An experimental study on carbon dioxide displacing coal bed methane under supercritical conditions

Identifying the effects of carbon dioxide displacing coal bed methane under supercritical condition can provide a theoretical basis for the carbon dioxide injection parameters of deep coal seam. Regarding Sihe mine anthracite and Yuwu mine lean coal as the research objects, the adsorption experiments and displacement experiments of carbon dioxide and coal bed methane under supercritical conditions were carried out. According to the nature of the volumetric method for testing adsorption, the absolute adsorption of carbon dioxide and coal bed methane under different pressures was calculated and the Langmuir pressure and Langmuir volume of carbon dioxide and coal bed methane were obtained. With Langmuir isothermal adsorption model and its extensions, the desorption rate of carbon dioxide displacing coal bed methane at unit pressure drop under supercritical pressure range and low pressure range were calculated. The results showed that the desorption rate of the carbon dioxide displacing coal bed methane at unit pressure drop under supercritical pressure range or low pressure range both are higher than the desorption rate of coal bed methane in the natural desorption states at unit pressure drop. Desorption rate of coal bed methane at unit pressure drop under the supercritical pressure range or low pressure range for Anthracite increased by 268.13% and 8.71%, and lean coal increased by 73.71% and 3.75%; The effect of carbon dioxide displacing coal bed methane under supercritical pressure range was more obvious.