Determination on limit production value of coalbed methane vertical well under different coal reservoir permeability

In order to find out the limit production value of a coalbed methane well under the condition of different coal reservoir permeability and to ensure the sustain able stable high production of coalbed methane,according to the coal reservoir geometric model,the relationship between the start pressure gradient and permeability and t he gas well test,seepage theory and in combination with the lab measuring and test,a limit production value mathematic model of the coalbed methane vertical well under t he condition of different coal reservoir permeability was established.The verified results of Shizhuang Block exploration development information showed that when the limi t production value was close to the average production value of the production peak,with the rational control of the gas production,the stable production period could be ke pt in sustainable and high production.When other conditions were the same the limit production value would be increased in power with the permeability increased and wou Id be increased in index with the water production time of the single phase water flow stage expanded.When the coal reservoir permeability was relatively low,to possibly e xpand the water drainage time at the single phase water flow stage would be a key measure to improve the gas production value of the coalbed methane well.