Kinetic Behavior of Sorption and Strain during Coal–Gas Interaction

The fundamental understanding of the coal–gas interaction is important for improving coalbed methane (CBM) extraction efficiency. However, the sorption and strain kinetics of gas adsorption–desorption on coal still need to be further explored due to the unclear mechanism. In this paper, a series of isotherm sorption experiments monitoring sorption and strain versus time are performed. The results show that sorption and strain kinetics exhibit three-stage evolution behavior controlled by coal pore structure and interface sorption sites. Different gases, pressures, and sorption processes have significant effects on kinetic behavior. Moreover, the apparent strain obtained from a combination of sorption-induced deformation and gas-loading compression is anisotropic and asynchronous. For the apparent strain, the sorption-induced deformation is the main controlling factor, followed by gas-loading compression. The relationship between sorption and strain is approximately linear, but it is also affected by gas, pressure, and the sorption process. This fundamental exploration of the coal–gas interaction has implications for efficient CBM extraction.