Abstract:

Coal measures area group of multiply superposed reservoirs which contain coalbed methane, shale gas and tight sandstone gas(there is also a gas hydrate reservoir lying on the Jurassic coal seam in the Muli coalfield, Qinghai Province); the transitional coal measures mainly contain coalbed methane and shale gas;the inland coal measures feature coalbed methane and tight sandstone gas; the mixed reservoir containing coalbed methane and shale gas often appears in coal measures owing to the coalmudsand structure system. In China, coalbed methane resources are about 36.8×1012 m3; shale gas and tight gas resources are about 32×1012 m3 and 20×1012 m3 respectively in coal measure(not including the Northeast China). The economic benefit of developing three kinds of gas individually is not obvious; but it has some convenient conditions, such as stress relief with three kinds of gas drainage by vertical surface wells and by crossmeasures boreholes in underground mine. Technology of separated reservoirs drainage was designed by adding hanging case and communicating tubes.

Key words: unconventional gas, coal measure, coalbed methane, shale gas, tight sandstone gas, gas hydrate