Foam Gel with Enhanced Water Retention and Air Leakage Blocking for Effective Coalfield Fire Control

Coalfield fires can be prevented by blocking the air leakage channels. This paper analyzes and compares the thermal stability of foam and foam gel and their application to coalfield fire prevention and control. The average water loss rate and water separation rate of the foam gel are found to be 9.2 and 206 times lower than those of the foam, respectively. The average water use efficiency of the foam gel was 95.96%, which was 10.8 times higher than that of the foam, 8.88%. In terms of the plugging properties, the stabilization time and pressure of the foam gel are 60 min and −0.045 MPa, respectively, whereas those of the foam are 125 min and −0.008 MPa. The results of a field application in the Sandaoba fire area in Miquan, Xinjiang, China showed that the temperature of the observation hole in the foam test target area decreased and then rapidly rebounded, reaching a maximum temperature of 250°C after 72 h. In contrast, the temperature of the observation hole in the foam gel test target area remained essentially stable after decreasing to approximately 70°C. This response indicates that the foam gel treatment effectively influenced the thermal and oxygen-supply conditions around the central observation hole located approximately 4 m from the injection boreholes. The blocking of air leakage channels using foam gel therefore effectively prevents further reignition of the internal coal.