Experimental study on coal bed methane displacement and recovery by super critical carbon dioxide injection.

A new experimental equipment MCQ-II for supercritical CO2-ECBM recovery test with large size specimen was designed. The equipment can measure the specimen swelling during the supercritical CO2-ECBM recovery test. With the equipment, series of experiments for supercritical CO2 seepage and CH4 recovery with supercritical CO2 displacement were carried out. It is found that, under the conditions of 50 °C and constant volumetric stress, supercritical CO2 permeability is positively related to the infiltrating pressure, while it is negatively related to the confined volumetric stress. It turns out that supercritical CO2 permeability in the coal is higher than CO2 in general condition. The rise of volumetric stress and pore pressure will increase the supercritical CO2 adsorption. Under 48 MPa and 60 MPa volumetric stress, 10. 82 to 17. 52 and 16. 12 to 20. 40 units of carbon dioxide can be stored in per unit of coal, respectively. During the process of CH4 adsorption, CO2 adsorption and CH4 displacement by CO2, coal swelling volumetric percentage is recorded. In the experiment of CH4 displacement by supercritical CO2, more CH4 and CO2 were injected to specimen No. 1 (weakly caking coal) than specimen No. 2 (coking coal),but the replacement ratio of carbon dioxide to methane and the CO2 storage rate are almost equal, 4.01/4.16, 20.05%/20.09% Respectively. [ABSTRACT FROM AUTHOR]