Methane hydrate formation characteristics under different initial conditions and their impact on coal seam properties

Due to the unique structural characteristics of hydrate, it has a potential application value in coal and gas outburst prevention in coal mines. Given the complexity of subsurface environments, it is essential to investigate the hydrate formation kinetics under varied initial conditions, as well as the subsequent impacts of hydrate formation on coal seam properties. This research mainly focuses on the hydrate formation process in coal samples with different coalification degrees under different initial pressure and water saturation conditions by using the designed hydrate formation system. The results show that gas consumption and hydrate saturation can be greatly enhanced by increasing the initial water saturation and pressure, which is favorable to reduce the coal seam gas pressure and improve the coal seam peak strength. The calculation results suggest that hydrate formation at varying saturation reduces the gas pressure by 53.05% ∼ 91.33% and increases the peak strength of coal across the tested confining pressure by 36.45% ∼ 59%. Furthermore, this study found that hydrate formation kinetics are significantly enhanced in lignite compared to that in anthracite, which may be attributed to structural variations associated with the coalification degree. The underlying mechanism requires further research in the future. The data obtained in this study regarding the effect of hydrate formation under different initial conditions on coal seam properties demonstrate the feasibility of preventing gas disasters in coal via controlling the initial conditions.