Typical indexes analysis of different drainage phases for CBM U-shaped well in southern Shizhuang Block of Qinshui Basin

In order to provide the references for coalbed methane U-shaped well drainage system establishment and optimization, based on the reasonable analysis of the typical periods indexes for coalbed methane U-shaped wells drainage in Southern Shizhuang Block,the authors put forward that the drainage process could be divided i nto single drainage phase,wavelike rising phase and high production and steady phase.In the whole drainage process,some typical indexes were selected,including initial g as breakthrough time, initial cumulative water production,initial water level descending amplitude,initial water level descending rate, initial drainage rate,wavelike rising time, variation range of gas pressure,average distance from working fluid level to coal seam roof,typical high gas production,typical water production,typical gas pressure,averag e distance from coal seam floor to working fluid level.The analysis of drainage typical indexes showed that the initial water level descending rate should be controlled belo W5 m/ d in the first phase ,the casing pressure should be stabilized in 0 ~0.45 MPa while the working fluid level was kept below 10 m from the coal seam roof in the secon d phase,and the typical gas pressure should be stabilized in 0.01 ~ 0.03 MPa while the working fluid level was kept around the coal seam floor in the third phase.