1�� College of Construction Engineering��Jilin University��Changchun 130026��China; 2�� Institude of Exploration Techniques��CAGS��Langfang 065000��Hebei��China

Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining��which could promote further decomposition and expand mining areas of gas hydrate�� Steam heat calculation would provide the basis for the design of heating device and the choice of the field test parameters�� There were piping heat loss in the process of mining�� The heat transfer of steam flowing in the pipe was steady��so the heat loss could be obtained easily by formula calculation�� The power of stratum heating should be determined by numerical simulation for the process of heating was dynamic and the equations were usually nonlinear�� The selected mining conditions were 500-millimeter mining radius��10 centigrade mining temperature and 180 centigrade steam temperature�� Heat loss and best heating power��obtained by formula calculation and numerical simulation��were 21�� 35 W/m and 20 kW��