimental findings with adsorption potential theory and the SDR adsorption model, we developed comprehensive models for adsorbed, free, and total gas contents as functions of P/T and water/gas volume saturation. Utilizing these models, we predicted vertical variations in adsorbed and free gas contents within the coal seam. Our results revealed that the interplay between positive reservoir pressure effects and adverse reservoir temperature effects influenced both adsorbed and free methane gases. With increasing burial depth, the influence of pressure on adsorbed gas diminished, while temperature effects became more pronounced. Conversely, free gas content responded noticeably to reservoir pressure, with temperature exerting a marginal influence. Additionally, we performed a numerical simulation to reconstruct the thermal history, burial trajectory, and evolution of reservoir pressure for the No.3 coal seam. The simulation results served as foundational data for understanding the evolution of free and adsorbed gas contents across different geological epochs within the in-situ reservoir. Our findings unveiled a four-stage evolutionary progression in both adsorbed and free gas contents, correlating with the uplift and subsidence of the coal seam. In conclusion, our study provides a conceptual model elucidating the intricate, deep-time evolution process and mechanisms governing the occurrence of multiphase gases across distinct geological epochs. The implications of this research are crucial for accurately evaluating gas-in-place resources and guiding the exploration and development of deep coalbed methane resources.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139938802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Graphitization: Microstructural and microtextural transformations of residual char from international coal combustion ash","authors":"Ana Cláudia Santos ,&nbsp;Charlotte Badenhorst ,&nbsp;Barbara Białecka ,&nbsp;Ignacio Cameán ,&nbsp;Alexandra Guedes ,&nbsp;Karen Moreira ,&nbsp;Georgeta Predeanu ,&nbsp;Isabel Suárez-Ruiz ,&nbsp;Nicola Wagner ,&nbsp;Bruno Valentim","doi":"10.1016/j.coal.2024.104470","DOIUrl":"10.1016/j.coal.2024.104470","url":null,"abstract":"<div><p>Natural graphite is a critical raw material and its substitution in some applications will contribute to reduce its supply risk. Coal ash, which is still produced in high amounts, contains a carbonaceous solid residue (char) that may be a substitute of natural graphite. For this purpose, char may be graphitized and used in electrocatalysis reactions, however char properties depend on coal rank, composition and combustion conditions that affect the graphitization process. Research on industrial coal char graphitization is limited, resulting in restricted comprehension of the contributing factors. In order to provide novel insights, industrial residual chars (derived from Poland, Portugal, Romania and South Africa) subjected to high-temperature treatments (carbonization at 1000 °C followed by treatment at 2600 °C under environmental pressure) were examined regarding their microstructural and microtextural transformations. The samples were studied by focussing on its heterogeneity, namely its specific properties and interactions, including elemental composition, optical character, and structure. Furthermore, the evolution of structural order of selected char morphotypes in samples derived from coal of similar rank was assessed using Raman microspectroscopy.</p><p>The results highlighted a set of aspects that could have influenced the transformations experienced by the different chars during high temperature treatments (graphitization). It was found that Hydrogen might play a role in the graphitization ability of isotropic chars derived from low rank coal. The prior preferential orientation of the Basic Structural Units (BSU) contributes to achieve a higher graphitization degree, but it can be enhanced or hindered by other factors, e.g., hydrogen content. Raman microspectroscopy showed that char morphotypes from the same group underwent different transformations during graphitization, indicating that morphotypes or sections with unfused optical character may be more prone to graphitization. However, the existence of disordered domains and specific microtextures, such as polyhedral pores identified under TEM, likely hindered further graphitization. Further research on this topic is needed.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000272/pdfft?md5=c7fdcadbd61538f5d1581d9b12a46d8b&pid=1-s2.0-S0166516224000272-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139916403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In situ coal permeability and favorable development methods for coalbed methane (CBM) extraction in China: From real data","authors":"Shida Chen ,&nbsp;Shu Tao ,&nbsp;Dazhen Tang","doi":"10.1016/j.coal.2024.104472","DOIUrl":"10.1016/j.coal.2024.104472","url":null,"abstract":"<div><p>Permeability plays a significant role in the economic viability of coalbed methane (CBM) development. In China, in situ permeability obtained from injection fall-off tests range from 0.0001 to 41 mD at depths of 130–1728 m, with the majority (78%) falling between 0.01 and 1 mD. Coal reservoirs with high rank, common cleat mineralization, and depth-dependent high stress may result in extremely low permeability. Low-rank coal and cataclastic coal exhibit more favorable permeability conditions at shallow depths. Heterogeneity in coal rank, coal texture, and stress magnitude results in a discrete distribution of permeability both regionally and vertically. Most deep seams are highly compressed with extremely low permeability (&lt;0.1 mD) as high stress levels. Multilateral horizontal wells work best with high permeability seams, while vertical wells with conventional hydraulic fracturing demonstrate limited adaptability to deep and low-permeability seams due to insufficient proppant-supported fractures. With increasing depth, both vertical and horizontal wells should employ larger fracturing scales to create effectively supported zones with higher fracture conductivity and reduced stress sensitivity to enhance CBM productivity. Horizontal wells with large-scale volume fracturing demonstrate superior performance compared to vertical wells in extracting CBM from deep, low-permeability, and high gas saturation reservoirs.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139916371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}