Abstract
Understanding the influence of temperature on the gas seepage of coal seams is helpful to achieve the efficient extraction of underground coal seam gas. Thermal coal‐gas interactions involve a series of complex interactions between gas and solid coal. Although the interactions between coal and gas have been studied thoroughly, few studies have considered the temperature evolution characteristics of coal seam gas extraction under the condition of variable temperature because of the complexity of the temperature effect on gas drainage. In this study, the fully coupled transient model combines the relationship of gas flow, heat transfer, coal mass deformation, and gas migration under variable temperature conditions and represents an important nonlinear response to gas migration caused by the change of effective stress. Then, this complex model is implemented into a finite element (FE) model and solved through the numerical method. Its reliability was verified by comparing with historical data. Finally, the effect of temperature on coal permeability and gas pressure is studied. The results reveal that the gas pressure in coal fracture is generally higher than that in the matrix blocks. The higher temperature of the coal seam induces the faster increase of the gas pressure. Temperature has a great effect on the gas seepage behavior in the coal seams.
Highlights
Coal seam gas is an important natural source and an important part in the clean energy structure in China [1]
Temperature has an obvious effect on the adsorption capacity of coal seam gas, which is negatively correlated with the increase of temperature [9,10,11]
Zhu et al [16] analyzed the influence of temperature on coal permeability based on a complex thermal-hydrological-mechanical model and found that sorption-induced volumetric strain affected the seepage behavior of coal seam significantly
Summary
Coal seam gas is an important natural source and an important part in the clean energy structure in China [1]. E thermal stimulation of gas reservoir triggers the complex interaction between coal, gas, and temperature. It changes the deformation behavior of coal, as well as the heat and gas flow. Zhu et al [16] analyzed the influence of temperature on coal permeability based on a complex thermal-hydrological-mechanical model and found that sorption-induced volumetric strain affected the seepage behavior of coal seam significantly. Qu et al [18] developed a new thermal model with gas flow and matrix adsorption and suggested that the increase in temperature leads to the decrease in coal swelling and larger cleat aperture and higher coal permeability. The effect of temperature on coal permeability and gas pressure is studied based on this coupled model
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