Mechanisms and field application of in-situ heat injection-enhanced gas drainage

The low permeability of coal seams and strong adsorption of methane considerably inhibit gas drainage; thus, developing a method for efficient gas drainage is crucial. The heat injection-enhanced gas drainage tests were carried out in the laboratory and coal mine, and the gas drainage effect and mechanism of heat injection method were studied. Then, through numerical simulation, the gas production law of heat injection method was analyzed from the perspective of water and gas migration. Indoor experiments demonstrated that heat injection strengthened methane desorption and relieved the inhibitory effect of water on gas. The gas drainage effect of field tests was remarkable, and the gas concentration and daily gas production increased by over 10 and 100 times, respectively. During heat injection, water occupied the migration channel of gas, and the inhibition of water on gas was greater than the promotion of temperature, resulting in the reduction of gas production; After heat injection, high temperature promoted gas desorption and relieved the inhibition of water on gas, resulting in a significant increase in gas production. The gas production law obtained from the numerical simulation showed a high degree of consistency with field tests. The results can provide a reference for gas control.