Coalbed gas or coalbed methane as a clean nonconventional natural gas has been caused a widely attention in the world. Although there were many countries engaging in the coalbed gas exploration and development, only few countries, such as America,Canada and Australia have achieved commercialized development. Based on the coalbed gas genetic type, the basins in these countries can be divided into two types:one is the basins mainly in biogenic gas, such as Power River basin, Surat basin and Alberta basin; the other is mainly in thermogenic gas basins, such as San Juan basin and Qinshui basin. Recently, mixture gas with biogenic and thermogenic gases is gradually discovered in many basins or coalfields in the world
