Study on the Temperature Dependence of Pore Evolution and Seepage Characteristics of Coal Based on 3D Reconstruction Method

To investigate the thermal damage characteristics of and its regulatory on seepage performance, this article reconstructed the 3D geometric structure of coal and quantitatively analyzed the variation of structure parameters including pore, throat, and permeability. The results show that with the increase of temperature, the pore structures extend from internal pore-enriched areas toward the surface of coal. Below 200°C, pores mainly develop in the originally enriched areas, while above 200°C, the distribution of internal pore becomes more uniform, and pores at different locations shows approximately synchronous development. The average coordination number of pores and the number of throats increase, and the equivalent radius of throats expands while the tortuosity decreases. At temperatures below 200°C, the increase of permeability is primarily due to the rise in the number of pathways. Above 200°C, the size of throats becomes the dominant factor. Within 350°C to 400°C, intense pyrolysis of coal led to the fluctuations in pore structures and seepage parameters. The findings clarify the temperature response of pore structures and seepage performances of coal, providing theoretical guidance for the heat transfer and mass migration mechanism of high-temperature coal in the fire zone.