Abstract: Using multi-branch horizontal wells can greatly increase the drainage area of reservoirs and effectively raise gas production. Based on gas transient flow theory, the pressure drop analytical solution of the horizontal gas well in parallel with x-axis is concluded according to Newman's product principle and Green function. Combined with rotation of axes, the transient deliverability equation for horizontal gas well is derived with α angle to the x-axis. And then the transient deliverability forecasting model for multi-branch horizontal gas wells is presented based on the principle of pressure drop superposition. The analysis result shows that: (1) the production of multibranch horizontal wells in gas reservoirs increases with the increasing of number of the branches, but interference effect strengthens, production growth range decreases when the number increases, indicating that there is an optimal value of the number of branches; (2) according to the optimal number of branches, the production is declining with time, followed by tending to a certain value, and the flow reaches pseudo-steady state.

Key words: horizontal well, gas well, branch well, deliverability, productivity, analysis