# Influences of Different Factors and Sensitivity Analysis of Permeability of Gassy Coal
## 1 Introduction  
Coalbed methane (CBM) is a new, clean, and efficient energy source, with China's CBM reserves exceeding 40 trillion m\({}^{3}\), making it an abundant resource with significant potential for utilization. At present, the main utilization method of CBM is CBM extraction, and permeability is a key parameter describing the mobility performance of methane in coal, which has an important impact on CBM extraction [1, 2, 3, 4, 5, 6, 7]. There are many factors influencing the permeability of gas-containing coal, such as axial pressure, confine pressure, temperature, gas pressure, etc., and the sensitivity of each influencing factor to the permeability of gas-containing coal varies [8, 9, 10, 11, 12, 13, 14]. Therefore, it is of great significance to analyze the factors that influence and sensitivity of the permeability of gas-containing coal for the efficient extraction of coalbed methane. The permeability of gas-containing coal is influenced by various factors, such as gas pressure, effective stress, temperature, water content, etc. Many scholars have carried out extensive research on the influence of these factors on the permeability of gas-containing coal [15; 16; 17; 18], yielding valuable results. Stress, as an important factor affecting permeability, influences coal body permeability in five main ways: the stress state of the coal body, stress-induced damage, physical properties of the coal body, matrix deformation, and methane adsorption capacity [19; 20]. [PERSON] et al. [21] research concluded that the porosity and permeability of anthracic coal decrease exponentially with increasing effective stress, with significant changes observed below 5-6 MPa and enhanced stress sensitivity at higher moisture content and temperature. [PERSON] et al. [22] concluded that both the effective stress coefficient and gas slippage have a significant influence on coal permeability, with the slippage effect being more pronounced at low gas pressures and the cleat exhibiting more vulnerability to deformation compared to the bedding. The effects of temperature on the permeability of the coal body mainly include thermal expansion and deformation of the coal body, changes in methane adsorption, and thermal cracking damage [23; 24]. [PERSON] et al. [25] research concluded that the cyclic temperature impact significantly enhances coal permeability, with new fractures and increased permeability observed as the temperature difference rises. [PERSON] et al. [26] measured the porosity of the coal body after heat treatment by the NMR method and found that the porosity of the coal body showed a general increase with the increase in temperature. The effect of water content on the permeability of the coal body mainly includes filling pores, swelling effect, reducing friction, and changing the coals' physical properties [27; 28]. [PERSON] and [PERSON] [29] found that temperature significantly influences coal permeability, with higher temperatures leading to a marked decrease in the absolute permeability of raw coal to gases, while the effect on briquette coal permeability is negligible and can be compensated by changes in the dynamic viscosity factor. [PERSON] et al. [30] research concluded that the peak strength, axial strain, and permeability of water-bearing raw coal decrease with water content and confining pressure, while permeability increases with unloading and exhibits volatility with axial strain, following an exponential decay function with effective stress. [PERSON] et al. [31] research concluded that the effective gas permeability of coal cores decreases with increasing water content and effective stress, with a linear relationship to water content and an exponential relationship to effective stress, influenced by changes in permeation pore structure. In addition, many permeability models have been developed to quantitatively characterize seepage in coal seams. [PERSON] et al.