Laboratory study and prediction on coal permeability of Qinshui Basin

As one key parameter for coalbed recovery, cleat compressibility has not been well studied in China. In this study, a Chinese coal sample from Qinshui Basin, Shanxi province, was measured using different gases, including He, N-2, CH4 and CO2 with different effective stresses and temperatures. Based on the experimental data, the Langmur constants were calculated and curves of adsorption and permeability were drawn, respectively. The experimental results show that effective stress has important effect on permeability. Permeability decreases with increasing effective stress under the same pore pressure for all four kinds of gases at constant temperature of 35 degrees C. On the basis of experimental results, cleat compressibility was calculated by fitting data to equations. The calculated results also show that cleat compressibility decreases with increasing pore pressure at 35 degrees C for all four gases. Moreover, with increasing temperature, cleat compressibility increases only a little. Based on the analysis