Experiment study of coal permeability under different temperature and stress

Abstract

The relationship between coal permeability and the temperature or stress of the sample was determined by CH{sub 4} or He permeability measurements made under different temperatures and stresses. The results show that the relationship between coal permeability and temperature under different effective stress is not always a monotonically increasing or decreasing function. There is an inflection in permeability when the temperature increases. Under low effective stress the stress from thermal expansion is larger than the applied effective stress. Then the coal expands outside and the permeability increases as the temperature increases, showing a positive exponential relationship. Under high effective stress thermal stress is smaller than the effective stress and the coal expands inside. Then the permeability decreases as the temperature increases in a negative exponential relationship. These discoveries explain past, conflicting results. 11 refs., 5 figs.