单轴加载煤孔裂隙各向异性核磁共振特征

为了研究煤孔裂隙各向异性,进一步揭示煤微观结构及物性特征。选取平顶山矿区八矿煤样,采用核磁共振（NMR）方法,对比分析单轴加载前后煤样的横向弛豫谱（T₂）特征和核磁成像（MRI）特征。实验结果表明,煤的T₂谱特征具有显著的各向异性:平行于层理且垂直主裂隙X方向T₂谱为3峰谱图,平行于层理且平行主裂隙Y方向T₂谱为双峰谱图,垂直层理Z方向T₂谱主要以单峰为主;单轴加载后煤样T₂谱面积、孔隙度减小,X、Y方向煤样孔隙变化引起的峰面积所占比例下降,裂隙变化引起的峰面积占比例上升;Z方向裂隙变化引起的峰面积占比例下降;MRI揭示出,单轴加载后平行层理方向煤样孔裂隙大部分闭合,部分裂隙产生径向变形;加载方向裂隙大部分闭合,压实效应显著。综上所述,单轴加载下,煤样各向异性特征显著,同时表明核磁共振技术是研究煤孔裂隙微观变化的有效手段。      

不同含水性无烟煤CO2吸附行为及其对地质封存的启示

深部煤层CO₂地质封存是助力“碳达峰碳中和”战略的重要途径,煤层含水性对以CO₂吸附封存为主的深部煤层CO₂地质封存能力影响显著。以无烟煤为例,开展了45℃下干燥、平衡水、饱和水煤样高压CO₂等温吸附实验,校正了饱和水煤样过剩吸附曲线,利用改进的D-R吸附模型拟合得到三者吸附能力与吸附热,对比了不同含水条件下CO₂绝对吸附曲线,阐释了饱和水增强无烟煤吸附能力的微观作用机理。结果表明:(1)干燥、平衡水、饱和水煤样CO₂吸附能力分别为56.72、45.19和48.36 cm3/g,吸附热分别为29.42、26.23和27.24 kJ/mol。(2) CO₂密度小于0.16 g/cm3(6.48 MPa)时,无烟煤CO₂绝对吸附量大小顺序为干燥煤样、饱和水煤样和平衡水煤样,而CO₂进入超临界状态后,顺序变为饱和水煤样、干燥煤样和平衡水煤样。(3)水分子优先占据高能吸附位是平衡水煤样吸附能力减弱的主要原因,而煤?水体系与CO₂相互作用强于CO₂与H₂O竞争吸附下的煤?CO₂相互作用是饱和水煤样在CO₂超临界阶段吸附能力高于干燥煤样的根本原因。(4)吸附封存是煤层CO₂地质封存的主要形式,深部煤储层条件下,煤层饱和水对超临界CO₂增储作用更为明显,高压注水是提高深部煤层CO₂地质封存潜力,改善煤储层渗透性的有效手段。      

参照镜煤反射率用电子探针测定煤中有机硫

根据镜煤反射率与碳含量的关系,估计出煤中碳及相应的氢、氦、氧的含量,再将电子探针所测煤中有机硫与标样疏的X射线强度比值作为硫含量的近似值,计算出煤中有机硫的ZAF校正因子。最后用ZAF,法得到有机硫的含量。实验表明其结果与化学分析一致。     

中国煤中有机硫的分布及其成因

对来自全国26个省、市、自治区的290个煤样中有机硫的质量分数测试及研究,发现煤中有机硫质量分数基本分布在0%1.0%范围内。在低硫煤中硫分以有机硫为主,在高硫煤中以无机硫为主。中、高硫煤中,广西、湖南等地区很大一部分煤中硫分以有机硫为主。在所采集的样品中,高有机硫煤(有机硫>1%)均分布在华南、华北两大聚煤区,属于石炭、二叠纪煤。高有机硫煤中有机硫质量分数的变化与变质程度无明显关系。煤炭形成过程中海水作用的影响,是导致煤中有机硫含量偏高的最主要原因。      

高煤级煤—隐晶质石墨的Raman光谱表征及结构演化

拉曼光谱能够反映碳材料结构的有序程度和结构缺陷,可用来表征高煤级煤—隐晶质石墨演化过程中结构变化。通过对受岩浆热变质影响的不同变形变质程度样品的拉曼参数与面网间距（d₀₀₂）之间关系的研究表明:G峰位置与d₀₀₂呈现阶梯变化,能较好地区分出石墨与高煤级煤,S₂峰位、D₁、G半峰宽与d₀₀₂呈较好的线性关系;D₁与G峰峰位差和半峰宽比随d₀₀₂减小而减小,S₂与S₄峰的峰位差随d₀₀₂减小先增大后减小,而其强度比及面积比逐渐增大;d₀₀₂与拉曼参数关系显示两次明显的结构演化跃变,即无烟煤至变质无烟煤阶段,R_max>6.5%、P（D₁-G）<235 cm-1、P（S₂-S₄）>525 cm-1以及半峰宽比显著下降、L_a/L_c迅速降低,为芳构化、芳环缩合作用增强向芳环叠片拼叠转变;半石墨至石墨演化阶段,P（D₁-G）、I_D1/I_G与A_D1/A_G显著降低,L_a、L_c迅速增加。以d₀₀₂为标度能较好地反映煤结构在不同演化阶段的Raman光谱特征。      

基于扫描电镜、孔隙-裂隙分析系统和气体吸附的煤孔隙结构联合表征

为了定量表征煤的孔隙结构,研究煤孔隙特征与吸附性能的内在联系,采用低温液氮吸附法（LP-N₂GA）、CO₂吸附法、扫描电镜（SEM）和孔隙-裂隙分析系统（PCAS）对6种不同变质程度煤样进行孔隙相关分析.煤样孔隙分布相似时,煤样对N₂和CO₂的吸附能力、孔隙率的近似概率密度和孔隙面积（中孔）与煤的挥发分呈负相关,煤样孔隙的分形维数与煤的挥发分呈正相关.煤样的孔隙分布差异较大时,煤样对N₂和CO₂的最大吸附容量与孔隙分布有关.建立了煤纳米孔结构的联合表征模式,该表征模式能够更有效地研究和分析煤中的孔隙,包括孔隙数目、孔隙面积、孔隙周长、平均形状因子、孔隙率、分形维数和孔径分布,将SEM-PCAS与气体吸附方法相结合对煤的孔隙结构进行定量联合表征的模式是可行的.      

ScCO2-H2O作用下不同煤级煤化学结构变化的实验研究

超临界二氧化碳（ScCO₂）–H₂O–煤地球化学反应可造成煤物理结构和化学结构的改变,对煤层注CO₂增采甲烷的有效性尤为关键。为了探讨ScCO₂-H₂O-煤反应对不同变质程度煤化学结构的影响,选择3个不同煤化程度煤样,在自主研制的ScCO₂-H₂O-煤地球化学反应模拟实验装置中模拟1000m埋深条件下煤样与ScCO₂和去离子水反应240h,并对反应前后的煤样分别进行了X射线衍射和拉曼光谱实验,对比分析了反应前后煤样晶体结构和碳有序度的变化特征。测试结果表明:ScCO₂-H₂O反应破坏了煤的晶体完整性和碳有序度,改变了煤的大分子结构,且对低阶煤和中–高阶煤具有不同的影响,反应提高了低阶煤的平行定向程度,使其结构更加紧凑,减小了面网间距,而使中–高阶煤中无序单元增加,面网间距增大。该研究结果为CO₂-ECBM项目实施中ScCO₂-H₂O作用对煤储层吸附解吸特征和孔渗特征影响的研究奠定了微观尺度基础。      

含水饱和度对中阶煤储层应力敏感性影响实验

为了查明含水饱和度对中阶煤储层应力敏感性的影响,对煤层气井储层改造及排采工作提供指导,利用自主设计的实验装置开展了黔西松河矿龙潭组1+3号、15号煤干燥、含水及饱水条件下液测、气测渗透率应力敏感性实验,分析了煤样渗透率、渗透率损害率、渗透率不可逆损害率、应力敏感性系数变化特征。研究结果表明:随着含水饱和度升高,中阶煤液测渗透率应力敏感性增强,加卸载造成的渗透率不可逆损害率增大。含水饱和度升高导致初始气测渗透率降低,干燥煤样孔裂隙闭合程度高,饱水煤样因束缚水饱和度高,具有较强的气测渗透率应力敏感性。干燥煤样、含水煤样适宜采用幂函数表征无因次气测渗透率与有效应力的关系,饱水煤样则更适合采用负指数函数表征两者关系。中阶煤储层压裂及排采过程中应重视储层保护,当煤储层含水性较弱时,应优先考虑采用CO₂或N₂泡沫压裂方式进行储层改造。      

煤岩组分化学结构随热演化变化与生烃性研究

应用显微傅立叶红外光谱分析,研究了胜利油田附近的石炭系太原组煤烃源岩中主要生烃有机组分化学结构特征。结果表明,荧光镜质体富含芳烃结构和含氧有机结构,而树脂体和角质体富含脂肪烃结构,荧光镜质体和树脂体烷基烃碳链短或支化程度高。随热演化程度增高,荧光镜质体和树脂体红外光谱参数(CH₂+CH₃) C=C和CH₂ CH₃比值逐渐减小,而孢子体和角质体的这两个参数先增后减,反映出荧光镜质体与树脂体具早期生烃特点,而孢子体与角质体生烃演化具弱—强—弱特性,具生烃高峰期。      

大别山北麓高煤级煤的变形——变质类型

对中国东部大别造山带前陆盆地石炭纪含煤岩系的高煤级煤进行了深入研究,划分出3种变形——变质类型。构造——热变质类型煤样采自剪切应变带内,煤镜质组反射率各向异性显著,煤结构参数L_c最大,L_a/L_c和d₀₀₂最小,TEM下存在局部石墨化现象,呈现动力变质特征。岩浆热变质类型煤样受中生代花岗岩侵入体异常高温影响,Ro_max和Ro_bi较大,显微镜下呈非均质结构,L_a/L_c在3类煤中最大。区域变质类型煤的Ro_max最小,但仍远远高于稳定地区相近地质时代煤,反映了造山带旁侧构造——热活动背景下有机质的高演化程度。     

二氧化氯对煤储层物性改变的机理研究

二氧化氯在作为煤储层压裂破胶剂的同时,兼具降低煤的亲甲烷能力和化学增透作用。查明二氧化氯对煤储层物性改变的内在机理,对深部煤储层改造摒弃传统活性水改用高粘压裂液有重要意义。通过对二氧化氯改性前后的不同变质程度煤样的压汞和Raman光谱测试,对比分析了煤样改性前后的孔隙结构和化学结构的变化特征。测试结果表明:煤样改性后孔隙度和孔容不同程度增加,比表面积降低;改性后煤的脂肪链的支链化程度和芳香环的缩合程度均降低,煤结构单元缺陷增加,芳碳总量相对减少。可见,煤储层物性改变的机理在于煤孔隙结构及其大分子结构发生了相应变化。      

煤红外光谱的精细解析及其煤化作用机制

应用傅立叶红外光谱(FTIR)分析技术,采用计算机曲线拟合方法对红外光谱进行分峰处理,通过对自然演化系列和人工模拟实验系列样品的研究,定量分析了不同煤化程度煤的红外光谱特征。研究表明,煤的红外光谱在一定程度上可以定量表征煤化作用程度。含氧基团和烷基侧链随煤化程度的增高以不同的速度发生脱落,且脱落的速度具有明显的阶段性:羧基的减少主要发生在R_{max为0.5%之前,但可以持续到肥煤阶段;脂肪基团的脱落主要发生在沥青化作用阶段内,并导致生成大量的烃类,沥青化作用之前发生的脂肪基团的脱落是煤的未熟和低熟油形成的主要原因;在沥青化阶段之后的高演化阶段,煤中的烷基侧链已经脱落殆尽,芳环缩合程度明显提高。红外光谱的分峰技术和定量,为精细解析煤的结构特征和煤化作用研究提供了一种新的方法。}      

Quality of selected coal seams from Indiana: implications for carbonization

The chemical properties of two high-volatile bituminous coals, the Danville Coal Member of the Dugger Formation and the Lower Block Coal Member of the Brazil Formation from southern Indiana, were compared to understand the differences in their coking behavior. It was determined that of the two, the Lower Block has better characteristics for coking. Observed factors that contribute to the differences in the coking behavior of the coals include carbon content, organic sulfur content, and oxygen/carbon (O/C) ratios. The Lower Block coal has greater carbon content than the Danville coal, leading to a lower O/C ratio, which is more favorable for coking. Organic sulfur content is higher in the Lower Block coal, and a strong correlation was found between organic sulfur and plasticity. The majority of the data for both seams plot in the Type III zone on a van Krevelen diagram, and several samples from the Lower Block coal plot into the Type II zone, suggesting a perhydrous character for those samples. This divergence in properties between the Lower Block and Danville coals may account for the superior coking behavior of the Lower Block coal.     

鄂尔多斯盆地煤的灰分和硫、磷、氯含量研究

详细阐述了鄂尔多斯盆地煤的灰分产率和硫、磷及氯含量的空间及垂向分布规律,并探讨了煤中硫。磷及氯含量的影响因素。研究结果表明,石炭-二叠纪煤以中灰煤为主,部分为高灰煤;低灰煤仅分布在局部地区,且灰分产率与全流呈负相关;延安组以特低灰—低灰煤为主,中灰煤次之,空间上灰分北高南低、东高西低;太原组以中高硫煤为主,山西组则以低硫煤为特征,空间上呈南高北低、西高车低之趋势;延安组亦以低硫煤为主。煤中形态硫以黄铁矿硫为主,有机硫次之,硫酸盐硫极少。从太原组到山西组再到延安组,煤中硫呈递减趋势,这与聚煤环境的变化密切相关。该盆地煤含磷低,少部分为特低磷煤。煤中氯的质量分数值平均为425．8×10-6,空间上中南部高、北西部低;垂向上,下部煤层中氯的含量高于中上部煤层,这可能与煤中氯的成因有关。     

Distribution, isotopic variation and origin of sulfur in coals in the Wuda coalfield, Inner Mongolia, China

This paper describes coal petrographic characteristics, sulfur abundance, distribution and isotopic signature in coals in the Wuda coalfield, Inner Mongolia, northern China. Petrographic studies suggest that depositional environment influences petrographic composition. The No. 9 and No. 10 coal seams, which are thought to have formed on a tidal delta plain, have high collodetrinite contents (up to 66.1%) indicating enhanced gelification and bacteria activity during coal accumulation, and also have the highest sulfur content (3.46% and 3.42%). Both organic and pyritic sulfur isotope values (−12.3‰ to 5.8‰ and −18.7‰ to 1.1‰, respectively) are variable and generally tend to be more negative in high-sulfur coals than those in low-sulfur coals in the Wuda coalfield. The negative sulfur isotope values indicate that a large portion of sulfur in the high-sulfur coals has a bacterial origin. Sulfur isotopic compositions and variations within the section were used to propose a model to explain the origin of sulfur in these coals. The presence of pyritized rod-like bacteria, cyanophyte's gelatinous sheaths and degraded algae organic matter suggests that bacteria, and perhaps algae, may play an important role in the formation of these high-sulfur coals.     

中阶构造煤等温吸附/解吸特征及机理

选择四个不同变形程度的中阶煤样品作为研究对象,通过开展煤样的等温CH4吸附/解吸实验、X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)测试分析,研究了构造煤等温吸附/解吸性随煤变形程度的演化特征及其地球化学机理.结果表明,构造煤等温CH4吸附和解吸曲线随压力升高均呈现先快速增大后逐渐稳定的变化趋势,符合I型等温线...     

The distribution of sulfur and organic matter in various fractions of peat: origins of sulfur in coal

The peat-forming systems of the Okefenokee Swamp are viewed as modern progenitors of coal. Taxodium and Nymphaea-derived peat-forming systems were characterized in terms of (1) organic fractions and (2) the distribution of organic/inorganic sulfur in each organic fraction (water soluble, benzene/methanol soluble, humin, humic acid, fulvic acid). The humin fraction is the largest organic fraction in both environments, approaching 70% of the total organic matter in the Nymphaea-derived environment. Humin origins are discussed in terms of a humic acid precursor, and undecomposed plant material. It is suggested that each depth of peat represents a diagenetic history of events which the authors believe occurred primarily when the currently buried peat was at the surface. The sulfur content of both peat-forming areas is low (0.23–0.27%); organic sulfur is the dominant sulfur form. Humin contains 50–80% of the total sulfur and of this, 80% is organic sulfur. Ester-sulfate appears to be especially prevalent in the fulvic acid fraction. The sulfur content of freshwater-derived peats is similar in quantity and distribution to that found in low sulfur coals.     

Petrographic, mineralogy, and geochemistry of coals of Pabedana, Kerman Province, Central Iran

This paper discusses the result of the detailed investigations carried out on the coal characteristics, including coal petrography and its geochemistry of the Pabedana region. A total of 16 samples were collected from four coal seams d2, d4, d5, and d6 of the Pabedana underground mine which is located in the central part of the Central-East Iranian Microcontinent. These samples were reduced to four samples through composite sampling of each seam and were analyzed for their petrographic, mineralogical, and geochemical compositions. Proximate analysis data of the Pabedana coals indicate no major variations in the moisture, ash, volatile matter, and fixed carbon contents in the coals of different seams. Based on sulfur content, the Pabedana coals may be classified as low-sulfur coals. The low-sulfur contents in the Pabedana coal and relatively low proportion of pyritic sulfur suggest a possible fresh water environment during the deposition of the peat of the Pabedana coal. X-ray diffraction and petrographic analyses indicate the presence of pyrite in coal samples. The Pabedana coals have been classified as a high volatile, bituminous coal in accordance with the vitrinite reflectance values (58.75–74.32 %) and other rank parameters (carbon, calorific value, and volatile matter content). The maceral analysis and reflectance study suggest that the coals in all the four seams are of good quality with low maceral matter association. Mineralogical investigations indicate that the inorganic fraction in the Pabedana coal samples is dominated by carbonates; thus, constituting the major inorganic fraction of the coal samples. Illite, kaolinite, muscovite, quartz, feldspar, apatite, and hematite occur as minor or trace phases. The variation in major elements content is relatively narrow between different coal seams. Elements Sc,, Zr, Ga, Ge, La, As, W, Ce, Sb, Nb, Th, Pb, Se, Tl, Bi, Hg, Re, Li, Zn, Mo, and Ba show varying negative correlation with ash yield. These elements possibly have an organic affinity and may be present as primary biological concentrations either with tissues in living condition and/or through sorption and formation of organometallic compounds.     

Origin and distribution of biomarkers in the sulphur rich Utrillas coal basin – Teruel mining district – Spain

The Utrillas coal facies are located in the Maestrazgo basin in NE Spain. This mining district of Teruel contains sub-bituminous deposits from the Middle Albian (Lower Cretaceous 105 Ma) in areas near a delta estuary with abundant sulphur. The high sulphur content is due to an influx of sulphate caused by the geological recycling of Triassic gypsum from the catchment area into the delta estuary. In some outcrops, the weathered coal reveals leonardite deposits. The depositional environment of the basin originated coals, some of which are currently mined. The organic matter of the coals has been the object of scattered reports. Studies have focused on bulk pyrolysis parameters and microscopic observation in Utrillas samples, as well as the inorganic and insoluble organic fraction.We analysed the organic soluble extract of the Utrillas coals using GC–MS in order to characterize their aliphatic, aromatic and organosulphur compounds. The biomarker distribution allowed us to recognize different inputs, assess their depositional palaeoenvironment and finally determine their degree of maturity. In particular, homologous series of hopanes related to eubacteria were present. Biomarkers characteristic of higher plant inputs were also widely distributed (e.g. phyllocladane or C₂₉ steranes). The presence of linear alkylbenzenes allowed us to recognize the palaeodepositional reducing environments where they were deposited. Specifically, thienylhopanes were associated with sulphur-reducing environments. Finally, the abundance of unsaturated biomarkers such as diacholestenes indicated low-maturity coals. Various aromatic ratios such as the methylphenanthrene index also suggested diagenesis in the initial stage.