Effect of magma intrusion on the occurrence of coal gas in the Wolonghu coalfield

Chemical analysis, methane isothermal adsorption studies, and mercury porosimetry were performed on ten samples taken from the magma intrusion boundary in the Wolonghu coalfield. The physico-chemical properties of coals from the magma intrusion region are compared to those from the normal regions. The results show that the volatile content (Vad), the limiting adsorption constant (a), and the initial methane diffusion rate of samples from the magma intrusion region are generally smaller than those values from samples from the normal region. The number three coal sample from the magma intrusion region has a large vitrinite reflectance, well developed macropores, a small surface area, and weak methane adsorption capacity. The number ten coal sample from the normal region has a small vitrinite reflectance, well developed micropores, a large surface area, and a strong methane adsorption capacity. The maceral of the coal samples from the magma intrusion region and the normal region are similar. The coal in the area near the magma intrusion boundary is rich in methane and is an area where coal and gas outbursts often occur.