Abstract To thoroughly understand the mechanism of permeability change and improve production in coalbed methane development, it is important to clarify the evolution characteristics and influencing factors of matrix compressibility for various coal ranks. This paper presents calculations of matrix compressibility coefficients of different rank coals through mercury intrusion porosimetry (MIP) and N2 adsorption. Furthermore, the evolution of coal material and pores based on coal rank is analyzed to study their effect on matrix compressibility coefficients. The results show that the relationship between matrix compressibility coefficients and coal rank is a cubic polynomial function, in which two inflection points are situated in the maximum vitrinite reflectance (Ro,max) = 1.3% and 2.5%. For coals with Ro,max 1.0%, in which the micropore structure will be broken when pressure exceeds 150 MPa. The coals with greater fractal dimension are more sensitive to stress. The matrix compression can lead to reduction of micropore volume and can make the micropore structure more irregular. It indicates that the increasing of effective stress with gas discharge could reduce the permeability of the reservoir and enhance the adsorption of micropore.

中文翻译：

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不同煤级煤基体可压缩性特征及其影响因素研究*

摘要 为了深入理解煤层气开发中渗透率变化的机理，提高产量，明确各煤级基体可压缩性的演化特征及影响因素具有重要意义。本文介绍了通过压汞法 (MIP) 和 N2 吸附计算不同煤级煤的基质压缩系数。此外，分析了基于煤阶的煤质和孔隙演化，研究了它们对基体压缩系数的影响。结果表明，基体压缩系数与煤级的关系是三次多项式函数，其中两个拐点位于最大镜质反射率(Ro,max)=1.3%和2.5%。对于含 Ro,max 1.0% 的煤，其中微孔结构在压力超过 150 MPa 时会被破坏。分形维数越大的煤对应力越敏感。基质压缩会导致微孔体积减少，并使微孔结构更加不规则。表明随着放气有效应力的增加，储层渗透率降低，微孔吸附能力增强。