摘要
[目的]鄂尔多斯盆地宁东煤田蕴藏丰富的富油煤资源,其中石炭-二叠系煤层由于热演化及沉积环境差异导致富油煤赋存较为特殊.[方法]以红墩子矿区和四股泉矿区煤为研究对象,在分析富油煤赋存特点及关键物质组成基础上,探讨了煤化程度与沉积环境对煤焦油产率的控制作用.[结果与结论]结果表明:宁东煤田石炭-二叠系煤层焦油产率平均值介于 7.15%～11.07%,但不同区域、不同煤层及同煤层不同部位焦油产率普遍存在差异性.煤化程度是影响研究区富油煤赋存的核心地质控制因素,使得煤焦油产率随煤化程度升高呈现先增加后降低的变化趋势,峰值转折点为Cdaf=84%.煤化作用控制下,H/C、O/C与焦油产率之间呈现相近的演化趋势,同时造成活性组分(镜质组+壳质组)仅在Cdaf<84%时与焦油产率呈良好正相关性.成煤母质、气候条件和水体古盐度对煤焦油产率影响较小,但水体还原性及水动力条件间接影响了同煤级煤焦油产率的离散性.镜惰比(V/I)、凝胶化指数(GI)、灰成分指数(K)、U/Th及δU指示的成煤环境表现出覆水性深、闭塞潮湿、还原性强、木本组织少,有利于形成高焦油产率的富油煤;灰分产率、SiO2+Al2O3 等指示水动力条件强、陆源碎屑输入量大,不利于高焦油产率富油煤形成.
Abstract
[Objective]The Ningdong Coalfield of the Ordos Basin boasts abundant tar-rich coal resources,of which tar-rich coals in the Carboniferous-Permian coal seams exhibit unique occurrence characteristics due to differences in ther-mal evolution and sedimentary environments.[Methods]This study analyzed the occurrence characteristics and critical material composition of tar-rich coals in the Hongdunzi and Siguquan mining areas.Based on this,it explored the control-ling effects of the degree of coalification and sedimentary environment on the tar yield.[Results and Conclusions]The results indicate that the Carboniferous-Permian coal seams in the Ningdong Coalfield exhibit average tar yields ranging from 7.15%to 11.07%,which generally vary in different zones,different coal seams,and even different parts of the same coal seam.The degree of coalification is identified as a core geologic factor controlling the occurrence of tar-rich coals in the study area.With an increase in the degree of coalification,the tar yield trended upward initially and then downward,peaking at Cdaf=84%.Under the action of coalification,a similar evolutionary trend can be observed between the H/C and O/C ratios and the tar yield.Meanwhile,there were significant positive correlations between active compon-ents(i.e.,vitrinite and exinite)and the tar yield merely under Cdaf<84%.Coal-forming parent materials,climatic condi-tions,and paleosalinity of water bodies exert minor impacts on the tar yield.In contrast,the reducibility and hydro-dynamic conditions of water bodies indirectly affect the discreteness of the tar yield of coals at the same ranks.The vit-rinite/inertinite ratio(V/I),gelification index(GI),ash composition index(K),U/Th ratio,and δU values indicate that coal-forming environment features deep water,occlusion,moisture,strong reducibility,and small quantities of woody tissues,which are conducive to the formation of tar-rich coals with a high tar yield.In contrast,indices such as ash yield and SiO2+Al2O3 indicate strong hydrodynamic conditions and substantial quantities of terrigenous clast inputs,which are unfavorable for the formation of tar-rich coals with a high tar yield.
基金项目
宁夏自然科学基金优秀青年项目(2022AAC05064)
宁夏重点研发计划项目(2023BEG02058)
宁夏地质事业发展专项资金项目(640000223000000016748)
国家科技期刊平台
NSTL
万方数据