Real-time monitoring of induced strain during multi-stage ad-/desorption of methane on coal

The sorption-induced strain of coal is very important for the evaluation of coalbed methane productivity. Previous studies have focused on the strain properties of the equilibrium state, however, the time-dependent strain evolution behavior has been rarely considered. In this paper, to explore the time-dependent strain evolution behavior and the mechanism behind, we perform the real-time monitoring of induced strain during multi-stage sorption of methane on coal. The results show the multi-scale pore structure and the heterogeneous interface properties of coal determine the kinetics behavior of gas transport and sorption, which then dominates the time-dependent strain evolution properties. Single-stage sorption and multi-stage sorption are driven by high pressure and low pressure to complete continuous and discontinuous strain evolution, respectively. This differences in driving pressure and strain continuity have potential effects on strain kinetics. This study has potential implications for time-dependent production assessment of coalbed methane.