Experimental Study on Coal Damage Subjected to Microwave Heating

Coalbed methane (CBM) reservoirs usually require stimulation to enhance the permeability, thereby promoting CBM production. Realized by the conversion of the electromagnetic energy into heat, microwave heating may be an effective CBM stimulation method. In this study, the effects of microwave heating on the damage of coal were investigated through scanning electron microscope and ultrasonic wave tests. The results indicate that the mineral grain in coal generally disappears after microwave heating. For low-permeable coals with highly mineralized fractures, the dissolution of mineral could potentially enhance permeability and improve stress resilience. Microwave selective heating can lead to the opening and extension of original fractures and the generation of secondary fractures, reducing P-wave and S-wave velocity of coal. The stronger the anisotropy of coal is, the greater the microwave fracturing effect becomes. In a word, microwave heating has potential for assisting coalbed methane exploitation.