Coalbed methane mobility and affected to gas production dynamic in Laochang and Enhong Blocks of Eastern Yunnan

In order to analyze the reasons for the poor drainage performance of the CBM wells in the early stage in Laochang and Enhong Blocks of Eastern Yunnan,a systematic preparation was conducted on the coalbed methane geological parameters of Laochang Block and Enhong Block in Eastern Yunnan. A comparison and analysis were conducted on the coalbed methane mobility-permeability and desorption time of Laochang Block and Enhong Block. In combination with the analysis on gas production curves of the initial coalbed methane wells in the two blocks, the paper revealed the influence mechanism of the mobility the gas production dynamic and provided the proposals to control the initial water drainage speed. The result showed as the followings: ①Laochang and Enhong Blocks both were the low permeability coalbed methane blocks. The permeability of the coal reservoir in Laochang Block was generally lower than Enhong Block. The difference mainly was caused by the geostress intensity differences of the two blocks.②The desorption time of the coal and rock in Laochang Block was generally higher than Enhong Block and the difference was mainly caused by the coal grade differences of the coal and rock in the two blocks. ③Due to the initial water drainage speed of the previous coalbed methane wells was too fast, the peak gas production of the coalbed methane wells in Laochang Block and Enhong Block was not high. The initial water drainage speed too fast was more evident in Enhong Block and the desorption time of the coal and rock in Enhong Block was relatively short. Under the double function of the effective stress effect and the fast diffusion effect, thus the pressure released cone would be not favorably expanded. ④The initial water drainage speed control of the coalbed methane wells in Laochang Block and Enhong Block would be one of the important contents to the drainage operation system optimization of the coalbed methane wells in the future. Enhong Block with a relative short desorption time of the coal and rock should be more important to have a slow water drainage strategy.