Evolution of Permeability Rebound and Recovery Under the Influence of Gas Adsorption Thermal Effects

doi:10.12068/j.issn.1005-3026.2025.20230306

Abstract

Abstract:

The thermal quantity released/absorbed during gas adsorption/desorption significantly influences the evolution of permeability rebound and recovery in coal seams. Based on the thermo-hydro-mechanical （THM） coupling theory， this study investigates the temporal evolution of permeability rebound and recovery under single/multiple gas adsorption thermal effects and further assesses their impact on coalbed methane （CBM） extraction. Results indicate that under a single-factor influence， permeability rebound and recovery time exhibit a positive correlation with adsorption heat intensity， and its response to Langmuir’s constant is characterized similarly to the former and tends to stabilize when the adsorption performance parameter exceeds the critical value. Under multi-factor coupling， adsorption heat enhances permeability rebound and recovery on the temporal scale while the spatial scale is less susceptible to adsorption heat. Furthermore， neglecting adsorption thermal effects may lead to an over-estimation of the gas production increase induced by permeability rebound and recovery.

Key words: coalbed methane, permeability rebound, permeability recovery, gas adsorption thermal effects, extraction capacity

CLC Number:

TD 712

Zheng-dong LIU, Xiao-song LIN, Gang BAI, Chen SUN. Evolution of Permeability Rebound and Recovery Under the Influence of Gas Adsorption Thermal Effects[J]. Journal of Northeastern University(Natural Science), 2025, 46(5): 103-112.

Figures/Tables 16

Fig.1 Matching results between field test data and simulation results

Fig.2 Schematic diagram of permeability rebound and recovery time

Table 1 Parameters required in the numerical simulation model

参数	值	参数	值
煤层初始压力p₀/MPa	6.6	吸附时间τ/s	844 345
杨氏模量E/MPa	2 713	CH₄摩尔质量M_c/(kg·mol^-1)	0.016
基质杨氏模量E_m/MPa	8 139	CH₄动力黏度μ/Pa·s	1.08×10^-5
煤层压缩系数C_f/MPa^-1	0.139 2	CH₄导热系数 $λ$ _g/(W·m^-1·K^-1)	0.031
煤层密度ρ_c/(kg·m^-3)	1 250	煤骨架导热系数 $λ$ _s/(W·m^-1·K^-1)	0.191
气体常数R/(J·mol^-1·K^-1)	8.314	CH₄等量吸附热q_st/(J·mol^-1)	2 100
极限吸附量n_m/(m³·t^-1)	20	Langmuir 压力常数b/MPa^-1	1
煤骨架比热容c_s/(J·kg^-1·K^-1)	1 350	Langmuir 应变常数ε_L	0.126 6
泊松比v	0.35	CH₄比热容c_L/(J·kg^-1·K^-1)	2 160
初始渗透率k₀/cm²	4.935×10^-12	内部膨胀系数f	0.1
初始裂隙率ϕ_f	0.005	初始孔隙率ϕ_m	0.05

Table 1 Parameters required in the numerical simulation model

参数	值	参数	值
煤层初始压力p₀/MPa	6.6	吸附时间τ/s	844 345
杨氏模量E/MPa	2 713	CH₄摩尔质量M_c/(kg·mol^-1)	0.016
基质杨氏模量E_m/MPa	8 139	CH₄动力黏度μ/Pa·s	1.08×10^-5
煤层压缩系数C_f/MPa^-1	0.139 2	CH₄导热系数 $λ$ _g/(W·m^-1·K^-1)	0.031
煤层密度ρ_c/(kg·m^-3)	1 250	煤骨架导热系数 $λ$ _s/(W·m^-1·K^-1)	0.191
气体常数R/(J·mol^-1·K^-1)	8.314	CH₄等量吸附热q_st/(J·mol^-1)	2 100
极限吸附量n_m/(m³·t^-1)	20	Langmuir 压力常数b/MPa^-1	1
煤骨架比热容c_s/(J·kg^-1·K^-1)	1 350	Langmuir 应变常数ε_L	0.126 6
泊松比v	0.35	CH₄比热容c_L/(J·kg^-1·K^-1)	2 160
初始渗透率k₀/cm²	4.935×10^-12	内部膨胀系数f	0.1
初始裂隙率ϕ_f	0.005	初始孔隙率ϕ_m	0.05

Fig.3 Physical model and boundary conditions

Table 2 Simulation scheme under single factor condition

方案	n_m/(m³·t^-1)	b/MPa^-1	q_st/(J·mol^-1)
1	20	1	2 100
	40
	60
2	20	1	2 100
		2
		3
3	20	1	2 100
			2 600
			3 100

Fig.4 Permeability evolution patterns at monitoring points under different isochoric adsorption heat conditions

Fig.5 Relationship between permeability rebound and recovery time and isochoric adsorption heat

Fig.6 Rebound value at monitoring point A under different isothermal adsorption conditions

Fig.7 The change of permeability with time at point A

Fig.8 Permeability rebound time evolution

Fig.9 Permeability recovery time evolution

Table 3 Simulation scheme under multiple factor coupling condition

方案	n_m/(m³·t^-1)	b/MPa^-1	q_st /(J·mol^-1)
1	20	1	2 100
2	40	2	4 200
3	60	3	6 300

Fig.10 Differences in permeability evolution at monitoring points A

Fig.11 Differences in desorption and strain at monitoring point A

Fig.12 Differences in rebound and recovery time at different monitoring points

Fig.13 Difference of extraction capability with and without adsorption thermal effect

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