A new method for predicting productivity of fractured horizontal wells in low-permeability tight gas reservoir

Adopting potential theory, the superposition principle and the related principle of fluid mechanics, a steady mathematical model for fractured horizontal well is established considering interactive disturbance among fractures, pollution skin, non-uniform distribution of fracture, finite conductivity flow in fracture and wellbore, and fracture-wellbore convergent flows, non-Darcy flow in fracture. Then the numerical solution to the model is derived. The model is applied to predict an actual productivity of horizontal wells and to analyze the influence factors of productivity. Result shows that the model can be used for horizontal well productivity prediction with various complicated situations and it shows high accuracy. Due to the fracture's mutual interference, the production rate of fracture differs. Fractures on both ends of the horizontal wellbore have high yield, while fractures in middle have low yield. Horizontal well productivity increases with the growth of horizontal interval length, fracture half-length, and fracture conductivity. Pollution skin of fracture has significant effects on productivity. The increase of it leads to a sharp decline of productivity. Thus it is important to reduce the damage of fracturing operation on formation as much as possible. Within relatively reasonable fracture spacing scope, the effect of fracture distribution pattern on productivity is not obvious. Since wellbore radius affects wellbore pressure drop, its design should be in accordance with the productivity of the horizontal wells. ©, 2015, Science Press. All right reserved.