基于NMR的煤孔隙结构与渗流特征研究进展
A Review of Pore Structure and Seepage Characteristics of Coal Samples Based on NMR

煤孔隙结构及渗流特性方面的研究对煤矿瓦斯灾害防治具有重要意义。文中介绍了低场核磁共振技术(NMR)的基本原理，综述了孔隙结构与渗流特性方面的研究成果。结果表明：核磁共振技术是由于煤孔隙内含氢原子核受到射频磁场的作用发生偏转产生共振现象，由于纵向驰豫时间受分子扩散的影响测量时间较长，因此选用横向驰豫时间更能精确反映煤储层孔隙度；相对于其他研究方法，通过核磁共振弛豫谱可以快速、准确地得到孔径分布、孔隙度、流体分布及渗透率等物性参数，反映其微观孔隙结构信息；且在获取驰豫信号的基础上，结合一些辅助方法即可实现对煤渗流情况的实时观测。但是核磁共振驰豫谱分布图与其相对渗透率的具体关系还未可知。因此，今后的研究应致力于建立驰豫谱与相对渗透率两者之间的函数关系。
The research on coal pore structure and seepage characteristics is of great significance to the prevention and control of coal mine gas disasters. This paper introduces the basic principle of low-field nuclear magnetic resonance (NMR) technology, and summarizes the research results of pore structure and seepage characteristics. The results show that the nuclear magnetic resonance technology is due to the deflection of the hydrogen-containing atomic nucleus in the coal pore caused by the radio frequency magnetic field, and the longitudinal relaxation time is affected by the molecular diffusion. The measurement time is longer, so the transverse relaxation time can accurately reflect the porosity of the coal reservoir. Compared with other research methods, the physical parameters such as pore size distribution, porosity, fluid distribution and permeability can be quickly and accurately obtained by NMR relaxation spectrum, reflecting the microscopic pore structure information. On the basis of obtaining relaxation signals, combined with some auxiliary methods, real-time observation of coal seepage can be realized. However, the specific relationship between the NMR relaxation spectrum distribution and its relative permeability is still unknown. Therefore, future research should focus on establishing the functional relationship between relaxation spectrum and relative permeability.