Effect of the Hydrate Saturation of the Pores of Coal Bed on the Gradient of Gas Pressure and the Rise of Outburst Danger

Abstract

A substantial fraction of methane in undisturbed coal beds is present in the condensed latent state, so that methane evolution from coal may be not always quantitatively predicted reliably. On the basis of experimental data, an equation expressing the amount of gas hydrate through the sorption capacity and actual humidity of coal is obtained. Analysis showed that the gradient of gas pressure in the marginal zone of a coal bed is linearly dependent on the saturation of the pore space with the hydrate. The high gradient of gas pressure and high gas content of coal beds along with local disruption of coal and re-distribution of rock pressure are the major factors causing instantaneous outbursts of coal and gas.