Abstract: A self-developed multi-field coupling physical simulation testing system was employed to investigate the gas pressure, coal temperature, the deformation and other parameters evolution characteristics of coal reservoir during the process of extracting different adsorption gas. The results demonstrate that the gas pressure of coal reservoir decreased rapidly at the early stage of extraction, and formed a gas pressure equivalent plane with the center of the drill hole. The gas flow rate and pressure drop rate declined with the increase of distance. The stronger ability of adsorption, the lower the gas pressure drop rate and the longer the duration. The time evolution law of coal reservoir temperature and the time evolution law of gas pressure were consistent. Coal reservoir temperature decreased significantly at the early stage. At the late stage of extraction, under the influence of desorption of the adsorbed gas and heat exchange, the coal bed temperature appeared to decrease initially and then increase slightly. The closer position from extraction drill hole, the greater the pressure drop, the more obvious the coal bed temperature decreased and the greater the amount of coal deformation. The stronger the ability of adsorption is, the greater the deformation of the coal caused by gas extraction.

Key words: gas extraction, permeability, coal reservoir parameters, physical modeling