EXPERIMENTAL STUDY OF EFFECT OF TEMPERATURE ON COAL GAS PERMEABILITY UNDER GAS-SOLID COUPLING

To observe the effect of temperature on coal gas permeability, an experiment of coal gas permeability was carried out at different temperatures through a three-axial penetration instrument.The results show that, at different temperatures, the permeability of coals assumes a trend of quadric parabola, that is, the permeability first decreases and then increases as the effective stress decreases. In the early unloading, the degressive gradient of coal gas permeability is greater at lower temperature than at high temperature.In the late unloading, coal gas permeability ascending gradient is greater at high temperature than at low temperature.The results show that, in the process of coal bed gas mining, the change of coal gas permeability demonstrate three master phases of typical coal bed methane mining at different temperatures.The effective stress, gas heating and coal solid heating are the important factors influencing coal body permeability.In the early unloading, coal solid heating, expansion and effective stress play a leading role in permeability; in the later unloading, gas sliding and gas absorbing heat play a leading role in permeability.After experimental analysis, adopting the exploitation way of coal bed methane fracturing after injection will help to improve production of coal bed methane.