A gas apparent permeability model in coal micro/nano-pores considering the poroelastic effect and its application in gas extraction
LI Wei1，2，YANG Kang3，4，DENG Dong1，2，WANG Haifeng1，2
(1. National Engineering Research Center for Coal Mine Gas Control，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China；2. School of Safety Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China；3. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400044，
China；4. School of Resources and Safety Engineering，Chongqing University，Chongqing 400044，China)
Abstract：The poroelastic effect in micro/nano-pores of coal significantly affects gas production. However，it is currently rare for the poroelastic effect to be considered in gas apparent permeability model for micro/nano-pores. In order to investigate the influence of the poroelastic effect on gas flow mechanisms in micro/nano-pores，a gas apparent permeability model considering the dynamic evolution of pore size is constructed based on the poroelastic effect and multiple mechanism flow model in micro/nano-pores. The dominant flow mechanism of the dynamic apparent permeability model is determined and the contribution of slippage effect in micro/nano-pores to gas recovery production is evaluated. The results show that the poroelastic effect impacts the contribution of the slippage and the surface diffusion effects to the apparent permeability by influencing the evolution of pore size. As the pore pressure increases，the dynamic apparent permeability ratio(the ratio of the apparent permeability affected by the poroelastic effect to the initial apparent permeability) is controlled by the slippage effect and the poroelastic effect in turn. Additionally，the contribution of the slippage effect to the apparent permeability ratio decreases rapidly at lower pressure but decreases more gradually at higher pressure as the pressure increases. In the process of gas recovery from low-permeability coal seams，the contribution of the slippage effect to gas recovery production initially increases rapidly，then decreases gradually，and eventually reaches a slow increase. A smaller average pore size in micro/nano-pores leads to a greater contribution of the slippage effect to gas recovery production.
李 伟1，2，杨 康3，4，邓 东1，2，王海锋1，2. 考虑孔弹性效应的煤岩微纳米孔隙瓦斯表观渗透率模型及其在瓦斯抽采中的应用[J]. 岩石力学与工程学报, 2024, 43(3): 587-599.
LI Wei1，2，YANG Kang3，4，DENG Dong1，2，WANG Haifeng1，2. A gas apparent permeability model in coal micro/nano-pores considering the poroelastic effect and its application in gas extraction. , 2024, 43(3): 587-599.
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2024, Vol. 43 
