Methane Seepage Characteristics in Coal Seams under Microwave Radiation.

Microwave radiation is an effective method for simulating the exploitation of coalbed methane (CBM). Herein, structural coal seepage is evaluated using a self-developed experiment system to explore the temperature and permeability response changes exhibited by coal samples under microwave radiation and stress loading. Microwave radiation experiments are used to conduct the numerical simulation of the microwave radiation, and the temperatures and permeability values of the coal samples under simulated and experimental conditions are compared and analyzed. The results show that the higher the microwave radiation power, the higher the temperature of coal samples within the specified time. Under the same effective stress conditions, the higher the microwave radiation power and the longer the action time, the greater the coal sample permeability. Moreover, effective stress is shown to be important for permeability. The curve change trends and numerical values of the experiment and simulation are consistent, and the accuracy of the experiment and simulation is verified in both directions. Furthermore, a numerical model of coal seams under microwave radiation is established to simulate the change law of pressure, gas seepage velocity, and free methane content of actual coal seams under microwave radiation. It is concluded that the fast heating and stable temperature resulting from microwave radiation are beneficial for the crack propagation of coal near reservoirs. The results of this study provide a new technological method for actual CBM exploitation and a new research direction for unconventional natural gas energy output.