Analysis on gas and water output process of high rank coal reservoir in Southern Qinshui Basin

In order to study the control indicators for coalbed methane ( CBM) production, take the high rank coal at Southern Qinshui Basin as the study object, ba sed on the gas and water relative permeability test and the seepage physical similar simulation, the paper discussed the variation mechanism of the gas and water relat ive permeability in the micro-macro seepage network and further stated the gas and water output process of the seam. The results showed that the macro crack gas an d water relative permeability curve could be divided into a gas and water co-flow area and a pure gas flow area. The gas and water seepage curve of the micro cracks C ould be divided into a single phase water flow area, a gas and water co-flow area and a pure gas flow area. The liquid output process of the coal servitor could be concl uded as a water with gas process in the initial macro cracking development, single phase flow stage in the micro pore fissure, rising stage of the gas phase saturation, gas drive water process, single phase flow stage of the gas and the single phase flow stage of the gas in the macro cracks. Among them, the gas drive water process in the micro pore fissure would be the key to the stable liquid production in the high gas production well and the output of the free gas would be the base to reduce the pre ssure of the seam wholly.