Numerical simulation of magma intrusion on the thermal evolution of low rank coal

Abstract To study the effect of magma intrusion on the thermal evolution of low-rank coal with high water content, the mathematical relationship between water content variation and thermal conductivity of low-rank coal was analyzed by COMSOL Multiphysics numerical simulation and field validation. Taking Daxing Mine in Tiefa coalfield as the research background, the effects of magma finite time intrusion mechanism and water volatilization in coal on thermal evolution and organic maturity of coal seam are investigated in this paper. The results show that as the sill thickness increases, the thermal evolution temperature of the coal seam increases, the required thermal evolution time increases and the final retention temperature increases after the coal seam is cooled down. Approaching the magma, the maximum temperature that the coal seam can reach increases, the maximum temperature lasts longer, and the final temperature retained by the coal seam becomes higher. The increase of water content of coal makes the thermal conductivity increase, and the rate of heat transfer from coal seam is accelerated, and more heat is transferred to distant places in the same time. At the same time, the heat lost by the magma in the same time increases, the time required for the cooling of the magma decreases, and the maximum temperature reached by the underlying coal seam is significantly lower. The presence of moisture weakens the thermal evolution of the magma to the coal seam and reduces the expected maturity of the coal. The results of average random vitrinite reflectance (Ro) and moisture examination of coal samples collected at the Daxing Mine site verified the numerical simulation results of magma thermal evolution.