Analysis on drainage features and drainage effect of coalbed methane well in Sihe Block

In order to study the long-term drainage features and drainage effect of a coalbed methane well, based on an actual production data of the early develop ed coalbed methane wells in Sihe Block, the theoretical analysis and experimental test as well as other methods were applied to analyze the long-term variation laws of the casing pressure, water production and gas production with the drainage time passed in the drainage process of the coalbed method wells and the verification was C onducted on the gas drainage effect. The study results showed that under the coalbed methane deposition condition with a less big difference, the drainage curve of the coalbed methane well within the block would have a close relation with the small structure. The casing pressure of the most methane wells would reach the peak value within a short time and then would be steadily decreased. The water production mainly concentrated at the first three years of the gas drainage stage. The gas producti on peak value would be appeared after 4 ~ 6 years of the gas drainage operation and the gas peak value of some methane wells would be appeared after 1 ~ 2 years of the gas drainage operations. The surface gas drainage effect of the coalbed methane wells was obvious, the input of the coal mine would be reduced, the mine heading speed would be increased and the gas overlimite accident occurred was reduced. Due to the coalbed methane well with a long drainage period, the gas production effe ct and drainage features at the different tectonic part would have a big difference features. According to the coalbed methane deposition conditions and the mining and heading speed in the underground mine, a surface well gas pre-drainage should be conducted in advance 10 ~ 15 years in the high gas content area.