Abstract: In order to obtain the migration and output laws of low permeability coalbed methane in mining of well group combined with thermal injection, a coupled thermal-solid-fluid mathematical model of coalbed methane was developed based on the theory of heat transfer, elastic mechanics, seepage mechanics, and rock mechanics. Combined with the geological parameters of 3# coal seam of Shanxi Formation in Lu'an mining area, the finite software was utilized to simulate seepage rules in the mining process. Under different well pattern, 10 d thermal stimulation and 100 d mining were carried out respectively, and the curves of related parameters, temperature, and stress and gas pressure variation were drawn. The results show that the average velocity of heat transfer of coal seam is 1.57 m/d after 10 d steam injection in the 35 m effective area of thermal stimulation. With the increase of well number and the decrease of well spacing, along the radial direction of well,the well group interference is strengthened, the reservoir pressure drops more quickly, the gas desorption area increases, and the production of well is promoted significantly. The production of cumulative coalbed methane of seven wells heat injection with 20 m well-bore spacing is 2.01 times of that of five wells with 30 m well-bore spacing without heat injection. The simulation results show the advantages of heat injection and inter-well interference,and provide a theoretical basis for coalbed methane mining technology of multi-well combined with thermal injection in low permeability reservoirs.

Key words: low permeability coal-bed methane, thermal stimulation mining, thermal-solid-fluid coupling, inter-well interference, numerical simulation