Study on combined coalbed methane drainage system of multi seams in Zhijin Block,Guizhou

in orderto improve the production scope of the coal bed methane resouces under the condition ofthe multi seams and to discover the related drainageand controlsystem in conbiation wth the miurti and thi seans.large varied space between seans low permeabilityof ther geological features of the Zhejin Block.thepaper analyzed the causes of the " up seam exposed.1ow seam non-desorption and low producion eficiency of a single well" cured in the actual development pocess . with the comparison analysis on the drainage control and the production effect of the combied drainage well n the mutiseams.based on th discussion onte ltuid level reduction.casing pressure control and gas production and water production variation aw,the couping relationship betveen the pressure reducion and adsopton was defined. T'he stucy showed tat the " low velocity low casing-lader type pressure reducton' drainage system coud mest the combied dainage fech ical equrements of the multi seams and could effectively improve the single well production of the coal bed methane.