Influence of coal reservoir sensitivity on CBM drainage and control strategy in Faer Mining Area

In order to reduce the impact of coal reservoir sensitivity on coal mining, studies were carried out to investigate the sensitivity characteristics of coal seam in Faer Mining Area, an attempt to provide guidance for controlling coal bed methane drainage in the area.Sensitivity experiments were carried out to No.16 coal seam in the Faer Mining Are, which studied the permeability under different flow rates, different net stresses and with different cumulative injection multiples，the flow velocity sensitivity，stress sensitivity and water sensitivity damage characteristics of coal reservoir were studied，and analysis was performed to assess the impact from the critical water yield，stress sensitive critical value and sensitivity damage of coal seam on drainage mining，a control strategy for reducing stress sensitive damage in coalbed methane well of Faer Mining Area was proposed at the end.The results indicate that coal reservoir of the No.16 coal seam in Faer Mining Area is subject to moderately strong speed-sensitive damage，strong stress-sensitive damage，and moderately strong water-sensitive damage.In order to reduce the speed-sensitive damage to CBM wells at the initial stage of water production，the fluid velocity of coal seam should be kept low，with the water production of experimental coal seam not exceeding 2.46 m3/d.The stress sensitive critical value of the experimental coal seam is 7 MPa, when the net stress value is lower than the critical value，the coal seam is highly sensitive to stress changes，and the permeability of the coal seam decreases rapidly as the net stress value increases；the water-sensitive harm from the produced water on the coal seam increase at an accelerating rate with higher salinity of the produced water in CBM wells，and as the sa-linity decreases, the water-sensitive harm to the coal seam tends to decrease gradually.This study would provide important guidance for reducing fracture and sensitive damages to CBM wells throughout mining process.