This paper investigates the permeability change caused by reactions with different minerals in coal after injecting carbon dioxide for providing an experimental support for increasing the flow conductivity of the coal reservoir, and also for the improvement of the permeability based on the test of the nitrogen adsorption, the mineral composition and the permeability of medium-high rank coal (Tunlan mine and Sihe mine). The permeability change model is built based on the nonlinear regression analysis of the initial permeability, the reaction time and the improved permeability. The results indicate that the permeability of medium-high rank coal increases first and then decreases with time after injecting the carbon dioxide as a result of CO₂-water-rock interaction; The permeability of the Sihe coal samples reaches the maximum value first, followed by the Tunlan coal samples, and the improving effect of permeability of the Sihe coal samples is shown to be better than that of the Tunlan coal samples; For the best improvements, the initial permeability is about 0.2×10^-3 to 0.4×10^-3 μm²; Finally, the reliability of the mathematical model is verified.

coal bed methane  /  different rank  /  permeability  /  minerals  /  injection of CO₂