Experimental study on migration yield law of coal-bed methane under the condition of saturated steam

In order to obtain the migration yield law of coal-bed methane (CBM) in a low permeability coal reservoir in the process of steam injection exploitation,an experiment set of desorption and seepage under the conditions of triax- ial stress and steam was designed and the experiment about methane migration yield features in coal at different satu- rated steam pressures was conducted. The results show that the migration yield of methane exhibits the Langmuir trend with a desorption time at a certain confining and axial pressure;with the increase of saturated steam pressure,the mi- gration yield increases,but its growth rate decreases gradually. The temperature of coal sample shows an exponential growth trend at different saturated steam pressures. A thermal saturation phenomenon is subsequently induced by re- ducing the heat exchange efficiency in a specified time and then the effect of heat injection is not obvious. There is no methane migration yield due to the sharp increase of stress in a short time after the steam injected in the coal sample. Then the migration velocity of methane increases exponentially with the stress decrease and free methane increase and migration yield increases finally. The maximum migration yield of methane in this experiment is 46. 3% higher than that without steam injection. The experimental results will provide a reference for the technical plan and yield predic- tion of CBM exploitation with steam injection.