Analysis on drainage system of coalbed methane high production well in south block of Shizhuang

in order to study the drainage system aff cted to the gas production of the coalbed mnethane wells in the South Block of Shizhuang.a compaiscn anaysis was conducted on the drainage curves of four high producton wells in the south bfock of Shizhuang. The paer d scovered and summaized th common fetues of he gas drainage curves from the high producton wells and optimized the drainage system suitable to the south block of Shihuang .The resuis showed that the drainage curves of the igh producion wells had ladderstyle vaiation law and features. After the wels in the gas producton.the vaiation of th botiom fowing pressure had four stages and they were a slow pressure drap stage,steady pressure reduction stagerapid drop stage and stable stage.The s ow pressure drop stage was atrnstionalstae fom the water pumping and prssure drop stage to the instablegas producton stage in the gas drainageintal perod. The reservoir prssure at the steadly pressure reduction stage would be steadili reduced and the pressure drop hopper would be stably extended to a far end. /n th pressure rapid drop stage.the inerierences occurred between the wells would make the pressure drop hoppers overlapping and expanded to the deep section and thegasproduction would be sharply increased.The stable stage would mean the botom f1owing pressure drop to a low lvel and keeing a long erod stabl ,the gas would be stably desorbed and the gas productiowould be stable at a high level. Before the rapid pressure drop stage.thecasing pressure should be kept in stable,th n thecasing pressure coult be slovwl released and would be favorable to protect the reservoir.The boton fowing pressure should be seadil reduced before the gas occured in the well and afer th gas occured inthe well the drainage system with a ladder-style variation would be favorable to the high production of the gas drainage wells in the study area.