College of Geology and Environment, Xi’an University of Science and Technology
Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation,Xi’ an University of Science and Technology
SHCCIG Caojiatan Mining Co., Ltd.
College of Petroleum Engineering and Environmental Engineering, Yan’ an University

为探讨陕北富油煤形成的沉积环境和控制因素,采用井下刻槽和钻探定向取样相结合的方法采集了曹家滩矿井2-2煤的垂向剖面煤样,对样品的煤岩煤质参数和等离子低温灰化样的地球化学参数进行了系统测试,从有机显微煤岩组成和无机地球化学特征方面研究了2-2煤层形成的沉积环境,探讨了焦油产率与沉积环境之间的关系,揭示了富油煤形成的主要控制因素。结果表明:曹家滩矿井2-2煤层以亮煤、暗淡煤为主,显微煤岩组成以惰质组为主、镜质组次之,壳质组含量较少;低温灰化样无机矿物组成主要是方解石、石英和黏土,元素组成以Ca、Si、Fe、Al、S、Mg和Na为主;微量元素中大多数元素处于亏损,仅有Cs、Ba属于轻度富集;稀土元素含量均值9.91μg/g,低于世界煤均值68.47μg/g;煤相分析显示2-2煤主要形成于干燥森林沼泽和潮湿森林沼泽中,成煤植物以低木本植物为主,整体属于弱还原的陆相淡水沉积环境、水动力条件弱,沉积期以温湿和干热的过渡气候为主,晚期出现了古气候由温湿向干热气候转变;显示了2-2煤焦油产率与镜质组含量、凝胶化指数、Sr/Ba、Ni/Co、Ce/La等呈正相关关系,但与植物保存指数、植被指数及Fe2O3、Fe2O3+CaO+MgO、MnO2含量呈负相关关系。富油煤在分布上具有中高等镜质组含量、中高凝胶化程度和低木本组分的特征,即植物组织保存程度低、凝胶化程度较高、低木本植物,以及有适量的陆源碎屑物质供应、适量盐度的还原沉积环境更有利于富油煤的生成。

In order to explore the sedimentary environment and control factors of the formation of tar- rich coal in northern Shaanxi, a combined method of underground grooving and directional drilling sam- pling was used to collect the vertical profile of coal seam 2- 2 in Caojiatan mine. A comprehensive suite of tests was then conducted on both the coal-rock and coal-quality parameters of the collected samples, as well as the geochemical parameters of the plasma low-temperature ashed samples. The sedimentary environment of the formation of coal seam 2- 2 was studied from the aspects of organic microscopic coal rock composition and inorganic geochemical characteristics. Within this framework, the correlation be- tween tar yield and sedimentary conditions was explored, ultimately unveiling the primary factors influ- encing the formation of tar-rich coal in our study locale. The findings reveal that the 2- 2 coal seams in Caojiatan mine predominantly consist of bright and dull coal. Microcoal analysis indicates a predomi- nance of inertinite, followed by vitrinite, with a notably low liptinite. The inorganic minerals of low-tem- perature podzolic samples are mainly calcite, quartz and clay. The major elements are Ca, Si, Fe, Al, S, Mg and Na. Notably, most trace elements are present in deficit concentrations, except for a slight en- richment in Cs and Ba. The average rare earth element content stands at 10. 00 μg / g, significantly be- low the global coal average of 68. 47 μg / g. Coal phase analysis points to a formation within dry and hu- mid forest swamps, dominated by low woody plants as the primary coal-forming vegetation. This suggests a weakly reducing terrestrial freshwater environment with subdued hydrodynamic conditions. During the sedimentary period, there was a climatic transition from warm and wet to dry and hot conditions, with a late-stage shift towards drier and hotter paleoclimates. Furthermore, a positive correlation is established between the coal tar yield of 2- 2 coal and parameters such as vitrinite content, gelation index, Sr/ Ba, Ni/ Co, and Ce / La ratios. Conversely, a negative correlation is observed with plant preservation index, vegetation index, as well as Fe2O3, Fe2O3 + CaO + MgO, and MnO contents. In essence, the distribu- tion of tar-rich coal is marked by moderate to high vitrinite levels, a medium to high degree of gelation, and a low woody component— indicating that a combination of low plant tissue preservation, high gela- tion, low woody plant content, a moderate supply of terrigenous detritus, and a moderate salinity reduc- ing sedimentary environment are more conducive to the formation of tar-rich coal.

国家自然科学基金项目(42002194,42330808);陕煤化工集团科学技术研究计划项目(2021SMHKJ-A-J-07-02)

乔军伟,董伸培,苏刚,等.陕北曹家滩矿井富油煤地球化学特征及其沉积环境[J].西安科技大学学报,2024,44(2):289-300.

QIAO Junwei, DONG Shenpei, SU Gang, et al. Geochemical characteristics and sedimentary environment of tar-rich coal in Caojiatanmine, Northern Shaanxi[ J] . Journal of Xi’an University of Science and Technology, 2024, 44( 2) : 289-300.