Abstract: Based upon the composite patterns from three coalbed gas boundary types and seven coalbed gravity water types,the double phase liquid system of the gas water in coal reservoir is subdivided into three fundamental models,i.e.the open,semi open and close those,and the correlation of the models to the coalbed gas production potential is discussed in combination with some cases.The coalbed gas production potential may be relatively low in the open system because the coalbed gas and underground water in the system is active,be various in the semi open system because of the complex boundary conditions,and be relatively high in the close system in which the coal gas is sealed from the underground water.