Real-time monitoring of coalbed methane production network following liquid CO2 injection in a low-efficiency well network: Response to gas and water production characteristics

Abstract

Through real-time monitoring of gas composition, water ions, and productivity variations in multiple production wells after liquid CO2 injection, it reveals differences in reservoir response characteristics and geological control mechanisms between coalbed methane production wells. The results show that CO2 forms preferential migration channels along low ground stress and high-altitude directions. The production wells are divided into efficient stimulation wells, inefficiency stimulation wells, inhibition wells, and unaffected wells according to stimulation effect. The efficient stimulation wells show that the stimulation mode is CO2 displacement. The gas production increases significantly, with a maximum increase rate of 46.85 %. The N2 component in the produced gas and the HCO3− + CO32− ions in the produced increase during the continuous injection. The inefficient stimulation wells and inhibition wells show CO2 driven water production mode. The N2 and CO2 component, and the HCO3− + CO32− ions increase during the injection process. And the formation of water-abundant zones around the production wells inhibits the production of gas. The unaffected well is not affected by CO2 injection and shows a natural gas production mode of drainage depressurization and desorption. The results of the study provide technical support for the implementation and evaluation of the CO2-ECBM project.