The load evolution characteristics of residual coal in abandoned mines and its influence on the adsorption and migration of methane

Accurate prediction of methane resource reserves is a key step in developing and utilizing abandoned mines. However, due to mining activities' interference, the load environment of the remaining coal has changed, which affects the adsorption and migration of methane gas and leads to the wrong evaluation of methane resource reserves. To study the influence of load on the adsorption and migration of methane in abandoned mines, we analyzed the space–time evolution of the load environment of residual coal in abandoned mines. We divided the residual coal into column-type and loose-type. Methane adsorption and migration experiments were carried out by changing the axial load of coal samples on the experimental device. The results show that: (1) the load of the residual coal in the abandoned mine shows a downward trend with the increase in the closing time. In space, the load path of column-type coal increases first and then decreases to a stable value, and the loose-type coal continues to increase to stability. (2) Before the coal is destroyed, with the axial load increasing, the methane adsorption quantity of column-type coal increases from 5.60 to 9.12 ml/g, and the loose-type coal increases from 7.28 to 13.99 ml/g. After the destruction of the coal, the adsorption quantity of the two types of residual coal decreased. (3) The permeability of coal decreases first and then increases with the increase in load. (4) Load should be considered when establishing an accurate methane storage model. The research can provide a theoretical basis and technical support for establishing an accurate methane storage model and efficiently utilizing abandoned mines.