Study on the Response Characteristics of the Pressure and Temperature Fields of Source Gas Injection under Loading Conditions

To study the safety of the source gas in coal seams after gas injection displacement, choosing N2 as an example, the pressure and temperature field variation characteristics of the source gas in coal were studied via experimental research, numerical simulation, and theoretical analysis methods, starting from the variation characteristics of the gas pressure and temperature fields in the coal. In this work, 2-9 MPa stress was applied to the top of the coal samples. The experimental results indicated that during the coal loading process, the gas pressure and temperature in the coal generally exhibited a decreasing trend and that the pressure and temperature could increase in some areas due to pore closure and frictional heat generation, but the increase range was not significant. Based on the numerical simulation results, in the 200 min loading process, the gas pressure inside the coal body decreased by approximately 0.25 MPa and the overall temperature slightly decreased. Only the temperature near the borehole greatly changed, and the maximum decrease reached approximately 8 & DEG;C. Considering the experimental and numerical simulation results, under the condition of stress concentration, the pressure and temperature fields of the source gas injected into the coal body mainly revealed a decreasing trend and the possibility of inducing outbursts was low.