Study On Improving The Seepage Performance Of Coal-bed Methane By Microwave Heating

The storage of coal-bed methane are extremely rich in China.At present,the characteristics of "abundance CBM reservoir with low permeability" has restricted the development of Chinese CBM industry a lot.The use of microwave heating to improve the low permeability of coal seam is a hot spot for the recent research and exploitation of coalbed methane.Based on the laboratory experiment,the relationship between permeability and pore pressure,effective stress and temperature is obtained.Combining with the theories of microwave engineering,thermodynamics and seepage mechanics,the multi-physics coupled mathematical model including low-permeability coalbed methane seepage process with microwave heating power and function of temperature and power microwave heating has been established.the following conclusions are obtained:Using the real three-axis experimental instrument with microwave control for experiments,The results show that the temperature of the coal sample increases with the increase of the power,and the microwave heating power is higher,and the internal temperature of the coal seam is higher than that of the microwave.According to the percolation experiment of microwave heating of coal samples,it is concluded that the effective stress increases with the pore pressure and the permeability decreases first and then increases with the same pressure and the same temperature.Based on the influencing factors of microwave heating power,the microwave propagation control equation,the temperature field control equation,deformation control equation,seepage equation are established by considering the influence of the electromagnetic field,stress field,temperature field and deformation field.The simultaneous equations get the mathematical model under the action of power microwave.The geometrical model of coalbed methane in power microwave heating and mining is used to analyze the temperature distribution under different power and frequency,and the law of pore pressure distribution and permeability change of coalbed methane with different power microwave heating.The results show that the coal seam permeability increases obviously when microwave heating is increased,the power of microwave is increased,the gas content of adsorbed gas is gradually reduced,the permeability of coal sample is increased,and the production of coalbed methane is increased.The higher the microwave power is,the greater the change rate is.