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煤岩结构的纳米级变形与变质变形环境有着较密切的关系.在不同变质变形环境中,煤岩结构可以发生显微变形,甚至可以表现在纳米级尺度上,由此并导致分子结构和纳米级孔隙结构(<100nm)的变化,后者是煤层气的主要吸附空间.通过X射线衍射和液氮吸附法对不同变质变形环境、不同变形系列构造煤大的分子结构与纳米级孔隙结构特征进行了深入研究,并结合高分辨透射电子显微镜对大分子结构和孔隙结构直观观测,结果表明:构造煤大分子基本结构单元(BSU)堆砌度Lc从低煤级变质变形环境至高煤级变质变形环境增长较快,这主要反映了不同变形机制下构造煤不同变质变形环境的差异.尽管温度因素对大分子结构参数Lc的变化也取重要作用,但应力作用更明显.煤BSU堆砌度Lc以及La/Lc参数的变化反映了构造变形强弱的变化,可以当作构造煤结构纳米级变形程度的指示剂.由于温度、压力的增大,主要是定向应力的作用,分子的局部定向性增强,BSU内各碳网及BSU间排列的秩理化程度明显增强.对于纳米级孔隙结构的变形,随着应力作用的增强,同一变质变形环境不同类型构造煤纳米级过渡孔孔容所占比例明显降低,微孔及其以下孔径段孔容明显增多,可见亚微孔和极微孔;过渡孔比表面积所占比例大幅度降低,而亚微孔却增加得较快.非均质结构煤孔隙参数与弱脆性变形煤相当.但不同变质变形环境构造煤的纳米级孔隙的变形又有所区别.温度与围压条件对纳米级孔隙特征参数的演化也有一定的作用,但应力的变化却对纳米级孔隙特征参数的演化起到主要作用.
Nanometer-scale deformation of coal-rock structure is closely related to the metamorphic deformation environment.Different metamorphic deformation environment, the coal-rock structure can be deformed microscopically, even on the nanoscale scale, and the molecular structure and nanometer Level pore structure (<100nm), which is the main adsorption space for CBM.Using X-ray diffraction and liquid nitrogen adsorption method for different metamorphic deformation environment, different deformation series of large coal molecular structure and nano-pore structure characteristics The results show that the Lc of the structural unit (BSU) of the structural coal macromolecules ranges from low-grade metamorphic deformation environment to high-grade metamorphic deformation The rapid growth of the environment mainly reflects the difference of different metamorphic deformation environments under different deformation mechanisms.Although the temperature factor plays an important role in the change of structural parameters Lc of macromolecules, the stress effect is more obvious. The change of La / Lc parameter reflects the change of tectonic deformation intensity, which can be used as an indicator of the degree of nanoscale deformation of coal structure. Due to the increase of temperature and pressure, the orientational stress mainly increases the local orientation of molecules, and the degree of physical and chemical rank of each carbon network and BSU in BSU increases obviously.For the deformation of nano-scale pore structure, with the stress effect , The proportion of pores of different types of structured coal in the same metamorphic deformation environment is obviously decreased, pore volume of micropore and its subsequent pore diameter obviously increases, showing sub-micropores and micropores; the proportion of transition pore specific surface area is large But the submicropores increase more rapidly.The pore parameters of heterogeneous coal are similar to those of weak brittle deformed coal.But the deformation of nano-scale pores of tectonic coal is different in different metamorphic deformation environments.Temperature and confining pressure conditions It also plays a certain role in the evolution of nano-pore parameters, but the change of stress plays a major role in the evolution of nano-pore parameters.