A PRELIMINARY APPROACH TO THEMAIN FOKMATTIVE CONDITIONS OF LARGE AND MIDDLE SIZE OF GAS FIELDS IN COAL-BEARING SYSTEMS

With a viewpoint of dynamic equilibrium,a preliminary approach has been made to the key factors which control over the formation of large and middle size of gas fields in coal-bearing systems on the basis of the studies on the typical coal-derived gas fields at home and abroad.It is proposed that source rocks, accumulation and preservation of natural gas should be essential conditions.