塔里木盆地东南缘下—中侏罗统煤层煤岩、煤质特征分析
Petrography and Quality Characteristics of LowerMiddle Jurassic Coal Seam in the Southeastern Tarim Basin

摘要： 塔里木盆地东南缘下—中侏罗统煤层沿阿尔金山前断续分布，其煤岩、煤质与典型的西北侏罗纪煤层具有明显不同。通过对和田布雅、于田普鲁、且末红柳沟等煤矿主采煤层样品进行煤岩、煤质鉴定及煤化指标等一系列综合研究分析，结果表明，主采煤层以光亮煤、半亮煤为主，其次是半暗煤、暗淡煤；煤岩组分以镜质组为主，壳质组含量少，具中-高镜惰比。因成煤沼泽的还原程度促进了无机硫分的形成，煤中全硫含量随镜质组含量的增加呈现逐渐增高的趋势，且煤层硫分与灰分整体具有明显的负相关关系。此外，煤层挥发分受不同种类硫分的影响，亦有明显差异性变化。在民丰凹陷中-高硫煤中，硫分以无机硫为主，随着硫分的升高挥发分亦有升高趋势；瓦石峡凹陷中-低硫煤受有机硫控制，对挥发分产率的影响不明显。民丰凹陷煤层的灰分指数高于瓦石峡凹陷，可见后者的成煤沼泽环境潜水面要比前者高得多。针对上述诸多因素分析，进一步揭示塔东南地区煤岩、煤质多样性变化受断陷湖盆以及局部水体较深的还原型沼泽环境控制，最终形成了中-高挥发分、中-低灰分、中-低硫分的煤质及富镜贫惰的煤岩特征。
Abstract: Petrology and quality of the LowerMiddle Jurassic coal seams in the southeastern margin of the Tarim basin (distributed intermittently along the Altyn Tagh) are very different from the Jurassic coal seams in northwestern China. To characterize these coal seams, various experiments including coal petrography, coal quality identification and coalification index have been conducted on a large amount of coal samples collected from the Hetian Buya, Yutian Pulu and Qiemo Hongliugou coal mines. The results reveal that the main mining layer consists mainly of clarain and semibright coal, followed by durain and semidull coal. The macerals are mainly characterized by vitrinite, with minor exinite and middlehigh V/I. In addition, the total sulfur content in the coal increases with the vitrinite content, due to the lower degree of coalforming swamp that promotes the formation of inorganic sulfur. Moreover, it is obvious that the content of coal seam sulfur decreases with the ash content. Similarly, the volatile content of coal seam affected by various sulfur contents is significantly different. The analyses also show that the main component of sulfur in the mediumhigh sulfur coal of the Minfeng sag is inorganic sulfur, and that the volatile fraction increases with increasing sulfur content. However, the productivity of volatile influence of organic sulfur is not obvious in the mediumlow sulfur coal in the Washixia sag. It is found that the ash composition index in the coal seam of the Minfeng sag is higher than that of the Washixia sag, which suggests that the water table of the coalforming swamp of the latter is much higher. Our results confirm that the change of coal petrology and coal quality diversity in the southeastern Tarim basin are controlled by the faulted lacustrine basin and the local water depth in the reducing swamp environment, which led to the mediumhigh volatility, mediumlow ash, mediumlow sulfur, and the rich vitrinitepoor inertinite coal features there