Effect of CO injection pressure on enhanced coal seam gas extraction.

The CO displacement of coal seam gas can simultaneously promote gas extraction and CO sequestration, with gas injection pressure being a key factor influencing both efficiency and safety. This study examined the impact of varying CO injection pressure on gas extraction and sequestration. The findings indicated that higher CO injection pressures reduced the gas injection and extraction time costs, increased the equilibrium pressure and coal seam temperature, and decreased carbon sequestration efficiency. As the CO injection pressure increased, the CH cumulative desorption capacity and desorption rate rose by 4.98%, the time to reach the residual gas content critical value (TLV of 2 m/t) shortened by 62.04 min, and the maximum CO storage per unit mass of coal increases by 3.6 m/t. Increasing the injection pressure enhanced gas desorption and CO sequestration. A higher CO injection pressure resulted in a higher CH yield rate and a reduced CO injection rate in the later stages. Therefore, it is advisable to reduce the CO injection pressure during the low efficiency desorption stage.