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Coal permeability related to matrix-fracture interaction at different temperatures and stresses
Journal of Petroleum Science and Engineering ( IF 5.168 ) Pub Date : 2021-01-19 , DOI: 10.1016/j.petrol.2021.108428
Zheng Gao , Bobo Li , Jianhua Li , Bin Wang , Chonghong Ren , Jiang Xu , Shuai Chen

Heat injection is considered to be an effective technique to increase Coalbed methane (CBM) production, which indicates the important role of temperature in gas flow. In this paper, two different experimental schemes have been designed, and the seepage tests concerning variable effective stress and variable pore pressure have been carried out respectively under different temperature conditions. A permeability model that considered the combined effect of temperature and stress was developed, and further extended so that it could be applied under other boundary conditions. An effective deformation factor fm was introduced to characterize the contribution of the change of coal matrix width to the change of fracture width, and the relationship between fm and temperature, under three boundary conditions, was quantitatively analyzed. Under constant pore pressure, the increase of effective stress will reduce the permeability. Under constant effective stress, an increase of pore pressure will lead to the decrease in permeability. Temperature would affect the permeability characteristics of coal from physical and chemical aspects, which were mainly manifested as inhibition, and this effect significantly weakened during the high stress stage. In terms of model matching, the permeability model results from each boundary condition were in good agreement with the measured results. In addition, the effective deformation factor fm increased exponentially over temperature under different boundary conditions. It is thought that these findings would provide a theoretical basis for the further study of coal matrix-fracture interaction, and CBM exploitation.



中文翻译:

在不同温度和应力下与基质-断裂相互作用相关的煤渗透性

热注入被认为是增加煤层气(CBM)产量的有效技术,这表明温度在气流中的重要作用。本文设计了两种不同的试验方案,分别在不同的温度条件下进行了有关有效应力变化和孔隙压力变化的渗流试验。建立了考虑温度和应力共同作用的渗透率模型,并将其进一步扩展,以便可以在其他边界条件下应用。引入有效变形因子f m来表征煤基质宽度变化对裂缝宽度变化的贡献,以及f m之间的关系。在三个边界条件下对温度进行了定量分析。在恒定的孔隙压力下,有效应力的增加将降低渗透率。在恒定有效应力下,孔隙压力的增加将导致渗透率降低。温度会从物理和化学方面影响煤的渗透性,主要表现为抑制作用,并且在高应力阶段这种作用会明显减弱。在模型匹配方面,每种边界条件的渗透率模型结果与实测结果吻合良好。另外,有效变形系数f m在不同边界条件下,温度随温度呈指数增长。认为这些发现将为进一步研究煤基质-断裂相互作用和煤层气开采提供理论依据。

更新日期:2021-02-04
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