Abstract: In order to enhance the effect of multiple branches horizontally-butted well for gas (methane) control and improve gas drainage rate, a model was built for production prediction. With the engineering background in Shaqu coal mine,the effectiveness of the model was authenticated, the distribution of gas inflow per unit length of well bore was studied, the effect of drilling morphology on its productivity was analyzed, The results show that the gas inflow into the main well of multiple branches horizontally-butted well has an u-shaped distribution, the gas inflow at the intersection is concave, the gas inflow into branch wells increases with the distance from the intersection point, that when the footage and the angle are the same, production of well bore with asymmetric structure is higher than that of the well bore with symmetric structure, that the productivity of horizontal wells increases with the increase of the angle between the main and branch well, and that when the total length of branch wells is constant, the productivity decreases with the increase of the number of multilateral wells.

Key words: coal bed methane, multiple branches horizontally-butted well, productivity, branch parameter, calculation model